highland.js

(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.highland = f()}})(function(){var define,module,exports;return (function(){function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s}return e})()({1:[function(require,module,exports){
var isFunction = require('./isFunction');

/**
 * Coerce observer callbacks into observer object or return observer object
 * if already created. Will throw an error if both an object and callback args
 * are provided.
 *
 * @id createObserver
 * @param {function|object} onNext Function to receive new values or observer
 * @param {function} [onError] Optional callback to receive errors.
 * @param {function} [onComplete] Optional callback when stream completes
 * @return {object} Observer object with next, error, and complete methods
 * @private
 *
 * createObserver(
 *     function (x) { console.log(x); },
 *     function (err) { console.error(err); },
 *     function () { console.log('done'); }
 * )
 *
 * createObserver(
 *     null,
 *     null,
 *     function () { console.log('done'); }
 * )
 *
 * createObserver({
 *     next: function (x) { console.log(x); },
 *     error: function (err) { console.error(err); },
 *     complete: function () { console.log('done'); }
 * })
 */
function createObserver (onNext, onError, onComplete) {
    var isObserver = onNext && !isFunction(onNext) && typeof onNext === 'object';

    // ensure if we have an observer that we don't also have callbacks. Users
    // must choose one.
    if (isObserver && (onError || onComplete)) {
        throw new Error('Subscribe requires either an observer object or optional callbacks.');
    }

    // onNext is actually an observer
    if (isObserver) {
        return onNext;
    }

    // Otherwise create an observer object
    return {
        next: onNext,
        error: onError,
        complete: onComplete,
    };
}

module.exports = createObserver;

},{"./isFunction":5}],2:[function(require,module,exports){
(function (global){
/**
 * Return a global context upon which to install Highland globals. Takes a
 * default namespace to use if both the node global and browser window
 * namespace cannot be found.
 *
 * @returns {object} Global namespace context
 */

// Use the nodejs global namespace
if (typeof global !== 'undefined') {
    module.exports = global;
}
// Use the browser window namespace
else if (typeof window !== 'undefined') {
    module.exports = window;
}
// If neither the global namespace or browser namespace is avaiable
// Use this module as the default context
else {
    module.exports = this;
}


}).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{}],3:[function(require,module,exports){
(function (process){
/**
 * Highland: the high-level streams library
 *
 * Highland may be freely distributed under the Apache 2.0 license.
 * http://github.com/caolan/highland
 * Copyright (c) Caolan McMahon
 *
 */


var inherits = require('util').inherits;
var EventEmitter = require('events').EventEmitter;
var Decoder = require('string_decoder').StringDecoder;

var createObserver = require('./createObserver');
var isFunction = require('./isFunction');
var IntMap = require('./intMap');
var ObservableSubscription = require('./observableSubscription');
var Queue = require('./queue');
var ReadableProxy = require('./readableProxy');

// Create quick slice reference variable for speed
var slice = Array.prototype.slice;
var hasOwn = Object.prototype.hasOwnProperty;

// Set up the global object.
var _global = require('./global');

// ES5 detected value, used for switch between ES5 and ES3 code
var isES5 = (function () {
    'use strict';
    return Function.prototype.bind && !this;
}());

function bindContext(fn, context) {
    if (isES5) {
        return fn.bind(context);
    }
    else {
        return function () {
            return fn.apply(context, arguments);
        };
    }
}

/**
 * The Stream constructor, accepts an array of values or a generator function
 * as an optional argument. This is typically the entry point to the Highland
 * APIs, providing a convenient way of chaining calls together.
 *
 * **Arrays -** Streams created from Arrays will emit each value of the Array
 * and then emit a [nil](#nil) value to signal the end of the Stream.
 *
 * **Generators -** These are functions which provide values for the Stream.
 * They are lazy and can be infinite, they can also be asynchronous (for
 * example, making a HTTP request). You emit values on the Stream by calling
 * `push(err, val)`, much like a standard Node.js callback. Once it has been
 * called, the generator function will not be called again unless you call
 * `next()`. This call to `next()` will signal you've finished processing the
 * current data and allow for the generator function to be called again. If the
 * Stream is still being consumed the generator function will then be called
 * again.
 *
 * You can also redirect a generator Stream by passing a new source Stream
 * to read from to next. For example: `next(other_stream)` - then any subsequent
 * calls will be made to the new source.
 *
 * **Node Readable Stream -** Pass in a Node Readable Stream object to wrap
 * it with the Highland API. Reading from the resulting Highland Stream will
 * begin piping the data from the Node Stream to the Highland Stream.
 *
 * A stream constructed in this way relies on `Readable#pipe` to end the
 * Highland Stream once there is no more data. Not all Readable Streams do
 * this. For example, `IncomingMessage` will only emit `close` when the client
 * aborts communications and will *not* properly call `end`. In this case, you
 * can provide an optional `onFinished` function with the signature
 * `onFinished(readable, callback)` as the second argument.
 *
 * This function will be passed the Readable and a callback that should called
 * when the Readable ends. If the Readable ended from an error, the error
 * should be passed as the first argument to the callback. `onFinished` should
 * bind to whatever listener is necessary to detect the Readable's completion.
 * If the callback is called multiple times, only the first invocation counts.
 * If the callback is called *after* the Readable has already ended (e.g., the
 * `pipe` method already called `end`), it will be ignored.
 *
 * The `onFinished` function may optionally return one of the following:
 *
 * - A cleanup function that will be called when the stream ends. It should
 * unbind any listeners that were added.
 * - An object with the following optional properties:
 *    - `onDestroy` - the cleanup function.
 *    - `continueOnError` - Whether or not to continue the stream when an
 *      error is passed to the callback. Set this to `true` if the Readable
 *      may continue to emit values after errors. Default: `false`.
 *
 * See [this issue](https://github.com/caolan/highland/issues/490) for a
 * discussion on why Highland cannot reliably detect stream completion for
 * all implementations and why the `onFinished` function is required.
 *
 * **EventEmitter / jQuery Elements -** Pass in both an event name and an
 * event emitter as the two arguments to the constructor and the first
 * argument emitted to the event handler will be written to the new Stream.
 *
 * You can pass a mapping hint as the third argument, which specifies how
 * event arguments are pushed into the stream. If no mapping hint is provided,
 * only the first value emitted with the event to the will be pushed onto the
 * Stream.
 *
 * If `mappingHint` is a number, an array of that length will be pushed onto
 * the stream, containing exactly that many parameters from the event. If it's
 * an array, it's used as keys to map the arguments into an object which is
 * pushed to the tream. If it is a function, it's called with the event
 * arguments, and the returned value is pushed.
 *
 * **Promise -** Accepts an ES6 / jQuery style promise and returns a
 * Highland Stream which will emit a single value (or an error). In case you use
 * [bluebird cancellation](http://bluebirdjs.com/docs/api/cancellation.html) Highland Stream will be empty for a cancelled promise.
 *
 * **Iterator -** Accepts an ES6 style iterator that implements the [iterator protocol](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_.22iterator.22_protocol):
 * yields all the values from the iterator using its `next()` method and terminates when the
 * iterator's done value returns true. If the iterator's `next()` method throws, the exception will be emitted as an error,
 * and the stream will be ended with no further calls to `next()`.
 *
 * **Iterable -** Accepts an object that implements the [iterable protocol](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_.22iterable.22_protocol),
 * i.e., contains a method that returns an object that conforms to the iterator protocol. The stream will use the
 * iterator defined in the `Symbol.iterator` property of the iterable object to generate emitted values.
 *
 * **Asynchronous Iterator -** Accepts an iterator produced by an ES8 [async generator function](https://github.com/tc39/proposal-async-iteration#async-generator-functions),
 * yields all the values from the iterator by resolving its `next()` method and terminates when the
 * iterator's done value returns true. If the iterator's `next()` method throws or rejects, the exception will be emitted as an error,
 * and the stream will be ended with no further calls to `next()`.
 *
 * **Asynchronous Iterable -** Accepts an object with a `Symbol.asyncIterator`
 * property that conforms to the [async iteration
 * spec](https://github.com/tc39/proposal-async-iteration#async-iterators-and-async-iterables).
 * The constructor will create a async iterator and use it to generator emitted
 * values.
 *
 * @id _(source)
 * @section Stream Objects
 * @name _(source)
 * @param {Array | Function | Iterator | Iterable | Promise | Readable Stream | String} source - (optional) source to take values from from
 * @param {Function} onFinished - (optional) a function that detects when the readable completes. Second argument. Only valid if `source` is a Readable.
 * @param {EventEmitter | jQuery Element} eventEmitter - (optional) An event emitter. Second argument. Only valid if `source` is a String.
 * @param {Array | Function | Number} mappingHint - (optional) how to pass the
 * arguments to the callback. Only valid if `source` is a String.
 * @api public
 *
 * // from an Array
 * _([1, 2, 3, 4]);
 *
 * // using a generator function
 * _(function (push, next) {
 *     push(null, 1);
 *     push(err);
 *     next();
 * });
 *
 * // a stream with no source, can pipe node streams through it etc.
 * var through = _();
 *
 * // wrapping a Node Readable Stream so you can easily manipulate it
 * _(readable).filter(hasSomething).pipe(writeable);
 *
 * // wrapping a Readable that may signify completion by emitting `close`
 * // (e.g., IncomingMessage).
 * _(req, function (req, callback) {
 *     req.on('end', callback)
 *         .on('close', callback)
 *         .on('error', callback);
 *
 *     return function () {
 *         req.removeListener('end', callback);
 *         req.removeListener('close', callback);
 *         req.removeListener('error', callback);
 *     };
 * }).pipe(writable);
 *
 * // wrapping a Readable that may emit values after errors.
 * _(req, function (req, callback) {
 *     req.on('error', callback);
 *
 *     return {
 *         onDestroy: function () {
 *             req.removeListener('error', callback);
 *         },
 *         continueOnError: true
 *     };
 * }).pipe(writable);
 *
 * // creating a stream from events
 * _('click', btn).each(handleEvent);
 *
 * // creating a stream from events with a mapping array
 * _('request', httpServer, ['req', 'res']).each(handleEvent);
 * //=> { req: IncomingMessage, res: ServerResponse }
 *
 * // creating a stream from events with a mapping function
 * _('request', httpServer, function(req, res) {
 *     return res;
 * }).each(handleEvent);
 * //=> IncomingMessage
 *
 * // from a Promise object
 * var foo = _($.getJSON('/api/foo'));
 *
 * // from an iterator
 * var map = new Map([['a', 1], ['b', 2]]);
 * var bar = _(map.values()).toArray(_.log);
 * //=> [1, 2]
 *
 * // from an iterable
 * var set = new Set([1, 2, 2, 3, 4]);
 * var bar = _(set).toArray(_.log);
 * //=> [1, 2, 3, 4]
 *
 * // from an async iterator
 * async function* generator() {
 *   yield 1;
 *   yield 2;
 * }
 * var stream = _(generator()).toArray(_.log);
 * //=> [1, 2]
 *
 * // from an async iterable
 * var asyncIterable = {
 *   [Symbol.asyncIterable]: generator
 * };
 * var stream = _(asyncIterable).toArray(_.log);
 * //=> [1, 2]
 */

/*eslint-disable no-multi-spaces */
var _ = exports = module.exports = __(Stream);
function __(StreamCtor) {
    return function (/*optional*/xs, /*optional*/secondArg, /*optional*/ mappingHint) {
        /*eslint-enable no-multi-spaces */
        var s = null;
        if (_.isUndefined(xs)) {
            // nothing else to do
            s = new StreamCtor();
            s.writable = true;
        }
        else if (_.isStream(xs)) {
            if (!(xs instanceof StreamCtor)) { // different subclass or version
                var ret = new StreamCtor();
                xs.on('error', bindContext(ret.write, ret));
                s = xs.pipe(ret);
            }
            else {
                s = xs;
            }
        }
        else if (_.isArray(xs)) {
            s = new StreamCtor();
            s._outgoing.enqueueAll(xs);
            s._outgoing.enqueue(_.nil);
        }
        else if (_.isFunction(xs)) {
            s = new StreamCtor(xs);
        }
        else if (_.isObject(xs)) {
            // check to see if we have a readable stream
            if (_.isFunction(xs.on) && _.isFunction(xs.pipe)) {
                var onFinish = _.isFunction(secondArg) ? secondArg : defaultReadableOnFinish;
                s = new StreamCtor();
                s.writable = true;
                pipeReadable(xs, onFinish, s);
                // s has to be writable so that the pipe works
                // return a non-writable stream
                return s.map(function (x) { return x; });
            }
            else if (_.isFunction(xs.then)) {
                // probably a promise
                s = promiseStream(StreamCtor, xs);
            }
            // must check iterators and iterables in this order
            // because generators are both iterators and iterables:
            // their Symbol.iterator method returns the `this` object
            // and an infinite loop would result otherwise
            else if (_.isFunction(xs.next)) {
                // probably an iterator. This handle both sync and async iterators.
                return iteratorStream(StreamCtor, xs);
            }
            else if (!_.isUndefined(_global.Symbol) && xs[_global.Symbol.iterator]) {
                // probably an iterable
                return iteratorStream(StreamCtor, xs[_global.Symbol.iterator]());
            }
            else if (!_.isUndefined(_global.Symbol) && xs[_global.Symbol.asyncIterator]) {
                // probably an async iterable
                return iteratorStream(StreamCtor, xs[_global.Symbol.asyncIterator]());
            }
            else {
                throw new Error(
                    'Object was not a stream, promise, iterator or iterable: ' + (typeof xs)
                );
            }
        }
        else if (_.isString(xs)) {
            var mapper = hintMapper(mappingHint);

            s = new StreamCtor();

            var callback_func = function () {
                var ctx = mapper.apply(this, arguments);
                s.write(ctx);
            };

            secondArg.on(xs, callback_func);
            var removeMethod = secondArg.removeListener // EventEmitter
                               || secondArg.unbind;     // jQuery

            if (removeMethod) {
                s._destructors.push(function() {
                    removeMethod.call(secondArg, xs, callback_func);
                });
            }
        }
        else {
            throw new Error(
                'Unexpected argument type to Stream constructor: ' + (typeof xs)
            );
        }

        return s;
    };
}
/*eslint-enable no-use-before-define */

function checkIsNumber(parameter, paramName) {
    if (typeof parameter != 'number') {
        throw new TypeError('Parameter "' + paramName + '" is not a number.');
    }
}

function checkRange(predicate, message) {
    if (!predicate) {
        throw new RangeError(message);
    }
}

_.isUndefined = function (x) {
    return typeof x === 'undefined';
};

_.isFunction = isFunction;

_.isObject = function (x) {
    return typeof x === 'object' && x !== null;
};

_.isString = function (x) {
    return typeof x === 'string';
};

_.isArray = Array.isArray || function (x) {
    return Object.prototype.toString.call(x) === '[object Array]';
};

// setImmediate browser fallback
if (typeof setImmediate === 'undefined') {
    _.setImmediate = function (fn) {
        setTimeout(fn, 0);
    };
}
else {
    // We don't use a direct alias since some tests depend
    // on allowing Sinon.Js to override the global
    // setImmediate.
    _.setImmediate = function (fn) {
        setImmediate(fn);
    };
}

/**
 * The end of stream marker. This is sent along the data channel of a Stream
 * to tell consumers that the Stream has ended. See the example map code for
 * an example of detecting the end of a Stream.
 *
 * Note: `nil` is setup as a global where possible. This makes it convenient
 * to access, but more importantly lets Streams from different Highland
 * instances work together and detect end-of-stream properly. This is mostly
 * useful for NPM where you may have many different Highland versions installed.
 *
 * @id nil
 * @section Utils
 * @name _.nil
 * @api public
 *
 * var map = function (iter, source) {
 *     return source.consume(function (err, val, push, next) {
 *         if (err) {
 *             push(err);
 *             next();
 *         }
 *         else if (val === _.nil) {
 *             push(null, val);
 *         }
 *         else {
 *             push(null, iter(val));
 *             next();
 *         }
 *     });
 * };
 */

// set up a global nil object in cases where you have multiple Highland
// instances installed (often via npm)
var nil = _.nil = require('./nil');

/**
 * Transforms a function with specific arity (all arguments must be
 * defined) in a way that it can be called as a chain of functions until
 * the arguments list is saturated.
 *
 * This function is not itself curryable.
 *
 * @id curry
 * @name _.curry(fn, [*arguments])
 * @section Functions
 * @param {Function} fn - the function to curry
 * @param args.. - any number of arguments to pre-apply to the function
 * @returns Function
 * @api public
 *
 * fn = curry(function (a, b, c) {
 *     return a + b + c;
 * });
 *
 * fn(1)(2)(3) == fn(1, 2, 3)
 * fn(1, 2)(3) == fn(1, 2, 3)
 * fn(1)(2, 3) == fn(1, 2, 3)
 */

_.curry = function (fn /* args... */) {
    var args = slice.call(arguments);
    return _.ncurry.apply(this, [fn.length].concat(args));
};

/**
 * Same as `curry` but with a specific number of arguments. This can be
 * useful when functions do not explicitly define all its parameters.
 *
 * This function is not itself curryable.
 *
 * @id ncurry
 * @name _.ncurry(n, fn, [args...])
 * @section Functions
 * @param {Number} n - the number of arguments to wait for before apply fn
 * @param {Function} fn - the function to curry
 * @param args... - any number of arguments to pre-apply to the function
 * @returns Function
 * @api public
 *
 * fn = ncurry(3, function () {
 *     return Array.prototype.join.call(arguments, '.');
 * });
 *
 * fn(1, 2, 3) == '1.2.3';
 * fn(1, 2)(3) == '1.2.3';
 * fn(1)(2)(3) == '1.2.3';
 */

_.ncurry = function (n, fn /* args... */) {
    var largs = slice.call(arguments, 2);
    if (largs.length >= n) {
        return fn.apply(this, largs.slice(0, n));
    }

    return _.partial.apply(this, [_.ncurry, n, fn].concat(largs));
};

/**
 * Partially applies the function (regardless of whether it has had curry
 * called on it). This will always postpone execution until at least the next
 * call of the partially applied function.
 *
 * @id partial
 * @name _.partial(fn, args...)
 * @section Functions
 * @param {Function} fn - function to partial apply
 * @param args... - the arguments to apply to the function
 * @api public
 *
 * var addAll = function () {
 *     var args = Array.prototype.slice.call(arguments);
 *     return foldl1(add, args);
 * };
 * var f = partial(addAll, 1, 2);
 * f(3, 4) == 10
 */

_.partial = function (f /* args... */) {
    var args = slice.call(arguments, 1);
    return function () {
        return f.apply(this, args.concat(slice.call(arguments)));
    };
};

/**
 * Evaluates the function `fn` with the argument positions swapped. Only
 * works with functions that accept two arguments.
 *
 * @id flip
 * @name _.flip(fn, [x, y])
 * @section Functions
 * @param {Function} fn - function to flip argument application for
 * @param x - parameter to apply to the right hand side of f
 * @param y - parameter to apply to the left hand side of f
 * @api public
 *
 * div(2, 4) == 0.5
 * flip(div, 2, 4) == 2
 * flip(div)(2, 4) == 2
 */

_.flip = _.curry(function (fn, x, y) { return fn(y, x); });

/**
 * Creates a composite function, which is the application of function1 to
 * the results of function2. You can pass an arbitrary number of arguments
 * and have them composed. This means you can't partially apply the compose
 * function itself.
 *
 * @id compose
 * @name _.compose(fn1, fn2, ...)
 * @section Functions
 * @api public
 *
 * var add1 = add(1);
 * var mul3 = mul(3);
 *
 * var add1mul3 = compose(mul3, add1);
 * add1mul3(2) == 9
 */

_.compose = function (/*functions...*/) {
    var fns = slice.call(arguments).reverse();
    return _.seq.apply(null, fns);
};

/**
 * The reversed version of [compose](#compose). Where arguments are in the
 * order of application.
 *
 * @id seq
 * @name _.seq(fn1, fn2, ...)
 * @section Functions
 * @api public
 *
 * var add1 = add(1);
 * var mul3 = mul(3);
 *
 * var add1mul3 = seq(add1, mul3);
 * add1mul3(2) == 9
 */

_.seq = function () {
    var fns = slice.call(arguments);
    return function () {
        if (!fns.length) {
            return null;
        }
        var r = fns[0].apply(this, arguments);
        for (var i = 1; i < fns.length; i++) {
            r = fns[i].call(this, r);
        }
        return r;
    };
};

function nop() {
    // Do nothing.
}

function defaultReadableOnFinish(readable, callback) {
    // It's possible that `close` is emitted *before* `end`, so we simply
    // cannot handle that case. See
    // https://github.com/caolan/highland/issues/490 for details.

    // pipe already pushes on end, so no need to bind to `end`.

    // write any errors into the stream
    readable.once('error', callback);

    return function () {
        readable.removeListener('error', callback);
    };
}

function pipeReadable(xs, onFinish, stream) {
    var response = onFinish(xs, streamEndCb);
    var unbound = false;

    var cleanup = null;
    var endOnError = true;

    if (_.isFunction(response)) {
        cleanup = response;
    }
    else if (response != null) {
        cleanup = response.onDestroy;
        endOnError = !response.continueOnError;
    }

    xs.pipe(stream);

    stream.onDestroy(unbind);

    function streamEndCb(error) {
        if (stream._nil_pushed) {
            return;
        }

        if (error) {
            stream.write(new StreamError(error));
        }

        if (error == null || endOnError) {
            unbind();
            stream.end();
        }
    }

    function unbind() {
        if (unbound) {
            return;
        }

        unbound = true;

        if (cleanup) {
            cleanup();
        }

        if (xs.unpipe) {
            xs.unpipe(stream);
        }
    }
}

function newPullFunction(xs) {
    return function pull(cb) {
        xs.pull(cb);
    };
}

function newDelegateGenerator(pull) {
    return function delegateGenerator(push, next) {
        var self = this;
        pull(function (err, x) {
            // Minor optimization to immediately call the
            // generator if requested.
            var old = self._defer_run_generator;
            self._defer_run_generator = true;

            push(err, x);
            if (x !== nil) {
                next();
            }

            self._defer_run_generator = old;
            if (!old && self._run_generator_deferred) {
                self._runGenerator();
            }
        });
    };
}

function promiseStream(StreamCtor, promise) {
    var nilScheduled = false;
    return new StreamCtor(function (push) {
        // We need to push asynchronously so that errors thrown from handling
        // these values are not caught by the promise. Also, return null so
        // that bluebird-based promises don't complain about handlers being
        // created but not returned. See
        // https://github.com/caolan/highland/issues/588.
        promise = promise.then(function (value) {
            nilScheduled = true;
            _.setImmediate(function () {
                push(null, value);
                push(null, nil);
            });
            return null;
        }, function (err) {
            nilScheduled = true;
            _.setImmediate(function () {
                push(err);
                push(null, nil);
            });
            return null;
        });

        // Using finally also handles bluebird promise cancellation, so we do
        // it if we can.
        if (_.isFunction(promise['finally'])) { // eslint-disable-line dot-notation
            promise['finally'](function () { // eslint-disable-line dot-notation
                if (!nilScheduled) {
                    _.setImmediate(function () {
                        push(null, nil);
                    });
                }
                return null;
            });
        }
    });
}

function iteratorStream(StreamCtor, it) {
    return new StreamCtor(function (push, next) {
        function pushIt(iterElem) {
            if (iterElem.done) {
                if (!_.isUndefined(iterElem.value)) {
                    // generators can return a final
                    // value on completion using return
                    // keyword otherwise value will be
                    // undefined
                    push(null, iterElem.value);
                }
                push(null, _.nil);
            }
            else {
                push(null, iterElem.value);
                next();
            }
        }

        try {
            var iterElem = it.next();

            if (_.isFunction(iterElem.then)) {
                iterElem
                    .then(pushIt)
                    .catch(function(err) {
                        push(err);
                        push(null, _.nil);
                    });
            }
            else {
                pushIt(iterElem);
            }
        }
        catch (err) {
            push(err);
            push(null, _.nil);
        }
    });
}

function hintMapper(mappingHint) {
    var mappingHintType = (typeof mappingHint);
    var mapper;

    if (mappingHintType === 'function') {
        mapper = mappingHint;
    }
    else if (mappingHintType === 'number') {
        mapper = function () {
            return slice.call(arguments, 0, mappingHint);
        };
    }
    else if (_.isArray(mappingHint)) {
        mapper = function () {
            var args = arguments;
            return mappingHint.reduce(function (ctx, hint, idx) {
                ctx[hint] = args[idx];
                return ctx;
            }, {});
        };
    }
    else {
        mapper = function (x) { return x; };
    }

    return mapper;
}

function pipeStream(src, dest, write, end, passAlongErrors) {
    var resume = null;
    if (!passAlongErrors) {
        src._send_events = true;
    }

    var s = src.consume(function (err, x, push, next) {
        var canContinue;
        if (err) {
            if (passAlongErrors) {
                canContinue = write.call(dest, new StreamError(err));
            }
            else {
                canContinue = true;
            }
        }
        else if (x === nil) {
            end.call(dest);
            return;
        }
        else {
            canContinue = write.call(dest, x);
        }

        if (canContinue !== false) {
            next();
        }
        else {
            resume = next;
        }
    });

    dest.on('drain', onConsumerDrain);

    // Since we don't keep a reference to piped-to streams,
    // save a callback that will unbind the event handler.
    src.onDestroy(function () {
        dest.removeListener('drain', onConsumerDrain);
    });

    dest.emit('pipe', src);

    // Calling resume() may cause data to be synchronously pushed.
    // That can cause data loss if the destination is a through stream and it
    // is unpaused. That is, this chain won't work correctly:
    //   stream.pipe(unpaused).pipe(otherDest);
    _.setImmediate(function () {
        s.resume();
    });
    return dest;

    function onConsumerDrain() {
        if (resume) {
            resume();
            resume = null;
        }
    }
}

/**
 * Actual Stream constructor wrapped the the main exported function
 */

function Stream(generator) {
    EventEmitter.call(this);

    // used to detect Highland Streams using isStream(x), this
    // will work even in cases where npm has installed multiple
    // versions, unlike an instanceof check
    this.__HighlandStream__ = true;

    this.id = ('' + Math.random()).substr(2, 6);

    this.paused = true;
    this.ended = false;

    // Old-style node Stream.pipe() checks for writable, and gulp checks for
    // readable. Discussion at https://github.com/caolan/highland/pull/438.
    this.readable = true;
    this.writable = false;

    this._outgoing = new Queue();
    this._observers = [];
    this._destructors = [];
    this._send_events = false;

    this._nil_pushed = false; // Sets to true when a nil has been queued.
    this._explicitly_destroyed = false; // Sets to true when destroy() is called.

    this._request = null;
    this._multiplexer = null;
    this._consumer = null;

    this._generator = generator;
    this._generator_requested = true;
    this._defer_run_generator = false;
    this._run_generator_deferred = false;

    // Signals whether or not a call to write() returned false, and thus we can
    // drain. This is only relevant for streams constructed with _().
    this._can_drain = false;

    var self = this;

    // These are defined here instead of on the prototype
    // because bind is super slow.
    this._push_fn = function (err, x) {
        if (x === nil) {
            // It's possible that next was called before the
            // nil, causing the generator to be deferred. This
            // is allowed since push can be called at any time.
            // We have to cancel the deferred call to preserve the
            // generator contract.
            self._run_generator_deferred = false;
        }

        // This will set _nil_pushed if necessary.
        self._writeOutgoing(err ? new StreamError(err) : x);
    };

    this._next_fn = function (xs) {
        if (self._explicitly_destroyed) {
            return;
        }

        // It's possible to get into a situation where a call to next() is
        // scheduled asynchonously, but before it is run, destroy() is called,
        // usually by a downstream consumer like take(1). The call to next()
        // still completes, and there is nothing the original caller can do can
        // do. We do not want to throw in that situation.
        if (self._nil_pushed) {
            throw new Error('Cannot call next after nil');
        }

        self._generator_requested = true;
        if (xs) {
            xs = self.create(xs);
            var pull = newPullFunction(xs);
            self._generator = newDelegateGenerator(pull);
        }

        if (!self.paused) {
            if (self._defer_run_generator) {
                self._run_generator_deferred = true;
            }
            else {
                _.setImmediate(function () {
                    self._runGenerator();
                });
            }
        }
    };

    this.on('newListener', function (ev) {
        if (ev === 'data') {
            self._send_events = true;
            _.setImmediate(bindContext(self.resume, self));
        }
        else if (ev === 'end') {
            // this property avoids us checking the length of the
            // listners subscribed to each event on each _send() call
            self._send_events = true;
        }
    });

    // TODO: write test to cover this removeListener code
    this.on('removeListener', function (ev) {
        if (ev === 'end' || ev === 'data') {
            var end_listeners = self.listeners('end').length;
            var data_listeners = self.listeners('data').length;
            if (end_listeners + data_listeners === 0) {
                // stop emitting events
                self._send_events = false;
            }
        }
    });
}
inherits(Stream, EventEmitter);

function _addMethod(proto, topLevel) {
    return function(name, f) {
        proto[name] = f;
        var n = f.length;
        function relevel(coerce) {
            return _.ncurry(n + 1, function () {
                var args = slice.call(arguments);
                var s = coerce(args.pop());
                return f.apply(s, args);
            });
        }
        topLevel[name] = relevel(topLevel);
        topLevel[name]._relevel = relevel;
    };
}

var addMethod = _addMethod(Stream.prototype, _);

function _addMethods(proto, topLevel, methods) {
    for (var p in methods) {
        if (hasOwn.call(methods, p)) {
            _addMethod(proto, topLevel)(p, methods[p]);
        }
    }
}

function _addToplevelMethod(topLevel) {
    return function (name, fn) {
        function relevel(_topLevel) {
            var bound = bindContext(fn, _topLevel);
            bound._relevel = relevel;
            return bound;
        }
        topLevel[name] = relevel(topLevel);
    };
}

var addToplevelMethod = _addToplevelMethod(_);

function _addToplevelMethods(topLevel, methods) {
    for (var p in methods) {
        if (hasOwn.call(methods, p)) {
            _addToplevelMethod(topLevel)(p, methods[p]);
        }
    }
}

function use(Super, originalTopLevel) {
    return function(methods, toplevelMethods) {
        function Sub() {
            Stream.apply(this, arguments);
        }
        inherits(Sub, Super);

        function topLevel() {
            return __(Sub).apply(null, arguments);
        }
        for (var p in originalTopLevel) {
            if (hasOwn.call(originalTopLevel, p)) {
                var fn = originalTopLevel[p];
                topLevel[p] = (typeof fn._relevel === 'function') ? fn._relevel(topLevel) : fn;
            }
        }
        _addMethods(Sub.prototype, topLevel, methods || {});
        _addToplevelMethods(topLevel, toplevelMethods || {});
        topLevel.use = use(Sub, topLevel);

        return topLevel;
    };
}

_.use = use(Stream, _);

/**
 * Creates a stream that sends a single value then ends.
 *
 * @id of
 * @section Utils
 * @name _.of(x)
 * @param x - the value to send
 * @returns Stream
 * @api public
 *
 * _.of(1).toArray(_.log); // => [1]
 */

addToplevelMethod('of', function (x) {
    return this([x]);
});
Stream['fantasy-land/of'] = Stream.of;
_['fantasy-land/of'] = _.of;

/**
 * Creates an empty stream.
 *
 * @id empty
 * @section Utils
 * @name _.empty()
 * @returns Stream
 * @api public
 *
 * _.empty().toArray(_.log); // => []
 */

addToplevelMethod('empty', function () {
    return this([]);
});
Stream['fantasy-land/empty'] = Stream.empty;
_['fantasy-land/empty'] = _.empty;
Stream['fantasy-land/zero'] = Stream.empty;
_['fantasy-land/zero'] = _.empty;

/**
 * Creates a stream that sends a single error then ends.
 *
 * @id fromError
 * @section Utils
 * @name _.fromError(err)
 * @param error - the error to send
 * @returns Stream
 * @api public
 *
 * _.fromError(new Error('Single Error')).toCallback(function (err, result) {
 *     // err contains Error('Single Error') object
 * }
 */

addToplevelMethod('fromError', function (error) {
    return _(function (push) {
        push(error);
        push(null, _.nil);
    });
});

Stream.prototype.create = function () {
    return __(this.constructor).apply(null, arguments);
};

Stream.prototype.createChild = function createChild(/*varargs*/) {
    var child = this.create.apply(this, arguments);
    child.onDestroy(bindContext(this.destroy, this));
    return child;
};

/**
 * Used as an Error marker when writing to a Stream's incoming buffer
 */

function StreamError(err) {
    this.__HighlandStreamError__ = true;
    this.error = err;
}

/**
 * Returns true if `x` is the end of stream marker.
 *
 * @id isNil
 * @section Utils
 * @name _.isNil(x)
 * @param x - the object to test
 * @api public
 */

_.isNil = function (x) {
    return x === _.nil;
};

/**
 * Returns true if `x` is a Highland Stream.
 *
 * @id isStream
 * @section Utils
 * @name _.isStream(x)
 * @param x - the object to test
 * @returns {Boolean}
 * @api public
 *
 * _.isStream('foo')  // => false
 * _.isStream(_([1,2,3]))  // => true
 */

_.isStream = function (x) {
    return _.isObject(x) && !!x.__HighlandStream__;
};

_._isStreamError = function (x) {
    return _.isObject(x) && !!x.__HighlandStreamError__;
};

/**
 * Sends errors / data to consumers, observers and event handlers
 */

Stream.prototype._send = function (token) {
    // console.log(this.id, '_send', token, this._send_events);

    var err = null,
        x;

    if (_._isStreamError(token)) {
        err = token.error;
        this.readable = false;
    }
    else {
        x = token;
    }

    if (x === nil) {
        // Per https://nodejs.org/docs/v0.8.28/api/stream.html#stream_stream_readable
        // streams stop being readable when they end or are destroyed
        this.readable = false;
    }

    if (this._request) {
        // Allow pull to be called within the callback function.
        var cb = this._request;
        this._request = null;

        // If we have a request, then it was from a pull() and we need to
        // pause.
        this.pause();
        cb(err, x);
    }

    // this._observers may be changed from under us,
    // so we keep a copy.
    var observers = this._observers;
    for (var j = 0, len2 = observers.length; j < len2; j++) {
        observers[j].write(token);
    }

    if (this._send_events) {
        if (err) {
            this.emit('error', err);
        }
        else if (x === nil) {
            this.emit('end');
        }
        else {
            this.emit('data', x);
        }
    }

    if (x === nil) {
        this._onEnd();
    }
};

Stream.prototype._onEnd = function _onEnd() {
    if (this.ended) {
        return;
    }

    this.pause();

    this.ended = true;

    // Don't use _removeObserver for efficiency reasons.
    var i, len, observer;
    for (i = 0, len = this._observers.length; i < len; i++) {
        observer = this._observers[i];
        if (observer.source === this) {
            observer.source = null;
        }
    }

    for (i = 0, len = this._destructors.length; i < len; i++) {
        this._destructors[i].call(this);
    }

    this._outgoing.clear();
    this._observers = [];
    this._destructors = [];

    this._request = null;
    this._multiplexer = null;
    this._consumer = null;

    this._generator = null;
    this._generator_requested = false;
    this._defer_run_generator = false;
    this._run_generator_deferred = false;
};

/**
 * Pauses the stream. All Highland Streams start in the paused state.
 *
 * It is unlikely that you will need to manually call this method.
 *
 * @id pause
 * @section Stream Objects
 * @name Stream.pause()
 * @api public
 *
 * var xs = _(generator);
 * xs.pause();
 */

addMethod('pause', function () {
    //console.log(['pause', this.id]);
    this.paused = true;
});

/*
 * Emit as many buffered token as possible, but not to exceed num.
 * If num is null, then emit as much as possible.
 */

Stream.prototype._emitNext = function (num) {
    var emitted = 0;

    while ((num == null || emitted < num) &&
            this._outgoing.length &&
            !this.paused) {
        this._send(this._outgoing.dequeue());
        emitted++;
    }
};

/**
 * Resumes a paused Stream. This will either read from the Stream's incoming
 * buffer or request more data from an upstream source. Never call this method
 * on a stream that has been consumed (via a call to [consume](#consume) or any
 * other transform).
 *
 * @id resume
 * @section Stream Objects
 * @name Stream.resume()
 * @api public
 *
 * var xs = _(generator);
 * xs.resume();
 */

addMethod('resume', function () {
    // console.log(this.id, 'resume', this.paused);
    if (!this.paused ||
            (this._consumer && this._consumer.paused) ||
            (this._multiplexer && this._multiplexer.paused)) {
        return;
    }

    this.paused = false;

    // Emit all pending tokens in _outgoing.
    if (this._outgoing.length) {
        this._emitNext();

        // The emit may have caused the stream to pause.
        if (this.paused) {
            return;
        }
    }

    if (this._generator) {
        this._runGenerator();
    }
    else if (this._can_drain) {
        // perhaps a node stream is being piped in
        this.emit('drain');
    }
});

/**
 * Ends a Stream. This is the same as sending a [nil](#nil) value as data.
 * You shouldn't need to call this directly, rather it will be called by
 * any [Node Readable Streams](http://nodejs.org/api/stream.html#stream_class_stream_readable)
 * you pipe in.
 *
 * Only call this function on streams that were constructed with no source
 * (i.e., with `_()`).
 *
 * @id end
 * @section Stream Objects
 * @name Stream.end()
 * @aprototype.ppi public
 *
 * mystream.end();
 */

addMethod('end', function () {
    if (this._nil_pushed) {
        // Allow ending multiple times.
        return;
    }

    this.write(nil);
});

/**
 * Pipes a Highland Stream to a [Node Writable
 * Stream](http://nodejs.org/api/stream.html#stream_class_stream_writable).
 * This will pull all the data from the source Highland Stream and write it to
 * the destination, automatically managing flow so that the destination is not
 * overwhelmed by a fast source.
 *
 * Users may optionally pass an object that may contain any of these fields:
 *
 * - `end` - Ends the destination when this stream ends. Default: `true`. This
 *   option has no effect if the destination is either `process.stdout` or
 *   `process.stderr`. Those two streams are never ended.
 *
 * Like [Readable#pipe](https://nodejs.org/api/stream.html#stream_readable_pipe_destination_options),
 * this function will throw errors if there is no `error` handler installed on
 * the stream.
 *
 * This function returns the destination so you can chain together `pipe` calls.
 *
 * **NOTE**: While Highland streams created via `_()` and [pipeline](#pipeline)
 * support being piped to, it is almost never appropriate to `pipe` from a
 * Highland stream to another Highland stream. Those two cases are meant for
 * use when piping from *Node* streams. You might be tempted to use `pipe` to
 * construct reusable transforms. Do not do it. See [through](#through) for a
 * better way.
 *
 * @id pipe
 * @section Consumption
 * @name Stream.pipe(dest, options)
 * @param {Writable Stream} dest - the destination to write all data to
 * @param {Object} options - (optional) pipe options.
 * @api public
 *
 * var source = _(generator);
 * var dest = fs.createWriteStream('myfile.txt')
 * source.pipe(dest);
 *
 * // chained call
 * source.pipe(through).pipe(dest);
 *
 * // DO NOT do this! It will not work. The stream returned by oddDoubler does
 * // not support being piped to.
 * function oddDoubler() {
 *     return _()
 *         return x % 2; // odd numbers only
 *     })
 *     .map(function (x) {
 *         return x * 2;
 *     });
 * }
 *
 * _([1, 2, 3, 4]).pipe(oddDoubler()) // => Garbage
 */

addMethod('pipe', function (dest, options) {
    options = options || {};

    // stdout and stderr are special case writables that cannot be closed
    var canClose = dest !== process.stdout && dest !== process.stderr && options.end !== false;

    var end;
    if (canClose) {
        end = dest.end;
    }
    else {
        end = nop;
    }

    return pipeStream(this, dest, dest.write, end, false);
});

/**
 * Destroys a stream by unlinking it from any consumers and sources. This will
 * stop all consumers from receiving events from this stream and removes this
 * stream as a consumer of any source stream.
 *
 * This function calls end() on the stream and unlinks it from any piped-to streams.
 *
 * @id destroy
 * @section Stream Objects
 * @name Stream.destroy()
 * @api public
 */

addMethod('destroy', function () {
    this._explicitly_destroyed = true;

    // Already destroyed.
    if (this.ended) {
        return;
    }

    this.readable = this.writable = false;

    if (!this._nil_pushed) {
        this.end();
    }

    this._onEnd();
});

Stream.prototype._writeOutgoing = function _writeOutgoing(token) {
    if (this._explicitly_destroyed) {
        return;
    }

    if (this._nil_pushed) {
        throw new Error('Cannot write to stream after nil');
    }

    if (token === _.nil) {
        this._nil_pushed = true;
    }

    //console.log('_writeOutgoing', token, this.id);
    if (token === nil || _._isStreamError(token)) {
        // Per https://nodejs.org/docs/v0.8.28/api/stream.html#stream_stream_writable
        // writable should turn false after end is called or an error occurs
        this.writable = false;
    }

    if (this.paused) {
        this._outgoing.enqueue(token);
    }
    else {
        this._send(token);
    }
};

/**
 * Runs the generator function for this Stream. If the generator is already
 * running (it has been called and not called next() yet) then this function
 * will do nothing.
 */

Stream.prototype._runGenerator = function () {
    //console.log(this.id, '_runGenerator');
    // if _generator already running, exit
    if (!this._generator_requested) {
        return;
    }

    if (this._defer_run_generator) {
        this._run_generator_deferred = true;
        return;
    }

    this._defer_run_generator = true;
    do {
        this._run_generator_deferred = false;
        this._generator_requested = false;

        // this._generator(this._push_fn, this._next_fn);

        var gen = this._generator;

        // Special handling for consume generators.
        if (gen.__ConsumeGenerator__) {
            var source = gen.source;
            if (source._outgoing.length) {
                var token = source._outgoing.dequeue();

                // Inline the pull -> resume -> _emitNext call chain.
                source._request = gen.pullCb;
                source.paused = false;
                source._send(token);
            }
            else {
                // Inline pull.
                source._request = gen.pullCb;
                source.resume();
            }
        }
        else {
            gen.call(this, this._push_fn, this._next_fn);
        }
    } while (this._run_generator_deferred);
    this._defer_run_generator = false;
};

/**
 * Removes an observer from this Stream.
 */

Stream.prototype._removeObserver = function (s) {
    this._observers = this._observers.filter(function (o) {
        return o !== s;
    });
    if (s.source === this) {
        s.source = null;
    }
};

/**
 * Consumes values from a Stream (once resumed) and returns a new Stream for
 * you to optionally push values onto using the provided push / next functions.
 *
 * This function forms the basis of many higher-level Stream operations.
 * It will not cause a paused stream to immediately resume, but behaves more
 * like a 'through' stream, handling values as they are read.
 *
 * @id consume
 * @section Transforms
 * @name Stream.consume(f)
 * @param {Function} f - the function to handle errors and values
 * @api public
 *
 * var filter = function (f, source) {
 *     return source.consume(function (err, x, push, next) {
 *         if (err) {
 *             // pass errors along the stream and consume next value
 *             push(err);
 *             next();
 *         }
 *         else if (x === _.nil) {
 *             // pass nil (end event) along the stream
 *             push(null, x);
 *         }
 *         else {
 *             // pass on the value only if the value passes the predicate
 *             if (f(x)) {
 *                 push(null, x);
 *             }
 *             next();
 *         }
 *     });
 * };
 */

addMethod('consume', function (f) {
    var source = this,
        consumer;

    if (this._consumer) {
        throw new Error(
            'Stream already being consumed, you must either fork() or observe()'
        );
    }

    if (this._multiplexer) {
        throw new Error(
            'Stream has been forked. You must either fork() or observe().'
        );
    }

    // This should be a subclass, but prototype resolution is slow, and
    // consume is on the critical path, so we inline it.
    var gen = function () {
        // Important. next may not be called outside of
        // pullCb.
        source.pull(pullCb);
    };

    gen.__ConsumeGenerator__ = true;
    gen.pullCb = pullCb;
    gen.source = source;

    consumer = this._consumer = this.createChild(gen);

    consumer.id = 'consume:' + consumer.id;

    return consumer;

    function pullCb(err, x) {
        // Minor optimization to immediately call the
        // generator if requested.
        if (consumer._defer_run_generator) {
            f(err, x, consumer._push_fn, consumer._next_fn);
        }
        else {
            consumer._defer_run_generator = true;
            f(err, x, consumer._push_fn, consumer._next_fn);
            consumer._defer_run_generator = false;

            if (consumer._run_generator_deferred) {
                consumer._runGenerator();
            }
        }
    }
});

/**
 * Consumes a single item from the Stream. Unlike consume, this function will
 * not provide a new stream for you to push values onto, and it will unsubscribe
 * as soon as it has a single error, value or nil from the source.
 *
 * You probably won't need to use this directly, but it is used internally by
 * some functions in the Highland library.
 *
 * @id pull
 * @section Consumption
 * @name Stream.pull(f)
 * @param {Function} f - the function to handle data
 * @api public
 *
 * xs.pull(function (err, x) {
 *     // do something
 * });
 */

addMethod('pull', function (f) {
    // console.log(this.id, 'pull', this._outgoing.toArray(), this.paused);
    if (f == null) {
        throw new Error('Cannot pull() with a null callback.');
    }

    if (this._request) {
        f(new Error('Cannot service a second pull() request while one is in progress.'));
    }

    // Register the callback and send a message.
    // Don't need to pause. _send will do it for us.
    this._request = f;
    this.resume();
});

/**
 * Writes a value to the Stream. If the Stream is paused it will go into the
 * Stream's incoming buffer, otherwise it will be immediately processed and
 * sent to the Stream's consumers (if any). Returns false if the Stream is
 * paused, true otherwise. This lets Node's pipe method handle back-pressure.
 *
 * You shouldn't need to call this yourself, but it may be called by Node
 * functions which treat Highland Streams as a [Node Writable Stream](http://nodejs.org/api/stream.html#stream_class_stream_writable).
 *
 * Only call this function on streams that were constructed with no source
 * (i.e., with `_()`).

 * @id write
 * @section Stream Objects
 * @name Stream.write(x)
 * @param x - the value to write to the Stream
 * @api public
 *
 * var xs = _();
 * xs.write(1);
 * xs.write(2);
 * xs.end();
 *
 * xs.toArray(function (ys) {
 *     // ys will be [1, 2]
 * });
 *
 * // Do *not* do this.
 * var xs2 = _().toArray(_.log);
 * xs2.write(1); // This call is illegal.
 */

addMethod('write', function (x) {
    // console.log(this.id, 'write', x, this.paused);
    this._writeOutgoing(x);

    if (!this._generator && this.paused) {
        this._can_drain = true;
    }

    return !this.paused;
});

/**
 * Forks a stream, allowing you to add additional consumers with shared
 * back-pressure. A stream forked to multiple consumers will only pull values
 * from its source as fast as the slowest consumer can handle them.
 *
 * **NOTE**: Do not depend on a consistent execution order between the forks.
 * This transform only guarantees that all forks will process a value `foo`
 * before any will process a second value `bar`. It does *not* guarantee the
 * order in which the forks process `foo`.
 *
 * **TIP**: Be careful about modifying stream values within the forks (or using
 * a library that does so). Since the same value will be passed to every fork,
 * changes made in one fork will be visible in any fork that executes after it.
 * Add to that the inconsistent execution order, and you can end up with subtle
 * data corruption bugs. If you need to modify any values, you should make a
 * copy and modify the copy instead.
 *
 * @id fork
 * @section Higher-order Streams
 * @name Stream.fork()
 * @api public
 *
 * var xs = _([1, 2, 3, 4]);
 * var ys = xs.fork();
 * var zs = xs.fork();
 *
 * // no values will be pulled from xs until zs also resume
 * ys.resume();
 *
 * // now both ys and zs will get values from xs
 * zs.resume();
 */

addMethod('fork', function () {
    if (this._requests) {
        throw new Error('Cannot fork a stream with an outstanding pull() request.');
    }

    if (this._consumer) {
        throw new Error('Cannot fork a stream that has already been consumed().');
    }

    if (!this._multiplexer) {
        this._multiplexer = new StreamMultiplexer(this);
    }

    var s = this._multiplexer.newStream();
    s.id = 'fork:' + s.id;
    return s;
});

/**
 * Observes a stream, allowing you to handle values as they are emitted, without
 * adding back-pressure or causing data to be pulled from the source. This can
 * be useful when you are performing two related queries on a stream where one
 * would block the other. Just be aware that a slow observer could fill up its
 * buffer and cause memory issues. Where possible, you should use [fork](#fork).
 *
 * @id observe
 * @section Higher-order Streams
 * @name Stream.observe()
 * @api public
 *
 * var xs = _([1, 2, 3, 4]);
 * var ys = xs.fork();
 * var zs = xs.observe();
 *
 * // now both zs and ys will receive data as fast as ys can handle it
 * ys.resume();
 */

addMethod('observe', function () {
    var s = this.create();
    s.id = 'observe:' + s.id;
    s.writable = false;

    var self = this;
    s.onDestroy(function () {
        self._removeObserver(s);
    });

    // s.source = this;
    this._observers.push(s);
    return s;
});

/**
 * Extracts errors from a Stream and applies them to an error handler
 * function. Returns a new Stream with the errors removed (unless the error
 * handler chooses to rethrow them using `push`). Errors can also be
 * transformed and put back onto the Stream as values.
 *
 * @id errors
 * @section Transforms
 * @name Stream.errors(f)
 * @param {Function} f - the function to pass all errors to
 * @api public
 *
 * getDocument.errors(function (err, push) {
 *     if (err.statusCode === 404) {
 *         // not found, return empty doc
 *         push(null, {});
 *     }
 *     else {
 *         // otherwise, re-throw the error
 *         push(err);
 *     }
 * });
 */

addMethod('errors', function (f) {
    return this.consume(function (err, x, push, next) {
        if (err) {
            f(err, push);
            next();
        }
        else if (x === nil) {
            push(null, nil);
        }
        else {
            push(null, x);
            next();
        }
    });
});

/**
 * Like the [errors](#errors) method, but emits a Stream end marker after
 * an Error is encountered.
 *
 * @id stopOnError
 * @section Transforms
 * @name Stream.stopOnError(f)
 * @param {Function} f - the function to handle an error
 * @api public
 *
 * brokenStream.stopOnError(function (err, push) {
 *     // console.error('Something broke: ' + err);
 *
 *     // Rethrow if needed
 *     // push(err);
 * });
 */

addMethod('stopOnError', function (f) {
    return this.consume(function (err, x, push, next) {
        if (err) {
            f(err, push);
            push(null, nil);
        }
        else if (x === nil) {
            push(null, nil);
        }
        else {
            push(null, x);
            next();
        }
    });
});

/**
 * Iterates over every value from the Stream, calling the iterator function
 * on each of them. This method consumes the Stream.
 *
 * If an error from the Stream reaches this call, it will emit an `error` event
 * (i.e., it will call `emit('error')` on the stream being consumed).  This
 * event will cause an error to be thrown if unhandled.
 *
 * While `each` consumes the stream, it is possible to chain [done](#done) (and
 * *only* `done`) after it.
 *
 * @id each
 * @section Consumption
 * @name Stream.each(f)
 * @param {Function} f - the iterator function
 * @api public
 *
 * _([1, 2, 3, 4]).each(function (x) {
 *     // will be called 4 times with x being 1, 2, 3 and 4
 * });
 */

addMethod('each', function (f) {
    var self = this;
    var s = this.consume(function (err, x, push, next) {
        if (err) {
            self.emit('error', err);
        }
        else if (x === nil) {
            push(null, nil);
        }
        else {
            f(x);
            next();
        }
    });
    s.resume();
    return s;
});

/**
 * Applies all values from a Stream as arguments to a function. This method consumes the stream.
 * `f` will always be called when the `nil` token is encountered, even when the stream is empty.
 *
 * @id apply
 * @section Consumption
 * @name Stream.apply(f)
 * @param {Function} f - the function to apply arguments to
 * @api public
 *
 * _([1, 2, 3]).apply(function (a, b, c) {
 *     // a === 1
 *     // b === 2
 *     // c === 3
 * });
 *
 * _([1, 2, 3]).apply(function (a) {
 *     // arguments.length === 3
 *     // a === 1
 * });
 */

addMethod('apply', function (f) {
    return this.toArray(function (args) {
        f.apply(null, args);
    });
});

/**
 * Collects all values from a Stream into an Array and calls a function with
 * the result. This method consumes the stream.
 *
 * If an error from the Stream reaches this call, it will emit an `error` event
 * (i.e., it will call `emit('error')` on the stream being consumed).  This
 * event will cause an error to be thrown if unhandled.
 *
 * @id toArray
 * @section Consumption
 * @name Stream.toArray(f)
 * @param {Function} f - the callback to provide the completed Array to
 * @api public
 *
 * _([1, 2, 3, 4]).toArray(function (x) {
 *     // parameter x will be [1,2,3,4]
 * });
 */

addMethod('toArray', function (f) {
    var self = this;
    return this.collect().pull(function (err, x) {
        if (err) {
            self.emit('error', err);
        }
        else {
            f(x);
        }
    });
});

/**
 * Calls a function once the Stream has ended. This method consumes the stream.
 * If the Stream has already ended, the function is called immediately.
 *
 * If an error from the Stream reaches this call, it will emit an `error` event
 * (i.e., it will call `emit('error')` on the stream being consumed).  This
 * event will cause an error to be thrown if unhandled.
 *
 * As a special case, it is possible to chain `done` after a call to
 * [each](#each) even though both methods consume the stream.
 *
 * @id done
 * @section Consumption
 * @name Stream.done(f)
 * @param {Function} f - the callback
 * @api public
 *
 * var total = 0;
 * _([1, 2, 3, 4]).each(function (x) {
 *     total += x;
 * }).done(function () {
 *     // total will be 10
 * });
 */

addMethod('done', function (f) {
    if (this.ended) {
        f();
        return null;
    }
    var self = this;
    return this.consume(function (err, x, push, next) {
        if (err) {
            self.emit('error', err);
        }
        else if (x === nil) {
            f();
        }
        else {
            next();
        }
    }).resume();
});

/**
 * Registers a callback that will be called when the stream is destroyed. The
 * callback will have its `this` variable bound to the stream being destroyed.
 *
 * This method can be used to free any resources that were allocated when
 * creating the stream.
 *
 * @id onDestroy
 * @section Consumption
 * @name Stream.onDestroy(f)
 * @param {Function} f - the callback
 * @api public
 *
 * var _([1]).onDestroy(function () {
 *     console.log('freed');
 * }).each(console.log);
 * // => 1
 * // => freed
 */

Stream.prototype.onDestroy = function onDestroy(f) {
    this._destructors.push(f);
    return this;
};

/**
 *
 * @id toCallbackHandler
 * @param {string} transformName Description to compose user-friendly error messages
 * @param {function} cb Node.js style callback
 * @return {function} Function passed to .consume
 * @private
 */
function toCallbackHandler(transformName, cb) {
    var value;
    var hasValue = false; // In case an emitted value === null or === undefined.
    return function (err, x, push, next) {
        if (err) {
            push(null, nil);
            if (hasValue) {
                cb(new Error(transformName + ' called on stream emitting multiple values'));
            }
            else {
                cb(err);
            }
        }
        else if (x === nil) {
            if (hasValue) {
                cb(null, value);
            }
            else {
                cb();
            }
        }
        else {
            if (hasValue) {
                push(null, nil);
                cb(new Error(transformName + ' called on stream emitting multiple values'));
            }
            else {
                value = x;
                hasValue = true;
                next();
            }
        }
    };
}


/**
 * Returns the result of a stream to a nodejs-style callback function.
 *
 * If the stream contains a single value, it will call `cb`
 * with the single item emitted by the stream (if present).
 * If the stream is empty, `cb` will be called without any arguments.
 * If an error is encountered in the stream, this function will stop
 * consumption and call `cb` with the error.
 * If the stream contains more than one item, it will stop consumption
 * and call `cb` with an error.
 *
 * @id toCallback
 * @section Consumption
 * @name Stream.toCallback(cb)
 * @param {Function} cb - the callback to provide the error/result to
 * @api public
 *
 * _([1, 2, 3, 4]).collect().toCallback(function (err, result) {
 *     // parameter result will be [1,2,3,4]
 *     // parameter err will be null
 * });
 */

addMethod('toCallback', function (cb) {
    this.consume(toCallbackHandler('toCallback', cb)).resume();
});


/**
 * Converts the result of a stream to Promise.
 *
 * If the stream contains a single value, it will return
 * with the single item emitted by the stream (if present).
 * If the stream is empty, `undefined` will be returned.
 * If an error is encountered in the stream, this function will stop
 * consumption and call `cb` with the error.
 * If the stream contains more than one item, it will stop consumption
 * and reject with an error.
 *
 * @id toPromise
 * @section Consumption
 * @name Stream.toPromise(PromiseCtor)
 * @param {Function} PromiseCtor - Promises/A+ compliant constructor
 * @api public
 *
 * _([1, 2, 3, 4]).collect().toPromise(Promise).then(function (result) {
 *     // parameter result will be [1,2,3,4]
 * });
 */

addMethod('toPromise', function (PromiseCtor) {
    var self = this;
    return new PromiseCtor(function(resolve, reject) {
        self.consume(toCallbackHandler('toPromise', function(err, res) {
            if (err) {
                reject(err);
            }
            else {
                resolve(res);
            }
        })).resume();
    });
});


/**
 * Consumes values using the Observable subscribe signature. Unlike other
 * consumption methods, subscribe can be called multiple times. Each
 * subscription will receive the current value before receiving the next value.
 * Subscribing to an already consumed stream will result in an error.
 *
 * Implements the Observable subscribe functionality as defined by the spec:
 * https://tc39.github.io/proposal-observable/#observable-prototype-subscribe
 *
 * @id subscribe
 * @section Consumption
 * @name Stream.subscribe(onNext, onError, onComplete)
 * @param {Function|object|null} onNext - Handler for next value or observer
 * @param {Function|null} onError - Handler function for errors.
 * @param {Function|null} onCompleted - Handler Function when stream is done.
 * @returns {ObservableSubscription} - Subscription with unsubscribed method
 * @api public
 *
 * // with callbacks
 * _([1, 2, 3, 4]).subscribe(
 *     function onNext (x) {
 *         // Called for each value that comes downstream
 *         console.log('Received onNext value', x);
 *     },
 *     function onError (err) {
 *         // Called one time with error or zero if no errors occur upstream
 *         console.error('Single highland stream error', err);
 *     },
 *     function onComplete () {
 *         // Receives no arguments
 *         // Called only once when stream is completed.
 *         console.log('Completed!');
 *     }
 * );
 *
 * // with an observer
 * _([1, 2, 3, 4]).subscribe({
 *     next (x) {
 *         console.log('Received next value', x);
 *     },
 *     error (err) {
 *         console.error('An error occurred upstream', err);
 *     },
 *     complete () {
 *         console.log('Completed!')
 *     }
 * });
 */

addMethod('subscribe', function (onNext, onError, onComplete) {
    var observer = createObserver(onNext, onError, onComplete);

    return new ObservableSubscription(this, observer);
});

/*
 * Create a variable we can use as a dynamic method name depending on the
 * environment.
 *
 * If Symbols are available get the observable symbol. Otherwise use the a
 * fallback string.
 * https://tc39.github.io/proposal-observable/#observable-prototype-@@observable
 *
 * Source taken from RxJS
 * https://github.com/ReactiveX/rxjs/commit/4a5aaafc99825ae9b61e410bc0b5e86c7ae75837#diff-d26bc4881b94c82f3c0ae7d3914e9577R13
 */
/* eslint-disable no-undef */
var observable = typeof Symbol === 'function' && Symbol.observable || '@@observable';
/* eslint-enable no-undef */

/**
 * Returns an Observable spec-compliant instance (itself) that has a subscribe
 * method and a Symbol.observable method. If Symbol is not available in the
 * current environment it defaults to '@@observable'. Used by other tools and
 * libraries that want to get an observable spec compliant stream interface.
 *
 * https://tc39.github.io/proposal-observable/#observable-prototype-@@observable
 *
 * @id Symbol.observable
 * @section Consumption
 * @name Symbol.observable
 * @api public
 *
 * _([1, 2, 3])[Symbol.observable || "@@observable"]().subscribe(x => {
 *     console.log("Received value", x);
 * });
 */

addMethod(observable, function () {
    return this;
});

/**
 * Converts the stream to a node Readable Stream for use in methods
 * or pipes that depend on the native stream type.
 *
 * The options parameter can be an object passed into the [`Readable`
 * constructor](http://nodejs.org/api/stream.html#stream_class_stream_readable).
 *
 * @id toNodeStream
 * @section Consumption
 * @name Stream.toNodeStream(options)
 * @param {Object} options - (optional) [`Readable` constructor](http://nodejs.org/api/stream.html#stream_class_stream_readable) options
 * @api public
 *
 * _(fs.createReadStream('./abc')).toNodeStream()
 * _(fs.createReadStream('./abc')).toNodeStream({objectMode: false})
 * _([{a: 1}]).toNodeStream({objectMode: true})
 */

addMethod('toNodeStream', function (options) {
    return new ReadableProxy(this, options, _.nil);
});


/**
 * Creates a new Stream of transformed values by applying a function to each
 * value from the source.
 *
 * @id map
 * @section Transforms
 * @name Stream.map(f)
 * @param {Function} f - the transformation function
 * @api public
 *
 * var doubled = _([1, 2, 3, 4]).map(function (x) {
 *     return x * 2;
 * }); // => 2, 4, 6, 8
 */

addMethod('map', function (f) {
    if (!_.isFunction(f)) {
        throw new Error('map expects a function as its only argument.');
    }
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(err, x);
        }
        else {
            var fnVal, fnErr;
            try {
                fnVal = f(x);
            }
            catch (e) {
                fnErr = e;
            }
            push(fnErr, fnVal);
            next();
        }
    });
});
Stream.prototype['fantasy-land/map'] = Stream.prototype.map;

/**
 * Creates a new Stream which applies a function to each value from the source
 * and re-emits the source value. Useful when you want to mutate the value or
 * perform side effects
 *
 * @id doto
 * @section Transforms
 * @name Stream.doto(f)
 * @param {Function} f - the function to apply
 * @api public
 *
 * var appended = _([[1], [2], [3], [4]]).doto(function (x) {
 *     x.push(1);
 * });
 *
 * _([1, 2, 3]).doto(console.log)
 * // 1
 * // 2
 * // 3
 * // => 1, 2, 3
 */

addMethod('doto', function (f) {
    return this.map(function (x) {
        f(x);
        return x;
    });
});

/**
 * An alias for the [doto](#doto) method.
 *
 * @id tap
 * @section Transforms
 * @name Stream.tap(f)
 * @param {Function} f - the function to apply
 * @api public
 *
 * _([1, 2, 3]).tap(console.log)
 */

Stream.prototype.tap = Stream.prototype.doto;
_.tap = _.doto;

/**
 * Limits number of values through the stream to a maximum of number of values
 * per window. Errors are not limited but allowed to pass through as soon as
 * they are read from the source.
 *
 * @id ratelimit
 * @section Transforms
 * @name Stream.ratelimit(num, ms)
 * @param {Number} num - the number of operations to perform per window
 * @param {Number} ms - the window of time to limit the operations in (in ms)
 * @api public
 *
 * _([1, 2, 3, 4, 5]).ratelimit(2, 100);
 *
 * // after 0ms => 1, 2
 * // after 100ms => 1, 2, 3, 4
 * // after 200ms => 1, 2, 3, 4, 5
 */

addMethod('ratelimit', function (num, ms) {
    if (num < 1) {
        throw new Error('Invalid number of operations per ms: ' + num);
    }
    var sent = 0;
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(null, nil);
        }
        else {
            if (sent < num) {
                sent++;
                push(null, x);
                next();
            }
            else {
                setTimeout(function () {
                    sent = 1;
                    push(null, x);
                    next();
                }, ms);
            }
        }
    });
});

/**
 * Creates a new Stream of values by applying each item in a Stream to an
 * iterator function which must return a (possibly empty) Stream. Each item on
 * these result Streams are then emitted on a single output Stream.
 *
 * This transform is functionally equivalent to `.map(f).sequence()`.
 *
 * @id flatMap
 * @section Higher-order Streams
 * @name Stream.flatMap(f)
 * @param {Function} f - the iterator function
 * @api public
 *
 * var readFile = _.wrapCallback(fs.readFile);
 * filenames.flatMap(readFile)
 */

addMethod('flatMap', function (f) {
    return this.map(f).sequence();
});
Stream.prototype['fantasy-land/chain'] = Stream.prototype.flatMap;

/**
 * Creates a new Stream of values by applying each item in a Stream to each
 * value in a Stream of functions
 *
 * @id ap
 * @section Higher-order Streams
 * @name Stream.ap(m)
 * @param {Stream} m - incoming stream of function(s) to apply to value(s) in stream
 * @api public
 *
 * var asyncUnit = () => _([]);
 * var asyncAutocomplete = e => _(fetch(`/autocomplete?s=${e.target.value}`));
 *
 * var fns = _('change', checkbox)
 *   .flatMap(e => _.of(e.target.checked ? asyncAutocomplete : asyncUnit));
 *
 * _('change', input)
 *   .ap(fns)
 *   .sequence()
 *   .map(showAutocompleteResults);
 */

addMethod('ap', function(m) {
    return _([
        this.map(function (u1) {
            return {
                u: u1,
            };
        }),
        m.map(function (m1) {
            return {
                m: m1,
            };
        }),
    ])
        .merge()
        .scan1(function (x, y) {
            return _.extend(y, x);
        })
        .filter(function (x) {
            return x.u && x.m;
        })
        .map(function (x) {
            return x.m(x.u);
        });
});
Stream.prototype['fantasy-land/ap'] = Stream.prototype.ap;

/**
 * Retrieves values associated with a given property from all elements in
 * the collection.
 *
 * @id pluck
 * @section Transforms
 * @name Stream.pluck(property)
 * @param {String} prop - the property to which values should be associated
 * @api public
 *
 * var docs = [
 *     {type: 'blogpost', title: 'foo'},
 *     {type: 'blogpost', title: 'bar'},
 *     {type: 'comment', title: 'baz'}
 * ];
 *
 * _(docs).pluck('title').toArray(function (xs) {
 *    // xs is now ['foo', 'bar', 'baz']
 * });
 */

addMethod('pluck', function (prop) {
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(err, x);
        }
        else if (_.isObject(x)) {
            push(null, x[prop]);
            next();
        }
        else {
            push(new Error(
                'Expected Object, got ' + (typeof x)
            ));
            next();
        }
    });
});

/**
 * Only applies the transformation strategy on Objects.
 * This helper is used in `pick` and `pickBy`
 **/

var objectOnly = _.curry(function(strategy, x) {
    if (_.isObject(x)) {
        return strategy(x);
    }
    else {
        throw new Error(
            'Expected Object, got ' + (typeof x)
        );
    }
});


/**
 *
 * Retrieves copies of all the elements in the collection
 * that satisfy a given predicate. Note: When using ES3,
 * only enumerable elements are selected. Both enumerable
 * and non-enumerable elements are selected when using ES5.
 *
 * @id pickBy
 * @section Transforms
 * @name Stream.pickBy(f)
 * @param {Function} f - the predicate function
 * @api public
 *
 *  var dogs = [
 *      {breed: 'chihuahua', name: 'Princess', age: 5},
 *      {breed: 'labrador', name: 'Rocky', age: 3},
 *      {breed: 'german-shepherd', name: 'Waffles', age: 9}
 *  ];

 *  _(dogs).pickBy(function (value, key) {
 *      return value > 4;
 *  }).toArray(function (xs) {
 *    // xs is now:
 *    [
 *      { age: 5 },
 *      {},
 *      { age: 9 }
 *    ]
 *  });
 */

addMethod('pickBy', function (f) {
    return this.map(objectOnly(function (x) {
        var out = {};

        // prevents testing overridden properties multiple times.
        var seen = isES5 ? Object.create(null) : {};
        var obj = x;  // variable used to traverse prototype chain
        function testAndAdd (prop) {
            if (seen[prop] !== true && f(x[prop], prop)) {
                out[prop] = x[prop];
                seen[prop] = true;
            }
        }
        if (isES5) {
            do {
                Object.getOwnPropertyNames(obj).forEach(testAndAdd);
                obj = Object.getPrototypeOf(obj);
            } while (obj);
        }
        else {
            for (var k in x) {
                testAndAdd(k);
            }
        }
        return out;
    }));
});

/**
 *
 * Retrieves copies of all elements in the collection,
 * with only the whitelisted keys. If one of the whitelisted
 * keys does not exist, it will be ignored.
 *
 * @id pick
 * @section Transforms
 * @name Stream.pick(properties)
 * @param {Array} properties - property names to white filter
 * @api public
 *
 * var dogs = [
 *      {breed: 'chihuahua', name: 'Princess', age: 5},
 *      {breed: 'labrador', name: 'Rocky', age: 3},
 *      {breed: 'german-shepherd', name: 'Waffles', age: 9}
 * ];
 *
 * _(dogs).pick(['breed', 'age']).toArray(function (xs) {
 *       // xs is now:
 *       [
 *           {breed: 'chihuahua', age: 5},
 *           {breed: 'labrador', age: 3},
 *           {breed: 'german-shepherd', age: 9}
 *       ]
 * });
 *
 * _(dogs).pick(['owner']).toArray(function (xs) {
 *      // xs is now:
 *      [
 *          {},
 *          {},
 *          {}
 *      ]
 * });*/

addMethod('pick', function (properties) {
    return this.map(objectOnly(function(x) {
        var out = {};
        for (var i = 0, length = properties.length; i < length; i++) {
            var p = properties[i];
            if (p in x) {
                out[p] = x[p];
            }
        }
        return out;
    }));
});

/**
 * Creates a new Stream that includes only the values that pass a truth test.
 *
 * @id filter
 * @section Transforms
 * @name Stream.filter(f)
 * @param {Function} f - the truth test function
 * @api public
 *
 * var evens = _([1, 2, 3, 4]).filter(function (x) {
 *     return x % 2 === 0;
 * });
 */

addMethod('filter', function (f) {
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(err, x);
        }
        else {
            var fnVal, fnErr;
            try {
                fnVal = f(x);
            }
            catch (e) {
                fnErr = e;
            }

            if (fnErr) {
                push(fnErr);
            }
            else if (fnVal) {
                push(null, x);
            }
            next();
        }
    });
});
Stream.prototype['fantasy-land/filter'] = Stream.prototype.filter;

/**
 * Filters using a predicate which returns a Stream. If you need to check
 * against an asynchronous data source when filtering a Stream, this can
 * be convenient. The Stream returned from the filter function should have
 * a Boolean as its first value (all other values on the Stream will be
 * disregarded).
 *
 * @id flatFilter
 * @section Higher-order Streams
 * @name Stream.flatFilter(f)
 * @param {Function} f - the truth test function which returns a Stream
 * @api public
 *
 * var checkExists = _.wrapCallback(fs.access);
 *
 * filenames.flatFilter(checkExists)
 */

addMethod('flatFilter', function (f) {
    return this.flatMap(function (x) {
        return f(x).take(1).otherwise(errorStream())
        .flatMap(function (bool) {
            return _(bool ? [x] : []);
        });
    });

    function errorStream() {
        return _(function (push) {
            push(new Error('Stream returned by function was empty.'));
            push(null, _.nil);
        });
    }
});

/**
 * The inverse of [filter](#filter).
 *
 * @id reject
 * @section Transforms
 * @name Stream.reject(f)
 * @param {Function} f - the truth test function
 * @api public
 *
 * var odds = _([1, 2, 3, 4]).reject(function (x) {
 *     return x % 2 === 0;
 * });
 */

addMethod('reject', function (f) {
    return this.filter(_.compose(_.not, f));
});

/**
 * A convenient form of [filter](#filter), which returns the first object from a
 * Stream that passes the provided truth test.
 *
 * @id find
 * @section Transforms
 * @name Stream.find(f)
 * @param {Function} f - the truth test function which returns a Stream
 * @api public
 *
 * var docs = [
 *     {type: 'blogpost', title: 'foo'},
 *     {type: 'blogpost', title: 'bar'},
 *     {type: 'comment', title: 'foo'}
 * ];
 *
 * var f = function (x) {
 *     return x.type == 'blogpost';
 * };
 *
 * _(docs).find(f);
 * // => {type: 'blogpost', title: 'foo'}
 *
 * // example with partial application
 * var firstBlogpost = _.find(f);
 *
 * firstBlogpost(docs)
 * // => {type: 'blogpost', title: 'foo'}
 */

addMethod('find', function (f) {
    return this.filter(f).take(1);
});

/**
 * A convenient form of [where](#where), which returns the first object from a
 * Stream that matches a set of property values. findWhere is to [where](#where) as [find](#find) is to [filter](#filter).
 *
 * @id findWhere
 * @section Transforms
 * @name Stream.findWhere(props)
 * @param {Object} props - the properties to match against
 * @api public
 *
 * var docs = [
 *     {type: 'blogpost', title: 'foo'},
 *     {type: 'blogpost', title: 'bar'},
 *     {type: 'comment', title: 'foo'}
 * ];
 *
 * _(docs).findWhere({type: 'blogpost'})
 * // => {type: 'blogpost', title: 'foo'}
 *
 * // example with partial application
 * var firstBlogpost = _.findWhere({type: 'blogpost'});
 *
 * firstBlogpost(docs)
 * // => {type: 'blogpost', title: 'foo'}
 */

addMethod('findWhere', function (props) {
    return this.where(props).take(1);
});


/**
 * A convenient form of [reduce](#reduce), which groups items based on a function or property name
 *
 * @id group
 * @section Transforms
 * @name Stream.group(f)
 * @param {Function | String} f - the function or property name on which to group,
 *                              toString() is called on the result of a function.
 * @api public
 *
 * var docs = [
 *     {type: 'blogpost', title: 'foo'},
 *     {type: 'blogpost', title: 'bar'},
 *     {type: 'comment', title: 'foo'}
 * ];
 *
 * var f = function (x) {
 *     return x.type;
 * };
 *
 * _(docs).group(f); OR _(docs).group('type');
 * // => {
 * // =>    'blogpost': [{type: 'blogpost', title: 'foo'}, {type: 'blogpost', title: 'bar'}]
 * // =>    'comment': [{type: 'comment', title: 'foo'}]
 * // =>  }
 *
 */

addMethod('group', function (f) {
    var lambda = _.isString(f) ? _.get(f) : f;
    return this.reduce(function (m, o) {
        var key = lambda(o);
        if (!hasOwn.call(m, key)) { m[key] = []; }
        m[key].push(o);
        return m;
    }, {});
});

/**
 * Filters a Stream to drop all non-truthy values.
 *
 * @id compact
 * @section Transforms
 * @name Stream.compact()
 * @api public
 *
 * var compacted = _([0, 1, false, 3, null, undefined, 6]).compact();
 * // => 1, 3, 6
 */

addMethod('compact', function () {
    return this.filter(function (x) {
        return x;
    });
});

/**
 * A convenient form of [filter](#filter), which returns all objects from a Stream
 * which match a set of property values.
 *
 * @id where
 * @section Transforms
 * @name Stream.where(props)
 * @param {Object} props - the properties to match against
 * @api public
 *
 * var docs = [
 *     {type: 'blogpost', title: 'foo'},
 *     {type: 'blogpost', title: 'bar'},
 *     {type: 'comment', title: 'foo'}
 * ];
 *
 * _(docs).where({title: 'foo'})
 * // => {type: 'blogpost', title: 'foo'}
 * // => {type: 'comment', title: 'foo'}
 *
 * // example with partial application
 * var getBlogposts = _.where({type: 'blogpost'});
 *
 * getBlogposts(docs)
 * // => {type: 'blogpost', title: 'foo'}
 * // => {type: 'blogpost', title: 'bar'}
 */

addMethod('where', function (props) {
    return this.filter(function (x) {
        for (var k in props) {
            if (x[k] !== props[k]) {
                return false;
            }
        }
        return true;
    });
});

/**
 * Filters out all duplicate values from the stream and keeps only the first
 * occurence of each value, using the provided function to define equality.
 *
 * Note:
 *
 * - Memory: In order to guarantee that each unique item is chosen only once,
 *   we need to keep an internal buffer of all unique values. This may outgrow
 *   the available memory if you are not cautious about the size of your stream
 *   and the number of unique objects you may receive on it.
 * - Errors: The comparison function should never throw an error. However, if
 *   it does, this transform will emit an error for each all that throws. This
 *   means that one value may turn into multiple errors.
 *
 * @id uniqBy
 * @section Transforms
 * @name Stream.uniqBy(compare)
 * @param {Function} compare - custom equality predicate
 * @api public
 *
 * var colors = [ 'blue', 'red', 'red', 'yellow', 'blue', 'red' ]
 *
 * _(colors).uniqBy(function(a, b) { return a[1] === b[1]; })
 * // => 'blue'
 * // => 'red'
 *
 */

addMethod('uniqBy', function (compare) {
    var uniques = [];
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(err, x);
        }
        else {
            var seen = false;
            var hasErr;
            for (var i = 0, len = uniques.length; i < len; i++) {
                try {
                    seen = compare(x, uniques[i]);
                }
                catch (e) {
                    hasErr = e;
                    seen = true;
                }
                if (seen) {
                    break;
                }
            }
            if (!seen) {
                uniques.push(x);
                push(null, x);
            }
            if (hasErr) {
                push(hasErr);
            }
            next();
        }
    });
});

/**
 * Filters out all duplicate values from the stream and keeps only the first
 * occurence of each value, using `===` to define equality.
 *
 * Like [uniqBy](#uniqBy), this transform needs to store a buffer containing
 * all unique values that has been encountered. Be careful about using this
 * transform on a stream that has many unique values.
 *
 * @id uniq
 * @section Transforms
 * @name Stream.uniq()
 * @api public
 *
 * var colors = [ 'blue', 'red', 'red', 'yellow', 'blue', 'red' ]
 *
 * _(colors).uniq()
 * // => 'blue'
 * // => 'red'
 * // => 'yellow'
 */

addMethod('uniq', function () {
    if (!_.isUndefined(_global.Set)) {
        var uniques = new _global.Set(),
            size = uniques.size;

        return this.consume(function (err, x, push, next) {
            if (err) {
                push(err);
                next();
            }
            else if (x === nil) {
                push(err, x);
            }
            // pass NaN through as Set does not respect strict
            // equality in this case.
            else if (x !== x) {
                push(null, x);
                next();
            }
            else {
                uniques.add(x);
                if (uniques.size > size) {
                    size = uniques.size;
                    push(null, x);
                }
                next();
            }
        });
    }
    return this.uniqBy(function (a, b) {
        return a === b;
    });
});

/**
 * Takes a *finite* stream of streams and returns a stream where the first
 * element from each separate stream is combined into a single data event,
 * followed by the second elements of each stream and so on until the shortest
 * input stream is exhausted.
 *
 * @id zipAll
 * @section Higher-order Streams
 * @name Stream.zipAll()
 * @api public
 *
 * _([
 *     _([1, 2, 3]),
 *     _([4, 5, 6]),
 *     _([7, 8, 9]),
 *     _([10, 11, 12])
 * ]).zipAll()
 * // => [1, 4, 7, 10], [2, 5, 8, 11], [3, 6, 9, 12]
 *
 * // shortest stream determines length of output stream
 * _([
 *     _([1, 2, 3, 4]),
 *     _([5, 6, 7, 8]),
 *     _([9, 10, 11, 12]),
 *     _([13, 14])
 * ]).zipAll()
 * // => [1, 5, 9, 13], [2, 6, 10, 14]
 */

addMethod('zipAll', function () {
    var returned = 0;
    var z = [];
    var finished = false;

    function nextValue(index, max, src, push, next) {
        src.pull(function (err, x) {
            if (err) {
                push(err);
                nextValue(index, max, src, push, next);
            }
            else if (x === _.nil) {
                if (!finished) {
                    finished = true;
                    push(null, nil);
                }
            }
            else {
                returned++;
                z[index] = x;
                if (returned === max) {
                    push(null, z);
                    next();
                }
            }
        });
    }

    var self = this;
    return self.collect().flatMap(function (array) {
        if (!array.length) {
            return self.create([]);
        }
        return self.create(function (push, next) {
            returned = 0;
            z = [];
            for (var i = 0, length = array.length; i < length; i++) {
                nextValue(i, length, array[i], push, next);
            }
        });
    });

});

/**
 * Takes a stream and a *finite* stream of `N` streams
 * and returns a stream of the corresponding `(N+1)`-tuples.
 *
 * @id zipEach
 * @section Higher-order Streams
 * @name Stream.zipEach(ys)
 * @param {Array | Stream} ys - the array of streams to combine values with
 * @api public
 *
 * _([1,2,3]).zipEach([[4, 5, 6], [7, 8, 9], [10, 11, 12]])
 * // => [1, 4, 7, 10], [2, 5, 8, 11], [3, 6, 9, 12]
 *
 * // shortest stream determines length of output stream
 * _([1, 2, 3, 4]).zipEach([[5, 6, 7, 8], [9, 10, 11, 12], [13, 14]])
 * // => [1, 5, 9, 13], [2, 6, 10, 14]
 */

addMethod('zipEach', function (ys) {
    return this.create([this])
        .concat(this.create(ys).map(bindContext(this.create, this)))
        .zipAll();
});

/**
 * Takes two Streams and returns a Stream of corresponding pairs. The size of
 * the resulting stream is the smaller of the two source streams.
 *
 * @id zip
 * @section Higher-order Streams
 * @name Stream.zip(ys)
 * @param {Array | Stream} ys - the other stream to combine values with
 * @api public
 *
 * _(['a', 'b', 'c']).zip([1, 2, 3])  // => ['a', 1], ['b', 2], ['c', 3]
 *
 * _(['a', 'b', 'c']).zip(_([1]))  // => ['a', 1]
 */

addMethod('zip', function (ys) {
    return this.create([this, this.create(ys)]).zipAll();
});

/**
 * Takes one Stream and batches incoming data into arrays of given length
 *
 * @id batch
 * @section Transforms
 * @name Stream.batch(n)
 * @param {Number} n - length of the array to batch
 * @api public
 *
 * _([1, 2, 3, 4, 5]).batch(2)  // => [1, 2], [3, 4], [5]
 */

addMethod('batch', function (n) {
    return this.batchWithTimeOrCount(-1, n);
});

/**
 * Takes one Stream and batches incoming data within a maximum time frame
 * into arrays of a maximum length.
 *
 * @id batchWithTimeOrCount
 * @section Transforms
 * @name Stream.batchWithTimeOrCount(ms, n)
 * @param {Number} ms - the maximum milliseconds to buffer a batch
 * @param {Number} n - the maximum length of the array to batch
 * @api public
 *
 * _(function (push) {
 *     push(1);
 *     push(2);
 *     push(3);
 *     setTimeout(push, 20, 4);
 * }).batchWithTimeOrCount(10, 2)
 *
 * // => [1, 2], [3], [4]
 */

addMethod('batchWithTimeOrCount', function (ms, n) {
    var batched = [],
        timeout;

    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            if (batched.length > 0) {
                push(null, batched);
                clearTimeout(timeout);
            }

            push(null, nil);
        }
        else {
            batched.push(x);

            if (batched.length === n) {
                push(null, batched);
                batched = [];
                clearTimeout(timeout);
            }
            else if (batched.length === 1 && ms >= 0) {
                timeout = setTimeout(function () {
                    push(null, batched);
                    batched = [];
                }, ms);
            }

            next();
        }
    });
});

/**
 * Creates a new Stream with the separator interspersed between the elements of the source.
 *
 * `intersperse` is effectively the inverse of [splitBy](#splitBy).
 *
 * @id intersperse
 * @section Transforms
 * @name Stream.intersperse(sep)
 * @param {String} sep - the value to intersperse between the source elements
 * @api public
 *
 * _(['ba', 'a', 'a']).intersperse('n')  // => 'ba', 'n', 'a', 'n', 'a'
 * _(['mississippi']).splitBy('ss').intersperse('ss')  // => 'mi', 'ss', 'i', 'ss', 'ippi'
 * _(['foo']).intersperse('bar')  // => 'foo'
 */

addMethod('intersperse', function (separator) {
    var started = false;
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(null, nil);
        }
        else {
            if (started) {
                push(null, separator);
            }
            else {
                started = true;
            }
            push(null, x);
            next();
        }
    });
});

/**
 * Splits the source Stream by a separator and emits the pieces in between, much like splitting a string.
 *
 * `splitBy` is effectively the inverse of [intersperse](#intersperse).
 *
 * @id splitBy
 * @section Transforms
 * @name Stream.splitBy(sep)
 * @param {String | RegExp} sep - the separator to split on
 * @api public
 *
 * _(['mis', 'si', 's', 'sippi']).splitBy('ss')  // => 'mi', 'i', 'ippi'
 * _(['ba', 'a', 'a']).intersperse('n').splitBy('n')  // => 'ba', 'a', 'a'
 * _(['foo']).splitBy('bar')  // => 'foo'
 */

addMethod('splitBy', function (sep) {
    var decoder = new Decoder();
    var buffer = false;

    function drain(x, push) {
        buffer = (buffer || '') + decoder.write(x);
        var pieces = buffer.split(sep);
        buffer = pieces.pop();

        pieces.forEach(function (piece) {
            push(null, piece);
        });
    }

    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            if (_.isString(buffer)) {
                drain(decoder.end(), push);
                push(null, buffer);
            }
            push(null, nil);
        }
        else {
            drain(x, push);
            next();
        }
    });
});

/**
 * [splitBy](#splitBy) over newlines.
 *
 * @id split
 * @section Transforms
 * @name Stream.split()
 * @api public
 *
 * _(['a\n', 'b\nc\n', 'd', '\ne']).split()  // => 'a', 'b', 'c', 'd', 'e'
 * _(['a\r\nb\nc']]).split()  // => 'a', 'b', 'c'
 */

addMethod('split', function () {
    return this.splitBy(/\r?\n/);
});

/**
 * Creates a new Stream with the values from the source in the range of `start`
 * (inclusive) to `end` (exclusive).
 *
 * @id slice
 * @section Transforms
 * @name Stream.slice(start, end)
 * @param {Number} start - (optional) integer representing index to start
 *     reading from source (inclusive). Defaults to `0` if not specified.
 * @param {Number} stop - (optional) integer representing index to stop
 *     reading from source (exclusive). Defaults to `Infinity` if not
 *     specified.
 * @throws {TypeError} if either parameters are not numbers.
 * @throws {RangeError} if either parameters are negative.
 * @api public
 *
 * _([1, 2, 3, 4]).slice(1, 3) // => 2, 3
 */

addMethod('slice', function(start, end) {
    if (start == null) {
        start = 0;
    }

    if (end == null) {
        end = Infinity;
    }

    checkIsNumber(start, 'start');
    checkIsNumber(end, 'end');
    checkRange(start >= 0, 'start cannot be negative.');
    checkRange(end >= 0, 'end cannot be negative.');

    var index = 0;

    if (start === 0 && end === Infinity) {
        return this;
    }
    else if (start >= end) {
        return _([]);
    }
    var s = this.consume(function (err, x, push, next) {
        var done = x === nil;
        if (err) {
            push(err);
        }
        else if (!done && index++ >= start) {
            push(null, x);
        }

        if (!done && index < end) {
            next();
        }
        else {
            push(null, nil);
        }
    });
    s.id = 'slice:' + s.id;
    return s;
});

/**
 * Creates a new Stream with the first `n` values from the source.
 *
 * @id take
 * @section Transforms
 * @name Stream.take(n)
 * @param {Number} n - integer representing number of values to read from source
 * @throws {TypeError} if `n` is not a number.
 * @throws {RangeError} if `n` is negative.
 * @api public
 *
 * _([1, 2, 3, 4]).take(2) // => 1, 2
 */

addMethod('take', function (n) {
    var s = this.slice(0, n);
    s.id = 'take:' + s.id;
    return s;
});

/**
 * Creates a new Stream with the first values from the source as long as the function
 * returns true.
 *
 * @id takeWhile
 * @section Transforms
 * @name Stream.takeWhile(f)
 * @param {Function} f - the filter function
 * @throws {TypeError} if `f` is not a function.
 * @api public
 *
 * _([1, 2, 3, 4]).takeWhile(x => x < 3) // => 1, 2
 */

addMethod('takeWhile', function (f) {
    if (!_.isFunction(f)) {
        throw new Error('takeWhile expects a function as its only argument.');
    }
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(err, x);
        }
        else {
            var fnVal, fnErr;
            try {
                fnVal = f(x);
            }
            catch (e) {
                fnErr = e;
            }
            if (fnErr) {
                push(fnErr, null);
                next();
            }
            else if (fnVal) {
                push(null, x);
                next();
            }
            else {
                push(null, nil);
            }
        }
    });
});

/**
 * Acts as the inverse of [`take(n)`](#take) - instead of returning the first
 * `n` values, it ignores the first `n` values and then emits the rest. All
 * errors (even ones emitted before the nth value) will be emitted.
 *
 * @id drop
 * @section Transforms
 * @name Stream.drop(n)
 * @param {Number} n - integer representing number of values to read from source
 * @throws {TypeError} if `n` is not a number.
 * @throws {RangeError} if `n` is negative.
 * @api public
 *
 * _([1, 2, 3, 4]).drop(2) // => 3, 4
 */

addMethod('drop', function (n) {
    return this.slice(n, Infinity);
});

/**
 * Creates a new Stream with only the first value from the source.
 *
 * @id head
 * @section Transforms
 * @name Stream.head()
 * @api public
 *
 * _([1, 2, 3, 4]).head() // => 1
 */

addMethod('head', function () {
    return this.take(1);
});

/**
 * Drops all values from the Stream apart from the last one (if any).
 *
 * @id last
 * @section Transforms
 * @name Stream.last()
 * @api public
 *
 * _([1, 2, 3, 4]).last()  // => 4
 */

addMethod('last', function () {
    var nothing = {};
    var prev = nothing;
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            if (prev !== nothing) {
                push(null, prev);
            }
            push(null, nil);
        }
        else {
            prev = x;
            next();
        }
    });
});

/**
 * Collects all values together then emits each value individually in sorted
 * order. The method for sorting the elements is defined by the comparator
 * function supplied as a parameter.
 *
 * The comparison function takes two arguments `a` and `b` and should return
 *
 * - a negative number if `a` should sort before `b`.
 * - a positive number if `a` should sort after `b`.
 * - zero if `a` and `b` may sort in any order (i.e., they are equal).
 *
 * This function must also define a [partial
 * order](https://en.wikipedia.org/wiki/Partially_ordered_set). If it does not,
 * the resulting ordering is undefined.
 *
 * @id sortBy
 * @section Transforms
 * @name Stream.sortBy(f)
 * @param {Function} f - the comparison function
 * @api public
 *
 * var sorts = _([3, 1, 4, 2]).sortBy(function (a, b) {
 *     return b - a;
 * }).toArray(_.log);
 *
 * //=> [4, 3, 2, 1]
 */

addMethod('sortBy', function (f) {
    return this.collect().invoke('sort', [f]).sequence();
});

/**
 * Collects all values together then emits each value individually but in sorted order.
 * The method for sorting the elements is ascending lexical.
 *
 * @id sort
 * @section Transforms
 * @name Stream.sort()
 * @api public
 *
 * var sorted = _(['b', 'z', 'g', 'r']).sort().toArray(_.log);
 * // => ['b', 'g', 'r', 'z']
 */

addMethod('sort', function () {
    return this.sortBy();
});


/**
 * Transforms a stream using an arbitrary target transform.
 *
 * If `target` is a function, this transform passes the current Stream to it,
 * returning the result.
 *
 * If `target` is a [Duplex
 * Stream](https://nodejs.org/api/stream.html#stream_class_stream_duplex_1),
 * this transform pipes the current Stream through it. It will always return a
 * Highland Stream (instead of the piped to target directly as in
 * [pipe](#pipe)). Any errors emitted will be propagated as Highland errors.
 *
 * **TIP**: Passing a function to `through` is a good way to implement complex
 * reusable stream transforms. You can even construct the function dynamically
 * based on certain inputs. See examples below.
 *
 * @id through
 * @section Higher-order Streams
 * @name Stream.through(target)
 * @param {Function | Duplex Stream} target - the stream to pipe through or a
 * function to call.
 * @api public
 *
 * // This is a static complex transform.
 * function oddDoubler(s) {
 *     return s.filter(function (x) {
 *         return x % 2; // odd numbers only
 *     })
 *     .map(function (x) {
 *         return x * 2;
 *     });
 * }
 *
 * // This is a dynamically-created complex transform.
 * function multiplyEvens(factor) {
 *     return function (s) {
 *         return s.filter(function (x) {
 *             return x % 2 === 0;
 *         })
 *         .map(function (x) {
 *             return x * factor;
 *         });
 *     };
 * }
 *
 * _([1, 2, 3, 4]).through(oddDoubler); // => 2, 6
 *
 * _([1, 2, 3, 4]).through(multiplyEvens(5)); // => 10, 20
 *
 * // Can also be used with Node Through Streams
 * _(filenames).through(jsonParser).map(function (obj) {
 *     // ...
 * });
 *
 * // All errors will be propagated as Highland errors
 * _(['zz{"a": 1}']).through(jsonParser).errors(function (err) {
 *   console.log(err); // => SyntaxError: Unexpected token z
 * });
 */

addMethod('through', function (target) {
    var output;

    if (_.isFunction(target)) {
        return target(this);
    }
    else {
        output = this.createChild();
        this.on('error', writeErr);
        target.on('error', writeErr);

        // Intentionally bypass this.pipe so that through() and pipe() can
        // evolve independently of each other.
        return pipeStream(this, target, target.write, target.end, false)
            .pipe(output);
    }

    function writeErr(err) {
        output.write(new StreamError(err));
    }
});

/**
 * Creates a 'Through Stream', which passes data through a pipeline
 * of functions or other through Streams. This is particularly useful
 * when combined with partial application of Highland functions to expose a
 * Node-compatible Through Stream.
 *
 * This is not a method on a Stream, and it only exposed at the top-level
 * as `_.pipeline`. It takes an arbitrary number of arguments.
 *
 * @id pipeline
 * @section Higher-order Streams
 * @name _.pipeline(...)
 * @api public
 *
 * var through = _.pipeline(
 *     _.map(parseJSON),
 *     _.filter(isBlogpost),
 *     _.reduce(collectCategories)
 *     _.through(otherPipeline)
 * );
 *
 * readStream.pipe(through).pipe(outStream);
 *
 * // Alternatively, you can use pipeline to manipulate a stream in
 * // the chained method call style:
 *
 * var through2 = _.pipeline(function (s) {
 *     return s.map(parseJSON).filter(isBlogpost); // etc.
 * });
 */

addToplevelMethod('pipeline', function (/*through...*/) {
    if (!arguments.length) {
        return this();
    }
    var start = arguments[0], rest, startHighland;
    if (!_.isStream(start) && !_.isFunction(start.resume)) {
        // not a Highland stream or Node stream, start with empty stream
        start = this();
        startHighland = start;
        rest = slice.call(arguments);
    }
    else {
        // got a stream as first argument, co-erce to Highland stream
        startHighland = this(start);
        rest = slice.call(arguments, 1);
    }

    var end = rest.reduce(function (src, dest) {
        return src.through(dest);
    }, startHighland);

    var wrapper = this(function (push, next) {
        end.pull(function (err, x) {
            push(err, x);
            if (x !== nil) {
                next();
            }
        });
    });

    wrapper.writable = true;

    wrapper.write = function (x) {
        return start.write(x);
    };

    wrapper.end = function () {
        wrapper.writable = false;
        return start.end();
    };

    start.on('drain', function () {
        wrapper.emit('drain');
    });

    return wrapper;
});

/**
 * Reads values from a Stream of Streams or Arrays, emitting them on a single
 * output Stream. This can be thought of as a [flatten](#flatten), just one
 * level deep, often used for resolving asynchronous actions such as a HTTP
 * request or reading a file.
 *
 * @id sequence
 * @section Higher-order Streams
 * @name Stream.sequence()
 * @api public
 *
 * var nums = _([
 *     _([1, 2, 3]),
 *     _([4, 5, 6])
 * ]);
 *
 * nums.sequence()  // => 1, 2, 3, 4, 5, 6
 *
 * // using sequence to read from files in series
 * var readFile = _.wrapCallback(fs.readFile);
 * filenames.map(readFile).sequence()
 */

addMethod('sequence', function () {
    var original = this;
    var curr = this;
    return this.create(function (push, next) {
        curr.pull(function (err, x) {
            if (err) {
                push(err);
                next();
            }
            else if (_.isArray(x)) {
                if (onOriginalStream()) {
                    // just send all values from array directly
                    x.forEach(function (y) {
                        push(null, y);
                    });
                }
                else {
                    push(null, x);
                }
                next();
            }
            else if (_.isStream(x)) {
                if (onOriginalStream()) {
                    // switch to reading new stream
                    curr = x;
                    next();
                }
                else {
                    // sequence only goes 1 level deep
                    push(null, x);
                    next();
                }
            }
            else if (x === nil) {
                if (onOriginalStream()) {
                    push(null, nil);
                }
                else {
                    // resume reading from original
                    curr = original;
                    next();
                }
            }
            else {
                if (onOriginalStream()) {
                    // we shouldn't be getting non-stream (or array)
                    // values from the top-level stream
                    push(new Error(
                        'Expected Stream, got ' + (typeof x)
                    ));
                    next();
                }
                else {
                    push(null, x);
                    next();
                }
            }
        });
    });

    function onOriginalStream() {
        return curr === original;
    }
});

/**
 * An alias for the [sequence](#sequence) method.
 *
 * @id series
 * @section Higher-order Streams
 * @name Stream.series()
 * @api public
 *
 * var readFile = _.wrapCallback(fs.readFile);
 * filenames.map(readFile).series()
 */

Stream.prototype.series = Stream.prototype.sequence;
_.series = _.sequence;

/**
 * Recursively reads values from a Stream which may contain nested Streams
 * or Arrays. As values or errors are encountered, they are emitted on a
 * single output Stream.
 *
 * @id flatten
 * @section Higher-order Streams
 * @name Stream.flatten()
 * @api public
 *
 * _([1, [2, 3], [[4]]]).flatten();  // => 1, 2, 3, 4
 *
 * var nums = _(
 *     _([1, 2, 3]),
 *     _([4, _([5, 6]) ])
 * );
 *
 * nums.flatten();  // => 1, 2, 3, 4, 5, 6
 */

addMethod('flatten', function () {
    var curr = this;
    var stack = [];
    return this.createChild(function (push, next) {
        curr.pull(function (err, x) {
            if (err) {
                push(err);
                next();
                return;
            }
            if (_.isArray(x)) {
                x = _(x);
            }
            if (_.isStream(x)) {
                stack.push(curr);
                curr = x;
                next();
            }
            else if (x === nil) {
                if (stack.length) {
                    curr = stack.pop();
                    next();
                }
                else {
                    push(null, nil);
                }
            }
            else {
                push(null, x);
                next();
            }
        });
    });
});

/**
 * Takes a Stream of Streams and reads from them in parallel, buffering
 * the results until they can be returned to the consumer in their original
 * order.
 *
 * @id parallel
 * @section Higher-order Streams
 * @name Stream.parallel(n)
 * @param {Number} n - the maximum number of concurrent reads/buffers
 * @api public
 *
 * var readFile = _.wrapCallback(fs.readFile);
 * var filenames = _(['foo.txt', 'bar.txt', 'baz.txt']);
 *
 * // read from up to 10 files at once
 * filenames.map(readFile).parallel(10);
 */

addMethod('parallel', function (n) {
    var source = this;
    var running = [];
    var ended = false;
    var reading_source = false;

    if (typeof n !== 'number') {
        throw new Error('Must specify a number to parallel().');
    }

    if (n <= 0) {
        throw new Error('The parallelism factor must be positive');
    }

    return this.create(function (push, next) {
        if (running.length < n && !ended && !reading_source) {
            // get another stream if not already waiting for one
            reading_source = true;
            source.pull(function (err, x) {
                reading_source = false;
                if (err) {
                    push(err);
                }
                else if (x === nil) {
                    ended = true;
                }
                else if (!_.isStream(x)) {
                    push(new Error('Expected Stream, got ' + (typeof x)));
                }
                else {
                    // got a new source, add it to the running array
                    var run = {stream: x, buffer: []};
                    running.push(run);
                    x.consume(function (_err, y, _push, _next) {
                        if (running[0] === run) {
                            // current output stream
                            if (y === nil) {
                                // remove self from running and check
                                // to see if we need to read from source again
                                running.shift();
                                flushBuffer();
                                next();

                            }
                            else {
                                // push directly onto parallel output stream
                                push(_err, y);
                            }
                        }
                        else {
                            // we're reading ahead, buffer the output
                            run.buffer.push([_err, y]);
                        }
                        if (y !== nil) {
                            // keep reading until we hit nil
                            _next();
                        }
                    }).resume();
                }
                // check if we need to get any more streams
                return next();
            });
        }
        else if (!running.length && ended) {
            // nothing more to do
            push(null, nil);
        }

        function flushBuffer() {
            while (running.length && running[0].buffer.length) {
                var buf = running[0].buffer;
                for (var i = 0; i < buf.length; i++) {
                    if (buf[i][1] === nil) {
                        // this stream has ended
                        running.shift();
                        break;
                    }
                    else {
                        // send the buffered output
                        push.apply(null, buf[i]);
                    }
                }
                buf.length = 0;
            }
        }
        // else wait for more data to arrive from running streams
    });
});

/**
 * Switches source to an alternate Stream if the current Stream is empty.
 *
 * @id otherwise
 * @section Higher-order Streams
 * @name Stream.otherwise(ys)
 * @param {Stream | Function} ys - alternate stream (or stream-returning function) to use if this stream is empty
 * @api public
 *
 * _([1,2,3]).otherwise(['foo'])  // => 1, 2, 3
 * _([]).otherwise(['foo'])       // => 'foo'
 *
 * _.otherwise(_(['foo']), _([1,2,3]))    // => 1, 2, 3
 * _.otherwise(_(['foo']), _([]))         // => 'foo'
 */

addMethod('otherwise', function (ys) {
    var xs = this;
    return xs.consume(function (err, x, push, next) {
        if (err) {
            // got an error, just keep going
            push(err);
            next();
        }
        else if (x === nil) {
            // hit the end without redirecting to xs, use alternative
            if (_.isFunction(ys)) {
                next(ys());
            }
            else {
                next(ys);
            }
        }
        else {
            // got a value, push it, then redirect to xs
            push(null, x);
            next(xs);
        }
    });
});
Stream.prototype['fantasy-land/alt'] = Stream.prototype.otherwise;

/**
 * Adds a value to the end of a Stream.
 *
 * @id append
 * @section Transforms
 * @name Stream.append(y)
 * @param y - the value to append to the Stream
 * @api public
 *
 * _([1, 2, 3]).append(4)  // => 1, 2, 3, 4
 */

addMethod('append', function (y) {
    return this.consume(function (err, x, push, next) {
        if (x === nil) {
            push(null, y);
            push(null, _.nil);
        }
        else {
            push(err, x);
            next();
        }
    });
});

/**
 * Boils down a Stream to a single value. The memo is the initial state
 * of the reduction, and each successive step of it should be returned by
 * the iterator function. The iterator is passed two arguments:
 * the memo and the next value.
 *
 * If the iterator throws an error, the reduction stops and the resulting
 * stream will emit that error instead of a value.
 *
 * @id reduce
 * @section Transforms
 * @name Stream.reduce(iterator, memo)
 * @param memo - the initial state of the reduction
 * @param {Function} iterator - the function which reduces the values
 * @api public
 *
 * var add = function (a, b) {
 *     return a + b;
 * };
 *
 * _([1, 2, 3, 4]).reduce(add, 0)  // => 10
 */

addMethod('reduce', function (f, z) {
    // This can't be implemented with scan(), because we don't know if the
    // errors that we see from the scan were thrown by the iterator or just
    // passed through from the source stream.
    return this.consume(function (err, x, push, next) {
        if (x === nil) {
            push(null, z);
            push(null, _.nil);
        }
        else if (err) {
            push(err);
            next();
        }
        else {
            try {
                z = f(z, x);
            }
            catch (e) {
                push(e);
                push(null, _.nil);
                return;
            }

            next();
        }
    });
});

/**
 * Same as [reduce](#reduce), but uses the first element as the initial
 * state instead of passing in a `memo` value.
 *
 * @id reduce1
 * @section Transforms
 * @name Stream.reduce1(iterator)
 * @param {Function} iterator - the function which reduces the values
 * @api public
 *
 * _([1, 2, 3, 4]).reduce1(add)  // => 10
 */

addMethod('reduce1', function (f) {
    var self = this;
    return self.createChild(function (push, next) {
        self.pull(function (err, x) {
            if (err) {
                push(err);
                next();
            }
            else if (x === nil) {
                push(null, nil);
            }
            else {
                next(self.reduce(f, x));
            }
        });
    });
});

/**
 * Groups all values into an Array and passes down the stream as a single
 * data event. This is a bit like doing [toArray](#toArray), but instead
 * of accepting a callback and consuming the stream, it passes the value on.
 *
 * @id collect
 * @section Transforms
 * @name Stream.collect()
 * @api public
 *
 * _(['foo', 'bar']).collect().toArray(function (xs) {
 *     // xs will be [['foo', 'bar']]
 * });
 */

addMethod('collect', function () {
    var xs = [];
    return this.consume(function (err, x, push, next) {
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(null, xs);
            push(null, nil);
        }
        else {
            xs.push(x);
            next();
        }
    });
});

/**
 * Like [reduce](#reduce), but emits each intermediate value of the
 * reduction as it is calculated.
 *
 * If the iterator throws an error, the scan will stop and the stream will
 * emit that error. Any intermediate values that were produced before the
 * error will still be emitted.
 *
 * @id scan
 * @section Transforms
 * @name Stream.scan(iterator, memo)
 * @param memo - the initial state of the reduction
 * @param {Function} iterator - the function which reduces the values
 * @api public
 *
 * _([1, 2, 3, 4]).scan(add, 0)  // => 0, 1, 3, 6, 10
 */

addMethod('scan', function (f, z) {
    var self = this;
    return this.create([z]).concat(
        self.consume(function (err, x, push, next) {
            if (x === nil) {
                push(null, _.nil);
            }
            else if (err) {
                push(err);
                next();
            }
            else {
                try {
                    z = f(z, x);
                }
                catch (e) {
                    push(e);
                    push(null, _.nil);
                    return;
                }

                push(null, z);
                next();
            }
        })
    );
});

/**
 * Same as [scan](#scan), but uses the first element as the initial
 * state instead of passing in a `memo` value.
 *
 * @id scan1
 * @section Transforms
 * @name Stream.scan1(iterator)
 * @param {Function} iterator - the function which reduces the values
 * @api public
 *
 * _([1, 2, 3, 4]).scan1(add)  // => 1, 3, 6, 10
 */

addMethod('scan1', function (f) {
    var self = this;
    return self.createChild(function (push, next) {
        self.pull(function (err, x) {
            if (err) {
                push(err);
                next();
            }
            else if (x === nil) {
                push(null, nil);
            }
            else {
                next(self.scan(f, x));
            }
        });
    });
});

function HighlandTransform(push) {
    this.push = push;
}

HighlandTransform.prototype['@@transducer/init'] = function () {
    return this.push;
};

HighlandTransform.prototype['@@transducer/result'] = function (push) {
    // Don't push nil here. Otherwise, we can't catch errors from `result`
    // and propagate them. The `transduce` implementation will do it.
    return push;
};

HighlandTransform.prototype['@@transducer/step'] = function (push, input) {
    push(null, input);
    return push;
};

/**
 * Applies the transformation defined by the the given *transducer* to the
 * stream. A transducer is any function that follows the
 * [Transducer Protocol](https://github.com/cognitect-labs/transducers-js#transformer-protocol).
 * See
 * [transduce-js](https://github.com/cognitect-labs/transducers-js#transducers-js)
 * for more details on what transducers actually are.
 *
 * The `result` object that is passed in through the
 * [Transformer Protocol](https://github.com/cognitect-labs/transducers-js#transformer-protocol)
 * will be the `push` function provided by the [consume](#consume) transform.
 *
 * Like [scan](#scan), if the transducer throws an exception, the transform
 * will stop and emit that error. Any intermediate values that were produced
 * before the error will still be emitted.
 *
 * @id transduce
 * @section Transforms
 * @name Stream.transduce(xf)
 * @param {Function} xf - The transducer.
 * @api public
 *
 * var xf = require('transducer-js').map(_.add(1));
 * _([1, 2, 3, 4]).transduce(xf);
 * // => 2, 3, 4, 5
 */

addMethod('transduce', function transduce(xf) {
    var transform = null,
        memo = null;

    return this.consume(function (err, x, push, next) {
        if (transform == null) {
            transform = xf(new HighlandTransform(push));
            memo = transform['@@transducer/init']();
        }

        if (err) {
            // Pass through errors, like we always do.
            push(err);
            next();
        }
        else if (x === _.nil) {
            // Push may be different from memo depending on the transducer that
            // we get.
            runResult(push, memo);
        }
        else {
            var res = runStep(push, memo, x);

            if (!res) {
                return;
            }

            memo = res;
            if (memo['@@transducer/reduced']) {
                runResult(memo['@@transducer/value']);
            }
            else {
                next();
            }
        }
    });

    function runResult(push, _memo) {
        try {
            transform['@@transducer/result'](_memo);
        }
        catch (e) {
            push(e);
        }
        push(null, _.nil);
    }

    function runStep(push, _memo, x) {
        try {
            return transform['@@transducer/step'](_memo, x);
        }
        catch (e) {
            push(e);
            push(null, _.nil);
            return null;
        }
    }
});

/**
 * Concatenates a Stream to the end of this Stream.
 *
 * Be aware that in the top-level export, the args may be in the reverse
 * order to what you'd expect `_([a], [b]) => b, a`, as this follows the
 * convention of other top-level exported functions which do `x` to `y`.
 *
 * @id concat
 * @section Higher-order Streams
 * @name Stream.concat(ys)
 * @param {Stream | Array} ys - the values to concatenate onto this Stream
 * @api public
 *
 * _([1, 2]).concat([3, 4])  // => 1, 2, 3, 4
 * _.concat([3, 4], [1, 2])  // => 1, 2, 3, 4
 */

addMethod('concat', function (ys) {
    ys = _(ys);
    return this.consume(function (err, x, push, next) {
        if (x === nil) {
            next(ys);
        }
        else {
            push(err, x);
            next();
        }
    });
});
Stream.prototype['fantasy-land/concat'] = Stream.prototype.concat;

/**
 * Takes a Stream of Streams and merges their values and errors into a
 * single new Stream. The merged stream ends when all source streams have
 * ended.
 *
 * Note that no guarantee is made with respect to the order in which
 * values for each stream end up in the merged stream. Values in the
 * merged stream will, however, respect the order they were emitted from
 * their respective streams.
 *
 * @id merge
 * @section Higher-order Streams
 * @name Stream.merge()
 * @api public
 *
 * var readFile = _.wrapCallback(fs.readFile);
 *
 * var txt = _(['foo.txt', 'bar.txt']).map(readFile)
 * var md = _(['baz.md']).map(readFile)
 *
 * _([txt, md]).merge();
 * // => contents of foo.txt, bar.txt and baz.txt in the order they were read
 */

addMethod('merge', function () {
    var self = this;
    var srcs = [];

    var srcsNeedPull = [],
        first = true,
        async = false;

    return this.create(function (push, next) {
        if (first) {
            first = false;
            getSourcesSync(push, next);
        }

        if (srcs.length === 0) {
            push(null, nil);
        }
        else if (srcsNeedPull.length) {
            pullFromAllSources(push, next);
            next();
        }
        else {
            async = true;
        }
    });

    // Make a handler for the main merge loop.
    function srcPullHandler(push, next, src) {
        return function (err, x) {
            if (err) {
                push(err);
                srcsNeedPull.push(src);
            }
            else if (x === nil) {
                srcs = srcs.filter(function (s) {
                    return s !== src;
                });
            }
            else {
                if (src === self) {
                    srcs.push(x);
                    srcsNeedPull.push(x);
                    srcsNeedPull.unshift(self);
                }
                else {
                    push(null, x);
                    srcsNeedPull.push(src);
                }
            }

            if (async) {
                async = false;
                next();
            }
        };
    }


    function pullFromAllSources(push, next) {
        var _srcs = srcsNeedPull;
        srcsNeedPull = [];
        _srcs.forEach(function (src) {
            src.pull(srcPullHandler(push, next, src));
        });
    }

    // Pulls as many sources as possible from self synchronously.
    function getSourcesSync(push, next) {
        // Shadows the outer async variable.
        var asynchronous;
        var done = false;

        var pull_cb = function(err, x) {
            asynchronous = false;
            if (done) {
                // This means the pull was async. Handle like
                // regular async.
                srcPullHandler(push, next, self)(err, x);
            }
            else {
                if (err) {
                    push(err);
                }
                else if (x === nil) {
                    done = true;
                }
                else {
                    srcs.push(x);
                    srcsNeedPull.push(x);
                }
            }
        };

        while (!done) {
            asynchronous = true;
            self.pull(pull_cb);

            // Async behavior, record self as a src and return.
            if (asynchronous) {
                done = true;
                srcs.unshift(self);
            }
        }
    }
});

/**
 * Takes a Stream of Streams and merges their values and errors into a
 * single new Stream, limitting the number of unpaused streams that can
 * running at any one time.
 *
 * Note that no guarantee is made with respect to the order in which
 * values for each stream end up in the merged stream. Values in the
 * merged stream will, however, respect the order they were emitted from
 * their respective streams.
 *
 * @id mergeWithLimit
 * @section Higher-order Streams
 * @name Stream.mergeWithLimit(n)
 * @param {Number} n - the maximum number of streams to run in parallel
 * @api public
 *
 * var readFile = _.wrapCallback(fs.readFile);
 *
 * var txt = _(['foo.txt', 'bar.txt']).flatMap(readFile)
 * var md = _(['baz.md']).flatMap(readFile)
 * var js = _(['bosh.js']).flatMap(readFile)
 *
 * _([txt, md, js]).mergeWithLimit(2);
 * // => contents of foo.txt, bar.txt, baz.txt and bosh.js in the order
 * // they were read, but bosh.js is not read until either foo.txt and bar.txt
 * // has completely been read or baz.md has been read
 */


addMethod('mergeWithLimit', function mergeWithLimit(n){
    var self = this;
    var processCount = 0;
    var waiting = false;
    if (typeof n !== 'number' || n < 1) {
        throw new Error('mergeWithLimit expects a positive number, but got: ' + n);
    }

    if (n === Infinity) {
        return this.merge();
    }
    return this.create(function(push, next){
        self.pull(function(err, x){
            var done = x === nil;
            if (err){
                push(err);
                next();
            }
            else if (x === nil) {
                push(null, nil);
            }
            else {
                processCount++;
                push(err, x);
                // console.log('start', x.id);
                x.onDestroy(function() {
                    processCount--;
                    // console.log('end', x.id);
                    if (waiting) {
                        // console.log('get more');
                        waiting = false;
                        next();
                    }
                });
                if (!done && processCount < n) {
                    next();
                }
                else {
                    // console.log('wait till something ends');
                    waiting = true;
                }
            }
        });
    }).merge();
});

/**
 * Calls a named method on each object from the Stream - returning
 * a new stream with the result of those calls.
 *
 * @id invoke
 * @section Transforms
 * @name Stream.invoke(method, args)
 * @param {String} method - the method name to call
 * @param {Array} args - the arguments to call the method with
 * @api public
 *
 * _(['foo', 'bar']).invoke('toUpperCase', [])  // => 'FOO', 'BAR'
 *
 * var readFile = _.wrapCallback(fs.readFile);
 * filenames.flatMap(readFile).invoke('toString', ['utf8']);
 */

addMethod('invoke', function (method, args) {
    return this.map(function (x) {
        return x[method].apply(x, args);
    });
});

/**
 * Takes a Stream of callback-accepting node-style functions,
 * [wraps](#wrapCallback) each one into a stream-returning function,
 * calls them with the arguments provided, and returns the results
 * as a Stream.
 *
 * This can be used as a control flow shortcut and draws parallels
 * with some control flow functions from [async](https://github.com/caolan/async).
 * A few rough correspondences include:
 *
 * - `.nfcall([]).series()` to `async.series()`
 * - `.nfcall([]).parallel(n)` to `async.parallelLimit(n)`
 * - `.nfcall(args)` to `async.applyEach(..., args)`
 * - `.nfcall(args).series()` to `async.applyEachSeries(..., args)`
 *
 * @id nfcall
 * @section Transforms
 * @name Stream.nfcall(args)
 * @param {Array} args - the arguments to call each function with
 * @api public
 *
 * _([
 *   function (callback) {
 *     setTimeout(function () {
 *       callback(null, 'one');
 *     }, 200);
 *   },
 *   function (callback) {
 *     setTimeout(function () {
 *       callback(null, 'two');
 *     }, 100);
 *   }
 * ]).nfcall([]).parallel(2).toArray(function (xs) {
 *   // xs is ['one', 'two'] even though second function had a shorter timeout
 * });
 *
 * _([enableSearch, updateSchema]).nfcall(['bucket']).toArray(callback);
 * // does roughly the same as
 * async.applyEach([enableSearch, updateSchema], 'bucket', callback);
 *
 * _([
 *   fs.appendFile,
 *   fs.appendFile
 * ]).nfcall(['example.txt', 'hello']).series().toArray(function() {
 *   // example.txt now contains 'hellohello'
 * });
 *
 */

addMethod('nfcall', function (args) {
    var wrap = _.wrapCallback._relevel(bindContext(this.create, this));
    return this.map(function (x) {
        return wrap(x).apply(x, args);
    });
});

/**
 * Ensures that only one data event is push downstream (or into the buffer)
 * every `ms` milliseconds, any other values are dropped.
 *
 * @id throttle
 * @section Transforms
 * @name Stream.throttle(ms)
 * @param {Number} ms - the minimum milliseconds between each value
 * @api public
 *
 * _('mousemove', document).throttle(1000);
 */

addMethod('throttle', function (ms) {
    var last = 0 - ms;
    return this.consume(function (err, x, push, next) {
        var now = new Date().getTime();
        if (err) {
            push(err);
            next();
        }
        else if (x === nil) {
            push(null, nil);
        }
        else if (now - ms >= last) {
            last = now;
            push(null, x);
            next();
        }
        else {
            next();
        }
    });
});

/**
 * Holds off pushing data events downstream until there has been no more
 * data for `ms` milliseconds. Sends the last value that occurred before
 * the delay, discarding all other values.
 *
 * **Implementation Note**: This transform will will not wait the full `ms`
 * delay to emit a pending value (if any) once it see a `nil`, as that
 * guarantees that there will be no more values.
 *
 * @id debounce
 * @section Transforms
 * @name Stream.debounce(ms)
 * @param {Number} ms - the milliseconds to wait before sending data
 * @api public
 *
 * function delay(x, ms, push) {
 *     setTimeout(function () {
 *         push(null, x);
 *     }, ms);
 * }
 *
 * // sends last keyup event after user has stopped typing for 1 second
 * $('keyup', textbox).debounce(1000);
 *
 * // A nil triggers the emit immediately
 * _(function (push, next) {
 *     delay(0, 100, push);
 *     delay(1, 200, push);
 *     delay(_.nil, 250, push);
 * }).debounce(75);
 * // => after 175ms => 1
 * // => after 250ms (not 275ms!) => 1 2
 */

addMethod('debounce', function (ms) {
    var t = null;
    var nothing = {};
    var last = nothing;

    return this.consume(function (err, x, push, next) {
        if (err) {
            // let errors through regardless
            push(err);
            next();
        }
        else if (x === nil) {
            if (t) {
                clearTimeout(t);
            }
            if (last !== nothing) {
                push(null, last);
            }
            push(null, nil);
        }
        else {
            last = x;
            if (t) {
                clearTimeout(t);
            }
            t = setTimeout(function () {
                push(null, x);
            }, ms);
            next();
        }
    });
});

/**
 * Creates a new Stream, which when read from, only returns the last
 * seen value from the source. The source stream does not experience
 * back-pressure. Useful if you're using a Stream to model a changing
 * property which you need to query periodically.
 *
 * @id latest
 * @section Transforms
 * @name Stream.latest()
 * @api public
 *
 * // slowThing will always get the last known mouse position
 * // when it asks for more data from the mousePosition stream
 * mousePosition.latest().map(slowThing)
 */

addMethod('latest', function () {
    var nothing = {},
        latest = nothing,
        errors = [],
        ended = false,
        onValue = null;

    this.consume(function (err, x, push, next) {
        if (onValue != null) {
            var cb = onValue;
            onValue = null;
            cb(err, x);
        }

        if (err) {
            errors.push(err);
            next();
        }
        else if (x === nil) {
            ended = true;
        }
        else {
            latest = x;
            next();
        }
    }).resume();

    return this.create(function (push, next) {
        var oldErrors = errors;
        errors = [];

        if (!oldErrors.length && latest === nothing && !ended) {
            // We haven't gotten any data yet. We can't call next
            // because that might cause the stream to call the generator
            // again, resulting in an infinite loop. Thus, we stick a
            // a callback to be called whenever we get a value.
            onValue = function (err, x) {
                push(err, x);
                if (x !== nil) {
                    next();
                }
            };
        }
        else {
            oldErrors.forEach(push);
            if (latest !== nothing) {
                push(null, latest);
            }
            if (ended) {
                push(null, nil);
            }
            else {
                next();
            }
        }
    });
});

function StreamMultiplexer(stream) {
    this._stream = stream;

    this._consumers = new IntMap();
    this._requests = new IntMap();
    this._nonce = 0;
    this._emitting = false;
    this._repeatEmit = false;
    this._cached_value = null;
    this.paused = true;

    var self = this;
    this._pullCb = function _pullCb(err, x) {
        self.paused = true;
        if (self._requests.size === self._consumers.size) {
            self._send(err, x);
        }
        else {
            self._saved_token = [err, x];
        }
    };
}

/**
 * Emit downstream. The caller must guarantee that
 * this._consumers.size === this._requests.size.
 *
 * @param err - an error.
 * @param x - a value.
 */

StreamMultiplexer.prototype._send = function _send(err, x) {
    // Take a snapshot of the current request since calling the callbacks
    // may trigger more request to be registered.
    var requests = this._requests;
    this._requests = new IntMap();

    requests.forEach(function (requestCb) {
        requestCb(err, x);
    });
};

/**
 * Emit if we've met the backpressure requirements.
 */
StreamMultiplexer.prototype._resume = function _resume() {
    if (this._emitting) {
        this._repeatEmit = true;
        return;
    }

    this._emitting = true;
    do {
        // use a repeat flag to avoid recursing pull() calls
        this._repeatEmit = false;

        if (this._requests.size === this._consumers.size) {
            if (this._saved_token) {
                var token = this._saved_token;
                this._saved_token = null;
                this.paused = true;
                this._send(token[0], token[1]);
            }
            else if (this.paused) {
                this.paused = false;
                this._stream.pull(this._pullCb);
            }
        }
    } while (this._repeatEmit);
    this._emitting = false;
};

StreamMultiplexer.prototype.pull = function pull(id, cb) {
    if (!cb) {
        return;
    }

    if (this._requests.has(id)) {
        cb(new Error('Cannot service a second pull() request while one is in progress.'));
        return;
    }

    this._requests.set(id, cb);

    this._resume();
};

StreamMultiplexer.prototype.newStream = function newStream() {
    var self = this,
        id = self._nonce++;

    self._consumers.set(id, true);

    var generator = newDelegateGenerator(function (cb) {
        self.pull(id, cb);
    });

    return new this._stream.constructor(generator)
        .onDestroy(function () {
            self.removeConsumer(id);
        });
};

StreamMultiplexer.prototype.removeConsumer = function removeConsumer(id) {
    if (!this._consumers.has(id)) {
        return;
    }

    this._consumers.delete(id);
    this._requests.delete(id);

    this._resume();
};

/**
 * Returns values from an Object as a Stream. Reads properties
 * lazily, so if you don't read from all keys on an object, not
 * all properties will be read from (may have an effect where getters
 * are used).
 *
 * @id values
 * @section Objects
 * @name _.values(obj)
 * @param {Object} obj - the object to return values from
 * @api public
 *
 * _.values({foo: 1, bar: 2, baz: 3})  // => 1, 2, 3
 */

_.values = function (obj) {
    return _.keys(obj).map(function (k) {
        return obj[k];
    });
};

/**
 * Returns keys from an Object as a Stream.
 *
 * @id keys
 * @section Objects
 * @name _.keys(obj)
 * @param {Object} obj - the object to return keys from
 * @api public
 *
 * _.keys({foo: 1, bar: 2, baz: 3})  // => 'foo', 'bar', 'baz'
 */

function keys (obj) {
    var keysArray = [];
    for (var k in obj) {
        if (hasOwn.call(obj, k)) {
            keysArray.push(k);
        }
    }
    return keysArray;
}

_.keys = function (obj) {
    return _(keys(obj));
};

/**
 * Returns key/value pairs for an Object as a Stream. Reads properties
 * lazily, so if you don't read from all keys on an object, not
 * all properties will be read from (may have an effect where getters
 * are used).
 *
 * @id pairs
 * @section Objects
 * @name _.pairs(obj)
 * @param {Object} obj - the object to return key/value pairs from
 * @api public
 *
 * _.pairs({foo: 1, bar: 2})  // => ['foo', 1], ['bar', 2]
 */

_.pairs = function (obj) {
    return _.keys(obj).map(function (k) {
        return [k, obj[k]];
    });
};

/**
 * Extends one object with the properties of another. **Note:** The
 * arguments are in the reverse order of other libraries such as
 * underscore. This is so it follows the convention of other functions in
 * this library and so you can more meaningfully partially apply it.
 *
 * @id extend
 * @section Objects
 * @name _.extend(a, b)
 * @param {Object} a - the properties to extend b with
 * @param {Object} b - the original object to extend
 * @api public
 *
 * _.extend({name: 'bar'}, {name: 'foo', price: 20})
 * // => {name: 'bar', price: 20}
 *
 * // example of partial application
 * var publish = _.extend({published: true});
 *
 * publish({title: 'test post'})
 * // => {title: 'test post', published: true}
 */

_.extend = _.curry(function (extensions, target) {
    for (var k in extensions) {
        if (hasOwn.call(extensions, k)) {
            target[k] = extensions[k];
        }
    }
    return target;
});

/**
 * Returns a property from an object.
 *
 * @id get
 * @section Objects
 * @name _.get(prop, obj)
 * @param {String} prop - the property to return
 * @param {Object} obj - the object to read properties from
 * @api public
 *
 * var obj = {foo: 'bar', baz: 123};
 * _.get('foo', obj) // => 'bar'
 *
 * // making use of partial application
 * var posts = [
 *   {title: 'one'},
 *   {title: 'two'},
 *   {title: 'three'}
 * ];
 *
 * _(posts).map(_.get('title'))  // => 'one', 'two', 'three'
 */

_.get = _.curry(function (prop, obj) {
    return obj[prop];
});

/**
 * Updates a property on an object, returning the updated object.
 *
 * @id set
 * @section Objects
 * @name _.set(prop, value, obj)
 * @param {String} prop - the property to return
 * @param value - the value to set the property to
 * @param {Object} obj - the object to set properties on
 * @api public
 *
 * var obj = {foo: 'bar', baz: 123};
 * _.set('foo', 'wheeee', obj) // => {foo: 'wheeee', baz: 123}
 *
 * // making use of partial application
 * var publish = _.set('published', true);
 *
 * publish({title: 'example'})  // => {title: 'example', published: true}
 */

_.set = _.curry(function (prop, val, obj) {
    obj[prop] = val;
    return obj;
});

/**
 * Logs values to the console, a simple wrapper around `console.log` that
 * it suitable for passing to other functions by reference without having to
 * call `bind`.
 *
 * @id log
 * @section Utils
 * @name _.log(args..)
 * @api public
 *
 * _.log('Hello, world!');
 *
 * _([1, 2, 3, 4]).each(_.log);
 */

_.log = function () {
    console.log.apply(console, arguments);
};

/**
 * Wraps a node-style async function which accepts a callback, transforming
 * it to a function which accepts the same arguments minus the callback and
 * returns a Highland Stream instead. The wrapped function keeps its context,
 * so you can safely use it as a method without binding (see the second
 * example below).
 *
 * `wrapCallback` also accepts an optional `mappingHint`, which specifies how
 * callback arguments are pushed to the stream. This can be used to handle
 * non-standard callback protocols that pass back more than one value.
 *
 * `mappingHint` can be a function, number, or array. See the documentation on
 * [EventEmitter Stream Objects](#Stream Objects) for details on the mapping
 * hint. If `mappingHint` is a function, it will be called with all but the
 * first argument that is passed to the callback. The first is still assumed to
 * be the error argument.
 *
 * @id wrapCallback
 * @section Utils
 * @name _.wrapCallback(f)
 * @param {Function} f - the node-style function to wrap
 * @param {Array | Function | Number} mappingHint - (optional) how to pass the
 * arguments to the callback
 * @api public
 *
 * var fs = require('fs');
 *
 * var readFile = _.wrapCallback(fs.readFile);
 *
 * readFile('example.txt').apply(function (data) {
 *     // data is now the contents of example.txt
 * });
 *
 * function Reader(file) {
 *     this.file = file;
 * }
 *
 * Reader.prototype.read = function(cb) {
 *     fs.readFile(this.file, cb);
 * };
 *
 * Reader.prototype.readStream = _.wrapCallback(Reader.prototype.read);
 */

/*eslint-disable no-multi-spaces */
addToplevelMethod('wrapCallback', function (f, /*optional*/mappingHint) {
    /*eslint-enable no-multi-spaces */
    var stream = this;
    var mapper = hintMapper(mappingHint);

    return function () {
        var self = this;
        var args = slice.call(arguments);
        return stream(function (push) {
            var cb = function (err) {
                if (err) {
                    push(err);
                }
                else {
                    var cbArgs = slice.call(arguments, 1);
                    var v = mapper.apply(this, cbArgs);
                    push(null, v);
                }
                push(null, nil);
            };
            f.apply(self, args.concat([cb]));
        });
    };
});

/**
 * Wraps a function that returns a promise, transforming it to a function
 * which accepts the same arguments and returns a Highland Stream instead.
 * The wrapped function keeps its context, so you can safely use it as a
 * method without binding.
 *
 * @id wrapAsync
 * @section Utils
 * @name _.wrapAsync(f)
 * @param {Function} f - the function that returns a promise
 * @api public
 *
 * var resolve = _.wrapAsync(Promise.resolve);
 * var reject = _.wrapAsync(Promise.reject);
 *
 * resolve([1, 2, 3]).apply(function (a, b, c) {
 *  // a === 1
 *  // b === 2
 *  // c === 3
 * });
 *
 * reject('boom').errors(function (err) {
 *   // err === 'boom'
 * });
 */

addToplevelMethod('wrapAsync', function (f) {
    var stream = this;
    return function () {
        var promise;
        try {
            promise = f.apply(this, arguments);
            if (!_.isObject(promise) || !_.isFunction(promise.then)) {
                return _.fromError(new Error('Wrapped function did not return a promise'));
            }
            return stream(promise);
        }
        catch (e) {
            return _.fromError(e);
        }
    };
});

/**
 * Takes an object or a constructor function and returns that object or
 * constructor with streamified versions of its function properties.
 * Passed constructors will also have their prototype functions
 * streamified.  This is useful for wrapping many node style async
 * functions at once, and for preserving those functions' context.
 *
 * @id streamifyAll
 * @section Utils
 * @name _.streamifyAll(source)
 * @param {Object | Function} source - the function or object with
 * node-style function properties.
 * @api public
 *
 * var fs = _.streamifyAll(require('fs'));
 *
 * fs.readFileStream('example.txt').apply(function (data) {
 *     // data is now the contents of example.txt
 * });
 */

function isClass (fn) {
    if (!(typeof fn === 'function' && fn.prototype)) { return false; }
    var getKeys = isES5 ? Object.getOwnPropertyNames : keys;
    var allKeys = getKeys(fn.prototype);
    return allKeys.length > 0 && !(allKeys.length === 1 &&
            allKeys[0] === 'constructor');
}

function inheritedKeys (obj) {
    var allProps = {};
    var curr = obj;
    var handleProp = function (prop) {
        allProps[prop] = true;
    };
    while (Object.getPrototypeOf(curr)) {
        var props = Object.getOwnPropertyNames(curr);
        props.forEach(handleProp);
        curr = Object.getPrototypeOf(curr);
    }
    return keys(allProps);
}

function streamifyAll (wrapCallback, inp, suffix) {
    // will not streamify inherited functions in ES3
    var getKeys = isES5 ? inheritedKeys : keys;
    var allKeys = getKeys(inp);

    for (var i = 0, len = allKeys.length; i < len; i++) {
        var key = allKeys[i];
        var val;

        // will skip context aware getters
        try {
            val = inp[key];
        }
        catch (e) {
            // Ignore
        }

        if (val && typeof val === 'function' && !isClass(val) &&
                !val.__HighlandStreamifiedFunction__) {

            var streamified = wrapCallback(val);
            streamified.__HighlandStreamifiedFunction__ = true;
            inp[key + suffix] = streamified;
        }
    }
    return inp;
}

addToplevelMethod('streamifyAll', function (arg) {
    if (typeof arg !== 'function' && typeof arg !== 'object') {
        throw new TypeError('takes an object or a constructor function');
    }
    var suffix = 'Stream';

    var ret = streamifyAll(this.wrapCallback, arg, suffix);
    if (isClass(arg)) {
        ret.prototype = streamifyAll(this.wrapCallback, arg.prototype, suffix);
    }
    return ret;
});

/**
 * Add two values. Can be partially applied.
 *
 * @id add
 * @section Operators
 * @name _.add(a, b)
 * @api public
 *
 * _.add(1, 2) === 3
 * _.add(1)(5) === 6
 */

_.add = _.curry(function (a, b) {
    return a + b;
});

/**
 * Perform logical negation on a value. If `x` is truthy then returns false,
 * otherwise returns true.
 *
 * @id not
 * @section Operators
 * @name _.not(x)
 * @param x - the value to negate
 * @api public
 *
 * _.not(true)   // => false
 * _.not(false)  // => true
 */

_.not = function (x) {
    return !x;
};

}).call(this,require('_process'))
},{"./createObserver":1,"./global":2,"./intMap":4,"./isFunction":5,"./nil":6,"./observableSubscription":7,"./queue":8,"./readableProxy":9,"_process":21,"events":12,"string_decoder":13,"util":41}],4:[function(require,module,exports){
(function (global){
var hasOwn = Object.prototype.hasOwnProperty;

/**
 * A very simple polyfill for Map with limited functionality
 * that only works for integer keys.
 */
function IntMap() {
    this.map = {};
    this.size = 0;
}

IntMap.prototype.set = function set(key, value) {
    if (this.has(key)) {
        this.map[key] = value;
    }
    else {
        this.map[key] = value;
        this.size++;
    }
    return this;
};

IntMap.prototype.get = function get(key) {
    return this.map[key];
};

IntMap.prototype.delete = function intMapDelete(key) {
    var deleted = this.has(key);
    if (deleted) {
        delete this.map[key];
        this.size--;
    }
    return deleted;
};

IntMap.prototype.has = function has(key) {
    return hasOwn.call(this.map, key);
};

IntMap.prototype.forEach = function forEach(f, thisArg) {
    for (var key in this.map) {
        f.call(thisArg, this.map[key], key, this);
    }
};

if (global.Map === void 0) {
    module.exports = IntMap;
}
else {
    module.exports = global.Map;
}

}).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{}],5:[function(require,module,exports){
/**
 * Predicate function takes a value and returns true if it is a function.
 *
 * @id isFunction
 * @name isFunction(x)
 * @param {any} x - Any value to test against
 * @returns {bool} True if x is a function
 */

function isFunction (x) {
    return typeof x === 'function';
}

module.exports = isFunction;

},{}],6:[function(require,module,exports){
var _global = require('./global');

/*
 * Resolve nil value from global namespace if it exists. This may happen when
 * there are multiple versions of highland (like npm).
 *
 * nil is only equal to itself:
 *
 * nil === {}  => false
 * nil === nil => true
 *
 * This property makes it valuable for determining a lack of input from a
 * falsey value such as nil or undefined. When a highland stream encounters
 * nil it knows for sure the intention is to end the stream.
 */

if (!_global.nil) {
    _global.nil = {};
}

module.exports = _global.nil;

},{"./global":2}],7:[function(require,module,exports){
var nil = require('./nil');

/**
 * An implementation of the TC39 Subscription object
 * https://tc39.github.io/proposal-observable/#subscription-objects
 *
 * This class is intended for internal use only.
 *
 * Constructor takes a source highland stream, and an observer object with
 * an optional next, error, and complete methods.
 *
 * Returns a subscription object with a closed boolean and unsubscribe
 * method.
 *
 * @id ObservableSubscription
 * @name ObservableSubscription
 * @param {stream} stream - Highland stream to subscribe to
 * @param {object} observer - Observer to publish from stream subscription
 * @api private
 */
function ObservableSubscription (stream, observer) {
    var self = this;

    // Set attributes
    this._source = stream.fork();
    this.closed = false;

    // Don't let users subscribe to an already completed stream
    if (stream.ended) {
        if (observer.error) {
            observer.error(new Error('Subscribe called on an already completed stream.'));
        }

        this._cleanup();

        return;
    }

    // Consume the stream and emit data to the observer
    this._source = this._source.consume(function (err, x, push, next) {
        if (err) {
            push(null, nil);
            if (observer.error) {
                observer.error(err);
            }
            self._cleanup();
        }
        else if (x === nil) {
            if (observer.complete) {
                observer.complete();
            }
            self._cleanup();
        }
        else {
            if (observer.next) {
                observer.next(x);
            }
            next();
        }
    });

    this._source.resume();
}

// Instance Methods

/**
 * Perform cleanup routine on a subscription. This can only be called once per
 * subscription. Once its closed the subscription cannot be cleaned up again.
 *
 * Note: This relies heavily upon side-effects and mutates itself.
 *
 * @id ObservableSubscription.prototype._cleanup(subscription)
 * @name ObservableSubscription.prototype._cleanup
 * @returns {undefined} Side-effectful function cleans up subscription
 * @api private
 */

ObservableSubscription.prototype._cleanup = function cleanup () {
    // Don't want to destroy\cleanup an already closed stream
    if (this.closed) {
        return;
    }
    this._source = null;
    this.closed = true;
};

/**
 * Destroy the stream resources and cleanup the subscription.
 * @id ObservableSubscription.prototype.unsubscribe()
 * @name ObservableSubscription.prototype.unsubscribe()
 * @returns {undefined} Side-effectful. Destroys stream and cleans up subscription.
 * @api private
 */

ObservableSubscription.prototype.unsubscribe = function unsubscribe () {
    // Don't want to destroy\cleanup an already closed stream
    if (this.closed) {
        return;
    }

    this._source.destroy();
    this._cleanup();
};

module.exports = ObservableSubscription;

},{"./nil":6}],8:[function(require,module,exports){
function Queue() {
    this._in = [];
    this._out = [];
    this.length = 0;
}

/*
 * Enqueue all elements of a list in order. Equivalent to
 *   list.forEach(queue.enqueue.bind(queue));
 */
Queue.prototype.enqueueAll = function enqueueList(list) {
    this._in = this._in.concat(list);
    this.length += list.length;
};

Queue.prototype.enqueue = function enqueue(item) {
    this._in.push(item);
    this.length++;
};

Queue.prototype.dequeue = function dequeue() {
    if (this._out.length) {
        this.length--;
        return this._out.pop();
    }
    else if (this._in.length) {
        this._out = this._in.reverse();
        this._in = [];
        this.length--;
        return this._out.pop();
    }
    else {
        return undefined;
    }
};

Queue.prototype.clear = function clear() {
    this._out = [];
    this._in = [];
    this.length = 0;
};

Queue.prototype.toArray = function toArray() {
    var res = [];
    res = res.concat(this._out);
    res.reverse();
    res = res.concat(this._in);
    return res;
};

Queue.prototype.toString = function toString() {
    return this.toArray().toString();
};

module.exports = Queue;

},{}],9:[function(require,module,exports){
var inherits = require('util').inherits;
var Readable = require('stream').Readable;

function ReadableProxy(stream, options, nil) {
    Readable.call(this, options);

    this._source = stream;
    this._is_reading = false;
    this._nil = nil;
}

inherits(ReadableProxy, Readable);

ReadableProxy.prototype._readOnce = function () {
    if (this._is_reading) {
        return;
    }

    var self = this;

    self._is_reading = true;
    self._source.pull(function (err, x) {
        self._is_reading = false;
        if (err) {
            self.emit('error', err);
            self._readOnce();
        }
        else if (x === self._nil) {
            self.push(null);
        }
        else {
            if (self.push(x)) {
                self._readOnce();
            }
        }
    });
};

ReadableProxy.prototype._read = function (ignore) {
    this._readOnce();
};

module.exports = ReadableProxy;

},{"stream":37,"util":41}],10:[function(require,module,exports){
'use strict'

exports.byteLength = byteLength
exports.toByteArray = toByteArray
exports.fromByteArray = fromByteArray

var lookup = []
var revLookup = []
var Arr = typeof Uint8Array !== 'undefined' ? Uint8Array : Array

var code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
for (var i = 0, len = code.length; i < len; ++i) {
  lookup[i] = code[i]
  revLookup[code.charCodeAt(i)] = i
}

// Support decoding URL-safe base64 strings, as Node.js does.
// See: https://en.wikipedia.org/wiki/Base64#URL_applications
revLookup['-'.charCodeAt(0)] = 62
revLookup['_'.charCodeAt(0)] = 63

function placeHoldersCount (b64) {
  var len = b64.length
  if (len % 4 > 0) {
    throw new Error('Invalid string. Length must be a multiple of 4')
  }

  // the number of equal signs (place holders)
  // if there are two placeholders, than the two characters before it
  // represent one byte
  // if there is only one, then the three characters before it represent 2 bytes
  // this is just a cheap hack to not do indexOf twice
  return b64[len - 2] === '=' ? 2 : b64[len - 1] === '=' ? 1 : 0
}

function byteLength (b64) {
  // base64 is 4/3 + up to two characters of the original data
  return (b64.length * 3 / 4) - placeHoldersCount(b64)
}

function toByteArray (b64) {
  var i, l, tmp, placeHolders, arr
  var len = b64.length
  placeHolders = placeHoldersCount(b64)

  arr = new Arr((len * 3 / 4) - placeHolders)

  // if there are placeholders, only get up to the last complete 4 chars
  l = placeHolders > 0 ? len - 4 : len

  var L = 0

  for (i = 0; i < l; i += 4) {
    tmp = (revLookup[b64.charCodeAt(i)] << 18) | (revLookup[b64.charCodeAt(i + 1)] << 12) | (revLookup[b64.charCodeAt(i + 2)] << 6) | revLookup[b64.charCodeAt(i + 3)]
    arr[L++] = (tmp >> 16) & 0xFF
    arr[L++] = (tmp >> 8) & 0xFF
    arr[L++] = tmp & 0xFF
  }

  if (placeHolders === 2) {
    tmp = (revLookup[b64.charCodeAt(i)] << 2) | (revLookup[b64.charCodeAt(i + 1)] >> 4)
    arr[L++] = tmp & 0xFF
  } else if (placeHolders === 1) {
    tmp = (revLookup[b64.charCodeAt(i)] << 10) | (revLookup[b64.charCodeAt(i + 1)] << 4) | (revLookup[b64.charCodeAt(i + 2)] >> 2)
    arr[L++] = (tmp >> 8) & 0xFF
    arr[L++] = tmp & 0xFF
  }

  return arr
}

function tripletToBase64 (num) {
  return lookup[num >> 18 & 0x3F] + lookup[num >> 12 & 0x3F] + lookup[num >> 6 & 0x3F] + lookup[num & 0x3F]
}

function encodeChunk (uint8, start, end) {
  var tmp
  var output = []
  for (var i = start; i < end; i += 3) {
    tmp = ((uint8[i] << 16) & 0xFF0000) + ((uint8[i + 1] << 8) & 0xFF00) + (uint8[i + 2] & 0xFF)
    output.push(tripletToBase64(tmp))
  }
  return output.join('')
}

function fromByteArray (uint8) {
  var tmp
  var len = uint8.length
  var extraBytes = len % 3 // if we have 1 byte left, pad 2 bytes
  var output = ''
  var parts = []
  var maxChunkLength = 16383 // must be multiple of 3

  // go through the array every three bytes, we'll deal with trailing stuff later
  for (var i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
    parts.push(encodeChunk(uint8, i, (i + maxChunkLength) > len2 ? len2 : (i + maxChunkLength)))
  }

  // pad the end with zeros, but make sure to not forget the extra bytes
  if (extraBytes === 1) {
    tmp = uint8[len - 1]
    output += lookup[tmp >> 2]
    output += lookup[(tmp << 4) & 0x3F]
    output += '=='
  } else if (extraBytes === 2) {
    tmp = (uint8[len - 2] << 8) + (uint8[len - 1])
    output += lookup[tmp >> 10]
    output += lookup[(tmp >> 4) & 0x3F]
    output += lookup[(tmp << 2) & 0x3F]
    output += '='
  }

  parts.push(output)

  return parts.join('')
}

},{}],11:[function(require,module,exports){

},{}],12:[function(require,module,exports){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

var objectCreate = Object.create || objectCreatePolyfill
var objectKeys = Object.keys || objectKeysPolyfill
var bind = Function.prototype.bind || functionBindPolyfill

function EventEmitter() {
  if (!this._events || !Object.prototype.hasOwnProperty.call(this, '_events')) {
    this._events = objectCreate(null);
    this._eventsCount = 0;
  }

  this._maxListeners = this._maxListeners || undefined;
}
module.exports = EventEmitter;

// Backwards-compat with node 0.10.x
EventEmitter.EventEmitter = EventEmitter;

EventEmitter.prototype._events = undefined;
EventEmitter.prototype._maxListeners = undefined;

// By default EventEmitters will print a warning if more than 10 listeners are
// added to it. This is a useful default which helps finding memory leaks.
var defaultMaxListeners = 10;

var hasDefineProperty;
try {
  var o = {};
  if (Object.defineProperty) Object.defineProperty(o, 'x', { value: 0 });
  hasDefineProperty = o.x === 0;
} catch (err) { hasDefineProperty = false }
if (hasDefineProperty) {
  Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
    enumerable: true,
    get: function() {
      return defaultMaxListeners;
    },
    set: function(arg) {
      // check whether the input is a positive number (whose value is zero or
      // greater and not a NaN).
      if (typeof arg !== 'number' || arg < 0 || arg !== arg)
        throw new TypeError('"defaultMaxListeners" must be a positive number');
      defaultMaxListeners = arg;
    }
  });
} else {
  EventEmitter.defaultMaxListeners = defaultMaxListeners;
}

// Obviously not all Emitters should be limited to 10. This function allows
// that to be increased. Set to zero for unlimited.
EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) {
  if (typeof n !== 'number' || n < 0 || isNaN(n))
    throw new TypeError('"n" argument must be a positive number');
  this._maxListeners = n;
  return this;
};

function $getMaxListeners(that) {
  if (that._maxListeners === undefined)
    return EventEmitter.defaultMaxListeners;
  return that._maxListeners;
}

EventEmitter.prototype.getMaxListeners = function getMaxListeners() {
  return $getMaxListeners(this);
};

// These standalone emit* functions are used to optimize calling of event
// handlers for fast cases because emit() itself often has a variable number of
// arguments and can be deoptimized because of that. These functions always have
// the same number of arguments and thus do not get deoptimized, so the code
// inside them can execute faster.
function emitNone(handler, isFn, self) {
  if (isFn)
    handler.call(self);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self);
  }
}
function emitOne(handler, isFn, self, arg1) {
  if (isFn)
    handler.call(self, arg1);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1);
  }
}
function emitTwo(handler, isFn, self, arg1, arg2) {
  if (isFn)
    handler.call(self, arg1, arg2);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1, arg2);
  }
}
function emitThree(handler, isFn, self, arg1, arg2, arg3) {
  if (isFn)
    handler.call(self, arg1, arg2, arg3);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1, arg2, arg3);
  }
}

function emitMany(handler, isFn, self, args) {
  if (isFn)
    handler.apply(self, args);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].apply(self, args);
  }
}

EventEmitter.prototype.emit = function emit(type) {
  var er, handler, len, args, i, events;
  var doError = (type === 'error');

  events = this._events;
  if (events)
    doError = (doError && events.error == null);
  else if (!doError)
    return false;

  // If there is no 'error' event listener then throw.
  if (doError) {
    if (arguments.length > 1)
      er = arguments[1];
    if (er instanceof Error) {
      throw er; // Unhandled 'error' event
    } else {
      // At least give some kind of context to the user
      var err = new Error('Unhandled "error" event. (' + er + ')');
      err.context = er;
      throw err;
    }
    return false;
  }

  handler = events[type];

  if (!handler)
    return false;

  var isFn = typeof handler === 'function';
  len = arguments.length;
  switch (len) {
      // fast cases
    case 1:
      emitNone(handler, isFn, this);
      break;
    case 2:
      emitOne(handler, isFn, this, arguments[1]);
      break;
    case 3:
      emitTwo(handler, isFn, this, arguments[1], arguments[2]);
      break;
    case 4:
      emitThree(handler, isFn, this, arguments[1], arguments[2], arguments[3]);
      break;
      // slower
    default:
      args = new Array(len - 1);
      for (i = 1; i < len; i++)
        args[i - 1] = arguments[i];
      emitMany(handler, isFn, this, args);
  }

  return true;
};

function _addListener(target, type, listener, prepend) {
  var m;
  var events;
  var existing;

  if (typeof listener !== 'function')
    throw new TypeError('"listener" argument must be a function');

  events = target._events;
  if (!events) {
    events = target._events = objectCreate(null);
    target._eventsCount = 0;
  } else {
    // To avoid recursion in the case that type === "newListener"! Before
    // adding it to the listeners, first emit "newListener".
    if (events.newListener) {
      target.emit('newListener', type,
          listener.listener ? listener.listener : listener);

      // Re-assign `events` because a newListener handler could have caused the
      // this._events to be assigned to a new object
      events = target._events;
    }
    existing = events[type];
  }

  if (!existing) {
    // Optimize the case of one listener. Don't need the extra array object.
    existing = events[type] = listener;
    ++target._eventsCount;
  } else {
    if (typeof existing === 'function') {
      // Adding the second element, need to change to array.
      existing = events[type] =
          prepend ? [listener, existing] : [existing, listener];
    } else {
      // If we've already got an array, just append.
      if (prepend) {
        existing.unshift(listener);
      } else {
        existing.push(listener);
      }
    }

    // Check for listener leak
    if (!existing.warned) {
      m = $getMaxListeners(target);
      if (m && m > 0 && existing.length > m) {
        existing.warned = true;
        var w = new Error('Possible EventEmitter memory leak detected. ' +
            existing.length + ' "' + String(type) + '" listeners ' +
            'added. Use emitter.setMaxListeners() to ' +
            'increase limit.');
        w.name = 'MaxListenersExceededWarning';
        w.emitter = target;
        w.type = type;
        w.count = existing.length;
        if (typeof console === 'object' && console.warn) {
          console.warn('%s: %s', w.name, w.message);
        }
      }
    }
  }

  return target;
}

EventEmitter.prototype.addListener = function addListener(type, listener) {
  return _addListener(this, type, listener, false);
};

EventEmitter.prototype.on = EventEmitter.prototype.addListener;

EventEmitter.prototype.prependListener =
    function prependListener(type, listener) {
      return _addListener(this, type, listener, true);
    };

function onceWrapper() {
  if (!this.fired) {
    this.target.removeListener(this.type, this.wrapFn);
    this.fired = true;
    switch (arguments.length) {
      case 0:
        return this.listener.call(this.target);
      case 1:
        return this.listener.call(this.target, arguments[0]);
      case 2:
        return this.listener.call(this.target, arguments[0], arguments[1]);
      case 3:
        return this.listener.call(this.target, arguments[0], arguments[1],
            arguments[2]);
      default:
        var args = new Array(arguments.length);
        for (var i = 0; i < args.length; ++i)
          args[i] = arguments[i];
        this.listener.apply(this.target, args);
    }
  }
}

function _onceWrap(target, type, listener) {
  var state = { fired: false, wrapFn: undefined, target: target, type: type, listener: listener };
  var wrapped = bind.call(onceWrapper, state);
  wrapped.listener = listener;
  state.wrapFn = wrapped;
  return wrapped;
}

EventEmitter.prototype.once = function once(type, listener) {
  if (typeof listener !== 'function')
    throw new TypeError('"listener" argument must be a function');
  this.on(type, _onceWrap(this, type, listener));
  return this;
};

EventEmitter.prototype.prependOnceListener =
    function prependOnceListener(type, listener) {
      if (typeof listener !== 'function')
        throw new TypeError('"listener" argument must be a function');
      this.prependListener(type, _onceWrap(this, type, listener));
      return this;
    };

// Emits a 'removeListener' event if and only if the listener was removed.
EventEmitter.prototype.removeListener =
    function removeListener(type, listener) {
      var list, events, position, i, originalListener;

      if (typeof listener !== 'function')
        throw new TypeError('"listener" argument must be a function');

      events = this._events;
      if (!events)
        return this;

      list = events[type];
      if (!list)
        return this;

      if (list === listener || list.listener === listener) {
        if (--this._eventsCount === 0)
          this._events = objectCreate(null);
        else {
          delete events[type];
          if (events.removeListener)
            this.emit('removeListener', type, list.listener || listener);
        }
      } else if (typeof list !== 'function') {
        position = -1;

        for (i = list.length - 1; i >= 0; i--) {
          if (list[i] === listener || list[i].listener === listener) {
            originalListener = list[i].listener;
            position = i;
            break;
          }
        }

        if (position < 0)
          return this;

        if (position === 0)
          list.shift();
        else
          spliceOne(list, position);

        if (list.length === 1)
          events[type] = list[0];

        if (events.removeListener)
          this.emit('removeListener', type, originalListener || listener);
      }

      return this;
    };

EventEmitter.prototype.removeAllListeners =
    function removeAllListeners(type) {
      var listeners, events, i;

      events = this._events;
      if (!events)
        return this;

      // not listening for removeListener, no need to emit
      if (!events.removeListener) {
        if (arguments.length === 0) {
          this._events = objectCreate(null);
          this._eventsCount = 0;
        } else if (events[type]) {
          if (--this._eventsCount === 0)
            this._events = objectCreate(null);
          else
            delete events[type];
        }
        return this;
      }

      // emit removeListener for all listeners on all events
      if (arguments.length === 0) {
        var keys = objectKeys(events);
        var key;
        for (i = 0; i < keys.length; ++i) {
          key = keys[i];
          if (key === 'removeListener') continue;
          this.removeAllListeners(key);
        }
        this.removeAllListeners('removeListener');
        this._events = objectCreate(null);
        this._eventsCount = 0;
        return this;
      }

      listeners = events[type];

      if (typeof listeners === 'function') {
        this.removeListener(type, listeners);
      } else if (listeners) {
        // LIFO order
        for (i = listeners.length - 1; i >= 0; i--) {
          this.removeListener(type, listeners[i]);
        }
      }

      return this;
    };

function _listeners(target, type, unwrap) {
  var events = target._events;

  if (!events)
    return [];

  var evlistener = events[type];
  if (!evlistener)
    return [];

  if (typeof evlistener === 'function')
    return unwrap ? [evlistener.listener || evlistener] : [evlistener];

  return unwrap ? unwrapListeners(evlistener) : arrayClone(evlistener, evlistener.length);
}

EventEmitter.prototype.listeners = function listeners(type) {
  return _listeners(this, type, true);
};

EventEmitter.prototype.rawListeners = function rawListeners(type) {
  return _listeners(this, type, false);
};

EventEmitter.listenerCount = function(emitter, type) {
  if (typeof emitter.listenerCount === 'function') {
    return emitter.listenerCount(type);
  } else {
    return listenerCount.call(emitter, type);
  }
};

EventEmitter.prototype.listenerCount = listenerCount;
function listenerCount(type) {
  var events = this._events;

  if (events) {
    var evlistener = events[type];

    if (typeof evlistener === 'function') {
      return 1;
    } else if (evlistener) {
      return evlistener.length;
    }
  }

  return 0;
}

EventEmitter.prototype.eventNames = function eventNames() {
  return this._eventsCount > 0 ? Reflect.ownKeys(this._events) : [];
};

// About 1.5x faster than the two-arg version of Array#splice().
function spliceOne(list, index) {
  for (var i = index, k = i + 1, n = list.length; k < n; i += 1, k += 1)
    list[i] = list[k];
  list.pop();
}

function arrayClone(arr, n) {
  var copy = new Array(n);
  for (var i = 0; i < n; ++i)
    copy[i] = arr[i];
  return copy;
}

function unwrapListeners(arr) {
  var ret = new Array(arr.length);
  for (var i = 0; i < ret.length; ++i) {
    ret[i] = arr[i].listener || arr[i];
  }
  return ret;
}

function objectCreatePolyfill(proto) {
  var F = function() {};
  F.prototype = proto;
  return new F;
}
function objectKeysPolyfill(obj) {
  var keys = [];
  for (var k in obj) if (Object.prototype.hasOwnProperty.call(obj, k)) {
    keys.push(k);
  }
  return k;
}
function functionBindPolyfill(context) {
  var fn = this;
  return function () {
    return fn.apply(context, arguments);
  };
}

},{}],13:[function(require,module,exports){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

'use strict';

/*<replacement>*/

var Buffer = require('safe-buffer').Buffer;
/*</replacement>*/

var isEncoding = Buffer.isEncoding || function (encoding) {
  encoding = '' + encoding;
  switch (encoding && encoding.toLowerCase()) {
    case 'hex':case 'utf8':case 'utf-8':case 'ascii':case 'binary':case 'base64':case 'ucs2':case 'ucs-2':case 'utf16le':case 'utf-16le':case 'raw':
      return true;
    default:
      return false;
  }
};

function _normalizeEncoding(enc) {
  if (!enc) return 'utf8';
  var retried;
  while (true) {
    switch (enc) {
      case 'utf8':
      case 'utf-8':
        return 'utf8';
      case 'ucs2':
      case 'ucs-2':
      case 'utf16le':
      case 'utf-16le':
        return 'utf16le';
      case 'latin1':
      case 'binary':
        return 'latin1';
      case 'base64':
      case 'ascii':
      case 'hex':
        return enc;
      default:
        if (retried) return; // undefined
        enc = ('' + enc).toLowerCase();
        retried = true;
    }
  }
};

// Do not cache `Buffer.isEncoding` when checking encoding names as some
// modules monkey-patch it to support additional encodings
function normalizeEncoding(enc) {
  var nenc = _normalizeEncoding(enc);
  if (typeof nenc !== 'string' && (Buffer.isEncoding === isEncoding || !isEncoding(enc))) throw new Error('Unknown encoding: ' + enc);
  return nenc || enc;
}

// StringDecoder provides an interface for efficiently splitting a series of
// buffers into a series of JS strings without breaking apart multi-byte
// characters.
exports.StringDecoder = StringDecoder;
function StringDecoder(encoding) {
  this.encoding = normalizeEncoding(encoding);
  var nb;
  switch (this.encoding) {
    case 'utf16le':
      this.text = utf16Text;
      this.end = utf16End;
      nb = 4;
      break;
    case 'utf8':
      this.fillLast = utf8FillLast;
      nb = 4;
      break;
    case 'base64':
      this.text = base64Text;
      this.end = base64End;
      nb = 3;
      break;
    default:
      this.write = simpleWrite;
      this.end = simpleEnd;
      return;
  }
  this.lastNeed = 0;
  this.lastTotal = 0;
  this.lastChar = Buffer.allocUnsafe(nb);
}

StringDecoder.prototype.write = function (buf) {
  if (buf.length === 0) return '';
  var r;
  var i;
  if (this.lastNeed) {
    r = this.fillLast(buf);
    if (r === undefined) return '';
    i = this.lastNeed;
    this.lastNeed = 0;
  } else {
    i = 0;
  }
  if (i < buf.length) return r ? r + this.text(buf, i) : this.text(buf, i);
  return r || '';
};

StringDecoder.prototype.end = utf8End;

// Returns only complete characters in a Buffer
StringDecoder.prototype.text = utf8Text;

// Attempts to complete a partial non-UTF-8 character using bytes from a Buffer
StringDecoder.prototype.fillLast = function (buf) {
  if (this.lastNeed <= buf.length) {
    buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, this.lastNeed);
    return this.lastChar.toString(this.encoding, 0, this.lastTotal);
  }
  buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, buf.length);
  this.lastNeed -= buf.length;
};

// Checks the type of a UTF-8 byte, whether it's ASCII, a leading byte, or a
// continuation byte. If an invalid byte is detected, -2 is returned.
function utf8CheckByte(byte) {
  if (byte <= 0x7F) return 0;else if (byte >> 5 === 0x06) return 2;else if (byte >> 4 === 0x0E) return 3;else if (byte >> 3 === 0x1E) return 4;
  return byte >> 6 === 0x02 ? -1 : -2;
}

// Checks at most 3 bytes at the end of a Buffer in order to detect an
// incomplete multi-byte UTF-8 character. The total number of bytes (2, 3, or 4)
// needed to complete the UTF-8 character (if applicable) are returned.
function utf8CheckIncomplete(self, buf, i) {
  var j = buf.length - 1;
  if (j < i) return 0;
  var nb = utf8CheckByte(buf[j]);
  if (nb >= 0) {
    if (nb > 0) self.lastNeed = nb - 1;
    return nb;
  }
  if (--j < i || nb === -2) return 0;
  nb = utf8CheckByte(buf[j]);
  if (nb >= 0) {
    if (nb > 0) self.lastNeed = nb - 2;
    return nb;
  }
  if (--j < i || nb === -2) return 0;
  nb = utf8CheckByte(buf[j]);
  if (nb >= 0) {
    if (nb > 0) {
      if (nb === 2) nb = 0;else self.lastNeed = nb - 3;
    }
    return nb;
  }
  return 0;
}

// Validates as many continuation bytes for a multi-byte UTF-8 character as
// needed or are available. If we see a non-continuation byte where we expect
// one, we "replace" the validated continuation bytes we've seen so far with
// a single UTF-8 replacement character ('\ufffd'), to match v8's UTF-8 decoding
// behavior. The continuation byte check is included three times in the case
// where all of the continuation bytes for a character exist in the same buffer.
// It is also done this way as a slight performance increase instead of using a
// loop.
function utf8CheckExtraBytes(self, buf, p) {
  if ((buf[0] & 0xC0) !== 0x80) {
    self.lastNeed = 0;
    return '\ufffd';
  }
  if (self.lastNeed > 1 && buf.length > 1) {
    if ((buf[1] & 0xC0) !== 0x80) {
      self.lastNeed = 1;
      return '\ufffd';
    }
    if (self.lastNeed > 2 && buf.length > 2) {
      if ((buf[2] & 0xC0) !== 0x80) {
        self.lastNeed = 2;
        return '\ufffd';
      }
    }
  }
}

// Attempts to complete a multi-byte UTF-8 character using bytes from a Buffer.
function utf8FillLast(buf) {
  var p = this.lastTotal - this.lastNeed;
  var r = utf8CheckExtraBytes(this, buf, p);
  if (r !== undefined) return r;
  if (this.lastNeed <= buf.length) {
    buf.copy(this.lastChar, p, 0, this.lastNeed);
    return this.lastChar.toString(this.encoding, 0, this.lastTotal);
  }
  buf.copy(this.lastChar, p, 0, buf.length);
  this.lastNeed -= buf.length;
}

// Returns all complete UTF-8 characters in a Buffer. If the Buffer ended on a
// partial character, the character's bytes are buffered until the required
// number of bytes are available.
function utf8Text(buf, i) {
  var total = utf8CheckIncomplete(this, buf, i);
  if (!this.lastNeed) return buf.toString('utf8', i);
  this.lastTotal = total;
  var end = buf.length - (total - this.lastNeed);
  buf.copy(this.lastChar, 0, end);
  return buf.toString('utf8', i, end);
}

// For UTF-8, a replacement character is added when ending on a partial
// character.
function utf8End(buf) {
  var r = buf && buf.length ? this.write(buf) : '';
  if (this.lastNeed) return r + '\ufffd';
  return r;
}

// UTF-16LE typically needs two bytes per character, but even if we have an even
// number of bytes available, we need to check if we end on a leading/high
// surrogate. In that case, we need to wait for the next two bytes in order to
// decode the last character properly.
function utf16Text(buf, i) {
  if ((buf.length - i) % 2 === 0) {
    var r = buf.toString('utf16le', i);
    if (r) {
      var c = r.charCodeAt(r.length - 1);
      if (c >= 0xD800 && c <= 0xDBFF) {
        this.lastNeed = 2;
        this.lastTotal = 4;
        this.lastChar[0] = buf[buf.length - 2];
        this.lastChar[1] = buf[buf.length - 1];
        return r.slice(0, -1);
      }
    }
    return r;
  }
  this.lastNeed = 1;
  this.lastTotal = 2;
  this.lastChar[0] = buf[buf.length - 1];
  return buf.toString('utf16le', i, buf.length - 1);
}

// For UTF-16LE we do not explicitly append special replacement characters if we
// end on a partial character, we simply let v8 handle that.
function utf16End(buf) {
  var r = buf && buf.length ? this.write(buf) : '';
  if (this.lastNeed) {
    var end = this.lastTotal - this.lastNeed;
    return r + this.lastChar.toString('utf16le', 0, end);
  }
  return r;
}

function base64Text(buf, i) {
  var n = (buf.length - i) % 3;
  if (n === 0) return buf.toString('base64', i);
  this.lastNeed = 3 - n;
  this.lastTotal = 3;
  if (n === 1) {
    this.lastChar[0] = buf[buf.length - 1];
  } else {
    this.lastChar[0] = buf[buf.length - 2];
    this.lastChar[1] = buf[buf.length - 1];
  }
  return buf.toString('base64', i, buf.length - n);
}

function base64End(buf) {
  var r = buf && buf.length ? this.write(buf) : '';
  if (this.lastNeed) return r + this.lastChar.toString('base64', 0, 3 - this.lastNeed);
  return r;
}

// Pass bytes on through for single-byte encodings (e.g. ascii, latin1, hex)
function simpleWrite(buf) {
  return buf.toString(this.encoding);
}

function simpleEnd(buf) {
  return buf && buf.length ? this.write(buf) : '';
}
},{"safe-buffer":36}],14:[function(require,module,exports){
/*!
 * The buffer module from node.js, for the browser.
 *
 * @author   Feross Aboukhadijeh <https://feross.org>
 * @license  MIT
 */
/* eslint-disable no-proto */

'use strict'

var base64 = require('base64-js')
var ieee754 = require('ieee754')

exports.Buffer = Buffer
exports.SlowBuffer = SlowBuffer
exports.INSPECT_MAX_BYTES = 50

var K_MAX_LENGTH = 0x7fffffff
exports.kMaxLength = K_MAX_LENGTH

/**
 * If `Buffer.TYPED_ARRAY_SUPPORT`:
 *   === true    Use Uint8Array implementation (fastest)
 *   === false   Print warning and recommend using `buffer` v4.x which has an Object
 *               implementation (most compatible, even IE6)
 *
 * Browsers that support typed arrays are IE 10+, Firefox 4+, Chrome 7+, Safari 5.1+,
 * Opera 11.6+, iOS 4.2+.
 *
 * We report that the browser does not support typed arrays if the are not subclassable
 * using __proto__. Firefox 4-29 lacks support for adding new properties to `Uint8Array`
 * (See: https://bugzilla.mozilla.org/show_bug.cgi?id=695438). IE 10 lacks support
 * for __proto__ and has a buggy typed array implementation.
 */
Buffer.TYPED_ARRAY_SUPPORT = typedArraySupport()

if (!Buffer.TYPED_ARRAY_SUPPORT && typeof console !== 'undefined' &&
    typeof console.error === 'function') {
  console.error(
    'This browser lacks typed array (Uint8Array) support which is required by ' +
    '`buffer` v5.x. Use `buffer` v4.x if you require old browser support.'
  )
}

function typedArraySupport () {
  // Can typed array instances can be augmented?
  try {
    var arr = new Uint8Array(1)
    arr.__proto__ = { __proto__: Uint8Array.prototype, foo: function () { return 42 } }
    return arr.foo() === 42
  } catch (e) {
    return false
  }
}

Object.defineProperty(Buffer.prototype, 'parent', {
  enumerable: true,
  get: function () {
    if (!Buffer.isBuffer(this)) return undefined
    return this.buffer
  }
})

Object.defineProperty(Buffer.prototype, 'offset', {
  enumerable: true,
  get: function () {
    if (!Buffer.isBuffer(this)) return undefined
    return this.byteOffset
  }
})

function createBuffer (length) {
  if (length > K_MAX_LENGTH) {
    throw new RangeError('The value "' + length + '" is invalid for option "size"')
  }
  // Return an augmented `Uint8Array` instance
  var buf = new Uint8Array(length)
  buf.__proto__ = Buffer.prototype
  return buf
}

/**
 * The Buffer constructor returns instances of `Uint8Array` that have their
 * prototype changed to `Buffer.prototype`. Furthermore, `Buffer` is a subclass of
 * `Uint8Array`, so the returned instances will have all the node `Buffer` methods
 * and the `Uint8Array` methods. Square bracket notation works as expected -- it
 * returns a single octet.
 *
 * The `Uint8Array` prototype remains unmodified.
 */

function Buffer (arg, encodingOrOffset, length) {
  // Common case.
  if (typeof arg === 'number') {
    if (typeof encodingOrOffset === 'string') {
      throw new TypeError(
        'The "string" argument must be of type string. Received type number'
      )
    }
    return allocUnsafe(arg)
  }
  return from(arg, encodingOrOffset, length)
}

// Fix subarray() in ES2016. See: https://github.com/feross/buffer/pull/97
if (typeof Symbol !== 'undefined' && Symbol.species != null &&
    Buffer[Symbol.species] === Buffer) {
  Object.defineProperty(Buffer, Symbol.species, {
    value: null,
    configurable: true,
    enumerable: false,
    writable: false
  })
}

Buffer.poolSize = 8192 // not used by this implementation

function from (value, encodingOrOffset, length) {
  if (typeof value === 'string') {
    return fromString(value, encodingOrOffset)
  }

  if (ArrayBuffer.isView(value)) {
    return fromArrayLike(value)
  }

  if (value == null) {
    throw TypeError(
      'The first argument must be one of type string, Buffer, ArrayBuffer, Array, ' +
      'or Array-like Object. Received type ' + (typeof value)
    )
  }

  if (isInstance(value, ArrayBuffer) ||
      (value && isInstance(value.buffer, ArrayBuffer))) {
    return fromArrayBuffer(value, encodingOrOffset, length)
  }

  if (typeof value === 'number') {
    throw new TypeError(
      'The "value" argument must not be of type number. Received type number'
    )
  }

  var valueOf = value.valueOf && value.valueOf()
  if (valueOf != null && valueOf !== value) {
    return Buffer.from(valueOf, encodingOrOffset, length)
  }

  var b = fromObject(value)
  if (b) return b

  if (typeof Symbol !== 'undefined' && Symbol.toPrimitive != null &&
      typeof value[Symbol.toPrimitive] === 'function') {
    return Buffer.from(
      value[Symbol.toPrimitive]('string'), encodingOrOffset, length
    )
  }

  throw new TypeError(
    'The first argument must be one of type string, Buffer, ArrayBuffer, Array, ' +
    'or Array-like Object. Received type ' + (typeof value)
  )
}

/**
 * Functionally equivalent to Buffer(arg, encoding) but throws a TypeError
 * if value is a number.
 * Buffer.from(str[, encoding])
 * Buffer.from(array)
 * Buffer.from(buffer)
 * Buffer.from(arrayBuffer[, byteOffset[, length]])
 **/
Buffer.from = function (value, encodingOrOffset, length) {
  return from(value, encodingOrOffset, length)
}

// Note: Change prototype *after* Buffer.from is defined to workaround Chrome bug:
// https://github.com/feross/buffer/pull/148
Buffer.prototype.__proto__ = Uint8Array.prototype
Buffer.__proto__ = Uint8Array

function assertSize (size) {
  if (typeof size !== 'number') {
    throw new TypeError('"size" argument must be of type number')
  } else if (size < 0) {
    throw new RangeError('The value "' + size + '" is invalid for option "size"')
  }
}

function alloc (size, fill, encoding) {
  assertSize(size)
  if (size <= 0) {
    return createBuffer(size)
  }
  if (fill !== undefined) {
    // Only pay attention to encoding if it's a string. This
    // prevents accidentally sending in a number that would
    // be interpretted as a start offset.
    return typeof encoding === 'string'
      ? createBuffer(size).fill(fill, encoding)
      : createBuffer(size).fill(fill)
  }
  return createBuffer(size)
}

/**
 * Creates a new filled Buffer instance.
 * alloc(size[, fill[, encoding]])
 **/
Buffer.alloc = function (size, fill, encoding) {
  return alloc(size, fill, encoding)
}

function allocUnsafe (size) {
  assertSize(size)
  return createBuffer(size < 0 ? 0 : checked(size) | 0)
}

/**
 * Equivalent to Buffer(num), by default creates a non-zero-filled Buffer instance.
 * */
Buffer.allocUnsafe = function (size) {
  return allocUnsafe(size)
}
/**
 * Equivalent to SlowBuffer(num), by default creates a non-zero-filled Buffer instance.
 */
Buffer.allocUnsafeSlow = function (size) {
  return allocUnsafe(size)
}

function fromString (string, encoding) {
  if (typeof encoding !== 'string' || encoding === '') {
    encoding = 'utf8'
  }

  if (!Buffer.isEncoding(encoding)) {
    throw new TypeError('Unknown encoding: ' + encoding)
  }

  var length = byteLength(string, encoding) | 0
  var buf = createBuffer(length)

  var actual = buf.write(string, encoding)

  if (actual !== length) {
    // Writing a hex string, for example, that contains invalid characters will
    // cause everything after the first invalid character to be ignored. (e.g.
    // 'abxxcd' will be treated as 'ab')
    buf = buf.slice(0, actual)
  }

  return buf
}

function fromArrayLike (array) {
  var length = array.length < 0 ? 0 : checked(array.length) | 0
  var buf = createBuffer(length)
  for (var i = 0; i < length; i += 1) {
    buf[i] = array[i] & 255
  }
  return buf
}

function fromArrayBuffer (array, byteOffset, length) {
  if (byteOffset < 0 || array.byteLength < byteOffset) {
    throw new RangeError('"offset" is outside of buffer bounds')
  }

  if (array.byteLength < byteOffset + (length || 0)) {
    throw new RangeError('"length" is outside of buffer bounds')
  }

  var buf
  if (byteOffset === undefined && length === undefined) {
    buf = new Uint8Array(array)
  } else if (length === undefined) {
    buf = new Uint8Array(array, byteOffset)
  } else {
    buf = new Uint8Array(array, byteOffset, length)
  }

  // Return an augmented `Uint8Array` instance
  buf.__proto__ = Buffer.prototype
  return buf
}

function fromObject (obj) {
  if (Buffer.isBuffer(obj)) {
    var len = checked(obj.length) | 0
    var buf = createBuffer(len)

    if (buf.length === 0) {
      return buf
    }

    obj.copy(buf, 0, 0, len)
    return buf
  }

  if (obj.length !== undefined) {
    if (typeof obj.length !== 'number' || numberIsNaN(obj.length)) {
      return createBuffer(0)
    }
    return fromArrayLike(obj)
  }

  if (obj.type === 'Buffer' && Array.isArray(obj.data)) {
    return fromArrayLike(obj.data)
  }
}

function checked (length) {
  // Note: cannot use `length < K_MAX_LENGTH` here because that fails when
  // length is NaN (which is otherwise coerced to zero.)
  if (length >= K_MAX_LENGTH) {
    throw new RangeError('Attempt to allocate Buffer larger than maximum ' +
                         'size: 0x' + K_MAX_LENGTH.toString(16) + ' bytes')
  }
  return length | 0
}

function SlowBuffer (length) {
  if (+length != length) { // eslint-disable-line eqeqeq
    length = 0
  }
  return Buffer.alloc(+length)
}

Buffer.isBuffer = function isBuffer (b) {
  return b != null && b._isBuffer === true &&
    b !== Buffer.prototype // so Buffer.isBuffer(Buffer.prototype) will be false
}

Buffer.compare = function compare (a, b) {
  if (isInstance(a, Uint8Array)) a = Buffer.from(a, a.offset, a.byteLength)
  if (isInstance(b, Uint8Array)) b = Buffer.from(b, b.offset, b.byteLength)
  if (!Buffer.isBuffer(a) || !Buffer.isBuffer(b)) {
    throw new TypeError(
      'The "buf1", "buf2" arguments must be one of type Buffer or Uint8Array'
    )
  }

  if (a === b) return 0

  var x = a.length
  var y = b.length

  for (var i = 0, len = Math.min(x, y); i < len; ++i) {
    if (a[i] !== b[i]) {
      x = a[i]
      y = b[i]
      break
    }
  }

  if (x < y) return -1
  if (y < x) return 1
  return 0
}

Buffer.isEncoding = function isEncoding (encoding) {
  switch (String(encoding).toLowerCase()) {
    case 'hex':
    case 'utf8':
    case 'utf-8':
    case 'ascii':
    case 'latin1':
    case 'binary':
    case 'base64':
    case 'ucs2':
    case 'ucs-2':
    case 'utf16le':
    case 'utf-16le':
      return true
    default:
      return false
  }
}

Buffer.concat = function concat (list, length) {
  if (!Array.isArray(list)) {
    throw new TypeError('"list" argument must be an Array of Buffers')
  }

  if (list.length === 0) {
    return Buffer.alloc(0)
  }

  var i
  if (length === undefined) {
    length = 0
    for (i = 0; i < list.length; ++i) {
      length += list[i].length
    }
  }

  var buffer = Buffer.allocUnsafe(length)
  var pos = 0
  for (i = 0; i < list.length; ++i) {
    var buf = list[i]
    if (isInstance(buf, Uint8Array)) {
      buf = Buffer.from(buf)
    }
    if (!Buffer.isBuffer(buf)) {
      throw new TypeError('"list" argument must be an Array of Buffers')
    }
    buf.copy(buffer, pos)
    pos += buf.length
  }
  return buffer
}

function byteLength (string, encoding) {
  if (Buffer.isBuffer(string)) {
    return string.length
  }
  if (ArrayBuffer.isView(string) || isInstance(string, ArrayBuffer)) {
    return string.byteLength
  }
  if (typeof string !== 'string') {
    throw new TypeError(
      'The "string" argument must be one of type string, Buffer, or ArrayBuffer. ' +
      'Received type ' + typeof string
    )
  }

  var len = string.length
  var mustMatch = (arguments.length > 2 && arguments[2] === true)
  if (!mustMatch && len === 0) return 0

  // Use a for loop to avoid recursion
  var loweredCase = false
  for (;;) {
    switch (encoding) {
      case 'ascii':
      case 'latin1':
      case 'binary':
        return len
      case 'utf8':
      case 'utf-8':
        return utf8ToBytes(string).length
      case 'ucs2':
      case 'ucs-2':
      case 'utf16le':
      case 'utf-16le':
        return len * 2
      case 'hex':
        return len >>> 1
      case 'base64':
        return base64ToBytes(string).length
      default:
        if (loweredCase) {
          return mustMatch ? -1 : utf8ToBytes(string).length // assume utf8
        }
        encoding = ('' + encoding).toLowerCase()
        loweredCase = true
    }
  }
}
Buffer.byteLength = byteLength

function slowToString (encoding, start, end) {
  var loweredCase = false

  // No need to verify that "this.length <= MAX_UINT32" since it's a read-only
  // property of a typed array.

  // This behaves neither like String nor Uint8Array in that we set start/end
  // to their upper/lower bounds if the value passed is out of range.
  // undefined is handled specially as per ECMA-262 6th Edition,
  // Section 13.3.3.7 Runtime Semantics: KeyedBindingInitialization.
  if (start === undefined || start < 0) {
    start = 0
  }
  // Return early if start > this.length. Done here to prevent potential uint32
  // coercion fail below.
  if (start > this.length) {
    return ''
  }

  if (end === undefined || end > this.length) {
    end = this.length
  }

  if (end <= 0) {
    return ''
  }

  // Force coersion to uint32. This will also coerce falsey/NaN values to 0.
  end >>>= 0
  start >>>= 0

  if (end <= start) {
    return ''
  }

  if (!encoding) encoding = 'utf8'

  while (true) {
    switch (encoding) {
      case 'hex':
        return hexSlice(this, start, end)

      case 'utf8':
      case 'utf-8':
        return utf8Slice(this, start, end)

      case 'ascii':
        return asciiSlice(this, start, end)

      case 'latin1':
      case 'binary':
        return latin1Slice(this, start, end)

      case 'base64':
        return base64Slice(this, start, end)

      case 'ucs2':
      case 'ucs-2':
      case 'utf16le':
      case 'utf-16le':
        return utf16leSlice(this, start, end)

      default:
        if (loweredCase) throw new TypeError('Unknown encoding: ' + encoding)
        encoding = (encoding + '').toLowerCase()
        loweredCase = true
    }
  }
}

// This property is used by `Buffer.isBuffer` (and the `is-buffer` npm package)
// to detect a Buffer instance. It's not possible to use `instanceof Buffer`
// reliably in a browserify context because there could be multiple different
// copies of the 'buffer' package in use. This method works even for Buffer
// instances that were created from another copy of the `buffer` package.
// See: https://github.com/feross/buffer/issues/154
Buffer.prototype._isBuffer = true

function swap (b, n, m) {
  var i = b[n]
  b[n] = b[m]
  b[m] = i
}

Buffer.prototype.swap16 = function swap16 () {
  var len = this.length
  if (len % 2 !== 0) {
    throw new RangeError('Buffer size must be a multiple of 16-bits')
  }
  for (var i = 0; i < len; i += 2) {
    swap(this, i, i + 1)
  }
  return this
}

Buffer.prototype.swap32 = function swap32 () {
  var len = this.length
  if (len % 4 !== 0) {
    throw new RangeError('Buffer size must be a multiple of 32-bits')
  }
  for (var i = 0; i < len; i += 4) {
    swap(this, i, i + 3)
    swap(this, i + 1, i + 2)
  }
  return this
}

Buffer.prototype.swap64 = function swap64 () {
  var len = this.length
  if (len % 8 !== 0) {
    throw new RangeError('Buffer size must be a multiple of 64-bits')
  }
  for (var i = 0; i < len; i += 8) {
    swap(this, i, i + 7)
    swap(this, i + 1, i + 6)
    swap(this, i + 2, i + 5)
    swap(this, i + 3, i + 4)
  }
  return this
}

Buffer.prototype.toString = function toString () {
  var length = this.length
  if (length === 0) return ''
  if (arguments.length === 0) return utf8Slice(this, 0, length)
  return slowToString.apply(this, arguments)
}

Buffer.prototype.toLocaleString = Buffer.prototype.toString

Buffer.prototype.equals = function equals (b) {
  if (!Buffer.isBuffer(b)) throw new TypeError('Argument must be a Buffer')
  if (this === b) return true
  return Buffer.compare(this, b) === 0
}

Buffer.prototype.inspect = function inspect () {
  var str = ''
  var max = exports.INSPECT_MAX_BYTES
  str = this.toString('hex', 0, max).replace(/(.{2})/g, '$1 ').trim()
  if (this.length > max) str += ' ... '
  return '<Buffer ' + str + '>'
}

Buffer.prototype.compare = function compare (target, start, end, thisStart, thisEnd) {
  if (isInstance(target, Uint8Array)) {
    target = Buffer.from(target, target.offset, target.byteLength)
  }
  if (!Buffer.isBuffer(target)) {
    throw new TypeError(
      'The "target" argument must be one of type Buffer or Uint8Array. ' +
      'Received type ' + (typeof target)
    )
  }

  if (start === undefined) {
    start = 0
  }
  if (end === undefined) {
    end = target ? target.length : 0
  }
  if (thisStart === undefined) {
    thisStart = 0
  }
  if (thisEnd === undefined) {
    thisEnd = this.length
  }

  if (start < 0 || end > target.length || thisStart < 0 || thisEnd > this.length) {
    throw new RangeError('out of range index')
  }

  if (thisStart >= thisEnd && start >= end) {
    return 0
  }
  if (thisStart >= thisEnd) {
    return -1
  }
  if (start >= end) {
    return 1
  }

  start >>>= 0
  end >>>= 0
  thisStart >>>= 0
  thisEnd >>>= 0

  if (this === target) return 0

  var x = thisEnd - thisStart
  var y = end - start
  var len = Math.min(x, y)

  var thisCopy = this.slice(thisStart, thisEnd)
  var targetCopy = target.slice(start, end)

  for (var i = 0; i < len; ++i) {
    if (thisCopy[i] !== targetCopy[i]) {
      x = thisCopy[i]
      y = targetCopy[i]
      break
    }
  }

  if (x < y) return -1
  if (y < x) return 1
  return 0
}

// Finds either the first index of `val` in `buffer` at offset >= `byteOffset`,
// OR the last index of `val` in `buffer` at offset <= `byteOffset`.
//
// Arguments:
// - buffer - a Buffer to search
// - val - a string, Buffer, or number
// - byteOffset - an index into `buffer`; will be clamped to an int32
// - encoding - an optional encoding, relevant is val is a string
// - dir - true for indexOf, false for lastIndexOf
function bidirectionalIndexOf (buffer, val, byteOffset, encoding, dir) {
  // Empty buffer means no match
  if (buffer.length === 0) return -1

  // Normalize byteOffset
  if (typeof byteOffset === 'string') {
    encoding = byteOffset
    byteOffset = 0
  } else if (byteOffset > 0x7fffffff) {
    byteOffset = 0x7fffffff
  } else if (byteOffset < -0x80000000) {
    byteOffset = -0x80000000
  }
  byteOffset = +byteOffset // Coerce to Number.
  if (numberIsNaN(byteOffset)) {
    // byteOffset: it it's undefined, null, NaN, "foo", etc, search whole buffer
    byteOffset = dir ? 0 : (buffer.length - 1)
  }

  // Normalize byteOffset: negative offsets start from the end of the buffer
  if (byteOffset < 0) byteOffset = buffer.length + byteOffset
  if (byteOffset >= buffer.length) {
    if (dir) return -1
    else byteOffset = buffer.length - 1
  } else if (byteOffset < 0) {
    if (dir) byteOffset = 0
    else return -1
  }

  // Normalize val
  if (typeof val === 'string') {
    val = Buffer.from(val, encoding)
  }

  // Finally, search either indexOf (if dir is true) or lastIndexOf
  if (Buffer.isBuffer(val)) {
    // Special case: looking for empty string/buffer always fails
    if (val.length === 0) {
      return -1
    }
    return arrayIndexOf(buffer, val, byteOffset, encoding, dir)
  } else if (typeof val === 'number') {
    val = val & 0xFF // Search for a byte value [0-255]
    if (typeof Uint8Array.prototype.indexOf === 'function') {
      if (dir) {
        return Uint8Array.prototype.indexOf.call(buffer, val, byteOffset)
      } else {
        return Uint8Array.prototype.lastIndexOf.call(buffer, val, byteOffset)
      }
    }
    return arrayIndexOf(buffer, [ val ], byteOffset, encoding, dir)
  }

  throw new TypeError('val must be string, number or Buffer')
}

function arrayIndexOf (arr, val, byteOffset, encoding, dir) {
  var indexSize = 1
  var arrLength = arr.length
  var valLength = val.length

  if (encoding !== undefined) {
    encoding = String(encoding).toLowerCase()
    if (encoding === 'ucs2' || encoding === 'ucs-2' ||
        encoding === 'utf16le' || encoding === 'utf-16le') {
      if (arr.length < 2 || val.length < 2) {
        return -1
      }
      indexSize = 2
      arrLength /= 2
      valLength /= 2
      byteOffset /= 2
    }
  }

  function read (buf, i) {
    if (indexSize === 1) {
      return buf[i]
    } else {
      return buf.readUInt16BE(i * indexSize)
    }
  }

  var i
  if (dir) {
    var foundIndex = -1
    for (i = byteOffset; i < arrLength; i++) {
      if (read(arr, i) === read(val, foundIndex === -1 ? 0 : i - foundIndex)) {
        if (foundIndex === -1) foundIndex = i
        if (i - foundIndex + 1 === valLength) return foundIndex * indexSize
      } else {
        if (foundIndex !== -1) i -= i - foundIndex
        foundIndex = -1
      }
    }
  } else {
    if (byteOffset + valLength > arrLength) byteOffset = arrLength - valLength
    for (i = byteOffset; i >= 0; i--) {
      var found = true
      for (var j = 0; j < valLength; j++) {
        if (read(arr, i + j) !== read(val, j)) {
          found = false
          break
        }
      }
      if (found) return i
    }
  }

  return -1
}

Buffer.prototype.includes = function includes (val, byteOffset, encoding) {
  return this.indexOf(val, byteOffset, encoding) !== -1
}

Buffer.prototype.indexOf = function indexOf (val, byteOffset, encoding) {
  return bidirectionalIndexOf(this, val, byteOffset, encoding, true)
}

Buffer.prototype.lastIndexOf = function lastIndexOf (val, byteOffset, encoding) {
  return bidirectionalIndexOf(this, val, byteOffset, encoding, false)
}

function hexWrite (buf, string, offset, length) {
  offset = Number(offset) || 0
  var remaining = buf.length - offset
  if (!length) {
    length = remaining
  } else {
    length = Number(length)
    if (length > remaining) {
      length = remaining
    }
  }

  var strLen = string.length

  if (length > strLen / 2) {
    length = strLen / 2
  }
  for (var i = 0; i < length; ++i) {
    var parsed = parseInt(string.substr(i * 2, 2), 16)
    if (numberIsNaN(parsed)) return i
    buf[offset + i] = parsed
  }
  return i
}

function utf8Write (buf, string, offset, length) {
  return blitBuffer(utf8ToBytes(string, buf.length - offset), buf, offset, length)
}

function asciiWrite (buf, string, offset, length) {
  return blitBuffer(asciiToBytes(string), buf, offset, length)
}

function latin1Write (buf, string, offset, length) {
  return asciiWrite(buf, string, offset, length)
}

function base64Write (buf, string, offset, length) {
  return blitBuffer(base64ToBytes(string), buf, offset, length)
}

function ucs2Write (buf, string, offset, length) {
  return blitBuffer(utf16leToBytes(string, buf.length - offset), buf, offset, length)
}

Buffer.prototype.write = function write (string, offset, length, encoding) {
  // Buffer#write(string)
  if (offset === undefined) {
    encoding = 'utf8'
    length = this.length
    offset = 0
  // Buffer#write(string, encoding)
  } else if (length === undefined && typeof offset === 'string') {
    encoding = offset
    length = this.length
    offset = 0
  // Buffer#write(string, offset[, length][, encoding])
  } else if (isFinite(offset)) {
    offset = offset >>> 0
    if (isFinite(length)) {
      length = length >>> 0
      if (encoding === undefined) encoding = 'utf8'
    } else {
      encoding = length
      length = undefined
    }
  } else {
    throw new Error(
      'Buffer.write(string, encoding, offset[, length]) is no longer supported'
    )
  }

  var remaining = this.length - offset
  if (length === undefined || length > remaining) length = remaining

  if ((string.length > 0 && (length < 0 || offset < 0)) || offset > this.length) {
    throw new RangeError('Attempt to write outside buffer bounds')
  }

  if (!encoding) encoding = 'utf8'

  var loweredCase = false
  for (;;) {
    switch (encoding) {
      case 'hex':
        return hexWrite(this, string, offset, length)

      case 'utf8':
      case 'utf-8':
        return utf8Write(this, string, offset, length)

      case 'ascii':
        return asciiWrite(this, string, offset, length)

      case 'latin1':
      case 'binary':
        return latin1Write(this, string, offset, length)

      case 'base64':
        // Warning: maxLength not taken into account in base64Write
        return base64Write(this, string, offset, length)

      case 'ucs2':
      case 'ucs-2':
      case 'utf16le':
      case 'utf-16le':
        return ucs2Write(this, string, offset, length)

      default:
        if (loweredCase) throw new TypeError('Unknown encoding: ' + encoding)
        encoding = ('' + encoding).toLowerCase()
        loweredCase = true
    }
  }
}

Buffer.prototype.toJSON = function toJSON () {
  return {
    type: 'Buffer',
    data: Array.prototype.slice.call(this._arr || this, 0)
  }
}

function base64Slice (buf, start, end) {
  if (start === 0 && end === buf.length) {
    return base64.fromByteArray(buf)
  } else {
    return base64.fromByteArray(buf.slice(start, end))
  }
}

function utf8Slice (buf, start, end) {
  end = Math.min(buf.length, end)
  var res = []

  var i = start
  while (i < end) {
    var firstByte = buf[i]
    var codePoint = null
    var bytesPerSequence = (firstByte > 0xEF) ? 4
      : (firstByte > 0xDF) ? 3
        : (firstByte > 0xBF) ? 2
          : 1

    if (i + bytesPerSequence <= end) {
      var secondByte, thirdByte, fourthByte, tempCodePoint

      switch (bytesPerSequence) {
        case 1:
          if (firstByte < 0x80) {
            codePoint = firstByte
          }
          break
        case 2:
          secondByte = buf[i + 1]
          if ((secondByte & 0xC0) === 0x80) {
            tempCodePoint = (firstByte & 0x1F) << 0x6 | (secondByte & 0x3F)
            if (tempCodePoint > 0x7F) {
              codePoint = tempCodePoint
            }
          }
          break
        case 3:
          secondByte = buf[i + 1]
          thirdByte = buf[i + 2]
          if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80) {
            tempCodePoint = (firstByte & 0xF) << 0xC | (secondByte & 0x3F) << 0x6 | (thirdByte & 0x3F)
            if (tempCodePoint > 0x7FF && (tempCodePoint < 0xD800 || tempCodePoint > 0xDFFF)) {
              codePoint = tempCodePoint
            }
          }
          break
        case 4:
          secondByte = buf[i + 1]
          thirdByte = buf[i + 2]
          fourthByte = buf[i + 3]
          if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80 && (fourthByte & 0xC0) === 0x80) {
            tempCodePoint = (firstByte & 0xF) << 0x12 | (secondByte & 0x3F) << 0xC | (thirdByte & 0x3F) << 0x6 | (fourthByte & 0x3F)
            if (tempCodePoint > 0xFFFF && tempCodePoint < 0x110000) {
              codePoint = tempCodePoint
            }
          }
      }
    }

    if (codePoint === null) {
      // we did not generate a valid codePoint so insert a
      // replacement char (U+FFFD) and advance only 1 byte
      codePoint = 0xFFFD
      bytesPerSequence = 1
    } else if (codePoint > 0xFFFF) {
      // encode to utf16 (surrogate pair dance)
      codePoint -= 0x10000
      res.push(codePoint >>> 10 & 0x3FF | 0xD800)
      codePoint = 0xDC00 | codePoint & 0x3FF
    }

    res.push(codePoint)
    i += bytesPerSequence
  }

  return decodeCodePointsArray(res)
}

// Based on http://stackoverflow.com/a/22747272/680742, the browser with
// the lowest limit is Chrome, with 0x10000 args.
// We go 1 magnitude less, for safety
var MAX_ARGUMENTS_LENGTH = 0x1000

function decodeCodePointsArray (codePoints) {
  var len = codePoints.length
  if (len <= MAX_ARGUMENTS_LENGTH) {
    return String.fromCharCode.apply(String, codePoints) // avoid extra slice()
  }

  // Decode in chunks to avoid "call stack size exceeded".
  var res = ''
  var i = 0
  while (i < len) {
    res += String.fromCharCode.apply(
      String,
      codePoints.slice(i, i += MAX_ARGUMENTS_LENGTH)
    )
  }
  return res
}

function asciiSlice (buf, start, end) {
  var ret = ''
  end = Math.min(buf.length, end)

  for (var i = start; i < end; ++i) {
    ret += String.fromCharCode(buf[i] & 0x7F)
  }
  return ret
}

function latin1Slice (buf, start, end) {
  var ret = ''
  end = Math.min(buf.length, end)

  for (var i = start; i < end; ++i) {
    ret += String.fromCharCode(buf[i])
  }
  return ret
}

function hexSlice (buf, start, end) {
  var len = buf.length

  if (!start || start < 0) start = 0
  if (!end || end < 0 || end > len) end = len

  var out = ''
  for (var i = start; i < end; ++i) {
    out += toHex(buf[i])
  }
  return out
}

function utf16leSlice (buf, start, end) {
  var bytes = buf.slice(start, end)
  var res = ''
  for (var i = 0; i < bytes.length; i += 2) {
    res += String.fromCharCode(bytes[i] + (bytes[i + 1] * 256))
  }
  return res
}

Buffer.prototype.slice = function slice (start, end) {
  var len = this.length
  start = ~~start
  end = end === undefined ? len : ~~end

  if (start < 0) {
    start += len
    if (start < 0) start = 0
  } else if (start > len) {
    start = len
  }

  if (end < 0) {
    end += len
    if (end < 0) end = 0
  } else if (end > len) {
    end = len
  }

  if (end < start) end = start

  var newBuf = this.subarray(start, end)
  // Return an augmented `Uint8Array` instance
  newBuf.__proto__ = Buffer.prototype
  return newBuf
}

/*
 * Need to make sure that buffer isn't trying to write out of bounds.
 */
function checkOffset (offset, ext, length) {
  if ((offset % 1) !== 0 || offset < 0) throw new RangeError('offset is not uint')
  if (offset + ext > length) throw new RangeError('Trying to access beyond buffer length')
}

Buffer.prototype.readUIntLE = function readUIntLE (offset, byteLength, noAssert) {
  offset = offset >>> 0
  byteLength = byteLength >>> 0
  if (!noAssert) checkOffset(offset, byteLength, this.length)

  var val = this[offset]
  var mul = 1
  var i = 0
  while (++i < byteLength && (mul *= 0x100)) {
    val += this[offset + i] * mul
  }

  return val
}

Buffer.prototype.readUIntBE = function readUIntBE (offset, byteLength, noAssert) {
  offset = offset >>> 0
  byteLength = byteLength >>> 0
  if (!noAssert) {
    checkOffset(offset, byteLength, this.length)
  }

  var val = this[offset + --byteLength]
  var mul = 1
  while (byteLength > 0 && (mul *= 0x100)) {
    val += this[offset + --byteLength] * mul
  }

  return val
}

Buffer.prototype.readUInt8 = function readUInt8 (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 1, this.length)
  return this[offset]
}

Buffer.prototype.readUInt16LE = function readUInt16LE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 2, this.length)
  return this[offset] | (this[offset + 1] << 8)
}

Buffer.prototype.readUInt16BE = function readUInt16BE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 2, this.length)
  return (this[offset] << 8) | this[offset + 1]
}

Buffer.prototype.readUInt32LE = function readUInt32LE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 4, this.length)

  return ((this[offset]) |
      (this[offset + 1] << 8) |
      (this[offset + 2] << 16)) +
      (this[offset + 3] * 0x1000000)
}

Buffer.prototype.readUInt32BE = function readUInt32BE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 4, this.length)

  return (this[offset] * 0x1000000) +
    ((this[offset + 1] << 16) |
    (this[offset + 2] << 8) |
    this[offset + 3])
}

Buffer.prototype.readIntLE = function readIntLE (offset, byteLength, noAssert) {
  offset = offset >>> 0
  byteLength = byteLength >>> 0
  if (!noAssert) checkOffset(offset, byteLength, this.length)

  var val = this[offset]
  var mul = 1
  var i = 0
  while (++i < byteLength && (mul *= 0x100)) {
    val += this[offset + i] * mul
  }
  mul *= 0x80

  if (val >= mul) val -= Math.pow(2, 8 * byteLength)

  return val
}

Buffer.prototype.readIntBE = function readIntBE (offset, byteLength, noAssert) {
  offset = offset >>> 0
  byteLength = byteLength >>> 0
  if (!noAssert) checkOffset(offset, byteLength, this.length)

  var i = byteLength
  var mul = 1
  var val = this[offset + --i]
  while (i > 0 && (mul *= 0x100)) {
    val += this[offset + --i] * mul
  }
  mul *= 0x80

  if (val >= mul) val -= Math.pow(2, 8 * byteLength)

  return val
}

Buffer.prototype.readInt8 = function readInt8 (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 1, this.length)
  if (!(this[offset] & 0x80)) return (this[offset])
  return ((0xff - this[offset] + 1) * -1)
}

Buffer.prototype.readInt16LE = function readInt16LE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 2, this.length)
  var val = this[offset] | (this[offset + 1] << 8)
  return (val & 0x8000) ? val | 0xFFFF0000 : val
}

Buffer.prototype.readInt16BE = function readInt16BE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 2, this.length)
  var val = this[offset + 1] | (this[offset] << 8)
  return (val & 0x8000) ? val | 0xFFFF0000 : val
}

Buffer.prototype.readInt32LE = function readInt32LE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 4, this.length)

  return (this[offset]) |
    (this[offset + 1] << 8) |
    (this[offset + 2] << 16) |
    (this[offset + 3] << 24)
}

Buffer.prototype.readInt32BE = function readInt32BE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 4, this.length)

  return (this[offset] << 24) |
    (this[offset + 1] << 16) |
    (this[offset + 2] << 8) |
    (this[offset + 3])
}

Buffer.prototype.readFloatLE = function readFloatLE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 4, this.length)
  return ieee754.read(this, offset, true, 23, 4)
}

Buffer.prototype.readFloatBE = function readFloatBE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 4, this.length)
  return ieee754.read(this, offset, false, 23, 4)
}

Buffer.prototype.readDoubleLE = function readDoubleLE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 8, this.length)
  return ieee754.read(this, offset, true, 52, 8)
}

Buffer.prototype.readDoubleBE = function readDoubleBE (offset, noAssert) {
  offset = offset >>> 0
  if (!noAssert) checkOffset(offset, 8, this.length)
  return ieee754.read(this, offset, false, 52, 8)
}

function checkInt (buf, value, offset, ext, max, min) {
  if (!Buffer.isBuffer(buf)) throw new TypeError('"buffer" argument must be a Buffer instance')
  if (value > max || value < min) throw new RangeError('"value" argument is out of bounds')
  if (offset + ext > buf.length) throw new RangeError('Index out of range')
}

Buffer.prototype.writeUIntLE = function writeUIntLE (value, offset, byteLength, noAssert) {
  value = +value
  offset = offset >>> 0
  byteLength = byteLength >>> 0
  if (!noAssert) {
    var maxBytes = Math.pow(2, 8 * byteLength) - 1
    checkInt(this, value, offset, byteLength, maxBytes, 0)
  }

  var mul = 1
  var i = 0
  this[offset] = value & 0xFF
  while (++i < byteLength && (mul *= 0x100)) {
    this[offset + i] = (value / mul) & 0xFF
  }

  return offset + byteLength
}

Buffer.prototype.writeUIntBE = function writeUIntBE (value, offset, byteLength, noAssert) {
  value = +value
  offset = offset >>> 0
  byteLength = byteLength >>> 0
  if (!noAssert) {
    var maxBytes = Math.pow(2, 8 * byteLength) - 1
    checkInt(this, value, offset, byteLength, maxBytes, 0)
  }

  var i = byteLength - 1
  var mul = 1
  this[offset + i] = value & 0xFF
  while (--i >= 0 && (mul *= 0x100)) {
    this[offset + i] = (value / mul) & 0xFF
  }

  return offset + byteLength
}

Buffer.prototype.writeUInt8 = function writeUInt8 (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 1, 0xff, 0)
  this[offset] = (value & 0xff)
  return offset + 1
}

Buffer.prototype.writeUInt16LE = function writeUInt16LE (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 2, 0xffff, 0)
  this[offset] = (value & 0xff)
  this[offset + 1] = (value >>> 8)
  return offset + 2
}

Buffer.prototype.writeUInt16BE = function writeUInt16BE (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 2, 0xffff, 0)
  this[offset] = (value >>> 8)
  this[offset + 1] = (value & 0xff)
  return offset + 2
}

Buffer.prototype.writeUInt32LE = function writeUInt32LE (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 4, 0xffffffff, 0)
  this[offset + 3] = (value >>> 24)
  this[offset + 2] = (value >>> 16)
  this[offset + 1] = (value >>> 8)
  this[offset] = (value & 0xff)
  return offset + 4
}

Buffer.prototype.writeUInt32BE = function writeUInt32BE (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 4, 0xffffffff, 0)
  this[offset] = (value >>> 24)
  this[offset + 1] = (value >>> 16)
  this[offset + 2] = (value >>> 8)
  this[offset + 3] = (value & 0xff)
  return offset + 4
}

Buffer.prototype.writeIntLE = function writeIntLE (value, offset, byteLength, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) {
    var limit = Math.pow(2, (8 * byteLength) - 1)

    checkInt(this, value, offset, byteLength, limit - 1, -limit)
  }

  var i = 0
  var mul = 1
  var sub = 0
  this[offset] = value & 0xFF
  while (++i < byteLength && (mul *= 0x100)) {
    if (value < 0 && sub === 0 && this[offset + i - 1] !== 0) {
      sub = 1
    }
    this[offset + i] = ((value / mul) >> 0) - sub & 0xFF
  }

  return offset + byteLength
}

Buffer.prototype.writeIntBE = function writeIntBE (value, offset, byteLength, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) {
    var limit = Math.pow(2, (8 * byteLength) - 1)

    checkInt(this, value, offset, byteLength, limit - 1, -limit)
  }

  var i = byteLength - 1
  var mul = 1
  var sub = 0
  this[offset + i] = value & 0xFF
  while (--i >= 0 && (mul *= 0x100)) {
    if (value < 0 && sub === 0 && this[offset + i + 1] !== 0) {
      sub = 1
    }
    this[offset + i] = ((value / mul) >> 0) - sub & 0xFF
  }

  return offset + byteLength
}

Buffer.prototype.writeInt8 = function writeInt8 (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 1, 0x7f, -0x80)
  if (value < 0) value = 0xff + value + 1
  this[offset] = (value & 0xff)
  return offset + 1
}

Buffer.prototype.writeInt16LE = function writeInt16LE (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 2, 0x7fff, -0x8000)
  this[offset] = (value & 0xff)
  this[offset + 1] = (value >>> 8)
  return offset + 2
}

Buffer.prototype.writeInt16BE = function writeInt16BE (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 2, 0x7fff, -0x8000)
  this[offset] = (value >>> 8)
  this[offset + 1] = (value & 0xff)
  return offset + 2
}

Buffer.prototype.writeInt32LE = function writeInt32LE (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000)
  this[offset] = (value & 0xff)
  this[offset + 1] = (value >>> 8)
  this[offset + 2] = (value >>> 16)
  this[offset + 3] = (value >>> 24)
  return offset + 4
}

Buffer.prototype.writeInt32BE = function writeInt32BE (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000)
  if (value < 0) value = 0xffffffff + value + 1
  this[offset] = (value >>> 24)
  this[offset + 1] = (value >>> 16)
  this[offset + 2] = (value >>> 8)
  this[offset + 3] = (value & 0xff)
  return offset + 4
}

function checkIEEE754 (buf, value, offset, ext, max, min) {
  if (offset + ext > buf.length) throw new RangeError('Index out of range')
  if (offset < 0) throw new RangeError('Index out of range')
}

function writeFloat (buf, value, offset, littleEndian, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) {
    checkIEEE754(buf, value, offset, 4, 3.4028234663852886e+38, -3.4028234663852886e+38)
  }
  ieee754.write(buf, value, offset, littleEndian, 23, 4)
  return offset + 4
}

Buffer.prototype.writeFloatLE = function writeFloatLE (value, offset, noAssert) {
  return writeFloat(this, value, offset, true, noAssert)
}

Buffer.prototype.writeFloatBE = function writeFloatBE (value, offset, noAssert) {
  return writeFloat(this, value, offset, false, noAssert)
}

function writeDouble (buf, value, offset, littleEndian, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert) {
    checkIEEE754(buf, value, offset, 8, 1.7976931348623157E+308, -1.7976931348623157E+308)
  }
  ieee754.write(buf, value, offset, littleEndian, 52, 8)
  return offset + 8
}

Buffer.prototype.writeDoubleLE = function writeDoubleLE (value, offset, noAssert) {
  return writeDouble(this, value, offset, true, noAssert)
}

Buffer.prototype.writeDoubleBE = function writeDoubleBE (value, offset, noAssert) {
  return writeDouble(this, value, offset, false, noAssert)
}

// copy(targetBuffer, targetStart=0, sourceStart=0, sourceEnd=buffer.length)
Buffer.prototype.copy = function copy (target, targetStart, start, end) {
  if (!Buffer.isBuffer(target)) throw new TypeError('argument should be a Buffer')
  if (!start) start = 0
  if (!end && end !== 0) end = this.length
  if (targetStart >= target.length) targetStart = target.length
  if (!targetStart) targetStart = 0
  if (end > 0 && end < start) end = start

  // Copy 0 bytes; we're done
  if (end === start) return 0
  if (target.length === 0 || this.length === 0) return 0

  // Fatal error conditions
  if (targetStart < 0) {
    throw new RangeError('targetStart out of bounds')
  }
  if (start < 0 || start >= this.length) throw new RangeError('Index out of range')
  if (end < 0) throw new RangeError('sourceEnd out of bounds')

  // Are we oob?
  if (end > this.length) end = this.length
  if (target.length - targetStart < end - start) {
    end = target.length - targetStart + start
  }

  var len = end - start

  if (this === target && typeof Uint8Array.prototype.copyWithin === 'function') {
    // Use built-in when available, missing from IE11
    this.copyWithin(targetStart, start, end)
  } else if (this === target && start < targetStart && targetStart < end) {
    // descending copy from end
    for (var i = len - 1; i >= 0; --i) {
      target[i + targetStart] = this[i + start]
    }
  } else {
    Uint8Array.prototype.set.call(
      target,
      this.subarray(start, end),
      targetStart
    )
  }

  return len
}

// Usage:
//    buffer.fill(number[, offset[, end]])
//    buffer.fill(buffer[, offset[, end]])
//    buffer.fill(string[, offset[, end]][, encoding])
Buffer.prototype.fill = function fill (val, start, end, encoding) {
  // Handle string cases:
  if (typeof val === 'string') {
    if (typeof start === 'string') {
      encoding = start
      start = 0
      end = this.length
    } else if (typeof end === 'string') {
      encoding = end
      end = this.length
    }
    if (encoding !== undefined && typeof encoding !== 'string') {
      throw new TypeError('encoding must be a string')
    }
    if (typeof encoding === 'string' && !Buffer.isEncoding(encoding)) {
      throw new TypeError('Unknown encoding: ' + encoding)
    }
    if (val.length === 1) {
      var code = val.charCodeAt(0)
      if ((encoding === 'utf8' && code < 128) ||
          encoding === 'latin1') {
        // Fast path: If `val` fits into a single byte, use that numeric value.
        val = code
      }
    }
  } else if (typeof val === 'number') {
    val = val & 255
  }

  // Invalid ranges are not set to a default, so can range check early.
  if (start < 0 || this.length < start || this.length < end) {
    throw new RangeError('Out of range index')
  }

  if (end <= start) {
    return this
  }

  start = start >>> 0
  end = end === undefined ? this.length : end >>> 0

  if (!val) val = 0

  var i
  if (typeof val === 'number') {
    for (i = start; i < end; ++i) {
      this[i] = val
    }
  } else {
    var bytes = Buffer.isBuffer(val)
      ? val
      : Buffer.from(val, encoding)
    var len = bytes.length
    if (len === 0) {
      throw new TypeError('The value "' + val +
        '" is invalid for argument "value"')
    }
    for (i = 0; i < end - start; ++i) {
      this[i + start] = bytes[i % len]
    }
  }

  return this
}

// HELPER FUNCTIONS
// ================

var INVALID_BASE64_RE = /[^+/0-9A-Za-z-_]/g

function base64clean (str) {
  // Node takes equal signs as end of the Base64 encoding
  str = str.split('=')[0]
  // Node strips out invalid characters like \n and \t from the string, base64-js does not
  str = str.trim().replace(INVALID_BASE64_RE, '')
  // Node converts strings with length < 2 to ''
  if (str.length < 2) return ''
  // Node allows for non-padded base64 strings (missing trailing ===), base64-js does not
  while (str.length % 4 !== 0) {
    str = str + '='
  }
  return str
}

function toHex (n) {
  if (n < 16) return '0' + n.toString(16)
  return n.toString(16)
}

function utf8ToBytes (string, units) {
  units = units || Infinity
  var codePoint
  var length = string.length
  var leadSurrogate = null
  var bytes = []

  for (var i = 0; i < length; ++i) {
    codePoint = string.charCodeAt(i)

    // is surrogate component
    if (codePoint > 0xD7FF && codePoint < 0xE000) {
      // last char was a lead
      if (!leadSurrogate) {
        // no lead yet
        if (codePoint > 0xDBFF) {
          // unexpected trail
          if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
          continue
        } else if (i + 1 === length) {
          // unpaired lead
          if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
          continue
        }

        // valid lead
        leadSurrogate = codePoint

        continue
      }

      // 2 leads in a row
      if (codePoint < 0xDC00) {
        if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
        leadSurrogate = codePoint
        continue
      }

      // valid surrogate pair
      codePoint = (leadSurrogate - 0xD800 << 10 | codePoint - 0xDC00) + 0x10000
    } else if (leadSurrogate) {
      // valid bmp char, but last char was a lead
      if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
    }

    leadSurrogate = null

    // encode utf8
    if (codePoint < 0x80) {
      if ((units -= 1) < 0) break
      bytes.push(codePoint)
    } else if (codePoint < 0x800) {
      if ((units -= 2) < 0) break
      bytes.push(
        codePoint >> 0x6 | 0xC0,
        codePoint & 0x3F | 0x80
      )
    } else if (codePoint < 0x10000) {
      if ((units -= 3) < 0) break
      bytes.push(
        codePoint >> 0xC | 0xE0,
        codePoint >> 0x6 & 0x3F | 0x80,
        codePoint & 0x3F | 0x80
      )
    } else if (codePoint < 0x110000) {
      if ((units -= 4) < 0) break
      bytes.push(
        codePoint >> 0x12 | 0xF0,
        codePoint >> 0xC & 0x3F | 0x80,
        codePoint >> 0x6 & 0x3F | 0x80,
        codePoint & 0x3F | 0x80
      )
    } else {
      throw new Error('Invalid code point')
    }
  }

  return bytes
}

function asciiToBytes (str) {
  var byteArray = []
  for (var i = 0; i < str.length; ++i) {
    // Node's code seems to be doing this and not & 0x7F..
    byteArray.push(str.charCodeAt(i) & 0xFF)
  }
  return byteArray
}

function utf16leToBytes (str, units) {
  var c, hi, lo
  var byteArray = []
  for (var i = 0; i < str.length; ++i) {
    if ((units -= 2) < 0) break

    c = str.charCodeAt(i)
    hi = c >> 8
    lo = c % 256
    byteArray.push(lo)
    byteArray.push(hi)
  }

  return byteArray
}

function base64ToBytes (str) {
  return base64.toByteArray(base64clean(str))
}

function blitBuffer (src, dst, offset, length) {
  for (var i = 0; i < length; ++i) {
    if ((i + offset >= dst.length) || (i >= src.length)) break
    dst[i + offset] = src[i]
  }
  return i
}

// ArrayBuffer or Uint8Array objects from other contexts (i.e. iframes) do not pass
// the `instanceof` check but they should be treated as of that type.
// See: https://github.com/feross/buffer/issues/166
function isInstance (obj, type) {
  return obj instanceof type ||
    (obj != null && obj.constructor != null && obj.constructor.name != null &&
      obj.constructor.name === type.name)
}
function numberIsNaN (obj) {
  // For IE11 support
  return obj !== obj // eslint-disable-line no-self-compare
}

},{"base64-js":10,"ieee754":16}],15:[function(require,module,exports){
(function (Buffer){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

// NOTE: These type checking functions intentionally don't use `instanceof`
// because it is fragile and can be easily faked with `Object.create()`.

function isArray(arg) {
  if (Array.isArray) {
    return Array.isArray(arg);
  }
  return objectToString(arg) === '[object Array]';
}
exports.isArray = isArray;

function isBoolean(arg) {
  return typeof arg === 'boolean';
}
exports.isBoolean = isBoolean;

function isNull(arg) {
  return arg === null;
}
exports.isNull = isNull;

function isNullOrUndefined(arg) {
  return arg == null;
}
exports.isNullOrUndefined = isNullOrUndefined;

function isNumber(arg) {
  return typeof arg === 'number';
}
exports.isNumber = isNumber;

function isString(arg) {
  return typeof arg === 'string';
}
exports.isString = isString;

function isSymbol(arg) {
  return typeof arg === 'symbol';
}
exports.isSymbol = isSymbol;

function isUndefined(arg) {
  return arg === void 0;
}
exports.isUndefined = isUndefined;

function isRegExp(re) {
  return objectToString(re) === '[object RegExp]';
}
exports.isRegExp = isRegExp;

function isObject(arg) {
  return typeof arg === 'object' && arg !== null;
}
exports.isObject = isObject;

function isDate(d) {
  return objectToString(d) === '[object Date]';
}
exports.isDate = isDate;

function isError(e) {
  return (objectToString(e) === '[object Error]' || e instanceof Error);
}
exports.isError = isError;

function isFunction(arg) {
  return typeof arg === 'function';
}
exports.isFunction = isFunction;

function isPrimitive(arg) {
  return arg === null ||
         typeof arg === 'boolean' ||
         typeof arg === 'number' ||
         typeof arg === 'string' ||
         typeof arg === 'symbol' ||  // ES6 symbol
         typeof arg === 'undefined';
}
exports.isPrimitive = isPrimitive;

exports.isBuffer = Buffer.isBuffer;

function objectToString(o) {
  return Object.prototype.toString.call(o);
}

}).call(this,{"isBuffer":require("../../is-buffer/index.js")})
},{"../../is-buffer/index.js":18}],16:[function(require,module,exports){
exports.read = function (buffer, offset, isLE, mLen, nBytes) {
  var e, m
  var eLen = (nBytes * 8) - mLen - 1
  var eMax = (1 << eLen) - 1
  var eBias = eMax >> 1
  var nBits = -7
  var i = isLE ? (nBytes - 1) : 0
  var d = isLE ? -1 : 1
  var s = buffer[offset + i]

  i += d

  e = s & ((1 << (-nBits)) - 1)
  s >>= (-nBits)
  nBits += eLen
  for (; nBits > 0; e = (e * 256) + buffer[offset + i], i += d, nBits -= 8) {}

  m = e & ((1 << (-nBits)) - 1)
  e >>= (-nBits)
  nBits += mLen
  for (; nBits > 0; m = (m * 256) + buffer[offset + i], i += d, nBits -= 8) {}

  if (e === 0) {
    e = 1 - eBias
  } else if (e === eMax) {
    return m ? NaN : ((s ? -1 : 1) * Infinity)
  } else {
    m = m + Math.pow(2, mLen)
    e = e - eBias
  }
  return (s ? -1 : 1) * m * Math.pow(2, e - mLen)
}

exports.write = function (buffer, value, offset, isLE, mLen, nBytes) {
  var e, m, c
  var eLen = (nBytes * 8) - mLen - 1
  var eMax = (1 << eLen) - 1
  var eBias = eMax >> 1
  var rt = (mLen === 23 ? Math.pow(2, -24) - Math.pow(2, -77) : 0)
  var i = isLE ? 0 : (nBytes - 1)
  var d = isLE ? 1 : -1
  var s = value < 0 || (value === 0 && 1 / value < 0) ? 1 : 0

  value = Math.abs(value)

  if (isNaN(value) || value === Infinity) {
    m = isNaN(value) ? 1 : 0
    e = eMax
  } else {
    e = Math.floor(Math.log(value) / Math.LN2)
    if (value * (c = Math.pow(2, -e)) < 1) {
      e--
      c *= 2
    }
    if (e + eBias >= 1) {
      value += rt / c
    } else {
      value += rt * Math.pow(2, 1 - eBias)
    }
    if (value * c >= 2) {
      e++
      c /= 2
    }

    if (e + eBias >= eMax) {
      m = 0
      e = eMax
    } else if (e + eBias >= 1) {
      m = ((value * c) - 1) * Math.pow(2, mLen)
      e = e + eBias
    } else {
      m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen)
      e = 0
    }
  }

  for (; mLen >= 8; buffer[offset + i] = m & 0xff, i += d, m /= 256, mLen -= 8) {}

  e = (e << mLen) | m
  eLen += mLen
  for (; eLen > 0; buffer[offset + i] = e & 0xff, i += d, e /= 256, eLen -= 8) {}

  buffer[offset + i - d] |= s * 128
}

},{}],17:[function(require,module,exports){
if (typeof Object.create === 'function') {
  // implementation from standard node.js 'util' module
  module.exports = function inherits(ctor, superCtor) {
    ctor.super_ = superCtor
    ctor.prototype = Object.create(superCtor.prototype, {
      constructor: {
        value: ctor,
        enumerable: false,
        writable: true,
        configurable: true
      }
    });
  };
} else {
  // old school shim for old browsers
  module.exports = function inherits(ctor, superCtor) {
    ctor.super_ = superCtor
    var TempCtor = function () {}
    TempCtor.prototype = superCtor.prototype
    ctor.prototype = new TempCtor()
    ctor.prototype.constructor = ctor
  }
}

},{}],18:[function(require,module,exports){
/*!
 * Determine if an object is a Buffer
 *
 * @author   Feross Aboukhadijeh <https://feross.org>
 * @license  MIT
 */

// The _isBuffer check is for Safari 5-7 support, because it's missing
// Object.prototype.constructor. Remove this eventually
module.exports = function (obj) {
  return obj != null && (isBuffer(obj) || isSlowBuffer(obj) || !!obj._isBuffer)
}

function isBuffer (obj) {
  return !!obj.constructor && typeof obj.constructor.isBuffer === 'function' && obj.constructor.isBuffer(obj)
}

// For Node v0.10 support. Remove this eventually.
function isSlowBuffer (obj) {
  return typeof obj.readFloatLE === 'function' && typeof obj.slice === 'function' && isBuffer(obj.slice(0, 0))
}

},{}],19:[function(require,module,exports){
var toString = {}.toString;

module.exports = Array.isArray || function (arr) {
  return toString.call(arr) == '[object Array]';
};

},{}],20:[function(require,module,exports){
(function (process){
'use strict';

if (!process.version ||
    process.version.indexOf('v0.') === 0 ||
    process.version.indexOf('v1.') === 0 && process.version.indexOf('v1.8.') !== 0) {
  module.exports = { nextTick: nextTick };
} else {
  module.exports = process
}

function nextTick(fn, arg1, arg2, arg3) {
  if (typeof fn !== 'function') {
    throw new TypeError('"callback" argument must be a function');
  }
  var len = arguments.length;
  var args, i;
  switch (len) {
  case 0:
  case 1:
    return process.nextTick(fn);
  case 2:
    return process.nextTick(function afterTickOne() {
      fn.call(null, arg1);
    });
  case 3:
    return process.nextTick(function afterTickTwo() {
      fn.call(null, arg1, arg2);
    });
  case 4:
    return process.nextTick(function afterTickThree() {
      fn.call(null, arg1, arg2, arg3);
    });
  default:
    args = new Array(len - 1);
    i = 0;
    while (i < args.length) {
      args[i++] = arguments[i];
    }
    return process.nextTick(function afterTick() {
      fn.apply(null, args);
    });
  }
}


}).call(this,require('_process'))
},{"_process":21}],21:[function(require,module,exports){
// shim for using process in browser
var process = module.exports = {};

// cached from whatever global is present so that test runners that stub it
// don't break things.  But we need to wrap it in a try catch in case it is
// wrapped in strict mode code which doesn't define any globals.  It's inside a
// function because try/catches deoptimize in certain engines.

var cachedSetTimeout;
var cachedClearTimeout;

function defaultSetTimout() {
    throw new Error('setTimeout has not been defined');
}
function defaultClearTimeout () {
    throw new Error('clearTimeout has not been defined');
}
(function () {
    try {
        if (typeof setTimeout === 'function') {
            cachedSetTimeout = setTimeout;
        } else {
            cachedSetTimeout = defaultSetTimout;
        }
    } catch (e) {
        cachedSetTimeout = defaultSetTimout;
    }
    try {
        if (typeof clearTimeout === 'function') {
            cachedClearTimeout = clearTimeout;
        } else {
            cachedClearTimeout = defaultClearTimeout;
        }
    } catch (e) {
        cachedClearTimeout = defaultClearTimeout;
    }
} ())
function runTimeout(fun) {
    if (cachedSetTimeout === setTimeout) {
        //normal enviroments in sane situations
        return setTimeout(fun, 0);
    }
    // if setTimeout wasn't available but was latter defined
    if ((cachedSetTimeout === defaultSetTimout || !cachedSetTimeout) && setTimeout) {
        cachedSetTimeout = setTimeout;
        return setTimeout(fun, 0);
    }
    try {
        // when when somebody has screwed with setTimeout but no I.E. maddness
        return cachedSetTimeout(fun, 0);
    } catch(e){
        try {
            // When we are in I.E. but the script has been evaled so I.E. doesn't trust the global object when called normally
            return cachedSetTimeout.call(null, fun, 0);
        } catch(e){
            // same as above but when it's a version of I.E. that must have the global object for 'this', hopfully our context correct otherwise it will throw a global error
            return cachedSetTimeout.call(this, fun, 0);
        }
    }


}
function runClearTimeout(marker) {
    if (cachedClearTimeout === clearTimeout) {
        //normal enviroments in sane situations
        return clearTimeout(marker);
    }
    // if clearTimeout wasn't available but was latter defined
    if ((cachedClearTimeout === defaultClearTimeout || !cachedClearTimeout) && clearTimeout) {
        cachedClearTimeout = clearTimeout;
        return clearTimeout(marker);
    }
    try {
        // when when somebody has screwed with setTimeout but no I.E. maddness
        return cachedClearTimeout(marker);
    } catch (e){
        try {
            // When we are in I.E. but the script has been evaled so I.E. doesn't  trust the global object when called normally
            return cachedClearTimeout.call(null, marker);
        } catch (e){
            // same as above but when it's a version of I.E. that must have the global object for 'this', hopfully our context correct otherwise it will throw a global error.
            // Some versions of I.E. have different rules for clearTimeout vs setTimeout
            return cachedClearTimeout.call(this, marker);
        }
    }



}
var queue = [];
var draining = false;
var currentQueue;
var queueIndex = -1;

function cleanUpNextTick() {
    if (!draining || !currentQueue) {
        return;
    }
    draining = false;
    if (currentQueue.length) {
        queue = currentQueue.concat(queue);
    } else {
        queueIndex = -1;
    }
    if (queue.length) {
        drainQueue();
    }
}

function drainQueue() {
    if (draining) {
        return;
    }
    var timeout = runTimeout(cleanUpNextTick);
    draining = true;

    var len = queue.length;
    while(len) {
        currentQueue = queue;
        queue = [];
        while (++queueIndex < len) {
            if (currentQueue) {
                currentQueue[queueIndex].run();
            }
        }
        queueIndex = -1;
        len = queue.length;
    }
    currentQueue = null;
    draining = false;
    runClearTimeout(timeout);
}

process.nextTick = function (fun) {
    var args = new Array(arguments.length - 1);
    if (arguments.length > 1) {
        for (var i = 1; i < arguments.length; i++) {
            args[i - 1] = arguments[i];
        }
    }
    queue.push(new Item(fun, args));
    if (queue.length === 1 && !draining) {
        runTimeout(drainQueue);
    }
};

// v8 likes predictible objects
function Item(fun, array) {
    this.fun = fun;
    this.array = array;
}
Item.prototype.run = function () {
    this.fun.apply(null, this.array);
};
process.title = 'browser';
process.browser = true;
process.env = {};
process.argv = [];
process.version = ''; // empty string to avoid regexp issues
process.versions = {};

function noop() {}

process.on = noop;
process.addListener = noop;
process.once = noop;
process.off = noop;
process.removeListener = noop;
process.removeAllListeners = noop;
process.emit = noop;
process.prependListener = noop;
process.prependOnceListener = noop;

process.listeners = function (name) { return [] }

process.binding = function (name) {
    throw new Error('process.binding is not supported');
};

process.cwd = function () { return '/' };
process.chdir = function (dir) {
    throw new Error('process.chdir is not supported');
};
process.umask = function() { return 0; };

},{}],22:[function(require,module,exports){
module.exports = require('./lib/_stream_duplex.js');

},{"./lib/_stream_duplex.js":23}],23:[function(require,module,exports){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

// a duplex stream is just a stream that is both readable and writable.
// Since JS doesn't have multiple prototypal inheritance, this class
// prototypally inherits from Readable, and then parasitically from
// Writable.

'use strict';

/*<replacement>*/

var pna = require('process-nextick-args');
/*</replacement>*/

/*<replacement>*/
var objectKeys = Object.keys || function (obj) {
  var keys = [];
  for (var key in obj) {
    keys.push(key);
  }return keys;
};
/*</replacement>*/

module.exports = Duplex;

/*<replacement>*/
var util = require('core-util-is');
util.inherits = require('inherits');
/*</replacement>*/

var Readable = require('./_stream_readable');
var Writable = require('./_stream_writable');

util.inherits(Duplex, Readable);

var keys = objectKeys(Writable.prototype);
for (var v = 0; v < keys.length; v++) {
  var method = keys[v];
  if (!Duplex.prototype[method]) Duplex.prototype[method] = Writable.prototype[method];
}

function Duplex(options) {
  if (!(this instanceof Duplex)) return new Duplex(options);

  Readable.call(this, options);
  Writable.call(this, options);

  if (options && options.readable === false) this.readable = false;

  if (options && options.writable === false) this.writable = false;

  this.allowHalfOpen = true;
  if (options && options.allowHalfOpen === false) this.allowHalfOpen = false;

  this.once('end', onend);
}

// the no-half-open enforcer
function onend() {
  // if we allow half-open state, or if the writable side ended,
  // then we're ok.
  if (this.allowHalfOpen || this._writableState.ended) return;

  // no more data can be written.
  // But allow more writes to happen in this tick.
  pna.nextTick(onEndNT, this);
}

function onEndNT(self) {
  self.end();
}

Object.defineProperty(Duplex.prototype, 'destroyed', {
  get: function () {
    if (this._readableState === undefined || this._writableState === undefined) {
      return false;
    }
    return this._readableState.destroyed && this._writableState.destroyed;
  },
  set: function (value) {
    // we ignore the value if the stream
    // has not been initialized yet
    if (this._readableState === undefined || this._writableState === undefined) {
      return;
    }

    // backward compatibility, the user is explicitly
    // managing destroyed
    this._readableState.destroyed = value;
    this._writableState.destroyed = value;
  }
});

Duplex.prototype._destroy = function (err, cb) {
  this.push(null);
  this.end();

  pna.nextTick(cb, err);
};

function forEach(xs, f) {
  for (var i = 0, l = xs.length; i < l; i++) {
    f(xs[i], i);
  }
}
},{"./_stream_readable":25,"./_stream_writable":27,"core-util-is":15,"inherits":17,"process-nextick-args":20}],24:[function(require,module,exports){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

// a passthrough stream.
// basically just the most minimal sort of Transform stream.
// Every written chunk gets output as-is.

'use strict';

module.exports = PassThrough;

var Transform = require('./_stream_transform');

/*<replacement>*/
var util = require('core-util-is');
util.inherits = require('inherits');
/*</replacement>*/

util.inherits(PassThrough, Transform);

function PassThrough(options) {
  if (!(this instanceof PassThrough)) return new PassThrough(options);

  Transform.call(this, options);
}

PassThrough.prototype._transform = function (chunk, encoding, cb) {
  cb(null, chunk);
};
},{"./_stream_transform":26,"core-util-is":15,"inherits":17}],25:[function(require,module,exports){
(function (process,global){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

'use strict';

/*<replacement>*/

var pna = require('process-nextick-args');
/*</replacement>*/

module.exports = Readable;

/*<replacement>*/
var isArray = require('isarray');
/*</replacement>*/

/*<replacement>*/
var Duplex;
/*</replacement>*/

Readable.ReadableState = ReadableState;

/*<replacement>*/
var EE = require('events').EventEmitter;

var EElistenerCount = function (emitter, type) {
  return emitter.listeners(type).length;
};
/*</replacement>*/

/*<replacement>*/
var Stream = require('./internal/streams/stream');
/*</replacement>*/

/*<replacement>*/

var Buffer = require('safe-buffer').Buffer;
var OurUint8Array = global.Uint8Array || function () {};
function _uint8ArrayToBuffer(chunk) {
  return Buffer.from(chunk);
}
function _isUint8Array(obj) {
  return Buffer.isBuffer(obj) || obj instanceof OurUint8Array;
}

/*</replacement>*/

/*<replacement>*/
var util = require('core-util-is');
util.inherits = require('inherits');
/*</replacement>*/

/*<replacement>*/
var debugUtil = require('util');
var debug = void 0;
if (debugUtil && debugUtil.debuglog) {
  debug = debugUtil.debuglog('stream');
} else {
  debug = function () {};
}
/*</replacement>*/

var BufferList = require('./internal/streams/BufferList');
var destroyImpl = require('./internal/streams/destroy');
var StringDecoder;

util.inherits(Readable, Stream);

var kProxyEvents = ['error', 'close', 'destroy', 'pause', 'resume'];

function prependListener(emitter, event, fn) {
  // Sadly this is not cacheable as some libraries bundle their own
  // event emitter implementation with them.
  if (typeof emitter.prependListener === 'function') return emitter.prependListener(event, fn);

  // This is a hack to make sure that our error handler is attached before any
  // userland ones.  NEVER DO THIS. This is here only because this code needs
  // to continue to work with older versions of Node.js that do not include
  // the prependListener() method. The goal is to eventually remove this hack.
  if (!emitter._events || !emitter._events[event]) emitter.on(event, fn);else if (isArray(emitter._events[event])) emitter._events[event].unshift(fn);else emitter._events[event] = [fn, emitter._events[event]];
}

function ReadableState(options, stream) {
  Duplex = Duplex || require('./_stream_duplex');

  options = options || {};

  // Duplex streams are both readable and writable, but share
  // the same options object.
  // However, some cases require setting options to different
  // values for the readable and the writable sides of the duplex stream.
  // These options can be provided separately as readableXXX and writableXXX.
  var isDuplex = stream instanceof Duplex;

  // object stream flag. Used to make read(n) ignore n and to
  // make all the buffer merging and length checks go away
  this.objectMode = !!options.objectMode;

  if (isDuplex) this.objectMode = this.objectMode || !!options.readableObjectMode;

  // the point at which it stops calling _read() to fill the buffer
  // Note: 0 is a valid value, means "don't call _read preemptively ever"
  var hwm = options.highWaterMark;
  var readableHwm = options.readableHighWaterMark;
  var defaultHwm = this.objectMode ? 16 : 16 * 1024;

  if (hwm || hwm === 0) this.highWaterMark = hwm;else if (isDuplex && (readableHwm || readableHwm === 0)) this.highWaterMark = readableHwm;else this.highWaterMark = defaultHwm;

  // cast to ints.
  this.highWaterMark = Math.floor(this.highWaterMark);

  // A linked list is used to store data chunks instead of an array because the
  // linked list can remove elements from the beginning faster than
  // array.shift()
  this.buffer = new BufferList();
  this.length = 0;
  this.pipes = null;
  this.pipesCount = 0;
  this.flowing = null;
  this.ended = false;
  this.endEmitted = false;
  this.reading = false;

  // a flag to be able to tell if the event 'readable'/'data' is emitted
  // immediately, or on a later tick.  We set this to true at first, because
  // any actions that shouldn't happen until "later" should generally also
  // not happen before the first read call.
  this.sync = true;

  // whenever we return null, then we set a flag to say
  // that we're awaiting a 'readable' event emission.
  this.needReadable = false;
  this.emittedReadable = false;
  this.readableListening = false;
  this.resumeScheduled = false;

  // has it been destroyed
  this.destroyed = false;

  // Crypto is kind of old and crusty.  Historically, its default string
  // encoding is 'binary' so we have to make this configurable.
  // Everything else in the universe uses 'utf8', though.
  this.defaultEncoding = options.defaultEncoding || 'utf8';

  // the number of writers that are awaiting a drain event in .pipe()s
  this.awaitDrain = 0;

  // if true, a maybeReadMore has been scheduled
  this.readingMore = false;

  this.decoder = null;
  this.encoding = null;
  if (options.encoding) {
    if (!StringDecoder) StringDecoder = require('string_decoder/').StringDecoder;
    this.decoder = new StringDecoder(options.encoding);
    this.encoding = options.encoding;
  }
}

function Readable(options) {
  Duplex = Duplex || require('./_stream_duplex');

  if (!(this instanceof Readable)) return new Readable(options);

  this._readableState = new ReadableState(options, this);

  // legacy
  this.readable = true;

  if (options) {
    if (typeof options.read === 'function') this._read = options.read;

    if (typeof options.destroy === 'function') this._destroy = options.destroy;
  }

  Stream.call(this);
}

Object.defineProperty(Readable.prototype, 'destroyed', {
  get: function () {
    if (this._readableState === undefined) {
      return false;
    }
    return this._readableState.destroyed;
  },
  set: function (value) {
    // we ignore the value if the stream
    // has not been initialized yet
    if (!this._readableState) {
      return;
    }

    // backward compatibility, the user is explicitly
    // managing destroyed
    this._readableState.destroyed = value;
  }
});

Readable.prototype.destroy = destroyImpl.destroy;
Readable.prototype._undestroy = destroyImpl.undestroy;
Readable.prototype._destroy = function (err, cb) {
  this.push(null);
  cb(err);
};

// Manually shove something into the read() buffer.
// This returns true if the highWaterMark has not been hit yet,
// similar to how Writable.write() returns true if you should
// write() some more.
Readable.prototype.push = function (chunk, encoding) {
  var state = this._readableState;
  var skipChunkCheck;

  if (!state.objectMode) {
    if (typeof chunk === 'string') {
      encoding = encoding || state.defaultEncoding;
      if (encoding !== state.encoding) {
        chunk = Buffer.from(chunk, encoding);
        encoding = '';
      }
      skipChunkCheck = true;
    }
  } else {
    skipChunkCheck = true;
  }

  return readableAddChunk(this, chunk, encoding, false, skipChunkCheck);
};

// Unshift should *always* be something directly out of read()
Readable.prototype.unshift = function (chunk) {
  return readableAddChunk(this, chunk, null, true, false);
};

function readableAddChunk(stream, chunk, encoding, addToFront, skipChunkCheck) {
  var state = stream._readableState;
  if (chunk === null) {
    state.reading = false;
    onEofChunk(stream, state);
  } else {
    var er;
    if (!skipChunkCheck) er = chunkInvalid(state, chunk);
    if (er) {
      stream.emit('error', er);
    } else if (state.objectMode || chunk && chunk.length > 0) {
      if (typeof chunk !== 'string' && !state.objectMode && Object.getPrototypeOf(chunk) !== Buffer.prototype) {
        chunk = _uint8ArrayToBuffer(chunk);
      }

      if (addToFront) {
        if (state.endEmitted) stream.emit('error', new Error('stream.unshift() after end event'));else addChunk(stream, state, chunk, true);
      } else if (state.ended) {
        stream.emit('error', new Error('stream.push() after EOF'));
      } else {
        state.reading = false;
        if (state.decoder && !encoding) {
          chunk = state.decoder.write(chunk);
          if (state.objectMode || chunk.length !== 0) addChunk(stream, state, chunk, false);else maybeReadMore(stream, state);
        } else {
          addChunk(stream, state, chunk, false);
        }
      }
    } else if (!addToFront) {
      state.reading = false;
    }
  }

  return needMoreData(state);
}

function addChunk(stream, state, chunk, addToFront) {
  if (state.flowing && state.length === 0 && !state.sync) {
    stream.emit('data', chunk);
    stream.read(0);
  } else {
    // update the buffer info.
    state.length += state.objectMode ? 1 : chunk.length;
    if (addToFront) state.buffer.unshift(chunk);else state.buffer.push(chunk);

    if (state.needReadable) emitReadable(stream);
  }
  maybeReadMore(stream, state);
}

function chunkInvalid(state, chunk) {
  var er;
  if (!_isUint8Array(chunk) && typeof chunk !== 'string' && chunk !== undefined && !state.objectMode) {
    er = new TypeError('Invalid non-string/buffer chunk');
  }
  return er;
}

// if it's past the high water mark, we can push in some more.
// Also, if we have no data yet, we can stand some
// more bytes.  This is to work around cases where hwm=0,
// such as the repl.  Also, if the push() triggered a
// readable event, and the user called read(largeNumber) such that
// needReadable was set, then we ought to push more, so that another
// 'readable' event will be triggered.
function needMoreData(state) {
  return !state.ended && (state.needReadable || state.length < state.highWaterMark || state.length === 0);
}

Readable.prototype.isPaused = function () {
  return this._readableState.flowing === false;
};

// backwards compatibility.
Readable.prototype.setEncoding = function (enc) {
  if (!StringDecoder) StringDecoder = require('string_decoder/').StringDecoder;
  this._readableState.decoder = new StringDecoder(enc);
  this._readableState.encoding = enc;
  return this;
};

// Don't raise the hwm > 8MB
var MAX_HWM = 0x800000;
function computeNewHighWaterMark(n) {
  if (n >= MAX_HWM) {
    n = MAX_HWM;
  } else {
    // Get the next highest power of 2 to prevent increasing hwm excessively in
    // tiny amounts
    n--;
    n |= n >>> 1;
    n |= n >>> 2;
    n |= n >>> 4;
    n |= n >>> 8;
    n |= n >>> 16;
    n++;
  }
  return n;
}

// This function is designed to be inlinable, so please take care when making
// changes to the function body.
function howMuchToRead(n, state) {
  if (n <= 0 || state.length === 0 && state.ended) return 0;
  if (state.objectMode) return 1;
  if (n !== n) {
    // Only flow one buffer at a time
    if (state.flowing && state.length) return state.buffer.head.data.length;else return state.length;
  }
  // If we're asking for more than the current hwm, then raise the hwm.
  if (n > state.highWaterMark) state.highWaterMark = computeNewHighWaterMark(n);
  if (n <= state.length) return n;
  // Don't have enough
  if (!state.ended) {
    state.needReadable = true;
    return 0;
  }
  return state.length;
}

// you can override either this method, or the async _read(n) below.
Readable.prototype.read = function (n) {
  debug('read', n);
  n = parseInt(n, 10);
  var state = this._readableState;
  var nOrig = n;

  if (n !== 0) state.emittedReadable = false;

  // if we're doing read(0) to trigger a readable event, but we
  // already have a bunch of data in the buffer, then just trigger
  // the 'readable' event and move on.
  if (n === 0 && state.needReadable && (state.length >= state.highWaterMark || state.ended)) {
    debug('read: emitReadable', state.length, state.ended);
    if (state.length === 0 && state.ended) endReadable(this);else emitReadable(this);
    return null;
  }

  n = howMuchToRead(n, state);

  // if we've ended, and we're now clear, then finish it up.
  if (n === 0 && state.ended) {
    if (state.length === 0) endReadable(this);
    return null;
  }

  // All the actual chunk generation logic needs to be
  // *below* the call to _read.  The reason is that in certain
  // synthetic stream cases, such as passthrough streams, _read
  // may be a completely synchronous operation which may change
  // the state of the read buffer, providing enough data when
  // before there was *not* enough.
  //
  // So, the steps are:
  // 1. Figure out what the state of things will be after we do
  // a read from the buffer.
  //
  // 2. If that resulting state will trigger a _read, then call _read.
  // Note that this may be asynchronous, or synchronous.  Yes, it is
  // deeply ugly to write APIs this way, but that still doesn't mean
  // that the Readable class should behave improperly, as streams are
  // designed to be sync/async agnostic.
  // Take note if the _read call is sync or async (ie, if the read call
  // has returned yet), so that we know whether or not it's safe to emit
  // 'readable' etc.
  //
  // 3. Actually pull the requested chunks out of the buffer and return.

  // if we need a readable event, then we need to do some reading.
  var doRead = state.needReadable;
  debug('need readable', doRead);

  // if we currently have less than the highWaterMark, then also read some
  if (state.length === 0 || state.length - n < state.highWaterMark) {
    doRead = true;
    debug('length less than watermark', doRead);
  }

  // however, if we've ended, then there's no point, and if we're already
  // reading, then it's unnecessary.
  if (state.ended || state.reading) {
    doRead = false;
    debug('reading or ended', doRead);
  } else if (doRead) {
    debug('do read');
    state.reading = true;
    state.sync = true;
    // if the length is currently zero, then we *need* a readable event.
    if (state.length === 0) state.needReadable = true;
    // call internal read method
    this._read(state.highWaterMark);
    state.sync = false;
    // If _read pushed data synchronously, then `reading` will be false,
    // and we need to re-evaluate how much data we can return to the user.
    if (!state.reading) n = howMuchToRead(nOrig, state);
  }

  var ret;
  if (n > 0) ret = fromList(n, state);else ret = null;

  if (ret === null) {
    state.needReadable = true;
    n = 0;
  } else {
    state.length -= n;
  }

  if (state.length === 0) {
    // If we have nothing in the buffer, then we want to know
    // as soon as we *do* get something into the buffer.
    if (!state.ended) state.needReadable = true;

    // If we tried to read() past the EOF, then emit end on the next tick.
    if (nOrig !== n && state.ended) endReadable(this);
  }

  if (ret !== null) this.emit('data', ret);

  return ret;
};

function onEofChunk(stream, state) {
  if (state.ended) return;
  if (state.decoder) {
    var chunk = state.decoder.end();
    if (chunk && chunk.length) {
      state.buffer.push(chunk);
      state.length += state.objectMode ? 1 : chunk.length;
    }
  }
  state.ended = true;

  // emit 'readable' now to make sure it gets picked up.
  emitReadable(stream);
}

// Don't emit readable right away in sync mode, because this can trigger
// another read() call => stack overflow.  This way, it might trigger
// a nextTick recursion warning, but that's not so bad.
function emitReadable(stream) {
  var state = stream._readableState;
  state.needReadable = false;
  if (!state.emittedReadable) {
    debug('emitReadable', state.flowing);
    state.emittedReadable = true;
    if (state.sync) pna.nextTick(emitReadable_, stream);else emitReadable_(stream);
  }
}

function emitReadable_(stream) {
  debug('emit readable');
  stream.emit('readable');
  flow(stream);
}

// at this point, the user has presumably seen the 'readable' event,
// and called read() to consume some data.  that may have triggered
// in turn another _read(n) call, in which case reading = true if
// it's in progress.
// However, if we're not ended, or reading, and the length < hwm,
// then go ahead and try to read some more preemptively.
function maybeReadMore(stream, state) {
  if (!state.readingMore) {
    state.readingMore = true;
    pna.nextTick(maybeReadMore_, stream, state);
  }
}

function maybeReadMore_(stream, state) {
  var len = state.length;
  while (!state.reading && !state.flowing && !state.ended && state.length < state.highWaterMark) {
    debug('maybeReadMore read 0');
    stream.read(0);
    if (len === state.length)
      // didn't get any data, stop spinning.
      break;else len = state.length;
  }
  state.readingMore = false;
}

// abstract method.  to be overridden in specific implementation classes.
// call cb(er, data) where data is <= n in length.
// for virtual (non-string, non-buffer) streams, "length" is somewhat
// arbitrary, and perhaps not very meaningful.
Readable.prototype._read = function (n) {
  this.emit('error', new Error('_read() is not implemented'));
};

Readable.prototype.pipe = function (dest, pipeOpts) {
  var src = this;
  var state = this._readableState;

  switch (state.pipesCount) {
    case 0:
      state.pipes = dest;
      break;
    case 1:
      state.pipes = [state.pipes, dest];
      break;
    default:
      state.pipes.push(dest);
      break;
  }
  state.pipesCount += 1;
  debug('pipe count=%d opts=%j', state.pipesCount, pipeOpts);

  var doEnd = (!pipeOpts || pipeOpts.end !== false) && dest !== process.stdout && dest !== process.stderr;

  var endFn = doEnd ? onend : unpipe;
  if (state.endEmitted) pna.nextTick(endFn);else src.once('end', endFn);

  dest.on('unpipe', onunpipe);
  function onunpipe(readable, unpipeInfo) {
    debug('onunpipe');
    if (readable === src) {
      if (unpipeInfo && unpipeInfo.hasUnpiped === false) {
        unpipeInfo.hasUnpiped = true;
        cleanup();
      }
    }
  }

  function onend() {
    debug('onend');
    dest.end();
  }

  // when the dest drains, it reduces the awaitDrain counter
  // on the source.  This would be more elegant with a .once()
  // handler in flow(), but adding and removing repeatedly is
  // too slow.
  var ondrain = pipeOnDrain(src);
  dest.on('drain', ondrain);

  var cleanedUp = false;
  function cleanup() {
    debug('cleanup');
    // cleanup event handlers once the pipe is broken
    dest.removeListener('close', onclose);
    dest.removeListener('finish', onfinish);
    dest.removeListener('drain', ondrain);
    dest.removeListener('error', onerror);
    dest.removeListener('unpipe', onunpipe);
    src.removeListener('end', onend);
    src.removeListener('end', unpipe);
    src.removeListener('data', ondata);

    cleanedUp = true;

    // if the reader is waiting for a drain event from this
    // specific writer, then it would cause it to never start
    // flowing again.
    // So, if this is awaiting a drain, then we just call it now.
    // If we don't know, then assume that we are waiting for one.
    if (state.awaitDrain && (!dest._writableState || dest._writableState.needDrain)) ondrain();
  }

  // If the user pushes more data while we're writing to dest then we'll end up
  // in ondata again. However, we only want to increase awaitDrain once because
  // dest will only emit one 'drain' event for the multiple writes.
  // => Introduce a guard on increasing awaitDrain.
  var increasedAwaitDrain = false;
  src.on('data', ondata);
  function ondata(chunk) {
    debug('ondata');
    increasedAwaitDrain = false;
    var ret = dest.write(chunk);
    if (false === ret && !increasedAwaitDrain) {
      // If the user unpiped during `dest.write()`, it is possible
      // to get stuck in a permanently paused state if that write
      // also returned false.
      // => Check whether `dest` is still a piping destination.
      if ((state.pipesCount === 1 && state.pipes === dest || state.pipesCount > 1 && indexOf(state.pipes, dest) !== -1) && !cleanedUp) {
        debug('false write response, pause', src._readableState.awaitDrain);
        src._readableState.awaitDrain++;
        increasedAwaitDrain = true;
      }
      src.pause();
    }
  }

  // if the dest has an error, then stop piping into it.
  // however, don't suppress the throwing behavior for this.
  function onerror(er) {
    debug('onerror', er);
    unpipe();
    dest.removeListener('error', onerror);
    if (EElistenerCount(dest, 'error') === 0) dest.emit('error', er);
  }

  // Make sure our error handler is attached before userland ones.
  prependListener(dest, 'error', onerror);

  // Both close and finish should trigger unpipe, but only once.
  function onclose() {
    dest.removeListener('finish', onfinish);
    unpipe();
  }
  dest.once('close', onclose);
  function onfinish() {
    debug('onfinish');
    dest.removeListener('close', onclose);
    unpipe();
  }
  dest.once('finish', onfinish);

  function unpipe() {
    debug('unpipe');
    src.unpipe(dest);
  }

  // tell the dest that it's being piped to
  dest.emit('pipe', src);

  // start the flow if it hasn't been started already.
  if (!state.flowing) {
    debug('pipe resume');
    src.resume();
  }

  return dest;
};

function pipeOnDrain(src) {
  return function () {
    var state = src._readableState;
    debug('pipeOnDrain', state.awaitDrain);
    if (state.awaitDrain) state.awaitDrain--;
    if (state.awaitDrain === 0 && EElistenerCount(src, 'data')) {
      state.flowing = true;
      flow(src);
    }
  };
}

Readable.prototype.unpipe = function (dest) {
  var state = this._readableState;
  var unpipeInfo = { hasUnpiped: false };

  // if we're not piping anywhere, then do nothing.
  if (state.pipesCount === 0) return this;

  // just one destination.  most common case.
  if (state.pipesCount === 1) {
    // passed in one, but it's not the right one.
    if (dest && dest !== state.pipes) return this;

    if (!dest) dest = state.pipes;

    // got a match.
    state.pipes = null;
    state.pipesCount = 0;
    state.flowing = false;
    if (dest) dest.emit('unpipe', this, unpipeInfo);
    return this;
  }

  // slow case. multiple pipe destinations.

  if (!dest) {
    // remove all.
    var dests = state.pipes;
    var len = state.pipesCount;
    state.pipes = null;
    state.pipesCount = 0;
    state.flowing = false;

    for (var i = 0; i < len; i++) {
      dests[i].emit('unpipe', this, unpipeInfo);
    }return this;
  }

  // try to find the right one.
  var index = indexOf(state.pipes, dest);
  if (index === -1) return this;

  state.pipes.splice(index, 1);
  state.pipesCount -= 1;
  if (state.pipesCount === 1) state.pipes = state.pipes[0];

  dest.emit('unpipe', this, unpipeInfo);

  return this;
};

// set up data events if they are asked for
// Ensure readable listeners eventually get something
Readable.prototype.on = function (ev, fn) {
  var res = Stream.prototype.on.call(this, ev, fn);

  if (ev === 'data') {
    // Start flowing on next tick if stream isn't explicitly paused
    if (this._readableState.flowing !== false) this.resume();
  } else if (ev === 'readable') {
    var state = this._readableState;
    if (!state.endEmitted && !state.readableListening) {
      state.readableListening = state.needReadable = true;
      state.emittedReadable = false;
      if (!state.reading) {
        pna.nextTick(nReadingNextTick, this);
      } else if (state.length) {
        emitReadable(this);
      }
    }
  }

  return res;
};
Readable.prototype.addListener = Readable.prototype.on;

function nReadingNextTick(self) {
  debug('readable nexttick read 0');
  self.read(0);
}

// pause() and resume() are remnants of the legacy readable stream API
// If the user uses them, then switch into old mode.
Readable.prototype.resume = function () {
  var state = this._readableState;
  if (!state.flowing) {
    debug('resume');
    state.flowing = true;
    resume(this, state);
  }
  return this;
};

function resume(stream, state) {
  if (!state.resumeScheduled) {
    state.resumeScheduled = true;
    pna.nextTick(resume_, stream, state);
  }
}

function resume_(stream, state) {
  if (!state.reading) {
    debug('resume read 0');
    stream.read(0);
  }

  state.resumeScheduled = false;
  state.awaitDrain = 0;
  stream.emit('resume');
  flow(stream);
  if (state.flowing && !state.reading) stream.read(0);
}

Readable.prototype.pause = function () {
  debug('call pause flowing=%j', this._readableState.flowing);
  if (false !== this._readableState.flowing) {
    debug('pause');
    this._readableState.flowing = false;
    this.emit('pause');
  }
  return this;
};

function flow(stream) {
  var state = stream._readableState;
  debug('flow', state.flowing);
  while (state.flowing && stream.read() !== null) {}
}

// wrap an old-style stream as the async data source.
// This is *not* part of the readable stream interface.
// It is an ugly unfortunate mess of history.
Readable.prototype.wrap = function (stream) {
  var _this = this;

  var state = this._readableState;
  var paused = false;

  stream.on('end', function () {
    debug('wrapped end');
    if (state.decoder && !state.ended) {
      var chunk = state.decoder.end();
      if (chunk && chunk.length) _this.push(chunk);
    }

    _this.push(null);
  });

  stream.on('data', function (chunk) {
    debug('wrapped data');
    if (state.decoder) chunk = state.decoder.write(chunk);

    // don't skip over falsy values in objectMode
    if (state.objectMode && (chunk === null || chunk === undefined)) return;else if (!state.objectMode && (!chunk || !chunk.length)) return;

    var ret = _this.push(chunk);
    if (!ret) {
      paused = true;
      stream.pause();
    }
  });

  // proxy all the other methods.
  // important when wrapping filters and duplexes.
  for (var i in stream) {
    if (this[i] === undefined && typeof stream[i] === 'function') {
      this[i] = function (method) {
        return function () {
          return stream[method].apply(stream, arguments);
        };
      }(i);
    }
  }

  // proxy certain important events.
  for (var n = 0; n < kProxyEvents.length; n++) {
    stream.on(kProxyEvents[n], this.emit.bind(this, kProxyEvents[n]));
  }

  // when we try to consume some more bytes, simply unpause the
  // underlying stream.
  this._read = function (n) {
    debug('wrapped _read', n);
    if (paused) {
      paused = false;
      stream.resume();
    }
  };

  return this;
};

// exposed for testing purposes only.
Readable._fromList = fromList;

// Pluck off n bytes from an array of buffers.
// Length is the combined lengths of all the buffers in the list.
// This function is designed to be inlinable, so please take care when making
// changes to the function body.
function fromList(n, state) {
  // nothing buffered
  if (state.length === 0) return null;

  var ret;
  if (state.objectMode) ret = state.buffer.shift();else if (!n || n >= state.length) {
    // read it all, truncate the list
    if (state.decoder) ret = state.buffer.join('');else if (state.buffer.length === 1) ret = state.buffer.head.data;else ret = state.buffer.concat(state.length);
    state.buffer.clear();
  } else {
    // read part of list
    ret = fromListPartial(n, state.buffer, state.decoder);
  }

  return ret;
}

// Extracts only enough buffered data to satisfy the amount requested.
// This function is designed to be inlinable, so please take care when making
// changes to the function body.
function fromListPartial(n, list, hasStrings) {
  var ret;
  if (n < list.head.data.length) {
    // slice is the same for buffers and strings
    ret = list.head.data.slice(0, n);
    list.head.data = list.head.data.slice(n);
  } else if (n === list.head.data.length) {
    // first chunk is a perfect match
    ret = list.shift();
  } else {
    // result spans more than one buffer
    ret = hasStrings ? copyFromBufferString(n, list) : copyFromBuffer(n, list);
  }
  return ret;
}

// Copies a specified amount of characters from the list of buffered data
// chunks.
// This function is designed to be inlinable, so please take care when making
// changes to the function body.
function copyFromBufferString(n, list) {
  var p = list.head;
  var c = 1;
  var ret = p.data;
  n -= ret.length;
  while (p = p.next) {
    var str = p.data;
    var nb = n > str.length ? str.length : n;
    if (nb === str.length) ret += str;else ret += str.slice(0, n);
    n -= nb;
    if (n === 0) {
      if (nb === str.length) {
        ++c;
        if (p.next) list.head = p.next;else list.head = list.tail = null;
      } else {
        list.head = p;
        p.data = str.slice(nb);
      }
      break;
    }
    ++c;
  }
  list.length -= c;
  return ret;
}

// Copies a specified amount of bytes from the list of buffered data chunks.
// This function is designed to be inlinable, so please take care when making
// changes to the function body.
function copyFromBuffer(n, list) {
  var ret = Buffer.allocUnsafe(n);
  var p = list.head;
  var c = 1;
  p.data.copy(ret);
  n -= p.data.length;
  while (p = p.next) {
    var buf = p.data;
    var nb = n > buf.length ? buf.length : n;
    buf.copy(ret, ret.length - n, 0, nb);
    n -= nb;
    if (n === 0) {
      if (nb === buf.length) {
        ++c;
        if (p.next) list.head = p.next;else list.head = list.tail = null;
      } else {
        list.head = p;
        p.data = buf.slice(nb);
      }
      break;
    }
    ++c;
  }
  list.length -= c;
  return ret;
}

function endReadable(stream) {
  var state = stream._readableState;

  // If we get here before consuming all the bytes, then that is a
  // bug in node.  Should never happen.
  if (state.length > 0) throw new Error('"endReadable()" called on non-empty stream');

  if (!state.endEmitted) {
    state.ended = true;
    pna.nextTick(endReadableNT, state, stream);
  }
}

function endReadableNT(state, stream) {
  // Check that we didn't get one last unshift.
  if (!state.endEmitted && state.length === 0) {
    state.endEmitted = true;
    stream.readable = false;
    stream.emit('end');
  }
}

function forEach(xs, f) {
  for (var i = 0, l = xs.length; i < l; i++) {
    f(xs[i], i);
  }
}

function indexOf(xs, x) {
  for (var i = 0, l = xs.length; i < l; i++) {
    if (xs[i] === x) return i;
  }
  return -1;
}
}).call(this,require('_process'),typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{"./_stream_duplex":23,"./internal/streams/BufferList":28,"./internal/streams/destroy":29,"./internal/streams/stream":30,"_process":21,"core-util-is":15,"events":12,"inherits":17,"isarray":19,"process-nextick-args":20,"safe-buffer":36,"string_decoder/":31,"util":11}],26:[function(require,module,exports){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

// a transform stream is a readable/writable stream where you do
// something with the data.  Sometimes it's called a "filter",
// but that's not a great name for it, since that implies a thing where
// some bits pass through, and others are simply ignored.  (That would
// be a valid example of a transform, of course.)
//
// While the output is causally related to the input, it's not a
// necessarily symmetric or synchronous transformation.  For example,
// a zlib stream might take multiple plain-text writes(), and then
// emit a single compressed chunk some time in the future.
//
// Here's how this works:
//
// The Transform stream has all the aspects of the readable and writable
// stream classes.  When you write(chunk), that calls _write(chunk,cb)
// internally, and returns false if there's a lot of pending writes
// buffered up.  When you call read(), that calls _read(n) until
// there's enough pending readable data buffered up.
//
// In a transform stream, the written data is placed in a buffer.  When
// _read(n) is called, it transforms the queued up data, calling the
// buffered _write cb's as it consumes chunks.  If consuming a single
// written chunk would result in multiple output chunks, then the first
// outputted bit calls the readcb, and subsequent chunks just go into
// the read buffer, and will cause it to emit 'readable' if necessary.
//
// This way, back-pressure is actually determined by the reading side,
// since _read has to be called to start processing a new chunk.  However,
// a pathological inflate type of transform can cause excessive buffering
// here.  For example, imagine a stream where every byte of input is
// interpreted as an integer from 0-255, and then results in that many
// bytes of output.  Writing the 4 bytes {ff,ff,ff,ff} would result in
// 1kb of data being output.  In this case, you could write a very small
// amount of input, and end up with a very large amount of output.  In
// such a pathological inflating mechanism, there'd be no way to tell
// the system to stop doing the transform.  A single 4MB write could
// cause the system to run out of memory.
//
// However, even in such a pathological case, only a single written chunk
// would be consumed, and then the rest would wait (un-transformed) until
// the results of the previous transformed chunk were consumed.

'use strict';

module.exports = Transform;

var Duplex = require('./_stream_duplex');

/*<replacement>*/
var util = require('core-util-is');
util.inherits = require('inherits');
/*</replacement>*/

util.inherits(Transform, Duplex);

function afterTransform(er, data) {
  var ts = this._transformState;
  ts.transforming = false;

  var cb = ts.writecb;

  if (!cb) {
    return this.emit('error', new Error('write callback called multiple times'));
  }

  ts.writechunk = null;
  ts.writecb = null;

  if (data != null) // single equals check for both `null` and `undefined`
    this.push(data);

  cb(er);

  var rs = this._readableState;
  rs.reading = false;
  if (rs.needReadable || rs.length < rs.highWaterMark) {
    this._read(rs.highWaterMark);
  }
}

function Transform(options) {
  if (!(this instanceof Transform)) return new Transform(options);

  Duplex.call(this, options);

  this._transformState = {
    afterTransform: afterTransform.bind(this),
    needTransform: false,
    transforming: false,
    writecb: null,
    writechunk: null,
    writeencoding: null
  };

  // start out asking for a readable event once data is transformed.
  this._readableState.needReadable = true;

  // we have implemented the _read method, and done the other things
  // that Readable wants before the first _read call, so unset the
  // sync guard flag.
  this._readableState.sync = false;

  if (options) {
    if (typeof options.transform === 'function') this._transform = options.transform;

    if (typeof options.flush === 'function') this._flush = options.flush;
  }

  // When the writable side finishes, then flush out anything remaining.
  this.on('prefinish', prefinish);
}

function prefinish() {
  var _this = this;

  if (typeof this._flush === 'function') {
    this._flush(function (er, data) {
      done(_this, er, data);
    });
  } else {
    done(this, null, null);
  }
}

Transform.prototype.push = function (chunk, encoding) {
  this._transformState.needTransform = false;
  return Duplex.prototype.push.call(this, chunk, encoding);
};

// This is the part where you do stuff!
// override this function in implementation classes.
// 'chunk' is an input chunk.
//
// Call `push(newChunk)` to pass along transformed output
// to the readable side.  You may call 'push' zero or more times.
//
// Call `cb(err)` when you are done with this chunk.  If you pass
// an error, then that'll put the hurt on the whole operation.  If you
// never call cb(), then you'll never get another chunk.
Transform.prototype._transform = function (chunk, encoding, cb) {
  throw new Error('_transform() is not implemented');
};

Transform.prototype._write = function (chunk, encoding, cb) {
  var ts = this._transformState;
  ts.writecb = cb;
  ts.writechunk = chunk;
  ts.writeencoding = encoding;
  if (!ts.transforming) {
    var rs = this._readableState;
    if (ts.needTransform || rs.needReadable || rs.length < rs.highWaterMark) this._read(rs.highWaterMark);
  }
};

// Doesn't matter what the args are here.
// _transform does all the work.
// That we got here means that the readable side wants more data.
Transform.prototype._read = function (n) {
  var ts = this._transformState;

  if (ts.writechunk !== null && ts.writecb && !ts.transforming) {
    ts.transforming = true;
    this._transform(ts.writechunk, ts.writeencoding, ts.afterTransform);
  } else {
    // mark that we need a transform, so that any data that comes in
    // will get processed, now that we've asked for it.
    ts.needTransform = true;
  }
};

Transform.prototype._destroy = function (err, cb) {
  var _this2 = this;

  Duplex.prototype._destroy.call(this, err, function (err2) {
    cb(err2);
    _this2.emit('close');
  });
};

function done(stream, er, data) {
  if (er) return stream.emit('error', er);

  if (data != null) // single equals check for both `null` and `undefined`
    stream.push(data);

  // if there's nothing in the write buffer, then that means
  // that nothing more will ever be provided
  if (stream._writableState.length) throw new Error('Calling transform done when ws.length != 0');

  if (stream._transformState.transforming) throw new Error('Calling transform done when still transforming');

  return stream.push(null);
}
},{"./_stream_duplex":23,"core-util-is":15,"inherits":17}],27:[function(require,module,exports){
(function (process,global){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

// A bit simpler than readable streams.
// Implement an async ._write(chunk, encoding, cb), and it'll handle all
// the drain event emission and buffering.

'use strict';

/*<replacement>*/

var pna = require('process-nextick-args');
/*</replacement>*/

module.exports = Writable;

/* <replacement> */
function WriteReq(chunk, encoding, cb) {
  this.chunk = chunk;
  this.encoding = encoding;
  this.callback = cb;
  this.next = null;
}

// It seems a linked list but it is not
// there will be only 2 of these for each stream
function CorkedRequest(state) {
  var _this = this;

  this.next = null;
  this.entry = null;
  this.finish = function () {
    onCorkedFinish(_this, state);
  };
}
/* </replacement> */

/*<replacement>*/
var asyncWrite = !process.browser && ['v0.10', 'v0.9.'].indexOf(process.version.slice(0, 5)) > -1 ? setImmediate : pna.nextTick;
/*</replacement>*/

/*<replacement>*/
var Duplex;
/*</replacement>*/

Writable.WritableState = WritableState;

/*<replacement>*/
var util = require('core-util-is');
util.inherits = require('inherits');
/*</replacement>*/

/*<replacement>*/
var internalUtil = {
  deprecate: require('util-deprecate')
};
/*</replacement>*/

/*<replacement>*/
var Stream = require('./internal/streams/stream');
/*</replacement>*/

/*<replacement>*/

var Buffer = require('safe-buffer').Buffer;
var OurUint8Array = global.Uint8Array || function () {};
function _uint8ArrayToBuffer(chunk) {
  return Buffer.from(chunk);
}
function _isUint8Array(obj) {
  return Buffer.isBuffer(obj) || obj instanceof OurUint8Array;
}

/*</replacement>*/

var destroyImpl = require('./internal/streams/destroy');

util.inherits(Writable, Stream);

function nop() {}

function WritableState(options, stream) {
  Duplex = Duplex || require('./_stream_duplex');

  options = options || {};

  // Duplex streams are both readable and writable, but share
  // the same options object.
  // However, some cases require setting options to different
  // values for the readable and the writable sides of the duplex stream.
  // These options can be provided separately as readableXXX and writableXXX.
  var isDuplex = stream instanceof Duplex;

  // object stream flag to indicate whether or not this stream
  // contains buffers or objects.
  this.objectMode = !!options.objectMode;

  if (isDuplex) this.objectMode = this.objectMode || !!options.writableObjectMode;

  // the point at which write() starts returning false
  // Note: 0 is a valid value, means that we always return false if
  // the entire buffer is not flushed immediately on write()
  var hwm = options.highWaterMark;
  var writableHwm = options.writableHighWaterMark;
  var defaultHwm = this.objectMode ? 16 : 16 * 1024;

  if (hwm || hwm === 0) this.highWaterMark = hwm;else if (isDuplex && (writableHwm || writableHwm === 0)) this.highWaterMark = writableHwm;else this.highWaterMark = defaultHwm;

  // cast to ints.
  this.highWaterMark = Math.floor(this.highWaterMark);

  // if _final has been called
  this.finalCalled = false;

  // drain event flag.
  this.needDrain = false;
  // at the start of calling end()
  this.ending = false;
  // when end() has been called, and returned
  this.ended = false;
  // when 'finish' is emitted
  this.finished = false;

  // has it been destroyed
  this.destroyed = false;

  // should we decode strings into buffers before passing to _write?
  // this is here so that some node-core streams can optimize string
  // handling at a lower level.
  var noDecode = options.decodeStrings === false;
  this.decodeStrings = !noDecode;

  // Crypto is kind of old and crusty.  Historically, its default string
  // encoding is 'binary' so we have to make this configurable.
  // Everything else in the universe uses 'utf8', though.
  this.defaultEncoding = options.defaultEncoding || 'utf8';

  // not an actual buffer we keep track of, but a measurement
  // of how much we're waiting to get pushed to some underlying
  // socket or file.
  this.length = 0;

  // a flag to see when we're in the middle of a write.
  this.writing = false;

  // when true all writes will be buffered until .uncork() call
  this.corked = 0;

  // a flag to be able to tell if the onwrite cb is called immediately,
  // or on a later tick.  We set this to true at first, because any
  // actions that shouldn't happen until "later" should generally also
  // not happen before the first write call.
  this.sync = true;

  // a flag to know if we're processing previously buffered items, which
  // may call the _write() callback in the same tick, so that we don't
  // end up in an overlapped onwrite situation.
  this.bufferProcessing = false;

  // the callback that's passed to _write(chunk,cb)
  this.onwrite = function (er) {
    onwrite(stream, er);
  };

  // the callback that the user supplies to write(chunk,encoding,cb)
  this.writecb = null;

  // the amount that is being written when _write is called.
  this.writelen = 0;

  this.bufferedRequest = null;
  this.lastBufferedRequest = null;

  // number of pending user-supplied write callbacks
  // this must be 0 before 'finish' can be emitted
  this.pendingcb = 0;

  // emit prefinish if the only thing we're waiting for is _write cbs
  // This is relevant for synchronous Transform streams
  this.prefinished = false;

  // True if the error was already emitted and should not be thrown again
  this.errorEmitted = false;

  // count buffered requests
  this.bufferedRequestCount = 0;

  // allocate the first CorkedRequest, there is always
  // one allocated and free to use, and we maintain at most two
  this.corkedRequestsFree = new CorkedRequest(this);
}

WritableState.prototype.getBuffer = function getBuffer() {
  var current = this.bufferedRequest;
  var out = [];
  while (current) {
    out.push(current);
    current = current.next;
  }
  return out;
};

(function () {
  try {
    Object.defineProperty(WritableState.prototype, 'buffer', {
      get: internalUtil.deprecate(function () {
        return this.getBuffer();
      }, '_writableState.buffer is deprecated. Use _writableState.getBuffer ' + 'instead.', 'DEP0003')
    });
  } catch (_) {}
})();

// Test _writableState for inheritance to account for Duplex streams,
// whose prototype chain only points to Readable.
var realHasInstance;
if (typeof Symbol === 'function' && Symbol.hasInstance && typeof Function.prototype[Symbol.hasInstance] === 'function') {
  realHasInstance = Function.prototype[Symbol.hasInstance];
  Object.defineProperty(Writable, Symbol.hasInstance, {
    value: function (object) {
      if (realHasInstance.call(this, object)) return true;
      if (this !== Writable) return false;

      return object && object._writableState instanceof WritableState;
    }
  });
} else {
  realHasInstance = function (object) {
    return object instanceof this;
  };
}

function Writable(options) {
  Duplex = Duplex || require('./_stream_duplex');

  // Writable ctor is applied to Duplexes, too.
  // `realHasInstance` is necessary because using plain `instanceof`
  // would return false, as no `_writableState` property is attached.

  // Trying to use the custom `instanceof` for Writable here will also break the
  // Node.js LazyTransform implementation, which has a non-trivial getter for
  // `_writableState` that would lead to infinite recursion.
  if (!realHasInstance.call(Writable, this) && !(this instanceof Duplex)) {
    return new Writable(options);
  }

  this._writableState = new WritableState(options, this);

  // legacy.
  this.writable = true;

  if (options) {
    if (typeof options.write === 'function') this._write = options.write;

    if (typeof options.writev === 'function') this._writev = options.writev;

    if (typeof options.destroy === 'function') this._destroy = options.destroy;

    if (typeof options.final === 'function') this._final = options.final;
  }

  Stream.call(this);
}

// Otherwise people can pipe Writable streams, which is just wrong.
Writable.prototype.pipe = function () {
  this.emit('error', new Error('Cannot pipe, not readable'));
};

function writeAfterEnd(stream, cb) {
  var er = new Error('write after end');
  // TODO: defer error events consistently everywhere, not just the cb
  stream.emit('error', er);
  pna.nextTick(cb, er);
}

// Checks that a user-supplied chunk is valid, especially for the particular
// mode the stream is in. Currently this means that `null` is never accepted
// and undefined/non-string values are only allowed in object mode.
function validChunk(stream, state, chunk, cb) {
  var valid = true;
  var er = false;

  if (chunk === null) {
    er = new TypeError('May not write null values to stream');
  } else if (typeof chunk !== 'string' && chunk !== undefined && !state.objectMode) {
    er = new TypeError('Invalid non-string/buffer chunk');
  }
  if (er) {
    stream.emit('error', er);
    pna.nextTick(cb, er);
    valid = false;
  }
  return valid;
}

Writable.prototype.write = function (chunk, encoding, cb) {
  var state = this._writableState;
  var ret = false;
  var isBuf = !state.objectMode && _isUint8Array(chunk);

  if (isBuf && !Buffer.isBuffer(chunk)) {
    chunk = _uint8ArrayToBuffer(chunk);
  }

  if (typeof encoding === 'function') {
    cb = encoding;
    encoding = null;
  }

  if (isBuf) encoding = 'buffer';else if (!encoding) encoding = state.defaultEncoding;

  if (typeof cb !== 'function') cb = nop;

  if (state.ended) writeAfterEnd(this, cb);else if (isBuf || validChunk(this, state, chunk, cb)) {
    state.pendingcb++;
    ret = writeOrBuffer(this, state, isBuf, chunk, encoding, cb);
  }

  return ret;
};

Writable.prototype.cork = function () {
  var state = this._writableState;

  state.corked++;
};

Writable.prototype.uncork = function () {
  var state = this._writableState;

  if (state.corked) {
    state.corked--;

    if (!state.writing && !state.corked && !state.finished && !state.bufferProcessing && state.bufferedRequest) clearBuffer(this, state);
  }
};

Writable.prototype.setDefaultEncoding = function setDefaultEncoding(encoding) {
  // node::ParseEncoding() requires lower case.
  if (typeof encoding === 'string') encoding = encoding.toLowerCase();
  if (!(['hex', 'utf8', 'utf-8', 'ascii', 'binary', 'base64', 'ucs2', 'ucs-2', 'utf16le', 'utf-16le', 'raw'].indexOf((encoding + '').toLowerCase()) > -1)) throw new TypeError('Unknown encoding: ' + encoding);
  this._writableState.defaultEncoding = encoding;
  return this;
};

function decodeChunk(state, chunk, encoding) {
  if (!state.objectMode && state.decodeStrings !== false && typeof chunk === 'string') {
    chunk = Buffer.from(chunk, encoding);
  }
  return chunk;
}

// if we're already writing something, then just put this
// in the queue, and wait our turn.  Otherwise, call _write
// If we return false, then we need a drain event, so set that flag.
function writeOrBuffer(stream, state, isBuf, chunk, encoding, cb) {
  if (!isBuf) {
    var newChunk = decodeChunk(state, chunk, encoding);
    if (chunk !== newChunk) {
      isBuf = true;
      encoding = 'buffer';
      chunk = newChunk;
    }
  }
  var len = state.objectMode ? 1 : chunk.length;

  state.length += len;

  var ret = state.length < state.highWaterMark;
  // we must ensure that previous needDrain will not be reset to false.
  if (!ret) state.needDrain = true;

  if (state.writing || state.corked) {
    var last = state.lastBufferedRequest;
    state.lastBufferedRequest = {
      chunk: chunk,
      encoding: encoding,
      isBuf: isBuf,
      callback: cb,
      next: null
    };
    if (last) {
      last.next = state.lastBufferedRequest;
    } else {
      state.bufferedRequest = state.lastBufferedRequest;
    }
    state.bufferedRequestCount += 1;
  } else {
    doWrite(stream, state, false, len, chunk, encoding, cb);
  }

  return ret;
}

function doWrite(stream, state, writev, len, chunk, encoding, cb) {
  state.writelen = len;
  state.writecb = cb;
  state.writing = true;
  state.sync = true;
  if (writev) stream._writev(chunk, state.onwrite);else stream._write(chunk, encoding, state.onwrite);
  state.sync = false;
}

function onwriteError(stream, state, sync, er, cb) {
  --state.pendingcb;

  if (sync) {
    // defer the callback if we are being called synchronously
    // to avoid piling up things on the stack
    pna.nextTick(cb, er);
    // this can emit finish, and it will always happen
    // after error
    pna.nextTick(finishMaybe, stream, state);
    stream._writableState.errorEmitted = true;
    stream.emit('error', er);
  } else {
    // the caller expect this to happen before if
    // it is async
    cb(er);
    stream._writableState.errorEmitted = true;
    stream.emit('error', er);
    // this can emit finish, but finish must
    // always follow error
    finishMaybe(stream, state);
  }
}

function onwriteStateUpdate(state) {
  state.writing = false;
  state.writecb = null;
  state.length -= state.writelen;
  state.writelen = 0;
}

function onwrite(stream, er) {
  var state = stream._writableState;
  var sync = state.sync;
  var cb = state.writecb;

  onwriteStateUpdate(state);

  if (er) onwriteError(stream, state, sync, er, cb);else {
    // Check if we're actually ready to finish, but don't emit yet
    var finished = needFinish(state);

    if (!finished && !state.corked && !state.bufferProcessing && state.bufferedRequest) {
      clearBuffer(stream, state);
    }

    if (sync) {
      /*<replacement>*/
      asyncWrite(afterWrite, stream, state, finished, cb);
      /*</replacement>*/
    } else {
      afterWrite(stream, state, finished, cb);
    }
  }
}

function afterWrite(stream, state, finished, cb) {
  if (!finished) onwriteDrain(stream, state);
  state.pendingcb--;
  cb();
  finishMaybe(stream, state);
}

// Must force callback to be called on nextTick, so that we don't
// emit 'drain' before the write() consumer gets the 'false' return
// value, and has a chance to attach a 'drain' listener.
function onwriteDrain(stream, state) {
  if (state.length === 0 && state.needDrain) {
    state.needDrain = false;
    stream.emit('drain');
  }
}

// if there's something in the buffer waiting, then process it
function clearBuffer(stream, state) {
  state.bufferProcessing = true;
  var entry = state.bufferedRequest;

  if (stream._writev && entry && entry.next) {
    // Fast case, write everything using _writev()
    var l = state.bufferedRequestCount;
    var buffer = new Array(l);
    var holder = state.corkedRequestsFree;
    holder.entry = entry;

    var count = 0;
    var allBuffers = true;
    while (entry) {
      buffer[count] = entry;
      if (!entry.isBuf) allBuffers = false;
      entry = entry.next;
      count += 1;
    }
    buffer.allBuffers = allBuffers;

    doWrite(stream, state, true, state.length, buffer, '', holder.finish);

    // doWrite is almost always async, defer these to save a bit of time
    // as the hot path ends with doWrite
    state.pendingcb++;
    state.lastBufferedRequest = null;
    if (holder.next) {
      state.corkedRequestsFree = holder.next;
      holder.next = null;
    } else {
      state.corkedRequestsFree = new CorkedRequest(state);
    }
    state.bufferedRequestCount = 0;
  } else {
    // Slow case, write chunks one-by-one
    while (entry) {
      var chunk = entry.chunk;
      var encoding = entry.encoding;
      var cb = entry.callback;
      var len = state.objectMode ? 1 : chunk.length;

      doWrite(stream, state, false, len, chunk, encoding, cb);
      entry = entry.next;
      state.bufferedRequestCount--;
      // if we didn't call the onwrite immediately, then
      // it means that we need to wait until it does.
      // also, that means that the chunk and cb are currently
      // being processed, so move the buffer counter past them.
      if (state.writing) {
        break;
      }
    }

    if (entry === null) state.lastBufferedRequest = null;
  }

  state.bufferedRequest = entry;
  state.bufferProcessing = false;
}

Writable.prototype._write = function (chunk, encoding, cb) {
  cb(new Error('_write() is not implemented'));
};

Writable.prototype._writev = null;

Writable.prototype.end = function (chunk, encoding, cb) {
  var state = this._writableState;

  if (typeof chunk === 'function') {
    cb = chunk;
    chunk = null;
    encoding = null;
  } else if (typeof encoding === 'function') {
    cb = encoding;
    encoding = null;
  }

  if (chunk !== null && chunk !== undefined) this.write(chunk, encoding);

  // .end() fully uncorks
  if (state.corked) {
    state.corked = 1;
    this.uncork();
  }

  // ignore unnecessary end() calls.
  if (!state.ending && !state.finished) endWritable(this, state, cb);
};

function needFinish(state) {
  return state.ending && state.length === 0 && state.bufferedRequest === null && !state.finished && !state.writing;
}
function callFinal(stream, state) {
  stream._final(function (err) {
    state.pendingcb--;
    if (err) {
      stream.emit('error', err);
    }
    state.prefinished = true;
    stream.emit('prefinish');
    finishMaybe(stream, state);
  });
}
function prefinish(stream, state) {
  if (!state.prefinished && !state.finalCalled) {
    if (typeof stream._final === 'function') {
      state.pendingcb++;
      state.finalCalled = true;
      pna.nextTick(callFinal, stream, state);
    } else {
      state.prefinished = true;
      stream.emit('prefinish');
    }
  }
}

function finishMaybe(stream, state) {
  var need = needFinish(state);
  if (need) {
    prefinish(stream, state);
    if (state.pendingcb === 0) {
      state.finished = true;
      stream.emit('finish');
    }
  }
  return need;
}

function endWritable(stream, state, cb) {
  state.ending = true;
  finishMaybe(stream, state);
  if (cb) {
    if (state.finished) pna.nextTick(cb);else stream.once('finish', cb);
  }
  state.ended = true;
  stream.writable = false;
}

function onCorkedFinish(corkReq, state, err) {
  var entry = corkReq.entry;
  corkReq.entry = null;
  while (entry) {
    var cb = entry.callback;
    state.pendingcb--;
    cb(err);
    entry = entry.next;
  }
  if (state.corkedRequestsFree) {
    state.corkedRequestsFree.next = corkReq;
  } else {
    state.corkedRequestsFree = corkReq;
  }
}

Object.defineProperty(Writable.prototype, 'destroyed', {
  get: function () {
    if (this._writableState === undefined) {
      return false;
    }
    return this._writableState.destroyed;
  },
  set: function (value) {
    // we ignore the value if the stream
    // has not been initialized yet
    if (!this._writableState) {
      return;
    }

    // backward compatibility, the user is explicitly
    // managing destroyed
    this._writableState.destroyed = value;
  }
});

Writable.prototype.destroy = destroyImpl.destroy;
Writable.prototype._undestroy = destroyImpl.undestroy;
Writable.prototype._destroy = function (err, cb) {
  this.end();
  cb(err);
};
}).call(this,require('_process'),typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{"./_stream_duplex":23,"./internal/streams/destroy":29,"./internal/streams/stream":30,"_process":21,"core-util-is":15,"inherits":17,"process-nextick-args":20,"safe-buffer":36,"util-deprecate":38}],28:[function(require,module,exports){
'use strict';

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

var Buffer = require('safe-buffer').Buffer;
var util = require('util');

function copyBuffer(src, target, offset) {
  src.copy(target, offset);
}

module.exports = function () {
  function BufferList() {
    _classCallCheck(this, BufferList);

    this.head = null;
    this.tail = null;
    this.length = 0;
  }

  BufferList.prototype.push = function push(v) {
    var entry = { data: v, next: null };
    if (this.length > 0) this.tail.next = entry;else this.head = entry;
    this.tail = entry;
    ++this.length;
  };

  BufferList.prototype.unshift = function unshift(v) {
    var entry = { data: v, next: this.head };
    if (this.length === 0) this.tail = entry;
    this.head = entry;
    ++this.length;
  };

  BufferList.prototype.shift = function shift() {
    if (this.length === 0) return;
    var ret = this.head.data;
    if (this.length === 1) this.head = this.tail = null;else this.head = this.head.next;
    --this.length;
    return ret;
  };

  BufferList.prototype.clear = function clear() {
    this.head = this.tail = null;
    this.length = 0;
  };

  BufferList.prototype.join = function join(s) {
    if (this.length === 0) return '';
    var p = this.head;
    var ret = '' + p.data;
    while (p = p.next) {
      ret += s + p.data;
    }return ret;
  };

  BufferList.prototype.concat = function concat(n) {
    if (this.length === 0) return Buffer.alloc(0);
    if (this.length === 1) return this.head.data;
    var ret = Buffer.allocUnsafe(n >>> 0);
    var p = this.head;
    var i = 0;
    while (p) {
      copyBuffer(p.data, ret, i);
      i += p.data.length;
      p = p.next;
    }
    return ret;
  };

  return BufferList;
}();

if (util && util.inspect && util.inspect.custom) {
  module.exports.prototype[util.inspect.custom] = function () {
    var obj = util.inspect({ length: this.length });
    return this.constructor.name + ' ' + obj;
  };
}
},{"safe-buffer":36,"util":11}],29:[function(require,module,exports){
'use strict';

/*<replacement>*/

var pna = require('process-nextick-args');
/*</replacement>*/

// undocumented cb() API, needed for core, not for public API
function destroy(err, cb) {
  var _this = this;

  var readableDestroyed = this._readableState && this._readableState.destroyed;
  var writableDestroyed = this._writableState && this._writableState.destroyed;

  if (readableDestroyed || writableDestroyed) {
    if (cb) {
      cb(err);
    } else if (err && (!this._writableState || !this._writableState.errorEmitted)) {
      pna.nextTick(emitErrorNT, this, err);
    }
    return this;
  }

  // we set destroyed to true before firing error callbacks in order
  // to make it re-entrance safe in case destroy() is called within callbacks

  if (this._readableState) {
    this._readableState.destroyed = true;
  }

  // if this is a duplex stream mark the writable part as destroyed as well
  if (this._writableState) {
    this._writableState.destroyed = true;
  }

  this._destroy(err || null, function (err) {
    if (!cb && err) {
      pna.nextTick(emitErrorNT, _this, err);
      if (_this._writableState) {
        _this._writableState.errorEmitted = true;
      }
    } else if (cb) {
      cb(err);
    }
  });

  return this;
}

function undestroy() {
  if (this._readableState) {
    this._readableState.destroyed = false;
    this._readableState.reading = false;
    this._readableState.ended = false;
    this._readableState.endEmitted = false;
  }

  if (this._writableState) {
    this._writableState.destroyed = false;
    this._writableState.ended = false;
    this._writableState.ending = false;
    this._writableState.finished = false;
    this._writableState.errorEmitted = false;
  }
}

function emitErrorNT(self, err) {
  self.emit('error', err);
}

module.exports = {
  destroy: destroy,
  undestroy: undestroy
};
},{"process-nextick-args":20}],30:[function(require,module,exports){
module.exports = require('events').EventEmitter;

},{"events":12}],31:[function(require,module,exports){
'use strict';

var Buffer = require('safe-buffer').Buffer;

var isEncoding = Buffer.isEncoding || function (encoding) {
  encoding = '' + encoding;
  switch (encoding && encoding.toLowerCase()) {
    case 'hex':case 'utf8':case 'utf-8':case 'ascii':case 'binary':case 'base64':case 'ucs2':case 'ucs-2':case 'utf16le':case 'utf-16le':case 'raw':
      return true;
    default:
      return false;
  }
};

function _normalizeEncoding(enc) {
  if (!enc) return 'utf8';
  var retried;
  while (true) {
    switch (enc) {
      case 'utf8':
      case 'utf-8':
        return 'utf8';
      case 'ucs2':
      case 'ucs-2':
      case 'utf16le':
      case 'utf-16le':
        return 'utf16le';
      case 'latin1':
      case 'binary':
        return 'latin1';
      case 'base64':
      case 'ascii':
      case 'hex':
        return enc;
      default:
        if (retried) return; // undefined
        enc = ('' + enc).toLowerCase();
        retried = true;
    }
  }
};

// Do not cache `Buffer.isEncoding` when checking encoding names as some
// modules monkey-patch it to support additional encodings
function normalizeEncoding(enc) {
  var nenc = _normalizeEncoding(enc);
  if (typeof nenc !== 'string' && (Buffer.isEncoding === isEncoding || !isEncoding(enc))) throw new Error('Unknown encoding: ' + enc);
  return nenc || enc;
}

// StringDecoder provides an interface for efficiently splitting a series of
// buffers into a series of JS strings without breaking apart multi-byte
// characters.
exports.StringDecoder = StringDecoder;
function StringDecoder(encoding) {
  this.encoding = normalizeEncoding(encoding);
  var nb;
  switch (this.encoding) {
    case 'utf16le':
      this.text = utf16Text;
      this.end = utf16End;
      nb = 4;
      break;
    case 'utf8':
      this.fillLast = utf8FillLast;
      nb = 4;
      break;
    case 'base64':
      this.text = base64Text;
      this.end = base64End;
      nb = 3;
      break;
    default:
      this.write = simpleWrite;
      this.end = simpleEnd;
      return;
  }
  this.lastNeed = 0;
  this.lastTotal = 0;
  this.lastChar = Buffer.allocUnsafe(nb);
}

StringDecoder.prototype.write = function (buf) {
  if (buf.length === 0) return '';
  var r;
  var i;
  if (this.lastNeed) {
    r = this.fillLast(buf);
    if (r === undefined) return '';
    i = this.lastNeed;
    this.lastNeed = 0;
  } else {
    i = 0;
  }
  if (i < buf.length) return r ? r + this.text(buf, i) : this.text(buf, i);
  return r || '';
};

StringDecoder.prototype.end = utf8End;

// Returns only complete characters in a Buffer
StringDecoder.prototype.text = utf8Text;

// Attempts to complete a partial non-UTF-8 character using bytes from a Buffer
StringDecoder.prototype.fillLast = function (buf) {
  if (this.lastNeed <= buf.length) {
    buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, this.lastNeed);
    return this.lastChar.toString(this.encoding, 0, this.lastTotal);
  }
  buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, buf.length);
  this.lastNeed -= buf.length;
};

// Checks the type of a UTF-8 byte, whether it's ASCII, a leading byte, or a
// continuation byte.
function utf8CheckByte(byte) {
  if (byte <= 0x7F) return 0;else if (byte >> 5 === 0x06) return 2;else if (byte >> 4 === 0x0E) return 3;else if (byte >> 3 === 0x1E) return 4;
  return -1;
}

// Checks at most 3 bytes at the end of a Buffer in order to detect an
// incomplete multi-byte UTF-8 character. The total number of bytes (2, 3, or 4)
// needed to complete the UTF-8 character (if applicable) are returned.
function utf8CheckIncomplete(self, buf, i) {
  var j = buf.length - 1;
  if (j < i) return 0;
  var nb = utf8CheckByte(buf[j]);
  if (nb >= 0) {
    if (nb > 0) self.lastNeed = nb - 1;
    return nb;
  }
  if (--j < i) return 0;
  nb = utf8CheckByte(buf[j]);
  if (nb >= 0) {
    if (nb > 0) self.lastNeed = nb - 2;
    return nb;
  }
  if (--j < i) return 0;
  nb = utf8CheckByte(buf[j]);
  if (nb >= 0) {
    if (nb > 0) {
      if (nb === 2) nb = 0;else self.lastNeed = nb - 3;
    }
    return nb;
  }
  return 0;
}

// Validates as many continuation bytes for a multi-byte UTF-8 character as
// needed or are available. If we see a non-continuation byte where we expect
// one, we "replace" the validated continuation bytes we've seen so far with
// UTF-8 replacement characters ('\ufffd'), to match v8's UTF-8 decoding
// behavior. The continuation byte check is included three times in the case
// where all of the continuation bytes for a character exist in the same buffer.
// It is also done this way as a slight performance increase instead of using a
// loop.
function utf8CheckExtraBytes(self, buf, p) {
  if ((buf[0] & 0xC0) !== 0x80) {
    self.lastNeed = 0;
    return '\ufffd'.repeat(p);
  }
  if (self.lastNeed > 1 && buf.length > 1) {
    if ((buf[1] & 0xC0) !== 0x80) {
      self.lastNeed = 1;
      return '\ufffd'.repeat(p + 1);
    }
    if (self.lastNeed > 2 && buf.length > 2) {
      if ((buf[2] & 0xC0) !== 0x80) {
        self.lastNeed = 2;
        return '\ufffd'.repeat(p + 2);
      }
    }
  }
}

// Attempts to complete a multi-byte UTF-8 character using bytes from a Buffer.
function utf8FillLast(buf) {
  var p = this.lastTotal - this.lastNeed;
  var r = utf8CheckExtraBytes(this, buf, p);
  if (r !== undefined) return r;
  if (this.lastNeed <= buf.length) {
    buf.copy(this.lastChar, p, 0, this.lastNeed);
    return this.lastChar.toString(this.encoding, 0, this.lastTotal);
  }
  buf.copy(this.lastChar, p, 0, buf.length);
  this.lastNeed -= buf.length;
}

// Returns all complete UTF-8 characters in a Buffer. If the Buffer ended on a
// partial character, the character's bytes are buffered until the required
// number of bytes are available.
function utf8Text(buf, i) {
  var total = utf8CheckIncomplete(this, buf, i);
  if (!this.lastNeed) return buf.toString('utf8', i);
  this.lastTotal = total;
  var end = buf.length - (total - this.lastNeed);
  buf.copy(this.lastChar, 0, end);
  return buf.toString('utf8', i, end);
}

// For UTF-8, a replacement character for each buffered byte of a (partial)
// character needs to be added to the output.
function utf8End(buf) {
  var r = buf && buf.length ? this.write(buf) : '';
  if (this.lastNeed) return r + '\ufffd'.repeat(this.lastTotal - this.lastNeed);
  return r;
}

// UTF-16LE typically needs two bytes per character, but even if we have an even
// number of bytes available, we need to check if we end on a leading/high
// surrogate. In that case, we need to wait for the next two bytes in order to
// decode the last character properly.
function utf16Text(buf, i) {
  if ((buf.length - i) % 2 === 0) {
    var r = buf.toString('utf16le', i);
    if (r) {
      var c = r.charCodeAt(r.length - 1);
      if (c >= 0xD800 && c <= 0xDBFF) {
        this.lastNeed = 2;
        this.lastTotal = 4;
        this.lastChar[0] = buf[buf.length - 2];
        this.lastChar[1] = buf[buf.length - 1];
        return r.slice(0, -1);
      }
    }
    return r;
  }
  this.lastNeed = 1;
  this.lastTotal = 2;
  this.lastChar[0] = buf[buf.length - 1];
  return buf.toString('utf16le', i, buf.length - 1);
}

// For UTF-16LE we do not explicitly append special replacement characters if we
// end on a partial character, we simply let v8 handle that.
function utf16End(buf) {
  var r = buf && buf.length ? this.write(buf) : '';
  if (this.lastNeed) {
    var end = this.lastTotal - this.lastNeed;
    return r + this.lastChar.toString('utf16le', 0, end);
  }
  return r;
}

function base64Text(buf, i) {
  var n = (buf.length - i) % 3;
  if (n === 0) return buf.toString('base64', i);
  this.lastNeed = 3 - n;
  this.lastTotal = 3;
  if (n === 1) {
    this.lastChar[0] = buf[buf.length - 1];
  } else {
    this.lastChar[0] = buf[buf.length - 2];
    this.lastChar[1] = buf[buf.length - 1];
  }
  return buf.toString('base64', i, buf.length - n);
}

function base64End(buf) {
  var r = buf && buf.length ? this.write(buf) : '';
  if (this.lastNeed) return r + this.lastChar.toString('base64', 0, 3 - this.lastNeed);
  return r;
}

// Pass bytes on through for single-byte encodings (e.g. ascii, latin1, hex)
function simpleWrite(buf) {
  return buf.toString(this.encoding);
}

function simpleEnd(buf) {
  return buf && buf.length ? this.write(buf) : '';
}
},{"safe-buffer":36}],32:[function(require,module,exports){
module.exports = require('./readable').PassThrough

},{"./readable":33}],33:[function(require,module,exports){
exports = module.exports = require('./lib/_stream_readable.js');
exports.Stream = exports;
exports.Readable = exports;
exports.Writable = require('./lib/_stream_writable.js');
exports.Duplex = require('./lib/_stream_duplex.js');
exports.Transform = require('./lib/_stream_transform.js');
exports.PassThrough = require('./lib/_stream_passthrough.js');

},{"./lib/_stream_duplex.js":23,"./lib/_stream_passthrough.js":24,"./lib/_stream_readable.js":25,"./lib/_stream_transform.js":26,"./lib/_stream_writable.js":27}],34:[function(require,module,exports){
module.exports = require('./readable').Transform

},{"./readable":33}],35:[function(require,module,exports){
module.exports = require('./lib/_stream_writable.js');

},{"./lib/_stream_writable.js":27}],36:[function(require,module,exports){
/* eslint-disable node/no-deprecated-api */
var buffer = require('buffer')
var Buffer = buffer.Buffer

// alternative to using Object.keys for old browsers
function copyProps (src, dst) {
  for (var key in src) {
    dst[key] = src[key]
  }
}
if (Buffer.from && Buffer.alloc && Buffer.allocUnsafe && Buffer.allocUnsafeSlow) {
  module.exports = buffer
} else {
  // Copy properties from require('buffer')
  copyProps(buffer, exports)
  exports.Buffer = SafeBuffer
}

function SafeBuffer (arg, encodingOrOffset, length) {
  return Buffer(arg, encodingOrOffset, length)
}

// Copy static methods from Buffer
copyProps(Buffer, SafeBuffer)

SafeBuffer.from = function (arg, encodingOrOffset, length) {
  if (typeof arg === 'number') {
    throw new TypeError('Argument must not be a number')
  }
  return Buffer(arg, encodingOrOffset, length)
}

SafeBuffer.alloc = function (size, fill, encoding) {
  if (typeof size !== 'number') {
    throw new TypeError('Argument must be a number')
  }
  var buf = Buffer(size)
  if (fill !== undefined) {
    if (typeof encoding === 'string') {
      buf.fill(fill, encoding)
    } else {
      buf.fill(fill)
    }
  } else {
    buf.fill(0)
  }
  return buf
}

SafeBuffer.allocUnsafe = function (size) {
  if (typeof size !== 'number') {
    throw new TypeError('Argument must be a number')
  }
  return Buffer(size)
}

SafeBuffer.allocUnsafeSlow = function (size) {
  if (typeof size !== 'number') {
    throw new TypeError('Argument must be a number')
  }
  return buffer.SlowBuffer(size)
}

},{"buffer":14}],37:[function(require,module,exports){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

module.exports = Stream;

var EE = require('events').EventEmitter;
var inherits = require('inherits');

inherits(Stream, EE);
Stream.Readable = require('readable-stream/readable.js');
Stream.Writable = require('readable-stream/writable.js');
Stream.Duplex = require('readable-stream/duplex.js');
Stream.Transform = require('readable-stream/transform.js');
Stream.PassThrough = require('readable-stream/passthrough.js');

// Backwards-compat with node 0.4.x
Stream.Stream = Stream;



// old-style streams.  Note that the pipe method (the only relevant
// part of this class) is overridden in the Readable class.

function Stream() {
  EE.call(this);
}

Stream.prototype.pipe = function(dest, options) {
  var source = this;

  function ondata(chunk) {
    if (dest.writable) {
      if (false === dest.write(chunk) && source.pause) {
        source.pause();
      }
    }
  }

  source.on('data', ondata);

  function ondrain() {
    if (source.readable && source.resume) {
      source.resume();
    }
  }

  dest.on('drain', ondrain);

  // If the 'end' option is not supplied, dest.end() will be called when
  // source gets the 'end' or 'close' events.  Only dest.end() once.
  if (!dest._isStdio && (!options || options.end !== false)) {
    source.on('end', onend);
    source.on('close', onclose);
  }

  var didOnEnd = false;
  function onend() {
    if (didOnEnd) return;
    didOnEnd = true;

    dest.end();
  }


  function onclose() {
    if (didOnEnd) return;
    didOnEnd = true;

    if (typeof dest.destroy === 'function') dest.destroy();
  }

  // don't leave dangling pipes when there are errors.
  function onerror(er) {
    cleanup();
    if (EE.listenerCount(this, 'error') === 0) {
      throw er; // Unhandled stream error in pipe.
    }
  }

  source.on('error', onerror);
  dest.on('error', onerror);

  // remove all the event listeners that were added.
  function cleanup() {
    source.removeListener('data', ondata);
    dest.removeListener('drain', ondrain);

    source.removeListener('end', onend);
    source.removeListener('close', onclose);

    source.removeListener('error', onerror);
    dest.removeListener('error', onerror);

    source.removeListener('end', cleanup);
    source.removeListener('close', cleanup);

    dest.removeListener('close', cleanup);
  }

  source.on('end', cleanup);
  source.on('close', cleanup);

  dest.on('close', cleanup);

  dest.emit('pipe', source);

  // Allow for unix-like usage: A.pipe(B).pipe(C)
  return dest;
};

},{"events":12,"inherits":17,"readable-stream/duplex.js":22,"readable-stream/passthrough.js":32,"readable-stream/readable.js":33,"readable-stream/transform.js":34,"readable-stream/writable.js":35}],38:[function(require,module,exports){
(function (global){

/**
 * Module exports.
 */

module.exports = deprecate;

/**
 * Mark that a method should not be used.
 * Returns a modified function which warns once by default.
 *
 * If `localStorage.noDeprecation = true` is set, then it is a no-op.
 *
 * If `localStorage.throwDeprecation = true` is set, then deprecated functions
 * will throw an Error when invoked.
 *
 * If `localStorage.traceDeprecation = true` is set, then deprecated functions
 * will invoke `console.trace()` instead of `console.error()`.
 *
 * @param {Function} fn - the function to deprecate
 * @param {String} msg - the string to print to the console when `fn` is invoked
 * @returns {Function} a new "deprecated" version of `fn`
 * @api public
 */

function deprecate (fn, msg) {
  if (config('noDeprecation')) {
    return fn;
  }

  var warned = false;
  function deprecated() {
    if (!warned) {
      if (config('throwDeprecation')) {
        throw new Error(msg);
      } else if (config('traceDeprecation')) {
        console.trace(msg);
      } else {
        console.warn(msg);
      }
      warned = true;
    }
    return fn.apply(this, arguments);
  }

  return deprecated;
}

/**
 * Checks `localStorage` for boolean values for the given `name`.
 *
 * @param {String} name
 * @returns {Boolean}
 * @api private
 */

function config (name) {
  // accessing global.localStorage can trigger a DOMException in sandboxed iframes
  try {
    if (!global.localStorage) return false;
  } catch (_) {
    return false;
  }
  var val = global.localStorage[name];
  if (null == val) return false;
  return String(val).toLowerCase() === 'true';
}

}).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{}],39:[function(require,module,exports){
arguments[4][17][0].apply(exports,arguments)
},{"dup":17}],40:[function(require,module,exports){
module.exports = function isBuffer(arg) {
  return arg && typeof arg === 'object'
    && typeof arg.copy === 'function'
    && typeof arg.fill === 'function'
    && typeof arg.readUInt8 === 'function';
}
},{}],41:[function(require,module,exports){
(function (process,global){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

var formatRegExp = /%[sdj%]/g;
exports.format = function(f) {
  if (!isString(f)) {
    var objects = [];
    for (var i = 0; i < arguments.length; i++) {
      objects.push(inspect(arguments[i]));
    }
    return objects.join(' ');
  }

  var i = 1;
  var args = arguments;
  var len = args.length;
  var str = String(f).replace(formatRegExp, function(x) {
    if (x === '%%') return '%';
    if (i >= len) return x;
    switch (x) {
      case '%s': return String(args[i++]);
      case '%d': return Number(args[i++]);
      case '%j':
        try {
          return JSON.stringify(args[i++]);
        } catch (_) {
          return '[Circular]';
        }
      default:
        return x;
    }
  });
  for (var x = args[i]; i < len; x = args[++i]) {
    if (isNull(x) || !isObject(x)) {
      str += ' ' + x;
    } else {
      str += ' ' + inspect(x);
    }
  }
  return str;
};


// Mark that a method should not be used.
// Returns a modified function which warns once by default.
// If --no-deprecation is set, then it is a no-op.
exports.deprecate = function(fn, msg) {
  // Allow for deprecating things in the process of starting up.
  if (isUndefined(global.process)) {
    return function() {
      return exports.deprecate(fn, msg).apply(this, arguments);
    };
  }

  if (process.noDeprecation === true) {
    return fn;
  }

  var warned = false;
  function deprecated() {
    if (!warned) {
      if (process.throwDeprecation) {
        throw new Error(msg);
      } else if (process.traceDeprecation) {
        console.trace(msg);
      } else {
        console.error(msg);
      }
      warned = true;
    }
    return fn.apply(this, arguments);
  }

  return deprecated;
};


var debugs = {};
var debugEnviron;
exports.debuglog = function(set) {
  if (isUndefined(debugEnviron))
    debugEnviron = process.env.NODE_DEBUG || '';
  set = set.toUpperCase();
  if (!debugs[set]) {
    if (new RegExp('\\b' + set + '\\b', 'i').test(debugEnviron)) {
      var pid = process.pid;
      debugs[set] = function() {
        var msg = exports.format.apply(exports, arguments);
        console.error('%s %d: %s', set, pid, msg);
      };
    } else {
      debugs[set] = function() {};
    }
  }
  return debugs[set];
};


/**
 * Echos the value of a value. Trys to print the value out
 * in the best way possible given the different types.
 *
 * @param {Object} obj The object to print out.
 * @param {Object} opts Optional options object that alters the output.
 */
/* legacy: obj, showHidden, depth, colors*/
function inspect(obj, opts) {
  // default options
  var ctx = {
    seen: [],
    stylize: stylizeNoColor
  };
  // legacy...
  if (arguments.length >= 3) ctx.depth = arguments[2];
  if (arguments.length >= 4) ctx.colors = arguments[3];
  if (isBoolean(opts)) {
    // legacy...
    ctx.showHidden = opts;
  } else if (opts) {
    // got an "options" object
    exports._extend(ctx, opts);
  }
  // set default options
  if (isUndefined(ctx.showHidden)) ctx.showHidden = false;
  if (isUndefined(ctx.depth)) ctx.depth = 2;
  if (isUndefined(ctx.colors)) ctx.colors = false;
  if (isUndefined(ctx.customInspect)) ctx.customInspect = true;
  if (ctx.colors) ctx.stylize = stylizeWithColor;
  return formatValue(ctx, obj, ctx.depth);
}
exports.inspect = inspect;


// http://en.wikipedia.org/wiki/ANSI_escape_code#graphics
inspect.colors = {
  'bold' : [1, 22],
  'italic' : [3, 23],
  'underline' : [4, 24],
  'inverse' : [7, 27],
  'white' : [37, 39],
  'grey' : [90, 39],
  'black' : [30, 39],
  'blue' : [34, 39],
  'cyan' : [36, 39],
  'green' : [32, 39],
  'magenta' : [35, 39],
  'red' : [31, 39],
  'yellow' : [33, 39]
};

// Don't use 'blue' not visible on cmd.exe
inspect.styles = {
  'special': 'cyan',
  'number': 'yellow',
  'boolean': 'yellow',
  'undefined': 'grey',
  'null': 'bold',
  'string': 'green',
  'date': 'magenta',
  // "name": intentionally not styling
  'regexp': 'red'
};


function stylizeWithColor(str, styleType) {
  var style = inspect.styles[styleType];

  if (style) {
    return '\u001b[' + inspect.colors[style][0] + 'm' + str +
           '\u001b[' + inspect.colors[style][1] + 'm';
  } else {
    return str;
  }
}


function stylizeNoColor(str, styleType) {
  return str;
}


function arrayToHash(array) {
  var hash = {};

  array.forEach(function(val, idx) {
    hash[val] = true;
  });

  return hash;
}


function formatValue(ctx, value, recurseTimes) {
  // Provide a hook for user-specified inspect functions.
  // Check that value is an object with an inspect function on it
  if (ctx.customInspect &&
      value &&
      isFunction(value.inspect) &&
      // Filter out the util module, it's inspect function is special
      value.inspect !== exports.inspect &&
      // Also filter out any prototype objects using the circular check.
      !(value.constructor && value.constructor.prototype === value)) {
    var ret = value.inspect(recurseTimes, ctx);
    if (!isString(ret)) {
      ret = formatValue(ctx, ret, recurseTimes);
    }
    return ret;
  }

  // Primitive types cannot have properties
  var primitive = formatPrimitive(ctx, value);
  if (primitive) {
    return primitive;
  }

  // Look up the keys of the object.
  var keys = Object.keys(value);
  var visibleKeys = arrayToHash(keys);

  if (ctx.showHidden) {
    keys = Object.getOwnPropertyNames(value);
  }

  // IE doesn't make error fields non-enumerable
  // http://msdn.microsoft.com/en-us/library/ie/dww52sbt(v=vs.94).aspx
  if (isError(value)
      && (keys.indexOf('message') >= 0 || keys.indexOf('description') >= 0)) {
    return formatError(value);
  }

  // Some type of object without properties can be shortcutted.
  if (keys.length === 0) {
    if (isFunction(value)) {
      var name = value.name ? ': ' + value.name : '';
      return ctx.stylize('[Function' + name + ']', 'special');
    }
    if (isRegExp(value)) {
      return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
    }
    if (isDate(value)) {
      return ctx.stylize(Date.prototype.toString.call(value), 'date');
    }
    if (isError(value)) {
      return formatError(value);
    }
  }

  var base = '', array = false, braces = ['{', '}'];

  // Make Array say that they are Array
  if (isArray(value)) {
    array = true;
    braces = ['[', ']'];
  }

  // Make functions say that they are functions
  if (isFunction(value)) {
    var n = value.name ? ': ' + value.name : '';
    base = ' [Function' + n + ']';
  }

  // Make RegExps say that they are RegExps
  if (isRegExp(value)) {
    base = ' ' + RegExp.prototype.toString.call(value);
  }

  // Make dates with properties first say the date
  if (isDate(value)) {
    base = ' ' + Date.prototype.toUTCString.call(value);
  }

  // Make error with message first say the error
  if (isError(value)) {
    base = ' ' + formatError(value);
  }

  if (keys.length === 0 && (!array || value.length == 0)) {
    return braces[0] + base + braces[1];
  }

  if (recurseTimes < 0) {
    if (isRegExp(value)) {
      return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
    } else {
      return ctx.stylize('[Object]', 'special');
    }
  }

  ctx.seen.push(value);

  var output;
  if (array) {
    output = formatArray(ctx, value, recurseTimes, visibleKeys, keys);
  } else {
    output = keys.map(function(key) {
      return formatProperty(ctx, value, recurseTimes, visibleKeys, key, array);
    });
  }

  ctx.seen.pop();

  return reduceToSingleString(output, base, braces);
}


function formatPrimitive(ctx, value) {
  if (isUndefined(value))
    return ctx.stylize('undefined', 'undefined');
  if (isString(value)) {
    var simple = '\'' + JSON.stringify(value).replace(/^"|"$/g, '')
                                             .replace(/'/g, "\\'")
                                             .replace(/\\"/g, '"') + '\'';
    return ctx.stylize(simple, 'string');
  }
  if (isNumber(value))
    return ctx.stylize('' + value, 'number');
  if (isBoolean(value))
    return ctx.stylize('' + value, 'boolean');
  // For some reason typeof null is "object", so special case here.
  if (isNull(value))
    return ctx.stylize('null', 'null');
}


function formatError(value) {
  return '[' + Error.prototype.toString.call(value) + ']';
}


function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
  var output = [];
  for (var i = 0, l = value.length; i < l; ++i) {
    if (hasOwnProperty(value, String(i))) {
      output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
          String(i), true));
    } else {
      output.push('');
    }
  }
  keys.forEach(function(key) {
    if (!key.match(/^\d+$/)) {
      output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
          key, true));
    }
  });
  return output;
}


function formatProperty(ctx, value, recurseTimes, visibleKeys, key, array) {
  var name, str, desc;
  desc = Object.getOwnPropertyDescriptor(value, key) || { value: value[key] };
  if (desc.get) {
    if (desc.set) {
      str = ctx.stylize('[Getter/Setter]', 'special');
    } else {
      str = ctx.stylize('[Getter]', 'special');
    }
  } else {
    if (desc.set) {
      str = ctx.stylize('[Setter]', 'special');
    }
  }
  if (!hasOwnProperty(visibleKeys, key)) {
    name = '[' + key + ']';
  }
  if (!str) {
    if (ctx.seen.indexOf(desc.value) < 0) {
      if (isNull(recurseTimes)) {
        str = formatValue(ctx, desc.value, null);
      } else {
        str = formatValue(ctx, desc.value, recurseTimes - 1);
      }
      if (str.indexOf('\n') > -1) {
        if (array) {
          str = str.split('\n').map(function(line) {
            return '  ' + line;
          }).join('\n').substr(2);
        } else {
          str = '\n' + str.split('\n').map(function(line) {
            return '   ' + line;
          }).join('\n');
        }
      }
    } else {
      str = ctx.stylize('[Circular]', 'special');
    }
  }
  if (isUndefined(name)) {
    if (array && key.match(/^\d+$/)) {
      return str;
    }
    name = JSON.stringify('' + key);
    if (name.match(/^"([a-zA-Z_][a-zA-Z_0-9]*)"$/)) {
      name = name.substr(1, name.length - 2);
      name = ctx.stylize(name, 'name');
    } else {
      name = name.replace(/'/g, "\\'")
                 .replace(/\\"/g, '"')
                 .replace(/(^"|"$)/g, "'");
      name = ctx.stylize(name, 'string');
    }
  }

  return name + ': ' + str;
}


function reduceToSingleString(output, base, braces) {
  var numLinesEst = 0;
  var length = output.reduce(function(prev, cur) {
    numLinesEst++;
    if (cur.indexOf('\n') >= 0) numLinesEst++;
    return prev + cur.replace(/\u001b\[\d\d?m/g, '').length + 1;
  }, 0);

  if (length > 60) {
    return braces[0] +
           (base === '' ? '' : base + '\n ') +
           ' ' +
           output.join(',\n  ') +
           ' ' +
           braces[1];
  }

  return braces[0] + base + ' ' + output.join(', ') + ' ' + braces[1];
}


// NOTE: These type checking functions intentionally don't use `instanceof`
// because it is fragile and can be easily faked with `Object.create()`.
function isArray(ar) {
  return Array.isArray(ar);
}
exports.isArray = isArray;

function isBoolean(arg) {
  return typeof arg === 'boolean';
}
exports.isBoolean = isBoolean;

function isNull(arg) {
  return arg === null;
}
exports.isNull = isNull;

function isNullOrUndefined(arg) {
  return arg == null;
}
exports.isNullOrUndefined = isNullOrUndefined;

function isNumber(arg) {
  return typeof arg === 'number';
}
exports.isNumber = isNumber;

function isString(arg) {
  return typeof arg === 'string';
}
exports.isString = isString;

function isSymbol(arg) {
  return typeof arg === 'symbol';
}
exports.isSymbol = isSymbol;

function isUndefined(arg) {
  return arg === void 0;
}
exports.isUndefined = isUndefined;

function isRegExp(re) {
  return isObject(re) && objectToString(re) === '[object RegExp]';
}
exports.isRegExp = isRegExp;

function isObject(arg) {
  return typeof arg === 'object' && arg !== null;
}
exports.isObject = isObject;

function isDate(d) {
  return isObject(d) && objectToString(d) === '[object Date]';
}
exports.isDate = isDate;

function isError(e) {
  return isObject(e) &&
      (objectToString(e) === '[object Error]' || e instanceof Error);
}
exports.isError = isError;

function isFunction(arg) {
  return typeof arg === 'function';
}
exports.isFunction = isFunction;

function isPrimitive(arg) {
  return arg === null ||
         typeof arg === 'boolean' ||
         typeof arg === 'number' ||
         typeof arg === 'string' ||
         typeof arg === 'symbol' ||  // ES6 symbol
         typeof arg === 'undefined';
}
exports.isPrimitive = isPrimitive;

exports.isBuffer = require('./support/isBuffer');

function objectToString(o) {
  return Object.prototype.toString.call(o);
}


function pad(n) {
  return n < 10 ? '0' + n.toString(10) : n.toString(10);
}


var months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep',
              'Oct', 'Nov', 'Dec'];

// 26 Feb 16:19:34
function timestamp() {
  var d = new Date();
  var time = [pad(d.getHours()),
              pad(d.getMinutes()),
              pad(d.getSeconds())].join(':');
  return [d.getDate(), months[d.getMonth()], time].join(' ');
}


// log is just a thin wrapper to console.log that prepends a timestamp
exports.log = function() {
  console.log('%s - %s', timestamp(), exports.format.apply(exports, arguments));
};


/**
 * Inherit the prototype methods from one constructor into another.
 *
 * The Function.prototype.inherits from lang.js rewritten as a standalone
 * function (not on Function.prototype). NOTE: If this file is to be loaded
 * during bootstrapping this function needs to be rewritten using some native
 * functions as prototype setup using normal JavaScript does not work as
 * expected during bootstrapping (see mirror.js in r114903).
 *
 * @param {function} ctor Constructor function which needs to inherit the
 *     prototype.
 * @param {function} superCtor Constructor function to inherit prototype from.
 */
exports.inherits = require('inherits');

exports._extend = function(origin, add) {
  // Don't do anything if add isn't an object
  if (!add || !isObject(add)) return origin;

  var keys = Object.keys(add);
  var i = keys.length;
  while (i--) {
    origin[keys[i]] = add[keys[i]];
  }
  return origin;
};

function hasOwnProperty(obj, prop) {
  return Object.prototype.hasOwnProperty.call(obj, prop);
}

}).call(this,require('_process'),typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{"./support/isBuffer":40,"_process":21,"inherits":39}]},{},[3])(3)
});