d3v4-force.js

(function (global, factory) {
	typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
	typeof define === 'function' && define.amd ? define(['exports'], factory) :
	(factory((global.d3v4 = {})));
}(this, (function (exports) { 'use strict';

function center(x, y) {
  var nodes;

  if (x == null) x = 0;
  if (y == null) y = 0;

  function force() {
    var i,
        n = nodes.length,
        node,
        sx = 0,
        sy = 0;

    for (i = 0; i < n; ++i) {
      node = nodes[i], sx += node.x, sy += node.y;
    }

    for (sx = sx / n - x, sy = sy / n - y, i = 0; i < n; ++i) {
      node = nodes[i], node.x -= sx, node.y -= sy;
    }
  }

  force.initialize = function(_) {
    nodes = _;
  };

  force.x = function(_) {
    return arguments.length ? (x = +_, force) : x;
  };

  force.y = function(_) {
    return arguments.length ? (y = +_, force) : y;
  };

  return force;
}

function constant(x) {
  return function() {
    return x;
  };
}

function jiggle() {
  return (Math.random() - 0.5) * 1e-6;
}

function tree_add(d) {
  var x = +this._x.call(null, d),
      y = +this._y.call(null, d);
  return add(this.cover(x, y), x, y, d);
}

function add(tree, x, y, d) {
  if (isNaN(x) || isNaN(y)) return tree; // ignore invalid points

  var parent,
      node = tree._root,
      leaf = {data: d},
      x0 = tree._x0,
      y0 = tree._y0,
      x1 = tree._x1,
      y1 = tree._y1,
      xm,
      ym,
      xp,
      yp,
      right,
      bottom,
      i,
      j;

  // If the tree is empty, initialize the root as a leaf.
  if (!node) return tree._root = leaf, tree;

  // Find the existing leaf for the new point, or add it.
  while (node.length) {
    if (right = x >= (xm = (x0 + x1) / 2)) x0 = xm; else x1 = xm;
    if (bottom = y >= (ym = (y0 + y1) / 2)) y0 = ym; else y1 = ym;
    if (parent = node, !(node = node[i = bottom << 1 | right])) return parent[i] = leaf, tree;
  }

  // Is the new point is exactly coincident with the existing point?
  xp = +tree._x.call(null, node.data);
  yp = +tree._y.call(null, node.data);
  if (x === xp && y === yp) return leaf.next = node, parent ? parent[i] = leaf : tree._root = leaf, tree;

  // Otherwise, split the leaf node until the old and new point are separated.
  do {
    parent = parent ? parent[i] = new Array(4) : tree._root = new Array(4);
    if (right = x >= (xm = (x0 + x1) / 2)) x0 = xm; else x1 = xm;
    if (bottom = y >= (ym = (y0 + y1) / 2)) y0 = ym; else y1 = ym;
  } while ((i = bottom << 1 | right) === (j = (yp >= ym) << 1 | (xp >= xm)));
  return parent[j] = node, parent[i] = leaf, tree;
}

function addAll(data) {
  var d, i, n = data.length,
      x,
      y,
      xz = new Array(n),
      yz = new Array(n),
      x0 = Infinity,
      y0 = Infinity,
      x1 = -Infinity,
      y1 = -Infinity;

  // Compute the points and their extent.
  for (i = 0; i < n; ++i) {
    if (isNaN(x = +this._x.call(null, d = data[i])) || isNaN(y = +this._y.call(null, d))) continue;
    xz[i] = x;
    yz[i] = y;
    if (x < x0) x0 = x;
    if (x > x1) x1 = x;
    if (y < y0) y0 = y;
    if (y > y1) y1 = y;
  }

  // If there were no (valid) points, inherit the existing extent.
  if (x1 < x0) x0 = this._x0, x1 = this._x1;
  if (y1 < y0) y0 = this._y0, y1 = this._y1;

  // Expand the tree to cover the new points.
  this.cover(x0, y0).cover(x1, y1);

  // Add the new points.
  for (i = 0; i < n; ++i) {
    add(this, xz[i], yz[i], data[i]);
  }

  return this;
}

function tree_cover(x, y) {
  if (isNaN(x = +x) || isNaN(y = +y)) return this; // ignore invalid points

  var x0 = this._x0,
      y0 = this._y0,
      x1 = this._x1,
      y1 = this._y1;

  // If the quadtree has no extent, initialize them.
  // Integer extent are necessary so that if we later double the extent,
  // the existing quadrant boundaries don’t change due to floating point error!
  if (isNaN(x0)) {
    x1 = (x0 = Math.floor(x)) + 1;
    y1 = (y0 = Math.floor(y)) + 1;
  }

  // Otherwise, double repeatedly to cover.
  else if (x0 > x || x > x1 || y0 > y || y > y1) {
    var z = x1 - x0,
        node = this._root,
        parent,
        i;

    switch (i = (y < (y0 + y1) / 2) << 1 | (x < (x0 + x1) / 2)) {
      case 0: {
        do parent = new Array(4), parent[i] = node, node = parent;
        while (z *= 2, x1 = x0 + z, y1 = y0 + z, x > x1 || y > y1);
        break;
      }
      case 1: {
        do parent = new Array(4), parent[i] = node, node = parent;
        while (z *= 2, x0 = x1 - z, y1 = y0 + z, x0 > x || y > y1);
        break;
      }
      case 2: {
        do parent = new Array(4), parent[i] = node, node = parent;
        while (z *= 2, x1 = x0 + z, y0 = y1 - z, x > x1 || y0 > y);
        break;
      }
      case 3: {
        do parent = new Array(4), parent[i] = node, node = parent;
        while (z *= 2, x0 = x1 - z, y0 = y1 - z, x0 > x || y0 > y);
        break;
      }
    }

    if (this._root && this._root.length) this._root = node;
  }

  // If the quadtree covers the point already, just return.
  else return this;

  this._x0 = x0;
  this._y0 = y0;
  this._x1 = x1;
  this._y1 = y1;
  return this;
}

function tree_data() {
  var data = [];
  this.visit(function(node) {
    if (!node.length) do data.push(node.data); while (node = node.next)
  });
  return data;
}

function tree_extent(_) {
  return arguments.length
      ? this.cover(+_[0][0], +_[0][1]).cover(+_[1][0], +_[1][1])
      : isNaN(this._x0) ? undefined : [[this._x0, this._y0], [this._x1, this._y1]];
}

function Quad(node, x0, y0, x1, y1) {
  this.node = node;
  this.x0 = x0;
  this.y0 = y0;
  this.x1 = x1;
  this.y1 = y1;
}

function tree_find(x, y, radius) {
  var data,
      x0 = this._x0,
      y0 = this._y0,
      x1,
      y1,
      x2,
      y2,
      x3 = this._x1,
      y3 = this._y1,
      quads = [],
      node = this._root,
      q,
      i;

  if (node) quads.push(new Quad(node, x0, y0, x3, y3));
  if (radius == null) radius = Infinity;
  else {
    x0 = x - radius, y0 = y - radius;
    x3 = x + radius, y3 = y + radius;
    radius *= radius;
  }

  while (q = quads.pop()) {

    // Stop searching if this quadrant can’t contain a closer node.
    if (!(node = q.node)
        || (x1 = q.x0) > x3
        || (y1 = q.y0) > y3
        || (x2 = q.x1) < x0
        || (y2 = q.y1) < y0) continue;

    // Bisect the current quadrant.
    if (node.length) {
      var xm = (x1 + x2) / 2,
          ym = (y1 + y2) / 2;

      quads.push(
        new Quad(node[3], xm, ym, x2, y2),
        new Quad(node[2], x1, ym, xm, y2),
        new Quad(node[1], xm, y1, x2, ym),
        new Quad(node[0], x1, y1, xm, ym)
      );

      // Visit the closest quadrant first.
      if (i = (y >= ym) << 1 | (x >= xm)) {
        q = quads[quads.length - 1];
        quads[quads.length - 1] = quads[quads.length - 1 - i];
        quads[quads.length - 1 - i] = q;
      }
    }

    // Visit this point. (Visiting coincident points isn’t necessary!)
    else {
      var dx = x - +this._x.call(null, node.data),
          dy = y - +this._y.call(null, node.data),
          d2 = dx * dx + dy * dy;
      if (d2 < radius) {
        var d = Math.sqrt(radius = d2);
        x0 = x - d, y0 = y - d;
        x3 = x + d, y3 = y + d;
        data = node.data;
      }
    }
  }

  return data;
}

function tree_remove(d) {
  if (isNaN(x = +this._x.call(null, d)) || isNaN(y = +this._y.call(null, d))) return this; // ignore invalid points

  var parent,
      node = this._root,
      retainer,
      previous,
      next,
      x0 = this._x0,
      y0 = this._y0,
      x1 = this._x1,
      y1 = this._y1,
      x,
      y,
      xm,
      ym,
      right,
      bottom,
      i,
      j;

  // If the tree is empty, initialize the root as a leaf.
  if (!node) return this;

  // Find the leaf node for the point.
  // While descending, also retain the deepest parent with a non-removed sibling.
  if (node.length) while (true) {
    if (right = x >= (xm = (x0 + x1) / 2)) x0 = xm; else x1 = xm;
    if (bottom = y >= (ym = (y0 + y1) / 2)) y0 = ym; else y1 = ym;
    if (!(parent = node, node = node[i = bottom << 1 | right])) return this;
    if (!node.length) break;
    if (parent[(i + 1) & 3] || parent[(i + 2) & 3] || parent[(i + 3) & 3]) retainer = parent, j = i;
  }

  // Find the point to remove.
  while (node.data !== d) if (!(previous = node, node = node.next)) return this;
  if (next = node.next) delete node.next;

  // If there are multiple coincident points, remove just the point.
  if (previous) return next ? previous.next = next : delete previous.next, this;

  // If this is the root point, remove it.
  if (!parent) return this._root = next, this;

  // Remove this leaf.
  next ? parent[i] = next : delete parent[i];

  // If the parent now contains exactly one leaf, collapse superfluous parents.
  if ((node = parent[0] || parent[1] || parent[2] || parent[3])
      && node === (parent[3] || parent[2] || parent[1] || parent[0])
      && !node.length) {
    if (retainer) retainer[j] = node;
    else this._root = node;
  }

  return this;
}

function removeAll(data) {
  for (var i = 0, n = data.length; i < n; ++i) this.remove(data[i]);
  return this;
}

function tree_root() {
  return this._root;
}

function tree_size() {
  var size = 0;
  this.visit(function(node) {
    if (!node.length) do ++size; while (node = node.next)
  });
  return size;
}

function tree_visit(callback) {
  var quads = [], q, node = this._root, child, x0, y0, x1, y1;
  if (node) quads.push(new Quad(node, this._x0, this._y0, this._x1, this._y1));
  while (q = quads.pop()) {
    if (!callback(node = q.node, x0 = q.x0, y0 = q.y0, x1 = q.x1, y1 = q.y1) && node.length) {
      var xm = (x0 + x1) / 2, ym = (y0 + y1) / 2;
      if (child = node[3]) quads.push(new Quad(child, xm, ym, x1, y1));
      if (child = node[2]) quads.push(new Quad(child, x0, ym, xm, y1));
      if (child = node[1]) quads.push(new Quad(child, xm, y0, x1, ym));
      if (child = node[0]) quads.push(new Quad(child, x0, y0, xm, ym));
    }
  }
  return this;
}

function tree_visitAfter(callback) {
  var quads = [], next = [], q;
  if (this._root) quads.push(new Quad(this._root, this._x0, this._y0, this._x1, this._y1));
  while (q = quads.pop()) {
    var node = q.node;
    if (node.length) {
      var child, x0 = q.x0, y0 = q.y0, x1 = q.x1, y1 = q.y1, xm = (x0 + x1) / 2, ym = (y0 + y1) / 2;
      if (child = node[0]) quads.push(new Quad(child, x0, y0, xm, ym));
      if (child = node[1]) quads.push(new Quad(child, xm, y0, x1, ym));
      if (child = node[2]) quads.push(new Quad(child, x0, ym, xm, y1));
      if (child = node[3]) quads.push(new Quad(child, xm, ym, x1, y1));
    }
    next.push(q);
  }
  while (q = next.pop()) {
    callback(q.node, q.x0, q.y0, q.x1, q.y1);
  }
  return this;
}

function defaultX(d) {
  return d[0];
}

function tree_x(_) {
  return arguments.length ? (this._x = _, this) : this._x;
}

function defaultY(d) {
  return d[1];
}

function tree_y(_) {
  return arguments.length ? (this._y = _, this) : this._y;
}

function quadtree(nodes, x, y) {
  var tree = new Quadtree(x == null ? defaultX : x, y == null ? defaultY : y, NaN, NaN, NaN, NaN);
  return nodes == null ? tree : tree.addAll(nodes);
}

function Quadtree(x, y, x0, y0, x1, y1) {
  this._x = x;
  this._y = y;
  this._x0 = x0;
  this._y0 = y0;
  this._x1 = x1;
  this._y1 = y1;
  this._root = undefined;
}

function leaf_copy(leaf) {
  var copy = {data: leaf.data}, next = copy;
  while (leaf = leaf.next) next = next.next = {data: leaf.data};
  return copy;
}

var treeProto = quadtree.prototype = Quadtree.prototype;

treeProto.copy = function() {
  var copy = new Quadtree(this._x, this._y, this._x0, this._y0, this._x1, this._y1),
      node = this._root,
      nodes,
      child;

  if (!node) return copy;

  if (!node.length) return copy._root = leaf_copy(node), copy;

  nodes = [{source: node, target: copy._root = new Array(4)}];
  while (node = nodes.pop()) {
    for (var i = 0; i < 4; ++i) {
      if (child = node.source[i]) {
        if (child.length) nodes.push({source: child, target: node.target[i] = new Array(4)});
        else node.target[i] = leaf_copy(child);
      }
    }
  }

  return copy;
};

treeProto.add = tree_add;
treeProto.addAll = addAll;
treeProto.cover = tree_cover;
treeProto.data = tree_data;
treeProto.extent = tree_extent;
treeProto.find = tree_find;
treeProto.remove = tree_remove;
treeProto.removeAll = removeAll;
treeProto.root = tree_root;
treeProto.size = tree_size;
treeProto.visit = tree_visit;
treeProto.visitAfter = tree_visitAfter;
treeProto.x = tree_x;
treeProto.y = tree_y;

function x(d) {
  return d.x + d.vx;
}

function y(d) {
  return d.y + d.vy;
}

function collide(radius) {
  var nodes,
      radii,
      strength = 1,
      iterations = 1;

  if (typeof radius !== "function") radius = constant(radius == null ? 1 : +radius);

  function force() {
    var i, n = nodes.length,
        tree,
        node,
        xi,
        yi,
        ri,
        ri2;

    for (var k = 0; k < iterations; ++k) {
      tree = quadtree(nodes, x, y).visitAfter(prepare);
      for (i = 0; i < n; ++i) {
        node = nodes[i];
        ri = radii[node.index], ri2 = ri * ri;
        xi = node.x + node.vx;
        yi = node.y + node.vy;
        tree.visit(apply);
      }
    }

    function apply(quad, x0, y0, x1, y1) {
      var data = quad.data, rj = quad.r, r = ri + rj;
      if (data) {
        if (data.index > node.index) {
          var x = xi - data.x - data.vx,
              y = yi - data.y - data.vy,
              l = x * x + y * y;
          if (l < r * r) {
            if (x === 0) x = jiggle(), l += x * x;
            if (y === 0) y = jiggle(), l += y * y;
            l = (r - (l = Math.sqrt(l))) / l * strength;
            node.vx += (x *= l) * (r = (rj *= rj) / (ri2 + rj));
            node.vy += (y *= l) * r;
            data.vx -= x * (r = 1 - r);
            data.vy -= y * r;
          }
        }
        return;
      }
      return x0 > xi + r || x1 < xi - r || y0 > yi + r || y1 < yi - r;
    }
  }

  function prepare(quad) {
    if (quad.data) return quad.r = radii[quad.data.index];
    for (var i = quad.r = 0; i < 4; ++i) {
      if (quad[i] && quad[i].r > quad.r) {
        quad.r = quad[i].r;
      }
    }
  }

  function initialize() {
    if (!nodes) return;
    var i, n = nodes.length, node;
    radii = new Array(n);
    for (i = 0; i < n; ++i) node = nodes[i], radii[node.index] = +radius(node, i, nodes);
  }

  force.initialize = function(_) {
    nodes = _;
    initialize();
  };

  force.iterations = function(_) {
    return arguments.length ? (iterations = +_, force) : iterations;
  };

  force.strength = function(_) {
    return arguments.length ? (strength = +_, force) : strength;
  };

  force.radius = function(_) {
    return arguments.length ? (radius = typeof _ === "function" ? _ : constant(+_), initialize(), force) : radius;
  };

  return force;
}

var prefix = "$";

function Map() {}

Map.prototype = map.prototype = {
  constructor: Map,
  has: function(key) {
    return (prefix + key) in this;
  },
  get: function(key) {
    return this[prefix + key];
  },
  set: function(key, value) {
    this[prefix + key] = value;
    return this;
  },
  remove: function(key) {
    var property = prefix + key;
    return property in this && delete this[property];
  },
  clear: function() {
    for (var property in this) if (property[0] === prefix) delete this[property];
  },
  keys: function() {
    var keys = [];
    for (var property in this) if (property[0] === prefix) keys.push(property.slice(1));
    return keys;
  },
  values: function() {
    var values = [];
    for (var property in this) if (property[0] === prefix) values.push(this[property]);
    return values;
  },
  entries: function() {
    var entries = [];
    for (var property in this) if (property[0] === prefix) entries.push({key: property.slice(1), value: this[property]});
    return entries;
  },
  size: function() {
    var size = 0;
    for (var property in this) if (property[0] === prefix) ++size;
    return size;
  },
  empty: function() {
    for (var property in this) if (property[0] === prefix) return false;
    return true;
  },
  each: function(f) {
    for (var property in this) if (property[0] === prefix) f(this[property], property.slice(1), this);
  }
};

function map(object, f) {
  var map = new Map;

  // Copy constructor.
  if (object instanceof Map) object.each(function(value, key) { map.set(key, value); });

  // Index array by numeric index or specified key function.
  else if (Array.isArray(object)) {
    var i = -1,
        n = object.length,
        o;

    if (f == null) while (++i < n) map.set(i, object[i]);
    else while (++i < n) map.set(f(o = object[i], i, object), o);
  }

  // Convert object to map.
  else if (object) for (var key in object) map.set(key, object[key]);

  return map;
}

function Set() {}

var proto = map.prototype;

Set.prototype = set.prototype = {
  constructor: Set,
  has: proto.has,
  add: function(value) {
    value += "";
    this[prefix + value] = value;
    return this;
  },
  remove: proto.remove,
  clear: proto.clear,
  values: proto.keys,
  size: proto.size,
  empty: proto.empty,
  each: proto.each
};

function set(object, f) {
  var set = new Set;

  // Copy constructor.
  if (object instanceof Set) object.each(function(value) { set.add(value); });

  // Otherwise, assume it’s an array.
  else if (object) {
    var i = -1, n = object.length;
    if (f == null) while (++i < n) set.add(object[i]);
    else while (++i < n) set.add(f(object[i], i, object));
  }

  return set;
}

function index(d) {
  return d.index;
}

function find(nodeById, nodeId) {
  var node = nodeById.get(nodeId);
  if (!node) throw new Error("missing: " + nodeId);
  return node;
}

function link(links) {
  var id = index,
      strength = defaultStrength,
      strengths,
      distance = constant(30),
      distances,
      nodes,
      count,
      bias,
      iterations = 1;

  if (links == null) links = [];

  function defaultStrength(link) {
    return 1 / Math.min(count[link.source.index], count[link.target.index]);
  }

  function force(alpha) {
    for (var k = 0, n = links.length; k < iterations; ++k) {
      for (var i = 0, link, source, target, x, y, l, b; i < n; ++i) {
        link = links[i], source = link.source, target = link.target;
        x = target.x + target.vx - source.x - source.vx || jiggle();
        y = target.y + target.vy - source.y - source.vy || jiggle();
        l = Math.sqrt(x * x + y * y);
        l = (l - distances[i]) / l * alpha * strengths[i];
        x *= l, y *= l;
        target.vx -= x * (b = bias[i]);
        target.vy -= y * b;
        source.vx += x * (b = 1 - b);
        source.vy += y * b;
      }
    }
  }

  function initialize() {
    if (!nodes) return;

    var i,
        n = nodes.length,
        m = links.length,
        nodeById = map(nodes, id),
        link;

    for (i = 0, count = new Array(n); i < m; ++i) {
      link = links[i], link.index = i;
      if (typeof link.source !== "object") link.source = find(nodeById, link.source);
      if (typeof link.target !== "object") link.target = find(nodeById, link.target);
      count[link.source.index] = (count[link.source.index] || 0) + 1;
      count[link.target.index] = (count[link.target.index] || 0) + 1;
    }

    for (i = 0, bias = new Array(m); i < m; ++i) {
      link = links[i], bias[i] = count[link.source.index] / (count[link.source.index] + count[link.target.index]);
    }

    strengths = new Array(m), initializeStrength();
    distances = new Array(m), initializeDistance();
  }

  function initializeStrength() {
    if (!nodes) return;

    for (var i = 0, n = links.length; i < n; ++i) {
      strengths[i] = +strength(links[i], i, links);
    }
  }

  function initializeDistance() {
    if (!nodes) return;

    for (var i = 0, n = links.length; i < n; ++i) {
      distances[i] = +distance(links[i], i, links);
    }
  }

  force.initialize = function(_) {
    nodes = _;
    initialize();
  };

  force.links = function(_) {
    return arguments.length ? (links = _, initialize(), force) : links;
  };

  force.id = function(_) {
    return arguments.length ? (id = _, force) : id;
  };

  force.iterations = function(_) {
    return arguments.length ? (iterations = +_, force) : iterations;
  };

  force.strength = function(_) {
    return arguments.length ? (strength = typeof _ === "function" ? _ : constant(+_), initializeStrength(), force) : strength;
  };

  force.distance = function(_) {
    return arguments.length ? (distance = typeof _ === "function" ? _ : constant(+_), initializeDistance(), force) : distance;
  };

  return force;
}

var noop = {value: function() {}};

function dispatch() {
  for (var i = 0, n = arguments.length, _ = {}, t; i < n; ++i) {
    if (!(t = arguments[i] + "") || (t in _)) throw new Error("illegal type: " + t);
    _[t] = [];
  }
  return new Dispatch(_);
}

function Dispatch(_) {
  this._ = _;
}

function parseTypenames(typenames, types) {
  return typenames.trim().split(/^|\s+/).map(function(t) {
    var name = "", i = t.indexOf(".");
    if (i >= 0) name = t.slice(i + 1), t = t.slice(0, i);
    if (t && !types.hasOwnProperty(t)) throw new Error("unknown type: " + t);
    return {type: t, name: name};
  });
}

Dispatch.prototype = dispatch.prototype = {
  constructor: Dispatch,
  on: function(typename, callback) {
    var _ = this._,
        T = parseTypenames(typename + "", _),
        t,
        i = -1,
        n = T.length;

    // If no callback was specified, return the callback of the given type and name.
    if (arguments.length < 2) {
      while (++i < n) if ((t = (typename = T[i]).type) && (t = get(_[t], typename.name))) return t;
      return;
    }

    // If a type was specified, set the callback for the given type and name.
    // Otherwise, if a null callback was specified, remove callbacks of the given name.
    if (callback != null && typeof callback !== "function") throw new Error("invalid callback: " + callback);
    while (++i < n) {
      if (t = (typename = T[i]).type) _[t] = set$1(_[t], typename.name, callback);
      else if (callback == null) for (t in _) _[t] = set$1(_[t], typename.name, null);
    }

    return this;
  },
  copy: function() {
    var copy = {}, _ = this._;
    for (var t in _) copy[t] = _[t].slice();
    return new Dispatch(copy);
  },
  call: function(type, that) {
    if ((n = arguments.length - 2) > 0) for (var args = new Array(n), i = 0, n, t; i < n; ++i) args[i] = arguments[i + 2];
    if (!this._.hasOwnProperty(type)) throw new Error("unknown type: " + type);
    for (t = this._[type], i = 0, n = t.length; i < n; ++i) t[i].value.apply(that, args);
  },
  apply: function(type, that, args) {
    if (!this._.hasOwnProperty(type)) throw new Error("unknown type: " + type);
    for (var t = this._[type], i = 0, n = t.length; i < n; ++i) t[i].value.apply(that, args);
  }
};

function get(type, name) {
  for (var i = 0, n = type.length, c; i < n; ++i) {
    if ((c = type[i]).name === name) {
      return c.value;
    }
  }
}

function set$1(type, name, callback) {
  for (var i = 0, n = type.length; i < n; ++i) {
    if (type[i].name === name) {
      type[i] = noop, type = type.slice(0, i).concat(type.slice(i + 1));
      break;
    }
  }
  if (callback != null) type.push({name: name, value: callback});
  return type;
}

var frame = 0, // is an animation frame pending?
    timeout = 0, // is a timeout pending?
    interval = 0, // are any timers active?
    pokeDelay = 1000, // how frequently we check for clock skew
    taskHead,
    taskTail,
    clockLast = 0,
    clockNow = 0,
    clockSkew = 0,
    clock = typeof performance === "object" && performance.now ? performance : Date,
    setFrame = typeof window === "object" && window.requestAnimationFrame ? window.requestAnimationFrame.bind(window) : function(f) { setTimeout(f, 17); };

function now() {
  return clockNow || (setFrame(clearNow), clockNow = clock.now() + clockSkew);
}

function clearNow() {
  clockNow = 0;
}

function Timer() {
  this._call =
  this._time =
  this._next = null;
}

Timer.prototype = timer.prototype = {
  constructor: Timer,
  restart: function(callback, delay, time) {
    if (typeof callback !== "function") throw new TypeError("callback is not a function");
    time = (time == null ? now() : +time) + (delay == null ? 0 : +delay);
    if (!this._next && taskTail !== this) {
      if (taskTail) taskTail._next = this;
      else taskHead = this;
      taskTail = this;
    }
    this._call = callback;
    this._time = time;
    sleep();
  },
  stop: function() {
    if (this._call) {
      this._call = null;
      this._time = Infinity;
      sleep();
    }
  }
};

function timer(callback, delay, time) {
  var t = new Timer;
  t.restart(callback, delay, time);
  return t;
}

function timerFlush() {
  now(); // Get the current time, if not already set.
  ++frame; // Pretend we’ve set an alarm, if we haven’t already.
  var t = taskHead, e;
  while (t) {
    if ((e = clockNow - t._time) >= 0) t._call.call(null, e);
    t = t._next;
  }
  --frame;
}

function wake() {
  clockNow = (clockLast = clock.now()) + clockSkew;
  frame = timeout = 0;
  try {
    timerFlush();
  } finally {
    frame = 0;
    nap();
    clockNow = 0;
  }
}

function poke() {
  var now = clock.now(), delay = now - clockLast;
  if (delay > pokeDelay) clockSkew -= delay, clockLast = now;
}

function nap() {
  var t0, t1 = taskHead, t2, time = Infinity;
  while (t1) {
    if (t1._call) {
      if (time > t1._time) time = t1._time;
      t0 = t1, t1 = t1._next;
    } else {
      t2 = t1._next, t1._next = null;
      t1 = t0 ? t0._next = t2 : taskHead = t2;
    }
  }
  taskTail = t0;
  sleep(time);
}

function sleep(time) {
  if (frame) return; // Soonest alarm already set, or will be.
  if (timeout) timeout = clearTimeout(timeout);
  var delay = time - clockNow; // Strictly less than if we recomputed clockNow.
  if (delay > 24) {
    if (time < Infinity) timeout = setTimeout(wake, time - clock.now() - clockSkew);
    if (interval) interval = clearInterval(interval);
  } else {
    if (!interval) clockLast = clock.now(), interval = setInterval(poke, pokeDelay);
    frame = 1, setFrame(wake);
  }
}

function x$1(d) {
  return d.x;
}

function y$1(d) {
  return d.y;
}

var initialRadius = 10,
    initialAngle = Math.PI * (3 - Math.sqrt(5));

function simulation(nodes) {
  var simulation,
      alpha = 1,
      alphaMin = 0.001,
      alphaDecay = 1 - Math.pow(alphaMin, 1 / 300),
      alphaTarget = 0,
      velocityDecay = 0.6,
      forces = map(),
      stepper = timer(step),
      event = dispatch("tick", "end");

  if (nodes == null) nodes = [];

  function step() {
    tick();
    event.call("tick", simulation);
    if (alpha < alphaMin) {
      stepper.stop();
      event.call("end", simulation);
    }
  }

  function tick() {
    var i, n = nodes.length, node;

    alpha += (alphaTarget - alpha) * alphaDecay;

    forces.each(function(force) {
      force(alpha);
    });

    for (i = 0; i < n; ++i) {
      node = nodes[i];
      if (node.fx == null) node.x += node.vx *= velocityDecay;
      else node.x = node.fx, node.vx = 0;
      if (node.fy == null) node.y += node.vy *= velocityDecay;
      else node.y = node.fy, node.vy = 0;
    }
  }

  function initializeNodes() {
    for (var i = 0, n = nodes.length, node; i < n; ++i) {
      node = nodes[i], node.index = i;
      if (isNaN(node.x) || isNaN(node.y)) {
        var radius = initialRadius * Math.sqrt(i), angle = i * initialAngle;
        node.x = radius * Math.cos(angle);
        node.y = radius * Math.sin(angle);
      }
      if (isNaN(node.vx) || isNaN(node.vy)) {
        node.vx = node.vy = 0;
      }
    }
  }

  function initializeForce(force) {
    if (force.initialize) force.initialize(nodes);
    return force;
  }

  initializeNodes();

  return simulation = {
    tick: tick,

    restart: function() {
      return stepper.restart(step), simulation;
    },

    stop: function() {
      return stepper.stop(), simulation;
    },

    nodes: function(_) {
      return arguments.length ? (nodes = _, initializeNodes(), forces.each(initializeForce), simulation) : nodes;
    },

    alpha: function(_) {
      return arguments.length ? (alpha = +_, simulation) : alpha;
    },

    alphaMin: function(_) {
      return arguments.length ? (alphaMin = +_, simulation) : alphaMin;
    },

    alphaDecay: function(_) {
      return arguments.length ? (alphaDecay = +_, simulation) : +alphaDecay;
    },

    alphaTarget: function(_) {
      return arguments.length ? (alphaTarget = +_, simulation) : alphaTarget;
    },

    velocityDecay: function(_) {
      return arguments.length ? (velocityDecay = 1 - _, simulation) : 1 - velocityDecay;
    },

    force: function(name, _) {
      return arguments.length > 1 ? (_ == null ? forces.remove(name) : forces.set(name, initializeForce(_)), simulation) : forces.get(name);
    },

    find: function(x, y, radius) {
      var i = 0,
          n = nodes.length,
          dx,
          dy,
          d2,
          node,
          closest;

      if (radius == null) radius = Infinity;
      else radius *= radius;

      for (i = 0; i < n; ++i) {
        node = nodes[i];
        dx = x - node.x;
        dy = y - node.y;
        d2 = dx * dx + dy * dy;
        if (d2 < radius) closest = node, radius = d2;
      }

      return closest;
    },

    on: function(name, _) {
      return arguments.length > 1 ? (event.on(name, _), simulation) : event.on(name);
    }
  };
}

function manyBody() {
  var nodes,
      node,
      alpha,
      strength = constant(-30),
      strengths,
      distanceMin2 = 1,
      distanceMax2 = Infinity,
      theta2 = 0.81;

  function force(_) {
    var i, n = nodes.length, tree = quadtree(nodes, x$1, y$1).visitAfter(accumulate);
    for (alpha = _, i = 0; i < n; ++i) node = nodes[i], tree.visit(apply);
  }

  function initialize() {
    if (!nodes) return;
    var i, n = nodes.length, node;
    strengths = new Array(n);
    for (i = 0; i < n; ++i) node = nodes[i], strengths[node.index] = +strength(node, i, nodes);
  }

  function accumulate(quad) {
    var strength = 0, q, c, weight = 0, x, y, i;

    // For internal nodes, accumulate forces from child quadrants.
    if (quad.length) {
      for (x = y = i = 0; i < 4; ++i) {
        if ((q = quad[i]) && (c = Math.abs(q.value))) {
          strength += q.value, weight += c, x += c * q.x, y += c * q.y;
        }
      }
      quad.x = x / weight;
      quad.y = y / weight;
    }

    // For leaf nodes, accumulate forces from coincident quadrants.
    else {
      q = quad;
      q.x = q.data.x;
      q.y = q.data.y;
      do strength += strengths[q.data.index];
      while (q = q.next);
    }

    quad.value = strength;
  }

  function apply(quad, x1, _, x2) {
    if (!quad.value) return true;

    var x = quad.x - node.x,
        y = quad.y - node.y,
        w = x2 - x1,
        l = x * x + y * y;

    // Apply the Barnes-Hut approximation if possible.
    // Limit forces for very close nodes; randomize direction if coincident.
    if (w * w / theta2 < l) {
      if (l < distanceMax2) {
        if (x === 0) x = jiggle(), l += x * x;
        if (y === 0) y = jiggle(), l += y * y;
        if (l < distanceMin2) l = Math.sqrt(distanceMin2 * l);
        node.vx += x * quad.value * alpha / l;
        node.vy += y * quad.value * alpha / l;
      }
      return true;
    }

    // Otherwise, process points directly.
    else if (quad.length || l >= distanceMax2) return;

    // Limit forces for very close nodes; randomize direction if coincident.
    if (quad.data !== node || quad.next) {
      if (x === 0) x = jiggle(), l += x * x;
      if (y === 0) y = jiggle(), l += y * y;
      if (l < distanceMin2) l = Math.sqrt(distanceMin2 * l);
    }

    do if (quad.data !== node) {
      w = strengths[quad.data.index] * alpha / l;
      node.vx += x * w;
      node.vy += y * w;
    } while (quad = quad.next);
  }

  force.initialize = function(_) {
    nodes = _;
    initialize();
  };

  force.strength = function(_) {
    return arguments.length ? (strength = typeof _ === "function" ? _ : constant(+_), initialize(), force) : strength;
  };

  force.distanceMin = function(_) {
    return arguments.length ? (distanceMin2 = _ * _, force) : Math.sqrt(distanceMin2);
  };

  force.distanceMax = function(_) {
    return arguments.length ? (distanceMax2 = _ * _, force) : Math.sqrt(distanceMax2);
  };

  force.theta = function(_) {
    return arguments.length ? (theta2 = _ * _, force) : Math.sqrt(theta2);
  };

  return force;
}

function radial(radius, x, y) {
  var nodes,
      strength = constant(0.1),
      strengths,
      radiuses;

  if (typeof radius !== "function") radius = constant(+radius);
  if (x == null) x = 0;
  if (y == null) y = 0;

  function force(alpha) {
    for (var i = 0, n = nodes.length; i < n; ++i) {
      var node = nodes[i],
          dx = node.x - x || 1e-6,
          dy = node.y - y || 1e-6,
          r = Math.sqrt(dx * dx + dy * dy),
          k = (radiuses[i] - r) * strengths[i] * alpha / r;
      node.vx += dx * k;
      node.vy += dy * k;
    }
  }

  function initialize() {
    if (!nodes) return;
    var i, n = nodes.length;
    strengths = new Array(n);
    radiuses = new Array(n);
    for (i = 0; i < n; ++i) {
      radiuses[i] = +radius(nodes[i], i, nodes);
      strengths[i] = isNaN(radiuses[i]) ? 0 : +strength(nodes[i], i, nodes);
    }
  }

  force.initialize = function(_) {
    nodes = _, initialize();
  };

  force.strength = function(_) {
    return arguments.length ? (strength = typeof _ === "function" ? _ : constant(+_), initialize(), force) : strength;
  };

  force.radius = function(_) {
    return arguments.length ? (radius = typeof _ === "function" ? _ : constant(+_), initialize(), force) : radius;
  };

  force.x = function(_) {
    return arguments.length ? (x = +_, force) : x;
  };

  force.y = function(_) {
    return arguments.length ? (y = +_, force) : y;
  };

  return force;
}

function x$2(x) {
  var strength = constant(0.1),
      nodes,
      strengths,
      xz;

  if (typeof x !== "function") x = constant(x == null ? 0 : +x);

  function force(alpha) {
    for (var i = 0, n = nodes.length, node; i < n; ++i) {
      node = nodes[i], node.vx += (xz[i] - node.x) * strengths[i] * alpha;
    }
  }

  function initialize() {
    if (!nodes) return;
    var i, n = nodes.length;
    strengths = new Array(n);
    xz = new Array(n);
    for (i = 0; i < n; ++i) {
      strengths[i] = isNaN(xz[i] = +x(nodes[i], i, nodes)) ? 0 : +strength(nodes[i], i, nodes);
    }
  }

  force.initialize = function(_) {
    nodes = _;
    initialize();
  };

  force.strength = function(_) {
    return arguments.length ? (strength = typeof _ === "function" ? _ : constant(+_), initialize(), force) : strength;
  };

  force.x = function(_) {
    return arguments.length ? (x = typeof _ === "function" ? _ : constant(+_), initialize(), force) : x;
  };

  return force;
}

function y$2(y) {
  var strength = constant(0.1),
      nodes,
      strengths,
      yz;

  if (typeof y !== "function") y = constant(y == null ? 0 : +y);

  function force(alpha) {
    for (var i = 0, n = nodes.length, node; i < n; ++i) {
      node = nodes[i], node.vy += (yz[i] - node.y) * strengths[i] * alpha;
    }
  }

  function initialize() {
    if (!nodes) return;
    var i, n = nodes.length;
    strengths = new Array(n);
    yz = new Array(n);
    for (i = 0; i < n; ++i) {
      strengths[i] = isNaN(yz[i] = +y(nodes[i], i, nodes)) ? 0 : +strength(nodes[i], i, nodes);
    }
  }

  force.initialize = function(_) {
    nodes = _;
    initialize();
  };

  force.strength = function(_) {
    return arguments.length ? (strength = typeof _ === "function" ? _ : constant(+_), initialize(), force) : strength;
  };

  force.y = function(_) {
    return arguments.length ? (y = typeof _ === "function" ? _ : constant(+_), initialize(), force) : y;
  };

  return force;
}

function forceStraightenPaths(paths) {
    var _nodes,
        _inputPaths = paths || [],
        _paths, _id = function(n) { return n.index; },
        _angleForce = 0.1,
        _pathNodes = function(p) { return p.nodes; },
        _pathStrength = function(p) { return typeof p.strength !== 'undefined' ? +p.strength : 1; },
        _debug = false;
    var force = function(alpha) {
        function _dot(v1, v2) { return  v1.x*v2.x + v1.y*v2.y; }        function _len(v) { return Math.sqrt(v.x*v.x + v.y*v.y); }        function _angle(v1, v2) {
            var a = _dot(v1, v2) / (_len(v1)*_len(v2));
            a = Math.min(a, 1);
            a = Math.max(a, -1);
            return Math.acos(a);
        }        // perpendicular unit length vector
        function _pVec(v) {
            var xx = -v.y/v.x, yy = 1;
            var length = _len({x: xx, y: yy});
            return {x: xx/length, y: yy/length};
        }
        function _displaceAdjacent(node, angle, pVec, k) {
            var turn = Math.PI-angle,
                turn2 = turn*turn;
            return {
                kind: 'adjacent',
                x: pVec.x*turn2*k,
                y: pVec.y*turn2*k
            };
        }

        function _displaceCenter(dadj1, dadj2) {
            return {
                kind: 'center',
                x: -(dadj1.x + dadj2.x),
                y: -(dadj1.y + dadj2.y)
            };
        }

        function _offsetNode(node, disp) {
            node.x += disp.x;
            node.y += disp.y;
        }
        var report = [];
        _paths.forEach(function(path, i) {
            var pnodes = path.nodes,
                strength = path.strength;
            if(typeof strength !== 'number')
                strength = 1;
            if(pnodes.length < 3) return; // at least 3 nodes (and 2 edges):  A->B->C
            if(_debug) {
                report.push({
                    action: 'init',
                    nodes: pnodes.map(function(n) {
                        return {
                            id: _id(n),
                            x: n.x,
                            y: n.y
                        };
                    }),
                    edges: pnodes.reduce(function(p, n) {
                        if(!Array.isArray(p))
                            return [{source: _id(p), target: _id(n)}];
                        p.push({source: p[p.length-1].target, target: _id(n)});
                        return p;
                    })
                });
            }
            for(var i = 1; i < pnodes.length-1; ++i) {
                var current = pnodes[i];
                var prev = pnodes[i-1];
                var next = pnodes[i+1];

                // we can't do anything for two-cycles
                if(prev === next)
                    continue;

                // calculate the angle
                var vPrev = {x: prev.x - current.x, y: prev.y - current.y};
                var vNext = {x: next.x - current.x, y: next.y - current.y};

                var angle = _angle(vPrev, vNext); // angle in [0, PI]

                var pvecPrev = _pVec(vPrev);
                var pvecNext = _pVec(vNext);

                // make sure the perpendicular vector is in the
                // direction that makes the angle more towards 180 degree
                // 1. calculate the middle point of node 'prev' and 'next'
                var mid = {x: (prev.x+next.x)/2.0, y: (prev.y+next.y)/2.0};

                // 2. calculate the vectors: 'prev' pointing to 'mid', 'next' pointing to 'mid'
                var prev_mid = {x: mid.x-prev.x, y: mid.y-prev.y};
                var next_mid = {x: mid.x-next.x, y: mid.y-next.y};

                // 3. the 'correct' vector: the angle between pvec and prev_mid(next_mid) should
                //    be an obtuse angle
                pvecPrev = _angle(prev_mid, pvecPrev) >= Math.PI/2.0 ? pvecPrev : {x: -pvecPrev.x, y: -pvecPrev.y};
                pvecNext = _angle(next_mid, pvecNext) >= Math.PI/2.0 ? pvecNext : {x: -pvecNext.x, y: -pvecNext.y};

                // modify positions of nodes
                var prevDisp = _displaceAdjacent(prev, angle, pvecPrev, strength * _angleForce);
                var nextDisp = _displaceAdjacent(next, angle, pvecNext, strength * _angleForce);
                var centerDisp = _displaceCenter(prevDisp, nextDisp);
                if(_debug) {
                    report.push({
                        action: 'force',
                        nodes: [{
                            id: _id(prev),
                            x: prev.x,
                            y: prev.y,
                            force: prevDisp
                        }, {
                            id: _id(current),
                            x: current.x,
                            y: current.y,
                            force: centerDisp
                        }, {
                            id: _id(next),
                            x: next.x,
                            y: next.y,
                            force: nextDisp
                        }],
                        edges: [{
                            source: _id(prev),
                            target: _id(current)
                        }, {
                            source: _id(current),
                            target: _id(next)
                        }]
                    });
                }
                _offsetNode(prev, prevDisp);
                _offsetNode(next, nextDisp);
                _offsetNode(current, centerDisp);
            }
        });
        if(_debug)
            console.log(report);
    };
    function find(nodeById, nodeId) {
        var node = nodeById.get(nodeId);
        if(!node)
            throw new Error('node missing: ' + nodeId);
        return node;
    }
    function init() {
        if(!_nodes)
            return;
        var nodeById = d3.map(_nodes, _id);
        _paths = _inputPaths.map(function(path) {
            return {
                nodes: _pathNodes(path).map(function(n) {
                    return typeof n !== 'object' ?
                        find(nodeById, n) :
                        n;
                }),
                strength: _pathStrength(path)
            };
        });
    }
    force.initialize = function(nodes) {
        _nodes = nodes;
        init();
    };
    force.paths = function(paths) {
        if(!arguments.length) return _paths;
        _inputPaths = paths;
        init();
        return this;
    };
    force.id = function(id) {
        if(!arguments.length) return _id;
        _id = id;
        return this;
    };
    force.angleForce = function(angleForce) {
        if(!arguments.length) return _angleForce;
        _angleForce = angleForce;
        return this;
    };
    force.pathNodes = function(pathNodes) {
        if(!arguments.length) return _pathNodes;
        _pathNodes = pathNodes;
        return this;
    };
    force.pathStrength = function(pathStrength) {
        if(!arguments.length) return _pathStrength;
        _pathStrength = pathStrength;
        return this;
    };
    force.debug = function(debug) {
        if(!arguments.length) return _debug;
        _debug = debug;
        return this;
    };
    return force;
}

exports.forceCenter = center;
exports.forceCollide = collide;
exports.forceLink = link;
exports.forceManyBody = manyBody;
exports.forceRadial = radial;
exports.forceSimulation = simulation;
exports.forceX = x$2;
exports.forceY = y$2;
exports.forceStraightenPaths = forceStraightenPaths;

Object.defineProperty(exports, '__esModule', { value: true });

})));