index.js

/**
 * Implementation of the [multibase](https://github.com/multiformats/multibase) specification.
 *
 */
'use strict'

const constants = require('./constants')
const { encodeText, decodeText, concat } = require('./util')

/** @typedef {import('./base')} Base */
/** @typedef {import("./types").BaseNameOrCode} BaseNameOrCode */
/** @typedef {import("./types").BaseCode} BaseCode */
/** @typedef {import("./types").BaseName} BaseName */

/**
 * Create a new Uint8Array with the multibase varint+code.
 *
 * @param {BaseNameOrCode} nameOrCode - The multibase name or code number.
 * @param {Uint8Array} buf - The data to be prefixed with multibase.
 * @returns {Uint8Array}
 * @throws {Error} Will throw if the encoding is not supported
 */
function multibase (nameOrCode, buf) {
  if (!buf) {
    throw new Error('requires an encoded Uint8Array')
  }
  const { name, codeBuf } = encoding(nameOrCode)
  validEncode(name, buf)

  return concat([codeBuf, buf], codeBuf.length + buf.length)
}

/**
 * Encode data with the specified base and add the multibase prefix.
 *
 * @param {BaseNameOrCode} nameOrCode - The multibase name or code number.
 * @param {Uint8Array} buf - The data to be encoded.
 * @returns {Uint8Array}
 * @throws {Error} Will throw if the encoding is not supported
 *
 */
function encode (nameOrCode, buf) {
  const enc = encoding(nameOrCode)
  const data = encodeText(enc.encode(buf))

  return concat([enc.codeBuf, data], enc.codeBuf.length + data.length)
}

/**
 * Takes a Uint8Array or string encoded with multibase header, decodes it and
 * returns the decoded buffer
 *
 * @param {Uint8Array|string} data
 * @returns {Uint8Array}
 * @throws {Error} Will throw if the encoding is not supported
 *
 */
function decode (data) {
  if (data instanceof Uint8Array) {
    data = decodeText(data)
  }
  const prefix = data[0]

  // Make all encodings case-insensitive except the ones that include upper and lower chars in the alphabet
  if (['f', 'F', 'v', 'V', 't', 'T', 'b', 'B', 'c', 'C', 'h', 'k', 'K'].includes(prefix)) {
    data = data.toLowerCase()
  }
  const enc = encoding(/** @type {BaseCode} */(data[0]))
  return enc.decode(data.substring(1))
}

/**
 * Is the given data multibase encoded?
 *
 * @param {Uint8Array|string} data
 * @returns {false | string}
 */
function isEncoded (data) {
  if (data instanceof Uint8Array) {
    data = decodeText(data)
  }

  // Ensure bufOrString is a string
  if (Object.prototype.toString.call(data) !== '[object String]') {
    return false
  }

  try {
    const enc = encoding(/** @type {BaseCode} */(data[0]))
    return enc.name
  } catch (err) {
    return false
  }
}

/**
 * Validate encoded data
 *
 * @param {BaseNameOrCode} name
 * @param {Uint8Array} buf
 * @returns {void}
 * @throws {Error} Will throw if the encoding is not supported
 */
function validEncode (name, buf) {
  const enc = encoding(name)
  enc.decode(decodeText(buf))
}

/**
 * Get the encoding by name or code
 *
 * @param {BaseNameOrCode} nameOrCode
 * @returns {Base}
 * @throws {Error} Will throw if the encoding is not supported
 */
function encoding (nameOrCode) {
  if (constants.names[/** @type {BaseName} */(nameOrCode)]) {
    return constants.names[/** @type {BaseName} */(nameOrCode)]
  } else if (constants.codes[/** @type {BaseCode} */(nameOrCode)]) {
    return constants.codes[/** @type {BaseCode} */(nameOrCode)]
  } else {
    throw new Error(`Unsupported encoding: ${nameOrCode}`)
  }
}

/**
 * Get encoding from data
 *
 * @param {string|Uint8Array} data
 * @returns {Base}
 * @throws {Error} Will throw if the encoding is not supported
 */
function encodingFromData (data) {
  if (data instanceof Uint8Array) {
    data = decodeText(data)
  }

  return encoding(/** @type {BaseCode} */(data[0]))
}

exports = module.exports = multibase
exports.encode = encode
exports.decode = decode
exports.isEncoded = isEncoded
exports.encoding = encoding
exports.encodingFromData = encodingFromData
exports.names = Object.freeze(constants.names)
exports.codes = Object.freeze(constants.codes)