'use strict';

var events = require('events');
var Iterator = require('obliterator/iterator');
var take = require('obliterator/take');
var chain = require('obliterator/chain');

function _interopDefaultLegacy (e) { return e && typeof e === 'object' && 'default' in e ? e : { 'default': e }; }

var Iterator__default = /*#__PURE__*/_interopDefaultLegacy(Iterator);
var take__default = /*#__PURE__*/_interopDefaultLegacy(take);
var chain__default = /*#__PURE__*/_interopDefaultLegacy(chain);

function _typeof(obj) {
  "@babel/helpers - typeof";

  return _typeof = "function" == typeof Symbol && "symbol" == typeof Symbol.iterator ? function (obj) {
    return typeof obj;
  } : function (obj) {
    return obj && "function" == typeof Symbol && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj;
  }, _typeof(obj);
}
function _inheritsLoose(subClass, superClass) {
  subClass.prototype = Object.create(superClass.prototype);
  subClass.prototype.constructor = subClass;
  _setPrototypeOf(subClass, superClass);
}
function _getPrototypeOf(o) {
  _getPrototypeOf = Object.setPrototypeOf ? Object.getPrototypeOf.bind() : function _getPrototypeOf(o) {
    return o.__proto__ || Object.getPrototypeOf(o);
  };
  return _getPrototypeOf(o);
}
function _setPrototypeOf(o, p) {
  _setPrototypeOf = Object.setPrototypeOf ? Object.setPrototypeOf.bind() : function _setPrototypeOf(o, p) {
    o.__proto__ = p;
    return o;
  };
  return _setPrototypeOf(o, p);
}
function _isNativeReflectConstruct() {
  if (typeof Reflect === "undefined" || !Reflect.construct) return false;
  if (Reflect.construct.sham) return false;
  if (typeof Proxy === "function") return true;
  try {
    Boolean.prototype.valueOf.call(Reflect.construct(Boolean, [], function () {}));
    return true;
  } catch (e) {
    return false;
  }
}
function _construct(Parent, args, Class) {
  if (_isNativeReflectConstruct()) {
    _construct = Reflect.construct.bind();
  } else {
    _construct = function _construct(Parent, args, Class) {
      var a = [null];
      a.push.apply(a, args);
      var Constructor = Function.bind.apply(Parent, a);
      var instance = new Constructor();
      if (Class) _setPrototypeOf(instance, Class.prototype);
      return instance;
    };
  }
  return _construct.apply(null, arguments);
}
function _isNativeFunction(fn) {
  return Function.toString.call(fn).indexOf("[native code]") !== -1;
}
function _wrapNativeSuper(Class) {
  var _cache = typeof Map === "function" ? new Map() : undefined;
  _wrapNativeSuper = function _wrapNativeSuper(Class) {
    if (Class === null || !_isNativeFunction(Class)) return Class;
    if (typeof Class !== "function") {
      throw new TypeError("Super expression must either be null or a function");
    }
    if (typeof _cache !== "undefined") {
      if (_cache.has(Class)) return _cache.get(Class);
      _cache.set(Class, Wrapper);
    }
    function Wrapper() {
      return _construct(Class, arguments, _getPrototypeOf(this).constructor);
    }
    Wrapper.prototype = Object.create(Class.prototype, {
      constructor: {
        value: Wrapper,
        enumerable: false,
        writable: true,
        configurable: true
      }
    });
    return _setPrototypeOf(Wrapper, Class);
  };
  return _wrapNativeSuper(Class);
}
function _assertThisInitialized(self) {
  if (self === void 0) {
    throw new ReferenceError("this hasn't been initialised - super() hasn't been called");
  }
  return self;
}

/**
 * Graphology Utilities
 * =====================
 *
 * Collection of helpful functions used by the implementation.
 */

/**
 * Object.assign-like polyfill.
 *
 * @param  {object} target       - First object.
 * @param  {object} [...objects] - Objects to merge.
 * @return {object}
 */
function assignPolyfill() {
  var target = arguments[0];
  for (var i = 1, l = arguments.length; i < l; i++) {
    if (!arguments[i]) continue;
    for (var k in arguments[i]) {
      target[k] = arguments[i][k];
    }
  }
  return target;
}
var assign = assignPolyfill;
if (typeof Object.assign === 'function') assign = Object.assign;

/**
 * Function returning the first matching edge for given path.
 * Note: this function does not check the existence of source & target. This
 * must be performed by the caller.
 *
 * @param  {Graph}  graph  - Target graph.
 * @param  {any}    source - Source node.
 * @param  {any}    target - Target node.
 * @param  {string} type   - Type of the edge (mixed, directed or undirected).
 * @return {string|null}
 */
function getMatchingEdge(graph, source, target, type) {
  var sourceData = graph._nodes.get(source);
  var edge = null;
  if (!sourceData) return edge;
  if (type === 'mixed') {
    edge = sourceData.out && sourceData.out[target] || sourceData.undirected && sourceData.undirected[target];
  } else if (type === 'directed') {
    edge = sourceData.out && sourceData.out[target];
  } else {
    edge = sourceData.undirected && sourceData.undirected[target];
  }
  return edge;
}

/**
 * Checks whether the given value is a plain object.
 *
 * @param  {mixed}   value - Target value.
 * @return {boolean}
 */
function isPlainObject(value) {
  // NOTE: as per https://github.com/graphology/graphology/issues/149
  // this function has been loosened not to reject object instances
  // coming from other JavaScript contexts. It has also been chosen
  // not to improve it to avoid obvious false positives and avoid
  // taking a performance hit. People should really use TypeScript
  // if they want to avoid feeding subtly irrelvant attribute objects.
  return _typeof(value) === 'object' && value !== null;
}

/**
 * Checks whether the given object is empty.
 *
 * @param  {object}  o - Target Object.
 * @return {boolean}
 */
function isEmpty(o) {
  var k;
  for (k in o) {
    return false;
  }
  return true;
}

/**
 * Creates a "private" property for the given member name by concealing it
 * using the `enumerable` option.
 *
 * @param {object} target - Target object.
 * @param {string} name   - Member name.
 */
function privateProperty(target, name, value) {
  Object.defineProperty(target, name, {
    enumerable: false,
    configurable: false,
    writable: true,
    value: value
  });
}

/**
 * Creates a read-only property for the given member name & the given getter.
 *
 * @param {object}   target - Target object.
 * @param {string}   name   - Member name.
 * @param {mixed}    value  - The attached getter or fixed value.
 */
function readOnlyProperty(target, name, value) {
  var descriptor = {
    enumerable: true,
    configurable: true
  };
  if (typeof value === 'function') {
    descriptor.get = value;
  } else {
    descriptor.value = value;
    descriptor.writable = false;
  }
  Object.defineProperty(target, name, descriptor);
}

/**
 * Returns whether the given object constitute valid hints.
 *
 * @param {object} hints - Target object.
 */
function validateHints(hints) {
  if (!isPlainObject(hints)) return false;
  if (hints.attributes && !Array.isArray(hints.attributes)) return false;
  return true;
}

/**
 * Creates a function generating incremental ids for edges.
 *
 * @return {function}
 */
function incrementalIdStartingFromRandomByte() {
  var i = Math.floor(Math.random() * 256) & 0xff;
  return function () {
    return i++;
  };
}

/**
 * Graphology Custom Errors
 * =========================
 *
 * Defining custom errors for ease of use & easy unit tests across
 * implementations (normalized typology rather than relying on error
 * messages to check whether the correct error was found).
 */
var GraphError = /*#__PURE__*/function (_Error) {
  _inheritsLoose(GraphError, _Error);
  function GraphError(message) {
    var _this;
    _this = _Error.call(this) || this;
    _this.name = 'GraphError';
    _this.message = message;
    return _this;
  }
  return GraphError;
}( /*#__PURE__*/_wrapNativeSuper(Error));
var InvalidArgumentsGraphError = /*#__PURE__*/function (_GraphError) {
  _inheritsLoose(InvalidArgumentsGraphError, _GraphError);
  function InvalidArgumentsGraphError(message) {
    var _this2;
    _this2 = _GraphError.call(this, message) || this;
    _this2.name = 'InvalidArgumentsGraphError';

    // This is V8 specific to enhance stack readability
    if (typeof Error.captureStackTrace === 'function') Error.captureStackTrace(_assertThisInitialized(_this2), InvalidArgumentsGraphError.prototype.constructor);
    return _this2;
  }
  return InvalidArgumentsGraphError;
}(GraphError);
var NotFoundGraphError = /*#__PURE__*/function (_GraphError2) {
  _inheritsLoose(NotFoundGraphError, _GraphError2);
  function NotFoundGraphError(message) {
    var _this3;
    _this3 = _GraphError2.call(this, message) || this;
    _this3.name = 'NotFoundGraphError';

    // This is V8 specific to enhance stack readability
    if (typeof Error.captureStackTrace === 'function') Error.captureStackTrace(_assertThisInitialized(_this3), NotFoundGraphError.prototype.constructor);
    return _this3;
  }
  return NotFoundGraphError;
}(GraphError);
var UsageGraphError = /*#__PURE__*/function (_GraphError3) {
  _inheritsLoose(UsageGraphError, _GraphError3);
  function UsageGraphError(message) {
    var _this4;
    _this4 = _GraphError3.call(this, message) || this;
    _this4.name = 'UsageGraphError';

    // This is V8 specific to enhance stack readability
    if (typeof Error.captureStackTrace === 'function') Error.captureStackTrace(_assertThisInitialized(_this4), UsageGraphError.prototype.constructor);
    return _this4;
  }
  return UsageGraphError;
}(GraphError);

/**
 * Graphology Internal Data Classes
 * =================================
 *
 * Internal classes hopefully reduced to structs by engines & storing
 * necessary information for nodes & edges.
 *
 * Note that those classes don't rely on the `class` keyword to avoid some
 * cruft introduced by most of ES2015 transpilers.
 */

/**
 * MixedNodeData class.
 *
 * @constructor
 * @param {string} string     - The node's key.
 * @param {object} attributes - Node's attributes.
 */
function MixedNodeData(key, attributes) {
  // Attributes
  this.key = key;
  this.attributes = attributes;
  this.clear();
}
MixedNodeData.prototype.clear = function () {
  // Degrees
  this.inDegree = 0;
  this.outDegree = 0;
  this.undirectedDegree = 0;
  this.undirectedLoops = 0;
  this.directedLoops = 0;

  // Indices
  this["in"] = {};
  this.out = {};
  this.undirected = {};
};

/**
 * DirectedNodeData class.
 *
 * @constructor
 * @param {string} string     - The node's key.
 * @param {object} attributes - Node's attributes.
 */
function DirectedNodeData(key, attributes) {
  // Attributes
  this.key = key;
  this.attributes = attributes;
  this.clear();
}
DirectedNodeData.prototype.clear = function () {
  // Degrees
  this.inDegree = 0;
  this.outDegree = 0;
  this.directedLoops = 0;

  // Indices
  this["in"] = {};
  this.out = {};
};

/**
 * UndirectedNodeData class.
 *
 * @constructor
 * @param {string} string     - The node's key.
 * @param {object} attributes - Node's attributes.
 */
function UndirectedNodeData(key, attributes) {
  // Attributes
  this.key = key;
  this.attributes = attributes;
  this.clear();
}
UndirectedNodeData.prototype.clear = function () {
  // Degrees
  this.undirectedDegree = 0;
  this.undirectedLoops = 0;

  // Indices
  this.undirected = {};
};

/**
 * EdgeData class.
 *
 * @constructor
 * @param {boolean} undirected   - Whether the edge is undirected.
 * @param {string}  string       - The edge's key.
 * @param {string}  source       - Source of the edge.
 * @param {string}  target       - Target of the edge.
 * @param {object}  attributes   - Edge's attributes.
 */
function EdgeData(undirected, key, source, target, attributes) {
  // Attributes
  this.key = key;
  this.attributes = attributes;
  this.undirected = undirected;

  // Extremities
  this.source = source;
  this.target = target;
}
EdgeData.prototype.attach = function () {
  var outKey = 'out';
  var inKey = 'in';
  if (this.undirected) outKey = inKey = 'undirected';
  var source = this.source.key;
  var target = this.target.key;

  // Handling source
  this.source[outKey][target] = this;
  if (this.undirected && source === target) return;

  // Handling target
  this.target[inKey][source] = this;
};
EdgeData.prototype.attachMulti = function () {
  var outKey = 'out';
  var inKey = 'in';
  var source = this.source.key;
  var target = this.target.key;
  if (this.undirected) outKey = inKey = 'undirected';

  // Handling source
  var adj = this.source[outKey];
  var head = adj[target];
  if (typeof head === 'undefined') {
    adj[target] = this;

    // Self-loop optimization
    if (!(this.undirected && source === target)) {
      // Handling target
      this.target[inKey][source] = this;
    }
    return;
  }

  // Prepending to doubly-linked list
  head.previous = this;
  this.next = head;

  // Pointing to new head
  // NOTE: use mutating swap later to avoid lookup?
  adj[target] = this;
  this.target[inKey][source] = this;
};
EdgeData.prototype.detach = function () {
  var source = this.source.key;
  var target = this.target.key;
  var outKey = 'out';
  var inKey = 'in';
  if (this.undirected) outKey = inKey = 'undirected';
  delete this.source[outKey][target];

  // No-op delete in case of undirected self-loop
  delete this.target[inKey][source];
};
EdgeData.prototype.detachMulti = function () {
  var source = this.source.key;
  var target = this.target.key;
  var outKey = 'out';
  var inKey = 'in';
  if (this.undirected) outKey = inKey = 'undirected';

  // Deleting from doubly-linked list
  if (this.previous === undefined) {
    // We are dealing with the head

    // Should we delete the adjacency entry because it is now empty?
    if (this.next === undefined) {
      delete this.source[outKey][target];

      // No-op delete in case of undirected self-loop
      delete this.target[inKey][source];
    } else {
      // Detaching
      this.next.previous = undefined;

      // NOTE: could avoid the lookups by creating a #.become mutating method
      this.source[outKey][target] = this.next;

      // No-op delete in case of undirected self-loop
      this.target[inKey][source] = this.next;
    }
  } else {
    // We are dealing with another list node
    this.previous.next = this.next;

    // If not last
    if (this.next !== undefined) {
      this.next.previous = this.previous;
    }
  }
};

/**
 * Graphology Node Attributes methods
 * ===================================
 */
var NODE = 0;
var SOURCE = 1;
var TARGET = 2;
var OPPOSITE = 3;
function findRelevantNodeData(graph, method, mode, nodeOrEdge, nameOrEdge, add1, add2) {
  var nodeData, edgeData, arg1, arg2;
  nodeOrEdge = '' + nodeOrEdge;
  if (mode === NODE) {
    nodeData = graph._nodes.get(nodeOrEdge);
    if (!nodeData) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(nodeOrEdge, "\" node in the graph."));
    arg1 = nameOrEdge;
    arg2 = add1;
  } else if (mode === OPPOSITE) {
    nameOrEdge = '' + nameOrEdge;
    edgeData = graph._edges.get(nameOrEdge);
    if (!edgeData) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(nameOrEdge, "\" edge in the graph."));
    var source = edgeData.source.key;
    var target = edgeData.target.key;
    if (nodeOrEdge === source) {
      nodeData = edgeData.target;
    } else if (nodeOrEdge === target) {
      nodeData = edgeData.source;
    } else {
      throw new NotFoundGraphError("Graph.".concat(method, ": the \"").concat(nodeOrEdge, "\" node is not attached to the \"").concat(nameOrEdge, "\" edge (").concat(source, ", ").concat(target, ")."));
    }
    arg1 = add1;
    arg2 = add2;
  } else {
    edgeData = graph._edges.get(nodeOrEdge);
    if (!edgeData) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(nodeOrEdge, "\" edge in the graph."));
    if (mode === SOURCE) {
      nodeData = edgeData.source;
    } else {
      nodeData = edgeData.target;
    }
    arg1 = nameOrEdge;
    arg2 = add1;
  }
  return [nodeData, arg1, arg2];
}
function attachNodeAttributeGetter(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge, add1) {
    var _findRelevantNodeData = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge, add1),
      data = _findRelevantNodeData[0],
      name = _findRelevantNodeData[1];
    return data.attributes[name];
  };
}
function attachNodeAttributesGetter(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge) {
    var _findRelevantNodeData2 = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge),
      data = _findRelevantNodeData2[0];
    return data.attributes;
  };
}
function attachNodeAttributeChecker(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge, add1) {
    var _findRelevantNodeData3 = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge, add1),
      data = _findRelevantNodeData3[0],
      name = _findRelevantNodeData3[1];
    return data.attributes.hasOwnProperty(name);
  };
}
function attachNodeAttributeSetter(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge, add1, add2) {
    var _findRelevantNodeData4 = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge, add1, add2),
      data = _findRelevantNodeData4[0],
      name = _findRelevantNodeData4[1],
      value = _findRelevantNodeData4[2];
    data.attributes[name] = value;

    // Emitting
    this.emit('nodeAttributesUpdated', {
      key: data.key,
      type: 'set',
      attributes: data.attributes,
      name: name
    });
    return this;
  };
}
function attachNodeAttributeUpdater(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge, add1, add2) {
    var _findRelevantNodeData5 = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge, add1, add2),
      data = _findRelevantNodeData5[0],
      name = _findRelevantNodeData5[1],
      updater = _findRelevantNodeData5[2];
    if (typeof updater !== 'function') throw new InvalidArgumentsGraphError("Graph.".concat(method, ": updater should be a function."));
    var attributes = data.attributes;
    var value = updater(attributes[name]);
    attributes[name] = value;

    // Emitting
    this.emit('nodeAttributesUpdated', {
      key: data.key,
      type: 'set',
      attributes: data.attributes,
      name: name
    });
    return this;
  };
}
function attachNodeAttributeRemover(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge, add1) {
    var _findRelevantNodeData6 = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge, add1),
      data = _findRelevantNodeData6[0],
      name = _findRelevantNodeData6[1];
    delete data.attributes[name];

    // Emitting
    this.emit('nodeAttributesUpdated', {
      key: data.key,
      type: 'remove',
      attributes: data.attributes,
      name: name
    });
    return this;
  };
}
function attachNodeAttributesReplacer(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge, add1) {
    var _findRelevantNodeData7 = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge, add1),
      data = _findRelevantNodeData7[0],
      attributes = _findRelevantNodeData7[1];
    if (!isPlainObject(attributes)) throw new InvalidArgumentsGraphError("Graph.".concat(method, ": provided attributes are not a plain object."));
    data.attributes = attributes;

    // Emitting
    this.emit('nodeAttributesUpdated', {
      key: data.key,
      type: 'replace',
      attributes: data.attributes
    });
    return this;
  };
}
function attachNodeAttributesMerger(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge, add1) {
    var _findRelevantNodeData8 = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge, add1),
      data = _findRelevantNodeData8[0],
      attributes = _findRelevantNodeData8[1];
    if (!isPlainObject(attributes)) throw new InvalidArgumentsGraphError("Graph.".concat(method, ": provided attributes are not a plain object."));
    assign(data.attributes, attributes);

    // Emitting
    this.emit('nodeAttributesUpdated', {
      key: data.key,
      type: 'merge',
      attributes: data.attributes,
      data: attributes
    });
    return this;
  };
}
function attachNodeAttributesUpdater(Class, method, mode) {
  Class.prototype[method] = function (nodeOrEdge, nameOrEdge, add1) {
    var _findRelevantNodeData9 = findRelevantNodeData(this, method, mode, nodeOrEdge, nameOrEdge, add1),
      data = _findRelevantNodeData9[0],
      updater = _findRelevantNodeData9[1];
    if (typeof updater !== 'function') throw new InvalidArgumentsGraphError("Graph.".concat(method, ": provided updater is not a function."));
    data.attributes = updater(data.attributes);

    // Emitting
    this.emit('nodeAttributesUpdated', {
      key: data.key,
      type: 'update',
      attributes: data.attributes
    });
    return this;
  };
}

/**
 * List of methods to attach.
 */
var NODE_ATTRIBUTES_METHODS = [{
  name: function name(element) {
    return "get".concat(element, "Attribute");
  },
  attacher: attachNodeAttributeGetter
}, {
  name: function name(element) {
    return "get".concat(element, "Attributes");
  },
  attacher: attachNodeAttributesGetter
}, {
  name: function name(element) {
    return "has".concat(element, "Attribute");
  },
  attacher: attachNodeAttributeChecker
}, {
  name: function name(element) {
    return "set".concat(element, "Attribute");
  },
  attacher: attachNodeAttributeSetter
}, {
  name: function name(element) {
    return "update".concat(element, "Attribute");
  },
  attacher: attachNodeAttributeUpdater
}, {
  name: function name(element) {
    return "remove".concat(element, "Attribute");
  },
  attacher: attachNodeAttributeRemover
}, {
  name: function name(element) {
    return "replace".concat(element, "Attributes");
  },
  attacher: attachNodeAttributesReplacer
}, {
  name: function name(element) {
    return "merge".concat(element, "Attributes");
  },
  attacher: attachNodeAttributesMerger
}, {
  name: function name(element) {
    return "update".concat(element, "Attributes");
  },
  attacher: attachNodeAttributesUpdater
}];

/**
 * Attach every attributes-related methods to a Graph class.
 *
 * @param {function} Graph - Target class.
 */
function attachNodeAttributesMethods(Graph) {
  NODE_ATTRIBUTES_METHODS.forEach(function (_ref) {
    var name = _ref.name,
      attacher = _ref.attacher;
    // For nodes
    attacher(Graph, name('Node'), NODE);

    // For sources
    attacher(Graph, name('Source'), SOURCE);

    // For targets
    attacher(Graph, name('Target'), TARGET);

    // For opposites
    attacher(Graph, name('Opposite'), OPPOSITE);
  });
}

/**
 * Graphology Edge Attributes methods
 * ===================================
 */

/**
 * Attach an attribute getter method onto the provided class.
 *
 * @param {function} Class         - Target class.
 * @param {string}   method        - Method name.
 * @param {string}   type          - Type of the edge to find.
 */
function attachEdgeAttributeGetter(Class, method, type) {
  /**
   * Get the desired attribute for the given element (node or edge).
   *
   * Arity 2:
   * @param  {any}    element - Target element.
   * @param  {string} name    - Attribute's name.
   *
   * Arity 3 (only for edges):
   * @param  {any}     source - Source element.
   * @param  {any}     target - Target element.
   * @param  {string}  name   - Attribute's name.
   *
   * @return {mixed}          - The attribute's value.
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element, name) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 2) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element;
      var target = '' + name;
      name = arguments[2];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    return data.attributes[name];
  };
}

/**
 * Attach an attributes getter method onto the provided class.
 *
 * @param {function} Class       - Target class.
 * @param {string}   method      - Method name.
 * @param {string}   type        - Type of the edge to find.
 */
function attachEdgeAttributesGetter(Class, method, type) {
  /**
   * Retrieves all the target element's attributes.
   *
   * Arity 2:
   * @param  {any}    element - Target element.
   *
   * Arity 3 (only for edges):
   * @param  {any}     source - Source element.
   * @param  {any}     target - Target element.
   *
   * @return {object}          - The element's attributes.
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 1) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element,
        target = '' + arguments[1];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    return data.attributes;
  };
}

/**
 * Attach an attribute checker method onto the provided class.
 *
 * @param {function} Class       - Target class.
 * @param {string}   method      - Method name.
 * @param {string}   type        - Type of the edge to find.
 */
function attachEdgeAttributeChecker(Class, method, type) {
  /**
   * Checks whether the desired attribute is set for the given element (node or edge).
   *
   * Arity 2:
   * @param  {any}    element - Target element.
   * @param  {string} name    - Attribute's name.
   *
   * Arity 3 (only for edges):
   * @param  {any}     source - Source element.
   * @param  {any}     target - Target element.
   * @param  {string}  name   - Attribute's name.
   *
   * @return {boolean}
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element, name) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 2) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element;
      var target = '' + name;
      name = arguments[2];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    return data.attributes.hasOwnProperty(name);
  };
}

/**
 * Attach an attribute setter method onto the provided class.
 *
 * @param {function} Class         - Target class.
 * @param {string}   method        - Method name.
 * @param {string}   type          - Type of the edge to find.
 */
function attachEdgeAttributeSetter(Class, method, type) {
  /**
   * Set the desired attribute for the given element (node or edge).
   *
   * Arity 2:
   * @param  {any}    element - Target element.
   * @param  {string} name    - Attribute's name.
   * @param  {mixed}  value   - New attribute value.
   *
   * Arity 3 (only for edges):
   * @param  {any}     source - Source element.
   * @param  {any}     target - Target element.
   * @param  {string}  name   - Attribute's name.
   * @param  {mixed}  value   - New attribute value.
   *
   * @return {Graph}          - Returns itself for chaining.
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element, name, value) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 3) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element;
      var target = '' + name;
      name = arguments[2];
      value = arguments[3];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    data.attributes[name] = value;

    // Emitting
    this.emit('edgeAttributesUpdated', {
      key: data.key,
      type: 'set',
      attributes: data.attributes,
      name: name
    });
    return this;
  };
}

/**
 * Attach an attribute updater method onto the provided class.
 *
 * @param {function} Class         - Target class.
 * @param {string}   method        - Method name.
 * @param {string}   type          - Type of the edge to find.
 */
function attachEdgeAttributeUpdater(Class, method, type) {
  /**
   * Update the desired attribute for the given element (node or edge) using
   * the provided function.
   *
   * Arity 2:
   * @param  {any}      element - Target element.
   * @param  {string}   name    - Attribute's name.
   * @param  {function} updater - Updater function.
   *
   * Arity 3 (only for edges):
   * @param  {any}      source  - Source element.
   * @param  {any}      target  - Target element.
   * @param  {string}   name    - Attribute's name.
   * @param  {function} updater - Updater function.
   *
   * @return {Graph}            - Returns itself for chaining.
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element, name, updater) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 3) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element;
      var target = '' + name;
      name = arguments[2];
      updater = arguments[3];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    if (typeof updater !== 'function') throw new InvalidArgumentsGraphError("Graph.".concat(method, ": updater should be a function."));
    data.attributes[name] = updater(data.attributes[name]);

    // Emitting
    this.emit('edgeAttributesUpdated', {
      key: data.key,
      type: 'set',
      attributes: data.attributes,
      name: name
    });
    return this;
  };
}

/**
 * Attach an attribute remover method onto the provided class.
 *
 * @param {function} Class         - Target class.
 * @param {string}   method        - Method name.
 * @param {string}   type          - Type of the edge to find.
 */
function attachEdgeAttributeRemover(Class, method, type) {
  /**
   * Remove the desired attribute for the given element (node or edge).
   *
   * Arity 2:
   * @param  {any}    element - Target element.
   * @param  {string} name    - Attribute's name.
   *
   * Arity 3 (only for edges):
   * @param  {any}     source - Source element.
   * @param  {any}     target - Target element.
   * @param  {string}  name   - Attribute's name.
   *
   * @return {Graph}          - Returns itself for chaining.
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element, name) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 2) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element;
      var target = '' + name;
      name = arguments[2];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    delete data.attributes[name];

    // Emitting
    this.emit('edgeAttributesUpdated', {
      key: data.key,
      type: 'remove',
      attributes: data.attributes,
      name: name
    });
    return this;
  };
}

/**
 * Attach an attribute replacer method onto the provided class.
 *
 * @param {function} Class         - Target class.
 * @param {string}   method        - Method name.
 * @param {string}   type          - Type of the edge to find.
 */
function attachEdgeAttributesReplacer(Class, method, type) {
  /**
   * Replace the attributes for the given element (node or edge).
   *
   * Arity 2:
   * @param  {any}    element    - Target element.
   * @param  {object} attributes - New attributes.
   *
   * Arity 3 (only for edges):
   * @param  {any}     source     - Source element.
   * @param  {any}     target     - Target element.
   * @param  {object}  attributes - New attributes.
   *
   * @return {Graph}              - Returns itself for chaining.
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element, attributes) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 2) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element,
        target = '' + attributes;
      attributes = arguments[2];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    if (!isPlainObject(attributes)) throw new InvalidArgumentsGraphError("Graph.".concat(method, ": provided attributes are not a plain object."));
    data.attributes = attributes;

    // Emitting
    this.emit('edgeAttributesUpdated', {
      key: data.key,
      type: 'replace',
      attributes: data.attributes
    });
    return this;
  };
}

/**
 * Attach an attribute merger method onto the provided class.
 *
 * @param {function} Class         - Target class.
 * @param {string}   method        - Method name.
 * @param {string}   type          - Type of the edge to find.
 */
function attachEdgeAttributesMerger(Class, method, type) {
  /**
   * Merge the attributes for the given element (node or edge).
   *
   * Arity 2:
   * @param  {any}    element    - Target element.
   * @param  {object} attributes - Attributes to merge.
   *
   * Arity 3 (only for edges):
   * @param  {any}     source     - Source element.
   * @param  {any}     target     - Target element.
   * @param  {object}  attributes - Attributes to merge.
   *
   * @return {Graph}              - Returns itself for chaining.
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element, attributes) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 2) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element,
        target = '' + attributes;
      attributes = arguments[2];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    if (!isPlainObject(attributes)) throw new InvalidArgumentsGraphError("Graph.".concat(method, ": provided attributes are not a plain object."));
    assign(data.attributes, attributes);

    // Emitting
    this.emit('edgeAttributesUpdated', {
      key: data.key,
      type: 'merge',
      attributes: data.attributes,
      data: attributes
    });
    return this;
  };
}

/**
 * Attach an attribute updater method onto the provided class.
 *
 * @param {function} Class         - Target class.
 * @param {string}   method        - Method name.
 * @param {string}   type          - Type of the edge to find.
 */
function attachEdgeAttributesUpdater(Class, method, type) {
  /**
   * Update the attributes of the given element (node or edge).
   *
   * Arity 2:
   * @param  {any}      element - Target element.
   * @param  {function} updater - Updater function.
   *
   * Arity 3 (only for edges):
   * @param  {any}      source  - Source element.
   * @param  {any}      target  - Target element.
   * @param  {function} updater - Updater function.
   *
   * @return {Graph}            - Returns itself for chaining.
   *
   * @throws {Error} - Will throw if too many arguments are provided.
   * @throws {Error} - Will throw if any of the elements is not found.
   */
  Class.prototype[method] = function (element, updater) {
    var data;
    if (this.type !== 'mixed' && type !== 'mixed' && type !== this.type) throw new UsageGraphError("Graph.".concat(method, ": cannot find this type of edges in your ").concat(this.type, " graph."));
    if (arguments.length > 2) {
      if (this.multi) throw new UsageGraphError("Graph.".concat(method, ": cannot use a {source,target} combo when asking about an edge's attributes in a MultiGraph since we cannot infer the one you want information about."));
      var source = '' + element,
        target = '' + updater;
      updater = arguments[2];
      data = getMatchingEdge(this, source, target, type);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find an edge for the given path (\"").concat(source, "\" - \"").concat(target, "\")."));
    } else {
      if (type !== 'mixed') throw new UsageGraphError("Graph.".concat(method, ": calling this method with only a key (vs. a source and target) does not make sense since an edge with this key could have the other type."));
      element = '' + element;
      data = this._edges.get(element);
      if (!data) throw new NotFoundGraphError("Graph.".concat(method, ": could not find the \"").concat(element, "\" edge in the graph."));
    }
    if (typeof updater !== 'function') throw new InvalidArgumentsGraphError("Graph.".concat(method, ": provided updater is not a function."));
    data.attributes = updater(data.attributes);

    // Emitting
    this.emit('edgeAttributesUpdated', {
      key: data.key,
      type: 'update',
      attributes: data.attributes
    });
    return this;
  };
}

/**
 * List of methods to attach.
 */
var EDGE_ATTRIBUTES_METHODS = [{
  name: function name(element) {
    return "get".concat(element, "Attribute");
  },
  attacher: attachEdgeAttributeGetter
}, {
  name: function name(element) {
    return "get".concat(element, "Attributes");
  },
  attacher: attachEdgeAttributesGetter
}, {
  name: function name(element) {
    return "has".concat(element, "Attribute");
  },
  attacher: attachEdgeAttributeChecker
}, {
  name: function name(element) {
    return "set".concat(element, "Attribute");
  },
  attacher: attachEdgeAttributeSetter
}, {
  name: function name(element) {
    return "update".concat(element, "Attribute");
  },
  attacher: attachEdgeAttributeUpdater
}, {
  name: function name(element) {
    return "remove".concat(element, "Attribute");
  },
  attacher: attachEdgeAttributeRemover
}, {
  name: function name(element) {
    return "replace".concat(element, "Attributes");
  },
  attacher: attachEdgeAttributesReplacer
}, {
  name: function name(element) {
    return "merge".concat(element, "Attributes");
  },
  attacher: attachEdgeAttributesMerger
}, {
  name: function name(element) {
    return "update".concat(element, "Attributes");
  },
  attacher: attachEdgeAttributesUpdater
}];

/**
 * Attach every attributes-related methods to a Graph class.
 *
 * @param {function} Graph - Target class.
 */
function attachEdgeAttributesMethods(Graph) {
  EDGE_ATTRIBUTES_METHODS.forEach(function (_ref) {
    var name = _ref.name,
      attacher = _ref.attacher;
    // For edges
    attacher(Graph, name('Edge'), 'mixed');

    // For directed edges
    attacher(Graph, name('DirectedEdge'), 'directed');

    // For undirected edges
    attacher(Graph, name('UndirectedEdge'), 'undirected');
  });
}

/**
 * Graphology Edge Iteration
 * ==========================
 *
 * Attaching some methods to the Graph class to be able to iterate over a
 * graph's edges.
 */

/**
 * Definitions.
 */
var EDGES_ITERATION = [{
  name: 'edges',
  type: 'mixed'
}, {
  name: 'inEdges',
  type: 'directed',
  direction: 'in'
}, {
  name: 'outEdges',
  type: 'directed',
  direction: 'out'
}, {
  name: 'inboundEdges',
  type: 'mixed',
  direction: 'in'
}, {
  name: 'outboundEdges',
  type: 'mixed',
  direction: 'out'
}, {
  name: 'directedEdges',
  type: 'directed'
}, {
  name: 'undirectedEdges',
  type: 'undirected'
}];

/**
 * Function iterating over edges from the given object to match one of them.
 *
 * @param {object}   object   - Target object.
 * @param {function} callback - Function to call.
 */
function forEachSimple(breakable, object, callback, avoid) {
  var shouldBreak = false;
  for (var k in object) {
    if (k === avoid) continue;
    var edgeData = object[k];
    shouldBreak = callback(edgeData.key, edgeData.attributes, edgeData.source.key, edgeData.target.key, edgeData.source.attributes, edgeData.target.attributes, edgeData.undirected);
    if (breakable && shouldBreak) return edgeData.key;
  }
  return;
}
function forEachMulti(breakable, object, callback, avoid) {
  var edgeData, source, target;
  var shouldBreak = false;
  for (var k in object) {
    if (k === avoid) continue;
    edgeData = object[k];
    do {
      source = edgeData.source;
      target = edgeData.target;
      shouldBreak = callback(edgeData.key, edgeData.attributes, source.key, target.key, source.attributes, target.attributes, edgeData.undirected);
      if (breakable && shouldBreak) return edgeData.key;
      edgeData = edgeData.next;
    } while (edgeData !== undefined);
  }
  return;
}

/**
 * Function returning an iterator over edges from the given object.
 *
 * @param  {object}   object - Target object.
 * @return {Iterator}
 */
function createIterator(object, avoid) {
  var keys = Object.keys(object);
  var l = keys.length;
  var edgeData;
  var i = 0;
  return new Iterator__default["default"](function next() {
    do {
      if (!edgeData) {
        if (i >= l) return {
          done: true
        };
        var k = keys[i++];
        if (k === avoid) {
          edgeData = undefined;
          continue;
        }
        edgeData = object[k];
      } else {
        edgeData = edgeData.next;
      }
    } while (!edgeData);
    return {
      done: false,
      value: {
        edge: edgeData.key,
        attributes: edgeData.attributes,
        source: edgeData.source.key,
        target: edgeData.target.key,
        sourceAttributes: edgeData.source.attributes,
        targetAttributes: edgeData.target.attributes,
        undirected: edgeData.undirected
      }
    };
  });
}

/**
 * Function iterating over the egdes from the object at given key to match
 * one of them.
 *
 * @param {object}   object   - Target object.
 * @param {mixed}    k        - Neighbor key.
 * @param {function} callback - Callback to use.
 */
function forEachForKeySimple(breakable, object, k, callback) {
  var edgeData = object[k];
  if (!edgeData) return;
  var sourceData = edgeData.source;
  var targetData = edgeData.target;
  if (callback(edgeData.key, edgeData.attributes, sourceData.key, targetData.key, sourceData.attributes, targetData.attributes, edgeData.undirected) && breakable) return edgeData.key;
}
function forEachForKeyMulti(breakable, object, k, callback) {
  var edgeData = object[k];
  if (!edgeData) return;
  var shouldBreak = false;
  do {
    shouldBreak = callback(edgeData.key, edgeData.attributes, edgeData.source.key, edgeData.target.key, edgeData.source.attributes, edgeData.target.attributes, edgeData.undirected);
    if (breakable && shouldBreak) return edgeData.key;
    edgeData = edgeData.next;
  } while (edgeData !== undefined);
  return;
}

/**
 * Function returning an iterator over the egdes from the object at given key.
 *
 * @param  {object}   object   - Target object.
 * @param  {mixed}    k        - Neighbor key.
 * @return {Iterator}
 */
function createIteratorForKey(object, k) {
  var edgeData = object[k];
  if (edgeData.next !== undefined) {
    return new Iterator__default["default"](function () {
      if (!edgeData) return {
        done: true
      };
      var value = {
        edge: edgeData.key,
        attributes: edgeData.attributes,
        source: edgeData.source.key,
        target: edgeData.target.key,
        sourceAttributes: edgeData.source.attributes,
        targetAttributes: edgeData.target.attributes,
        undirected: edgeData.undirected
      };
      edgeData = edgeData.next;
      return {
        done: false,
        value: value
      };
    });
  }
  return Iterator__default["default"].of({
    edge: edgeData.key,
    attributes: edgeData.attributes,
    source: edgeData.source.key,
    target: edgeData.target.key,
    sourceAttributes: edgeData.source.attributes,
    targetAttributes: edgeData.target.attributes,
    undirected: edgeData.undirected
  });
}

/**
 * Function creating an array of edges for the given type.
 *
 * @param  {Graph}   graph - Target Graph instance.
 * @param  {string}  type  - Type of edges to retrieve.
 * @return {array}         - Array of edges.
 */
function createEdgeArray(graph, type) {
  if (graph.size === 0) return [];
  if (type === 'mixed' || type === graph.type) {
    if (typeof Array.from === 'function') return Array.from(graph._edges.keys());
    return take__default["default"](graph._edges.keys(), graph._edges.size);
  }
  var size = type === 'undirected' ? graph.undirectedSize : graph.directedSize;
  var list = new Array(size),
    mask = type === 'undirected';
  var iterator = graph._edges.values();
  var i = 0;
  var step, data;
  while (step = iterator.next(), step.done !== true) {
    data = step.value;
    if (data.undirected === mask) list[i++] = data.key;
  }
  return list;
}

/**
 * Function iterating over a graph's edges using a callback to match one of
 * them.
 *
 * @param  {Graph}    graph    - Target Graph instance.
 * @param  {string}   type     - Type of edges to retrieve.
 * @param  {function} callback - Function to call.
 */
function forEachEdge(breakable, graph, type, callback) {
  if (graph.size === 0) return;
  var shouldFilter = type !== 'mixed' && type !== graph.type;
  var mask = type === 'undirected';
  var step, data;
  var shouldBreak = false;
  var iterator = graph._edges.values();
  while (step = iterator.next(), step.done !== true) {
    data = step.value;
    if (shouldFilter && data.undirected !== mask) continue;
    var _data = data,
      key = _data.key,
      attributes = _data.attributes,
      source = _data.source,
      target = _data.target;
    shouldBreak = callback(key, attributes, source.key, target.key, source.attributes, target.attributes, data.undirected);
    if (breakable && shouldBreak) return key;
  }
  return;
}

/**
 * Function creating an iterator of edges for the given type.
 *
 * @param  {Graph}    graph - Target Graph instance.
 * @param  {string}   type  - Type of edges to retrieve.
 * @return {Iterator}
 */
function createEdgeIterator(graph, type) {
  if (graph.size === 0) return Iterator__default["default"].empty();
  var shouldFilter = type !== 'mixed' && type !== graph.type;
  var mask = type === 'undirected';
  var iterator = graph._edges.values();
  return new Iterator__default["default"](function next() {
    var step, data;

    // eslint-disable-next-line no-constant-condition
    while (true) {
      step = iterator.next();
      if (step.done) return step;
      data = step.value;
      if (shouldFilter && data.undirected !== mask) continue;
      break;
    }
    var value = {
      edge: data.key,
      attributes: data.attributes,
      source: data.source.key,
      target: data.target.key,
      sourceAttributes: data.source.attributes,
      targetAttributes: data.target.attributes,
      undirected: data.undirected
    };
    return {
      value: value,
      done: false
    };
  });
}

/**
 * Function iterating over a node's edges using a callback to match one of them.
 *
 * @param  {boolean}  multi     - Whether the graph is multi or not.
 * @param  {string}   type      - Type of edges to retrieve.
 * @param  {string}   direction - In or out?
 * @param  {any}      nodeData  - Target node's data.
 * @param  {function} callback  - Function to call.
 */
function forEachEdgeForNode(breakable, multi, type, direction, nodeData, callback) {
  var fn = multi ? forEachMulti : forEachSimple;
  var found;
  if (type !== 'undirected') {
    if (direction !== 'out') {
      found = fn(breakable, nodeData["in"], callback);
      if (breakable && found) return found;
    }
    if (direction !== 'in') {
      found = fn(breakable, nodeData.out, callback, !direction ? nodeData.key : undefined);
      if (breakable && found) return found;
    }
  }
  if (type !== 'directed') {
    found = fn(breakable, nodeData.undirected, callback);
    if (breakable && found) return found;
  }
  return;
}

/**
 * Function creating an array of edges for the given type & the given node.
 *
 * @param  {boolean} multi     - Whether the graph is multi or not.
 * @param  {string}  type      - Type of edges to retrieve.
 * @param  {string}  direction - In or out?
 * @param  {any}     nodeData  - Target node's data.
 * @return {array}             - Array of edges.
 */
function createEdgeArrayForNode(multi, type, direction, nodeData) {
  var edges = []; // TODO: possibility to know size beforehand or factorize with map

  forEachEdgeForNode(false, multi, type, direction, nodeData, function (key) {
    edges.push(key);
  });
  return edges;
}

/**
 * Function iterating over a node's edges using a callback.
 *
 * @param  {string}   type      - Type of edges to retrieve.
 * @param  {string}   direction - In or out?
 * @param  {any}      nodeData  - Target node's data.
 * @return {Iterator}
 */
function createEdgeIteratorForNode(type, direction, nodeData) {
  var iterator = Iterator__default["default"].empty();
  if (type !== 'undirected') {
    if (direction !== 'out' && typeof nodeData["in"] !== 'undefined') iterator = chain__default["default"](iterator, createIterator(nodeData["in"]));
    if (direction !== 'in' && typeof nodeData.out !== 'undefined') iterator = chain__default["default"](iterator, createIterator(nodeData.out, !direction ? nodeData.key : undefined));
  }
  if (type !== 'directed' && typeof nodeData.undirected !== 'undefined') {
    iterator = chain__default["default"](iterator, createIterator(nodeData.undirected));
  }
  return iterator;
}

/**
 * Function iterating over edges for the given path using a callback to match
 * one of them.
 *
 * @param  {string}   type       - Type of edges to retrieve.
 * @param  {boolean}  multi      - Whether the graph is multi.
 * @param  {string}   direction  - In or out?
 * @param  {NodeData} sourceData - Source node's data.
 * @param  {string}   target     - Target node.
 * @param  {function} callback   - Function to call.
 */
function forEachEdgeForPath(breakable, type, multi, direction, sourceData, target, callback) {
  var fn = multi ? forEachForKeyMulti : forEachForKeySimple;
  var found;
  if (type !== 'undirected') {
    if (typeof sourceData["in"] !== 'undefined' && direction !== 'out') {
      found = fn(breakable, sourceData["in"], target, callback);
      if (breakable && found) return found;
    }
    if (typeof sourceData.out !== 'undefined' && direction !== 'in' && (direction || sourceData.key !== target)) {
      found = fn(breakable, sourceData.out, target, callback);
      if (breakable && found) return found;
    }
  }
  if (type !== 'directed') {
    if (typeof sourceData.undirected !== 'undefined') {
      found = fn(breakable, sourceData.undirected, target, callback);
      if (breakable && found) return found;
    }
  }
  return;
}

/**
 * Function creating an array of edges for the given path.
 *
 * @param  {string}   type       - Type of edges to retrieve.
 * @param  {boolean}  multi      - Whether the graph is multi.
 * @param  {string}   direction  - In or out?
 * @param  {NodeData} sourceData - Source node's data.
 * @param  {any}      target     - Target node.
 * @return {array}               - Array of edges.
 */
function createEdgeArrayForPath(type, multi, direction, sourceData, target) {
  var edges = []; // TODO: possibility to know size beforehand or factorize with map

  forEachEdgeForPath(false, type, multi, direction, sourceData, target, function (key) {
    edges.push(key);
  });
  return edges;
}

/**
 * Function returning an iterator over edges for the given path.
 *
 * @param  {string}   type       - Type of edges to retrieve.
 * @param  {string}   direction  - In or out?
 * @param  {NodeData} sourceData - Source node's data.
 * @param  {string}   target     - Target node.
 * @param  {function} callback   - Function to call.
 */
function createEdgeIteratorForPath(type, direction, sourceData, target) {
  var iterator = Iterator__default["default"].empty();
  if (type !== 'undirected') {
    if (typeof sourceData["in"] !== 'undefined' && direction !== 'out' && target in sourceData["in"]) iterator = chain__default["default"](iterator, createIteratorForKey(sourceData["in"], target));
    if (typeof sourceData.out !== 'undefined' && direction !== 'in' && target in sourceData.out && (direction || sourceData.key !== target)) iterator = chain__default["default"](iterator, createIteratorForKey(sourceData.out, target));
  }
  if (type !== 'directed') {
    if (typeof sourceData.undirected !== 'undefined' && target in sourceData.undirected) iterator = chain__default["default"](iterator, createIteratorForKey(sourceData.undirected, target));
  }
  return iterator;
}

/**
 * Function attaching an edge array creator method to the Graph prototype.
 *
 * @param {function} Class       - Target class.
 * @param {object}   description - Method description.
 */
function attachEdgeArrayCreator(Class, description) {
  var name = description.name,
    type = description.type,
    direction = description.direction;

  /**
   * Function returning an array of certain edges.
   *
   * Arity 0: Return all the relevant edges.
   *
   * Arity 1: Return all of a node's relevant edges.
   * @param  {any}   node   - Target node.
   *
   * Arity 2: Return the relevant edges across the given path.
   * @param  {any}   source - Source node.
   * @param  {any}   target - Target node.
   *
   * @return {array|number} - The edges or the number of edges.
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  Class.prototype[name] = function (source, target) {
    // Early termination
    if (type !== 'mixed' && this.type !== 'mixed' && type !== this.type) return [];
    if (!arguments.length) return createEdgeArray(this, type);
    if (arguments.length === 1) {
      source = '' + source;
      var nodeData = this._nodes.get(source);
      if (typeof nodeData === 'undefined') throw new NotFoundGraphError("Graph.".concat(name, ": could not find the \"").concat(source, "\" node in the graph."));

      // Iterating over a node's edges
      return createEdgeArrayForNode(this.multi, type === 'mixed' ? this.type : type, direction, nodeData);
    }
    if (arguments.length === 2) {
      source = '' + source;
      target = '' + target;
      var sourceData = this._nodes.get(source);
      if (!sourceData) throw new NotFoundGraphError("Graph.".concat(name, ":  could not find the \"").concat(source, "\" source node in the graph."));
      if (!this._nodes.has(target)) throw new NotFoundGraphError("Graph.".concat(name, ":  could not find the \"").concat(target, "\" target node in the graph."));

      // Iterating over the edges between source & target
      return createEdgeArrayForPath(type, this.multi, direction, sourceData, target);
    }
    throw new InvalidArgumentsGraphError("Graph.".concat(name, ": too many arguments (expecting 0, 1 or 2 and got ").concat(arguments.length, ")."));
  };
}

/**
 * Function attaching a edge callback iterator method to the Graph prototype.
 *
 * @param {function} Class       - Target class.
 * @param {object}   description - Method description.
 */
function attachForEachEdge(Class, description) {
  var name = description.name,
    type = description.type,
    direction = description.direction;
  var forEachName = 'forEach' + name[0].toUpperCase() + name.slice(1, -1);

  /**
   * Function iterating over the graph's relevant edges by applying the given
   * callback.
   *
   * Arity 1: Iterate over all the relevant edges.
   * @param  {function} callback - Callback to use.
   *
   * Arity 2: Iterate over all of a node's relevant edges.
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   *
   * Arity 3: Iterate over the relevant edges across the given path.
   * @param  {any}      source   - Source node.
   * @param  {any}      target   - Target node.
   * @param  {function} callback - Callback to use.
   *
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  Class.prototype[forEachName] = function (source, target, callback) {
    // Early termination
    if (type !== 'mixed' && this.type !== 'mixed' && type !== this.type) return;
    if (arguments.length === 1) {
      callback = source;
      return forEachEdge(false, this, type, callback);
    }
    if (arguments.length === 2) {
      source = '' + source;
      callback = target;
      var nodeData = this._nodes.get(source);
      if (typeof nodeData === 'undefined') throw new NotFoundGraphError("Graph.".concat(forEachName, ": could not find the \"").concat(source, "\" node in the graph."));

      // Iterating over a node's edges
      // TODO: maybe attach the sub method to the instance dynamically?
      return forEachEdgeForNode(false, this.multi, type === 'mixed' ? this.type : type, direction, nodeData, callback);
    }
    if (arguments.length === 3) {
      source = '' + source;
      target = '' + target;
      var sourceData = this._nodes.get(source);
      if (!sourceData) throw new NotFoundGraphError("Graph.".concat(forEachName, ":  could not find the \"").concat(source, "\" source node in the graph."));
      if (!this._nodes.has(target)) throw new NotFoundGraphError("Graph.".concat(forEachName, ":  could not find the \"").concat(target, "\" target node in the graph."));

      // Iterating over the edges between source & target
      return forEachEdgeForPath(false, type, this.multi, direction, sourceData, target, callback);
    }
    throw new InvalidArgumentsGraphError("Graph.".concat(forEachName, ": too many arguments (expecting 1, 2 or 3 and got ").concat(arguments.length, ")."));
  };

  /**
   * Function mapping the graph's relevant edges by applying the given
   * callback.
   *
   * Arity 1: Map all the relevant edges.
   * @param  {function} callback - Callback to use.
   *
   * Arity 2: Map all of a node's relevant edges.
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   *
   * Arity 3: Map the relevant edges across the given path.
   * @param  {any}      source   - Source node.
   * @param  {any}      target   - Target node.
   * @param  {function} callback - Callback to use.
   *
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var mapName = 'map' + name[0].toUpperCase() + name.slice(1);
  Class.prototype[mapName] = function () {
    var args = Array.prototype.slice.call(arguments);
    var callback = args.pop();
    var result;

    // We know the result length beforehand
    if (args.length === 0) {
      var length = 0;
      if (type !== 'directed') length += this.undirectedSize;
      if (type !== 'undirected') length += this.directedSize;
      result = new Array(length);
      var i = 0;
      args.push(function (e, ea, s, t, sa, ta, u) {
        result[i++] = callback(e, ea, s, t, sa, ta, u);
      });
    }

    // We don't know the result length beforehand
    // TODO: we can in some instances of simple graphs, knowing degree
    else {
      result = [];
      args.push(function (e, ea, s, t, sa, ta, u) {
        result.push(callback(e, ea, s, t, sa, ta, u));
      });
    }
    this[forEachName].apply(this, args);
    return result;
  };

  /**
   * Function filtering the graph's relevant edges using the provided predicate
   * function.
   *
   * Arity 1: Filter all the relevant edges.
   * @param  {function} predicate - Predicate to use.
   *
   * Arity 2: Filter all of a node's relevant edges.
   * @param  {any}      node      - Target node.
   * @param  {function} predicate - Predicate to use.
   *
   * Arity 3: Filter the relevant edges across the given path.
   * @param  {any}      source    - Source node.
   * @param  {any}      target    - Target node.
   * @param  {function} predicate - Predicate to use.
   *
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var filterName = 'filter' + name[0].toUpperCase() + name.slice(1);
  Class.prototype[filterName] = function () {
    var args = Array.prototype.slice.call(arguments);
    var callback = args.pop();
    var result = [];
    args.push(function (e, ea, s, t, sa, ta, u) {
      if (callback(e, ea, s, t, sa, ta, u)) result.push(e);
    });
    this[forEachName].apply(this, args);
    return result;
  };

  /**
   * Function reducing the graph's relevant edges using the provided accumulator
   * function.
   *
   * Arity 1: Reduce all the relevant edges.
   * @param  {function} accumulator  - Accumulator to use.
   * @param  {any}      initialValue - Initial value.
   *
   * Arity 2: Reduce all of a node's relevant edges.
   * @param  {any}      node         - Target node.
   * @param  {function} accumulator  - Accumulator to use.
   * @param  {any}      initialValue - Initial value.
   *
   * Arity 3: Reduce the relevant edges across the given path.
   * @param  {any}      source       - Source node.
   * @param  {any}      target       - Target node.
   * @param  {function} accumulator  - Accumulator to use.
   * @param  {any}      initialValue - Initial value.
   *
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var reduceName = 'reduce' + name[0].toUpperCase() + name.slice(1);
  Class.prototype[reduceName] = function () {
    var args = Array.prototype.slice.call(arguments);
    if (args.length < 2 || args.length > 4) {
      throw new InvalidArgumentsGraphError("Graph.".concat(reduceName, ": invalid number of arguments (expecting 2, 3 or 4 and got ").concat(args.length, ")."));
    }
    if (typeof args[args.length - 1] === 'function' && typeof args[args.length - 2] !== 'function') {
      throw new InvalidArgumentsGraphError("Graph.".concat(reduceName, ": missing initial value. You must provide it because the callback takes more than one argument and we cannot infer the initial value from the first iteration, as you could with a simple array."));
    }
    var callback;
    var initialValue;
    if (args.length === 2) {
      callback = args[0];
      initialValue = args[1];
      args = [];
    } else if (args.length === 3) {
      callback = args[1];
      initialValue = args[2];
      args = [args[0]];
    } else if (args.length === 4) {
      callback = args[2];
      initialValue = args[3];
      args = [args[0], args[1]];
    }
    var accumulator = initialValue;
    args.push(function (e, ea, s, t, sa, ta, u) {
      accumulator = callback(accumulator, e, ea, s, t, sa, ta, u);
    });
    this[forEachName].apply(this, args);
    return accumulator;
  };
}

/**
 * Function attaching a breakable edge callback iterator method to the Graph
 * prototype.
 *
 * @param {function} Class       - Target class.
 * @param {object}   description - Method description.
 */
function attachFindEdge(Class, description) {
  var name = description.name,
    type = description.type,
    direction = description.direction;
  var findEdgeName = 'find' + name[0].toUpperCase() + name.slice(1, -1);

  /**
   * Function iterating over the graph's relevant edges in order to match
   * one of them using the provided predicate function.
   *
   * Arity 1: Iterate over all the relevant edges.
   * @param  {function} callback - Callback to use.
   *
   * Arity 2: Iterate over all of a node's relevant edges.
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   *
   * Arity 3: Iterate over the relevant edges across the given path.
   * @param  {any}      source   - Source node.
   * @param  {any}      target   - Target node.
   * @param  {function} callback - Callback to use.
   *
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  Class.prototype[findEdgeName] = function (source, target, callback) {
    // Early termination
    if (type !== 'mixed' && this.type !== 'mixed' && type !== this.type) return false;
    if (arguments.length === 1) {
      callback = source;
      return forEachEdge(true, this, type, callback);
    }
    if (arguments.length === 2) {
      source = '' + source;
      callback = target;
      var nodeData = this._nodes.get(source);
      if (typeof nodeData === 'undefined') throw new NotFoundGraphError("Graph.".concat(findEdgeName, ": could not find the \"").concat(source, "\" node in the graph."));

      // Iterating over a node's edges
      // TODO: maybe attach the sub method to the instance dynamically?
      return forEachEdgeForNode(true, this.multi, type === 'mixed' ? this.type : type, direction, nodeData, callback);
    }
    if (arguments.length === 3) {
      source = '' + source;
      target = '' + target;
      var sourceData = this._nodes.get(source);
      if (!sourceData) throw new NotFoundGraphError("Graph.".concat(findEdgeName, ":  could not find the \"").concat(source, "\" source node in the graph."));
      if (!this._nodes.has(target)) throw new NotFoundGraphError("Graph.".concat(findEdgeName, ":  could not find the \"").concat(target, "\" target node in the graph."));

      // Iterating over the edges between source & target
      return forEachEdgeForPath(true, type, this.multi, direction, sourceData, target, callback);
    }
    throw new InvalidArgumentsGraphError("Graph.".concat(findEdgeName, ": too many arguments (expecting 1, 2 or 3 and got ").concat(arguments.length, ")."));
  };

  /**
   * Function iterating over the graph's relevant edges in order to assert
   * whether any one of them matches the provided predicate function.
   *
   * Arity 1: Iterate over all the relevant edges.
   * @param  {function} callback - Callback to use.
   *
   * Arity 2: Iterate over all of a node's relevant edges.
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   *
   * Arity 3: Iterate over the relevant edges across the given path.
   * @param  {any}      source   - Source node.
   * @param  {any}      target   - Target node.
   * @param  {function} callback - Callback to use.
   *
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var someName = 'some' + name[0].toUpperCase() + name.slice(1, -1);
  Class.prototype[someName] = function () {
    var args = Array.prototype.slice.call(arguments);
    var callback = args.pop();
    args.push(function (e, ea, s, t, sa, ta, u) {
      return callback(e, ea, s, t, sa, ta, u);
    });
    var found = this[findEdgeName].apply(this, args);
    if (found) return true;
    return false;
  };

  /**
   * Function iterating over the graph's relevant edges in order to assert
   * whether all of them matche the provided predicate function.
   *
   * Arity 1: Iterate over all the relevant edges.
   * @param  {function} callback - Callback to use.
   *
   * Arity 2: Iterate over all of a node's relevant edges.
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   *
   * Arity 3: Iterate over the relevant edges across the given path.
   * @param  {any}      source   - Source node.
   * @param  {any}      target   - Target node.
   * @param  {function} callback - Callback to use.
   *
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var everyName = 'every' + name[0].toUpperCase() + name.slice(1, -1);
  Class.prototype[everyName] = function () {
    var args = Array.prototype.slice.call(arguments);
    var callback = args.pop();
    args.push(function (e, ea, s, t, sa, ta, u) {
      return !callback(e, ea, s, t, sa, ta, u);
    });
    var found = this[findEdgeName].apply(this, args);
    if (found) return false;
    return true;
  };
}

/**
 * Function attaching an edge iterator method to the Graph prototype.
 *
 * @param {function} Class       - Target class.
 * @param {object}   description - Method description.
 */
function attachEdgeIteratorCreator(Class, description) {
  var originalName = description.name,
    type = description.type,
    direction = description.direction;
  var name = originalName.slice(0, -1) + 'Entries';

  /**
   * Function returning an iterator over the graph's edges.
   *
   * Arity 0: Iterate over all the relevant edges.
   *
   * Arity 1: Iterate over all of a node's relevant edges.
   * @param  {any}   node   - Target node.
   *
   * Arity 2: Iterate over the relevant edges across the given path.
   * @param  {any}   source - Source node.
   * @param  {any}   target - Target node.
   *
   * @return {array|number} - The edges or the number of edges.
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  Class.prototype[name] = function (source, target) {
    // Early termination
    if (type !== 'mixed' && this.type !== 'mixed' && type !== this.type) return Iterator__default["default"].empty();
    if (!arguments.length) return createEdgeIterator(this, type);
    if (arguments.length === 1) {
      source = '' + source;
      var sourceData = this._nodes.get(source);
      if (!sourceData) throw new NotFoundGraphError("Graph.".concat(name, ": could not find the \"").concat(source, "\" node in the graph."));

      // Iterating over a node's edges
      return createEdgeIteratorForNode(type, direction, sourceData);
    }
    if (arguments.length === 2) {
      source = '' + source;
      target = '' + target;
      var _sourceData = this._nodes.get(source);
      if (!_sourceData) throw new NotFoundGraphError("Graph.".concat(name, ":  could not find the \"").concat(source, "\" source node in the graph."));
      if (!this._nodes.has(target)) throw new NotFoundGraphError("Graph.".concat(name, ":  could not find the \"").concat(target, "\" target node in the graph."));

      // Iterating over the edges between source & target
      return createEdgeIteratorForPath(type, direction, _sourceData, target);
    }
    throw new InvalidArgumentsGraphError("Graph.".concat(name, ": too many arguments (expecting 0, 1 or 2 and got ").concat(arguments.length, ")."));
  };
}

/**
 * Function attaching every edge iteration method to the Graph class.
 *
 * @param {function} Graph - Graph class.
 */
function attachEdgeIterationMethods(Graph) {
  EDGES_ITERATION.forEach(function (description) {
    attachEdgeArrayCreator(Graph, description);
    attachForEachEdge(Graph, description);
    attachFindEdge(Graph, description);
    attachEdgeIteratorCreator(Graph, description);
  });
}

/**
 * Graphology Neighbor Iteration
 * ==============================
 *
 * Attaching some methods to the Graph class to be able to iterate over
 * neighbors.
 */

/**
 * Definitions.
 */
var NEIGHBORS_ITERATION = [{
  name: 'neighbors',
  type: 'mixed'
}, {
  name: 'inNeighbors',
  type: 'directed',
  direction: 'in'
}, {
  name: 'outNeighbors',
  type: 'directed',
  direction: 'out'
}, {
  name: 'inboundNeighbors',
  type: 'mixed',
  direction: 'in'
}, {
  name: 'outboundNeighbors',
  type: 'mixed',
  direction: 'out'
}, {
  name: 'directedNeighbors',
  type: 'directed'
}, {
  name: 'undirectedNeighbors',
  type: 'undirected'
}];

/**
 * Helpers.
 */
function CompositeSetWrapper() {
  this.A = null;
  this.B = null;
}
CompositeSetWrapper.prototype.wrap = function (set) {
  if (this.A === null) this.A = set;else if (this.B === null) this.B = set;
};
CompositeSetWrapper.prototype.has = function (key) {
  if (this.A !== null && key in this.A) return true;
  if (this.B !== null && key in this.B) return true;
  return false;
};

/**
 * Function iterating over the given node's relevant neighbors to match
 * one of them using a predicated function.
 *
 * @param  {string}   type      - Type of neighbors.
 * @param  {string}   direction - Direction.
 * @param  {any}      nodeData  - Target node's data.
 * @param  {function} callback  - Callback to use.
 */
function forEachInObjectOnce(breakable, visited, nodeData, object, callback) {
  for (var k in object) {
    var edgeData = object[k];
    var sourceData = edgeData.source;
    var targetData = edgeData.target;
    var neighborData = sourceData === nodeData ? targetData : sourceData;
    if (visited && visited.has(neighborData.key)) continue;
    var shouldBreak = callback(neighborData.key, neighborData.attributes);
    if (breakable && shouldBreak) return neighborData.key;
  }
  return;
}
function forEachNeighbor(breakable, type, direction, nodeData, callback) {
  // If we want only undirected or in or out, we can roll some optimizations
  if (type !== 'mixed') {
    if (type === 'undirected') return forEachInObjectOnce(breakable, null, nodeData, nodeData.undirected, callback);
    if (typeof direction === 'string') return forEachInObjectOnce(breakable, null, nodeData, nodeData[direction], callback);
  }

  // Else we need to keep a set of neighbors not to return duplicates
  // We cheat by querying the other adjacencies
  var visited = new CompositeSetWrapper();
  var found;
  if (type !== 'undirected') {
    if (direction !== 'out') {
      found = forEachInObjectOnce(breakable, null, nodeData, nodeData["in"], callback);
      if (breakable && found) return found;
      visited.wrap(nodeData["in"]);
    }
    if (direction !== 'in') {
      found = forEachInObjectOnce(breakable, visited, nodeData, nodeData.out, callback);
      if (breakable && found) return found;
      visited.wrap(nodeData.out);
    }
  }
  if (type !== 'directed') {
    found = forEachInObjectOnce(breakable, visited, nodeData, nodeData.undirected, callback);
    if (breakable && found) return found;
  }
  return;
}

/**
 * Function creating an array of relevant neighbors for the given node.
 *
 * @param  {string}       type      - Type of neighbors.
 * @param  {string}       direction - Direction.
 * @param  {any}          nodeData  - Target node's data.
 * @return {Array}                  - The list of neighbors.
 */
function createNeighborArrayForNode(type, direction, nodeData) {
  // If we want only undirected or in or out, we can roll some optimizations
  if (type !== 'mixed') {
    if (type === 'undirected') return Object.keys(nodeData.undirected);
    if (typeof direction === 'string') return Object.keys(nodeData[direction]);
  }
  var neighbors = [];
  forEachNeighbor(false, type, direction, nodeData, function (key) {
    neighbors.push(key);
  });
  return neighbors;
}

/**
 * Function returning an iterator over the given node's relevant neighbors.
 *
 * @param  {string}   type      - Type of neighbors.
 * @param  {string}   direction - Direction.
 * @param  {any}      nodeData  - Target node's data.
 * @return {Iterator}
 */
function createDedupedObjectIterator(visited, nodeData, object) {
  var keys = Object.keys(object);
  var l = keys.length;
  var i = 0;
  return new Iterator__default["default"](function next() {
    var neighborData = null;
    do {
      if (i >= l) {
        if (visited) visited.wrap(object);
        return {
          done: true
        };
      }
      var edgeData = object[keys[i++]];
      var sourceData = edgeData.source;
      var targetData = edgeData.target;
      neighborData = sourceData === nodeData ? targetData : sourceData;
      if (visited && visited.has(neighborData.key)) {
        neighborData = null;
        continue;
      }
    } while (neighborData === null);
    return {
      done: false,
      value: {
        neighbor: neighborData.key,
        attributes: neighborData.attributes
      }
    };
  });
}
function createNeighborIterator(type, direction, nodeData) {
  // If we want only undirected or in or out, we can roll some optimizations
  if (type !== 'mixed') {
    if (type === 'undirected') return createDedupedObjectIterator(null, nodeData, nodeData.undirected);
    if (typeof direction === 'string') return createDedupedObjectIterator(null, nodeData, nodeData[direction]);
  }
  var iterator = Iterator__default["default"].empty();

  // Else we need to keep a set of neighbors not to return duplicates
  // We cheat by querying the other adjacencies
  var visited = new CompositeSetWrapper();
  if (type !== 'undirected') {
    if (direction !== 'out') {
      iterator = chain__default["default"](iterator, createDedupedObjectIterator(visited, nodeData, nodeData["in"]));
    }
    if (direction !== 'in') {
      iterator = chain__default["default"](iterator, createDedupedObjectIterator(visited, nodeData, nodeData.out));
    }
  }
  if (type !== 'directed') {
    iterator = chain__default["default"](iterator, createDedupedObjectIterator(visited, nodeData, nodeData.undirected));
  }
  return iterator;
}

/**
 * Function attaching a neighbors array creator method to the Graph prototype.
 *
 * @param {function} Class       - Target class.
 * @param {object}   description - Method description.
 */
function attachNeighborArrayCreator(Class, description) {
  var name = description.name,
    type = description.type,
    direction = description.direction;

  /**
   * Function returning an array of certain neighbors.
   *
   * @param  {any}   node   - Target node.
   * @return {array} - The neighbors of neighbors.
   *
   * @throws {Error} - Will throw if node is not found in the graph.
   */
  Class.prototype[name] = function (node) {
    // Early termination
    if (type !== 'mixed' && this.type !== 'mixed' && type !== this.type) return [];
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (typeof nodeData === 'undefined') throw new NotFoundGraphError("Graph.".concat(name, ": could not find the \"").concat(node, "\" node in the graph."));

    // Here, we want to iterate over a node's relevant neighbors
    return createNeighborArrayForNode(type === 'mixed' ? this.type : type, direction, nodeData);
  };
}

/**
 * Function attaching a neighbors callback iterator method to the Graph prototype.
 *
 * @param {function} Class       - Target class.
 * @param {object}   description - Method description.
 */
function attachForEachNeighbor(Class, description) {
  var name = description.name,
    type = description.type,
    direction = description.direction;
  var forEachName = 'forEach' + name[0].toUpperCase() + name.slice(1, -1);

  /**
   * Function iterating over all the relevant neighbors using a callback.
   *
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  Class.prototype[forEachName] = function (node, callback) {
    // Early termination
    if (type !== 'mixed' && this.type !== 'mixed' && type !== this.type) return;
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (typeof nodeData === 'undefined') throw new NotFoundGraphError("Graph.".concat(forEachName, ": could not find the \"").concat(node, "\" node in the graph."));

    // Here, we want to iterate over a node's relevant neighbors
    forEachNeighbor(false, type === 'mixed' ? this.type : type, direction, nodeData, callback);
  };

  /**
   * Function mapping the relevant neighbors using a callback.
   *
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var mapName = 'map' + name[0].toUpperCase() + name.slice(1);
  Class.prototype[mapName] = function (node, callback) {
    // TODO: optimize when size is known beforehand
    var result = [];
    this[forEachName](node, function (n, a) {
      result.push(callback(n, a));
    });
    return result;
  };

  /**
   * Function filtering the relevant neighbors using a callback.
   *
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var filterName = 'filter' + name[0].toUpperCase() + name.slice(1);
  Class.prototype[filterName] = function (node, callback) {
    var result = [];
    this[forEachName](node, function (n, a) {
      if (callback(n, a)) result.push(n);
    });
    return result;
  };

  /**
   * Function reducing the relevant neighbors using a callback.
   *
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var reduceName = 'reduce' + name[0].toUpperCase() + name.slice(1);
  Class.prototype[reduceName] = function (node, callback, initialValue) {
    if (arguments.length < 3) throw new InvalidArgumentsGraphError("Graph.".concat(reduceName, ": missing initial value. You must provide it because the callback takes more than one argument and we cannot infer the initial value from the first iteration, as you could with a simple array."));
    var accumulator = initialValue;
    this[forEachName](node, function (n, a) {
      accumulator = callback(accumulator, n, a);
    });
    return accumulator;
  };
}

/**
 * Function attaching a breakable neighbors callback iterator method to the
 * Graph prototype.
 *
 * @param {function} Class       - Target class.
 * @param {object}   description - Method description.
 */
function attachFindNeighbor(Class, description) {
  var name = description.name,
    type = description.type,
    direction = description.direction;
  var capitalizedSingular = name[0].toUpperCase() + name.slice(1, -1);
  var findName = 'find' + capitalizedSingular;

  /**
   * Function iterating over all the relevant neighbors using a callback.
   *
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   * @return {undefined}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  Class.prototype[findName] = function (node, callback) {
    // Early termination
    if (type !== 'mixed' && this.type !== 'mixed' && type !== this.type) return;
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (typeof nodeData === 'undefined') throw new NotFoundGraphError("Graph.".concat(findName, ": could not find the \"").concat(node, "\" node in the graph."));

    // Here, we want to iterate over a node's relevant neighbors
    return forEachNeighbor(true, type === 'mixed' ? this.type : type, direction, nodeData, callback);
  };

  /**
   * Function iterating over all the relevant neighbors to find if any of them
   * matches the given predicate.
   *
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var someName = 'some' + capitalizedSingular;
  Class.prototype[someName] = function (node, callback) {
    var found = this[findName](node, callback);
    if (found) return true;
    return false;
  };

  /**
   * Function iterating over all the relevant neighbors to find if all of them
   * matche the given predicate.
   *
   * @param  {any}      node     - Target node.
   * @param  {function} callback - Callback to use.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  var everyName = 'every' + capitalizedSingular;
  Class.prototype[everyName] = function (node, callback) {
    var found = this[findName](node, function (n, a) {
      return !callback(n, a);
    });
    if (found) return false;
    return true;
  };
}

/**
 * Function attaching a neighbors callback iterator method to the Graph prototype.
 *
 * @param {function} Class       - Target class.
 * @param {object}   description - Method description.
 */
function attachNeighborIteratorCreator(Class, description) {
  var name = description.name,
    type = description.type,
    direction = description.direction;
  var iteratorName = name.slice(0, -1) + 'Entries';

  /**
   * Function returning an iterator over all the relevant neighbors.
   *
   * @param  {any}      node     - Target node.
   * @return {Iterator}
   *
   * @throws {Error} - Will throw if there are too many arguments.
   */
  Class.prototype[iteratorName] = function (node) {
    // Early termination
    if (type !== 'mixed' && this.type !== 'mixed' && type !== this.type) return Iterator__default["default"].empty();
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (typeof nodeData === 'undefined') throw new NotFoundGraphError("Graph.".concat(iteratorName, ": could not find the \"").concat(node, "\" node in the graph."));

    // Here, we want to iterate over a node's relevant neighbors
    return createNeighborIterator(type === 'mixed' ? this.type : type, direction, nodeData);
  };
}

/**
 * Function attaching every neighbor iteration method to the Graph class.
 *
 * @param {function} Graph - Graph class.
 */
function attachNeighborIterationMethods(Graph) {
  NEIGHBORS_ITERATION.forEach(function (description) {
    attachNeighborArrayCreator(Graph, description);
    attachForEachNeighbor(Graph, description);
    attachFindNeighbor(Graph, description);
    attachNeighborIteratorCreator(Graph, description);
  });
}

/**
 * Graphology Adjacency Iteration
 * ===============================
 *
 * Attaching some methods to the Graph class to be able to iterate over a
 * graph's adjacency.
 */

/**
 * Function iterating over a simple graph's adjacency using a callback.
 *
 * @param {boolean}  breakable         - Can we break?
 * @param {boolean}  assymetric        - Whether to emit undirected edges only once.
 * @param {boolean}  disconnectedNodes - Whether to emit disconnected nodes.
 * @param {Graph}    graph             - Target Graph instance.
 * @param {callback} function          - Iteration callback.
 */
function forEachAdjacency(breakable, assymetric, disconnectedNodes, graph, callback) {
  var iterator = graph._nodes.values();
  var type = graph.type;
  var step, sourceData, neighbor, adj, edgeData, targetData, shouldBreak;
  while (step = iterator.next(), step.done !== true) {
    var hasEdges = false;
    sourceData = step.value;
    if (type !== 'undirected') {
      adj = sourceData.out;
      for (neighbor in adj) {
        edgeData = adj[neighbor];
        do {
          targetData = edgeData.target;
          hasEdges = true;
          shouldBreak = callback(sourceData.key, targetData.key, sourceData.attributes, targetData.attributes, edgeData.key, edgeData.attributes, edgeData.undirected);
          if (breakable && shouldBreak) return edgeData;
          edgeData = edgeData.next;
        } while (edgeData);
      }
    }
    if (type !== 'directed') {
      adj = sourceData.undirected;
      for (neighbor in adj) {
        if (assymetric && sourceData.key > neighbor) continue;
        edgeData = adj[neighbor];
        do {
          targetData = edgeData.target;
          if (targetData.key !== neighbor) targetData = edgeData.source;
          hasEdges = true;
          shouldBreak = callback(sourceData.key, targetData.key, sourceData.attributes, targetData.attributes, edgeData.key, edgeData.attributes, edgeData.undirected);
          if (breakable && shouldBreak) return edgeData;
          edgeData = edgeData.next;
        } while (edgeData);
      }
    }
    if (disconnectedNodes && !hasEdges) {
      shouldBreak = callback(sourceData.key, null, sourceData.attributes, null, null, null, null);
      if (breakable && shouldBreak) return null;
    }
  }
  return;
}

/**
 * Graphology Serialization Utilities
 * ===================================
 *
 * Collection of functions used by the graph serialization schemes.
 */

/**
 * Formats internal node data into a serialized node.
 *
 * @param  {any}    key  - The node's key.
 * @param  {object} data - Internal node's data.
 * @return {array}       - The serialized node.
 */
function serializeNode(key, data) {
  var serialized = {
    key: key
  };
  if (!isEmpty(data.attributes)) serialized.attributes = assign({}, data.attributes);
  return serialized;
}

/**
 * Formats internal edge data into a serialized edge.
 *
 * @param  {string} type - The graph's type.
 * @param  {any}    key  - The edge's key.
 * @param  {object} data - Internal edge's data.
 * @return {array}       - The serialized edge.
 */
function serializeEdge(type, key, data) {
  var serialized = {
    key: key,
    source: data.source.key,
    target: data.target.key
  };
  if (!isEmpty(data.attributes)) serialized.attributes = assign({}, data.attributes);
  if (type === 'mixed' && data.undirected) serialized.undirected = true;
  return serialized;
}

/**
 * Checks whether the given value is a serialized node.
 *
 * @param  {mixed} value - Target value.
 * @return {string|null}
 */
function validateSerializedNode(value) {
  if (!isPlainObject(value)) throw new InvalidArgumentsGraphError('Graph.import: invalid serialized node. A serialized node should be a plain object with at least a "key" property.');
  if (!('key' in value)) throw new InvalidArgumentsGraphError('Graph.import: serialized node is missing its key.');
  if ('attributes' in value && (!isPlainObject(value.attributes) || value.attributes === null)) throw new InvalidArgumentsGraphError('Graph.import: invalid attributes. Attributes should be a plain object, null or omitted.');
}

/**
 * Checks whether the given value is a serialized edge.
 *
 * @param  {mixed} value - Target value.
 * @return {string|null}
 */
function validateSerializedEdge(value) {
  if (!isPlainObject(value)) throw new InvalidArgumentsGraphError('Graph.import: invalid serialized edge. A serialized edge should be a plain object with at least a "source" & "target" property.');
  if (!('source' in value)) throw new InvalidArgumentsGraphError('Graph.import: serialized edge is missing its source.');
  if (!('target' in value)) throw new InvalidArgumentsGraphError('Graph.import: serialized edge is missing its target.');
  if ('attributes' in value && (!isPlainObject(value.attributes) || value.attributes === null)) throw new InvalidArgumentsGraphError('Graph.import: invalid attributes. Attributes should be a plain object, null or omitted.');
  if ('undirected' in value && typeof value.undirected !== 'boolean') throw new InvalidArgumentsGraphError('Graph.import: invalid undirectedness information. Undirected should be boolean or omitted.');
}

/**
 * Constants.
 */
var INSTANCE_ID = incrementalIdStartingFromRandomByte();

/**
 * Enums.
 */
var TYPES = new Set(['directed', 'undirected', 'mixed']);
var EMITTER_PROPS = new Set(['domain', '_events', '_eventsCount', '_maxListeners']);
var EDGE_ADD_METHODS = [{
  name: function name(verb) {
    return "".concat(verb, "Edge");
  },
  generateKey: true
}, {
  name: function name(verb) {
    return "".concat(verb, "DirectedEdge");
  },
  generateKey: true,
  type: 'directed'
}, {
  name: function name(verb) {
    return "".concat(verb, "UndirectedEdge");
  },
  generateKey: true,
  type: 'undirected'
}, {
  name: function name(verb) {
    return "".concat(verb, "EdgeWithKey");
  }
}, {
  name: function name(verb) {
    return "".concat(verb, "DirectedEdgeWithKey");
  },
  type: 'directed'
}, {
  name: function name(verb) {
    return "".concat(verb, "UndirectedEdgeWithKey");
  },
  type: 'undirected'
}];

/**
 * Default options.
 */
var DEFAULTS = {
  allowSelfLoops: true,
  multi: false,
  type: 'mixed'
};

/**
 * Abstract functions used by the Graph class for various methods.
 */

/**
 * Internal method used to add a node to the given graph
 *
 * @param  {Graph}   graph           - Target graph.
 * @param  {any}     node            - The node's key.
 * @param  {object}  [attributes]    - Optional attributes.
 * @return {NodeData}                - Created node data.
 */
function _addNode(graph, node, attributes) {
  if (attributes && !isPlainObject(attributes)) throw new InvalidArgumentsGraphError("Graph.addNode: invalid attributes. Expecting an object but got \"".concat(attributes, "\""));

  // String coercion
  node = '' + node;
  attributes = attributes || {};
  if (graph._nodes.has(node)) throw new UsageGraphError("Graph.addNode: the \"".concat(node, "\" node already exist in the graph."));
  var data = new graph.NodeDataClass(node, attributes);

  // Adding the node to internal register
  graph._nodes.set(node, data);

  // Emitting
  graph.emit('nodeAdded', {
    key: node,
    attributes: attributes
  });
  return data;
}

/**
 * Same as the above but without sanity checks because we call this in contexts
 * where necessary checks were already done.
 */
function unsafeAddNode(graph, node, attributes) {
  var data = new graph.NodeDataClass(node, attributes);
  graph._nodes.set(node, data);
  graph.emit('nodeAdded', {
    key: node,
    attributes: attributes
  });
  return data;
}

/**
 * Internal method used to add an arbitrary edge to the given graph.
 *
 * @param  {Graph}   graph           - Target graph.
 * @param  {string}  name            - Name of the child method for errors.
 * @param  {boolean} mustGenerateKey - Should the graph generate an id?
 * @param  {boolean} undirected      - Whether the edge is undirected.
 * @param  {any}     edge            - The edge's key.
 * @param  {any}     source          - The source node.
 * @param  {any}     target          - The target node.
 * @param  {object}  [attributes]    - Optional attributes.
 * @return {any}                     - The edge.
 *
 * @throws {Error} - Will throw if the graph is of the wrong type.
 * @throws {Error} - Will throw if the given attributes are not an object.
 * @throws {Error} - Will throw if source or target doesn't exist.
 * @throws {Error} - Will throw if the edge already exist.
 */
function addEdge(graph, name, mustGenerateKey, undirected, edge, source, target, attributes) {
  // Checking validity of operation
  if (!undirected && graph.type === 'undirected') throw new UsageGraphError("Graph.".concat(name, ": you cannot add a directed edge to an undirected graph. Use the #.addEdge or #.addUndirectedEdge instead."));
  if (undirected && graph.type === 'directed') throw new UsageGraphError("Graph.".concat(name, ": you cannot add an undirected edge to a directed graph. Use the #.addEdge or #.addDirectedEdge instead."));
  if (attributes && !isPlainObject(attributes)) throw new InvalidArgumentsGraphError("Graph.".concat(name, ": invalid attributes. Expecting an object but got \"").concat(attributes, "\""));

  // Coercion of source & target:
  source = '' + source;
  target = '' + target;
  attributes = attributes || {};
  if (!graph.allowSelfLoops && source === target) throw new UsageGraphError("Graph.".concat(name, ": source & target are the same (\"").concat(source, "\"), thus creating a loop explicitly forbidden by this graph 'allowSelfLoops' option set to false."));
  var sourceData = graph._nodes.get(source),
    targetData = graph._nodes.get(target);
  if (!sourceData) throw new NotFoundGraphError("Graph.".concat(name, ": source node \"").concat(source, "\" not found."));
  if (!targetData) throw new NotFoundGraphError("Graph.".concat(name, ": target node \"").concat(target, "\" not found."));

  // Must the graph generate an id for this edge?
  var eventData = {
    key: null,
    undirected: undirected,
    source: source,
    target: target,
    attributes: attributes
  };
  if (mustGenerateKey) {
    // NOTE: in this case we can guarantee that the key does not already
    // exist and is already correctly casted as a string
    edge = graph._edgeKeyGenerator();
  } else {
    // Coercion of edge key
    edge = '' + edge;

    // Here, we have a key collision
    if (graph._edges.has(edge)) throw new UsageGraphError("Graph.".concat(name, ": the \"").concat(edge, "\" edge already exists in the graph."));
  }

  // Here, we might have a source / target collision
  if (!graph.multi && (undirected ? typeof sourceData.undirected[target] !== 'undefined' : typeof sourceData.out[target] !== 'undefined')) {
    throw new UsageGraphError("Graph.".concat(name, ": an edge linking \"").concat(source, "\" to \"").concat(target, "\" already exists. If you really want to add multiple edges linking those nodes, you should create a multi graph by using the 'multi' option."));
  }

  // Storing some data
  var edgeData = new EdgeData(undirected, edge, sourceData, targetData, attributes);

  // Adding the edge to the internal register
  graph._edges.set(edge, edgeData);

  // Incrementing node degree counters
  var isSelfLoop = source === target;
  if (undirected) {
    sourceData.undirectedDegree++;
    targetData.undirectedDegree++;
    if (isSelfLoop) {
      sourceData.undirectedLoops++;
      graph._undirectedSelfLoopCount++;
    }
  } else {
    sourceData.outDegree++;
    targetData.inDegree++;
    if (isSelfLoop) {
      sourceData.directedLoops++;
      graph._directedSelfLoopCount++;
    }
  }

  // Updating relevant index
  if (graph.multi) edgeData.attachMulti();else edgeData.attach();
  if (undirected) graph._undirectedSize++;else graph._directedSize++;

  // Emitting
  eventData.key = edge;
  graph.emit('edgeAdded', eventData);
  return edge;
}

/**
 * Internal method used to add an arbitrary edge to the given graph.
 *
 * @param  {Graph}   graph           - Target graph.
 * @param  {string}  name            - Name of the child method for errors.
 * @param  {boolean} mustGenerateKey - Should the graph generate an id?
 * @param  {boolean} undirected      - Whether the edge is undirected.
 * @param  {any}     edge            - The edge's key.
 * @param  {any}     source          - The source node.
 * @param  {any}     target          - The target node.
 * @param  {object}  [attributes]    - Optional attributes.
 * @param  {boolean} [asUpdater]       - Are we updating or merging?
 * @return {any}                     - The edge.
 *
 * @throws {Error} - Will throw if the graph is of the wrong type.
 * @throws {Error} - Will throw if the given attributes are not an object.
 * @throws {Error} - Will throw if source or target doesn't exist.
 * @throws {Error} - Will throw if the edge already exist.
 */
function mergeEdge(graph, name, mustGenerateKey, undirected, edge, source, target, attributes, asUpdater) {
  // Checking validity of operation
  if (!undirected && graph.type === 'undirected') throw new UsageGraphError("Graph.".concat(name, ": you cannot merge/update a directed edge to an undirected graph. Use the #.mergeEdge/#.updateEdge or #.addUndirectedEdge instead."));
  if (undirected && graph.type === 'directed') throw new UsageGraphError("Graph.".concat(name, ": you cannot merge/update an undirected edge to a directed graph. Use the #.mergeEdge/#.updateEdge or #.addDirectedEdge instead."));
  if (attributes) {
    if (asUpdater) {
      if (typeof attributes !== 'function') throw new InvalidArgumentsGraphError("Graph.".concat(name, ": invalid updater function. Expecting a function but got \"").concat(attributes, "\""));
    } else {
      if (!isPlainObject(attributes)) throw new InvalidArgumentsGraphError("Graph.".concat(name, ": invalid attributes. Expecting an object but got \"").concat(attributes, "\""));
    }
  }

  // Coercion of source & target:
  source = '' + source;
  target = '' + target;
  var updater;
  if (asUpdater) {
    updater = attributes;
    attributes = undefined;
  }
  if (!graph.allowSelfLoops && source === target) throw new UsageGraphError("Graph.".concat(name, ": source & target are the same (\"").concat(source, "\"), thus creating a loop explicitly forbidden by this graph 'allowSelfLoops' option set to false."));
  var sourceData = graph._nodes.get(source);
  var targetData = graph._nodes.get(target);
  var edgeData;

  // Do we need to handle duplicate?
  var alreadyExistingEdgeData;
  if (!mustGenerateKey) {
    edgeData = graph._edges.get(edge);
    if (edgeData) {
      // Here, we need to ensure, if the user gave a key, that source & target
      // are consistent
      if (edgeData.source.key !== source || edgeData.target.key !== target) {
        // If source or target inconsistent
        if (!undirected || edgeData.source.key !== target || edgeData.target.key !== source) {
          // If directed, or source/target aren't flipped
          throw new UsageGraphError("Graph.".concat(name, ": inconsistency detected when attempting to merge the \"").concat(edge, "\" edge with \"").concat(source, "\" source & \"").concat(target, "\" target vs. (\"").concat(edgeData.source.key, "\", \"").concat(edgeData.target.key, "\")."));
        }
      }
      alreadyExistingEdgeData = edgeData;
    }
  }

  // Here, we might have a source / target collision
  if (!alreadyExistingEdgeData && !graph.multi && sourceData) {
    alreadyExistingEdgeData = undirected ? sourceData.undirected[target] : sourceData.out[target];
  }

  // Handling duplicates
  if (alreadyExistingEdgeData) {
    var info = [alreadyExistingEdgeData.key, false, false, false];

    // We can skip the attribute merging part if the user did not provide them
    if (asUpdater ? !updater : !attributes) return info;

    // Updating the attributes
    if (asUpdater) {
      var oldAttributes = alreadyExistingEdgeData.attributes;
      alreadyExistingEdgeData.attributes = updater(oldAttributes);
      graph.emit('edgeAttributesUpdated', {
        type: 'replace',
        key: alreadyExistingEdgeData.key,
        attributes: alreadyExistingEdgeData.attributes
      });
    }

    // Merging the attributes
    else {
      assign(alreadyExistingEdgeData.attributes, attributes);
      graph.emit('edgeAttributesUpdated', {
        type: 'merge',
        key: alreadyExistingEdgeData.key,
        attributes: alreadyExistingEdgeData.attributes,
        data: attributes
      });
    }
    return info;
  }
  attributes = attributes || {};
  if (asUpdater && updater) attributes = updater(attributes);

  // Must the graph generate an id for this edge?
  var eventData = {
    key: null,
    undirected: undirected,
    source: source,
    target: target,
    attributes: attributes
  };
  if (mustGenerateKey) {
    // NOTE: in this case we can guarantee that the key does not already
    // exist and is already correctly casted as a string
    edge = graph._edgeKeyGenerator();
  } else {
    // Coercion of edge key
    edge = '' + edge;

    // Here, we have a key collision
    if (graph._edges.has(edge)) throw new UsageGraphError("Graph.".concat(name, ": the \"").concat(edge, "\" edge already exists in the graph."));
  }
  var sourceWasAdded = false;
  var targetWasAdded = false;
  if (!sourceData) {
    sourceData = unsafeAddNode(graph, source, {});
    sourceWasAdded = true;
    if (source === target) {
      targetData = sourceData;
      targetWasAdded = true;
    }
  }
  if (!targetData) {
    targetData = unsafeAddNode(graph, target, {});
    targetWasAdded = true;
  }

  // Storing some data
  edgeData = new EdgeData(undirected, edge, sourceData, targetData, attributes);

  // Adding the edge to the internal register
  graph._edges.set(edge, edgeData);

  // Incrementing node degree counters
  var isSelfLoop = source === target;
  if (undirected) {
    sourceData.undirectedDegree++;
    targetData.undirectedDegree++;
    if (isSelfLoop) {
      sourceData.undirectedLoops++;
      graph._undirectedSelfLoopCount++;
    }
  } else {
    sourceData.outDegree++;
    targetData.inDegree++;
    if (isSelfLoop) {
      sourceData.directedLoops++;
      graph._directedSelfLoopCount++;
    }
  }

  // Updating relevant index
  if (graph.multi) edgeData.attachMulti();else edgeData.attach();
  if (undirected) graph._undirectedSize++;else graph._directedSize++;

  // Emitting
  eventData.key = edge;
  graph.emit('edgeAdded', eventData);
  return [edge, true, sourceWasAdded, targetWasAdded];
}

/**
 * Internal method used to drop an edge.
 *
 * @param  {Graph}    graph    - Target graph.
 * @param  {EdgeData} edgeData - Data of the edge to drop.
 */
function dropEdgeFromData(graph, edgeData) {
  // Dropping the edge from the register
  graph._edges["delete"](edgeData.key);

  // Updating related degrees
  var sourceData = edgeData.source,
    targetData = edgeData.target,
    attributes = edgeData.attributes;
  var undirected = edgeData.undirected;
  var isSelfLoop = sourceData === targetData;
  if (undirected) {
    sourceData.undirectedDegree--;
    targetData.undirectedDegree--;
    if (isSelfLoop) {
      sourceData.undirectedLoops--;
      graph._undirectedSelfLoopCount--;
    }
  } else {
    sourceData.outDegree--;
    targetData.inDegree--;
    if (isSelfLoop) {
      sourceData.directedLoops--;
      graph._directedSelfLoopCount--;
    }
  }

  // Clearing index
  if (graph.multi) edgeData.detachMulti();else edgeData.detach();
  if (undirected) graph._undirectedSize--;else graph._directedSize--;

  // Emitting
  graph.emit('edgeDropped', {
    key: edgeData.key,
    attributes: attributes,
    source: sourceData.key,
    target: targetData.key,
    undirected: undirected
  });
}

/**
 * Graph class
 *
 * @constructor
 * @param  {object}  [options] - Options:
 * @param  {boolean}   [allowSelfLoops] - Allow self loops?
 * @param  {string}    [type]           - Type of the graph.
 * @param  {boolean}   [map]            - Allow references as keys?
 * @param  {boolean}   [multi]          - Allow parallel edges?
 *
 * @throws {Error} - Will throw if the arguments are not valid.
 */
var Graph = /*#__PURE__*/function (_EventEmitter) {
  _inheritsLoose(Graph, _EventEmitter);
  function Graph(options) {
    var _this;
    _this = _EventEmitter.call(this) || this;

    //-- Solving options
    options = assign({}, DEFAULTS, options);

    // Enforcing options validity
    if (typeof options.multi !== 'boolean') throw new InvalidArgumentsGraphError("Graph.constructor: invalid 'multi' option. Expecting a boolean but got \"".concat(options.multi, "\"."));
    if (!TYPES.has(options.type)) throw new InvalidArgumentsGraphError("Graph.constructor: invalid 'type' option. Should be one of \"mixed\", \"directed\" or \"undirected\" but got \"".concat(options.type, "\"."));
    if (typeof options.allowSelfLoops !== 'boolean') throw new InvalidArgumentsGraphError("Graph.constructor: invalid 'allowSelfLoops' option. Expecting a boolean but got \"".concat(options.allowSelfLoops, "\"."));

    //-- Private properties

    // Utilities
    var NodeDataClass = options.type === 'mixed' ? MixedNodeData : options.type === 'directed' ? DirectedNodeData : UndirectedNodeData;
    privateProperty(_assertThisInitialized(_this), 'NodeDataClass', NodeDataClass);

    // Internal edge key generator

    // NOTE: this internal generator produce keys that are strings
    // composed of a weird prefix, an incremental instance id starting from
    // a random byte and finally an internal instance incremental id.
    // All this to avoid intra-frame and cross-frame adversarial inputs
    // that can force a single #.addEdge call to degenerate into a O(n)
    // available key search loop.

    // It also ensures that automatically generated edge keys are unlikely
    // to produce collisions with arbitrary keys given by users.
    var instancePrefix = 'geid_' + INSTANCE_ID() + '_';
    var edgeId = 0;
    var edgeKeyGenerator = function edgeKeyGenerator() {
      var availableEdgeKey;
      do {
        availableEdgeKey = instancePrefix + edgeId++;
      } while (_this._edges.has(availableEdgeKey));
      return availableEdgeKey;
    };

    // Indexes
    privateProperty(_assertThisInitialized(_this), '_attributes', {});
    privateProperty(_assertThisInitialized(_this), '_nodes', new Map());
    privateProperty(_assertThisInitialized(_this), '_edges', new Map());
    privateProperty(_assertThisInitialized(_this), '_directedSize', 0);
    privateProperty(_assertThisInitialized(_this), '_undirectedSize', 0);
    privateProperty(_assertThisInitialized(_this), '_directedSelfLoopCount', 0);
    privateProperty(_assertThisInitialized(_this), '_undirectedSelfLoopCount', 0);
    privateProperty(_assertThisInitialized(_this), '_edgeKeyGenerator', edgeKeyGenerator);

    // Options
    privateProperty(_assertThisInitialized(_this), '_options', options);

    // Emitter properties
    EMITTER_PROPS.forEach(function (prop) {
      return privateProperty(_assertThisInitialized(_this), prop, _this[prop]);
    });

    //-- Properties readers
    readOnlyProperty(_assertThisInitialized(_this), 'order', function () {
      return _this._nodes.size;
    });
    readOnlyProperty(_assertThisInitialized(_this), 'size', function () {
      return _this._edges.size;
    });
    readOnlyProperty(_assertThisInitialized(_this), 'directedSize', function () {
      return _this._directedSize;
    });
    readOnlyProperty(_assertThisInitialized(_this), 'undirectedSize', function () {
      return _this._undirectedSize;
    });
    readOnlyProperty(_assertThisInitialized(_this), 'selfLoopCount', function () {
      return _this._directedSelfLoopCount + _this._undirectedSelfLoopCount;
    });
    readOnlyProperty(_assertThisInitialized(_this), 'directedSelfLoopCount', function () {
      return _this._directedSelfLoopCount;
    });
    readOnlyProperty(_assertThisInitialized(_this), 'undirectedSelfLoopCount', function () {
      return _this._undirectedSelfLoopCount;
    });
    readOnlyProperty(_assertThisInitialized(_this), 'multi', _this._options.multi);
    readOnlyProperty(_assertThisInitialized(_this), 'type', _this._options.type);
    readOnlyProperty(_assertThisInitialized(_this), 'allowSelfLoops', _this._options.allowSelfLoops);
    readOnlyProperty(_assertThisInitialized(_this), 'implementation', function () {
      return 'graphology';
    });
    return _this;
  }
  var _proto = Graph.prototype;
  _proto._resetInstanceCounters = function _resetInstanceCounters() {
    this._directedSize = 0;
    this._undirectedSize = 0;
    this._directedSelfLoopCount = 0;
    this._undirectedSelfLoopCount = 0;
  }

  /**---------------------------------------------------------------------------
   * Read
   **---------------------------------------------------------------------------
   */

  /**
   * Method returning whether the given node is found in the graph.
   *
   * @param  {any}     node - The node.
   * @return {boolean}
   */;
  _proto.hasNode = function hasNode(node) {
    return this._nodes.has('' + node);
  }

  /**
   * Method returning whether the given directed edge is found in the graph.
   *
   * Arity 1:
   * @param  {any}     edge - The edge's key.
   *
   * Arity 2:
   * @param  {any}     source - The edge's source.
   * @param  {any}     target - The edge's target.
   *
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the arguments are invalid.
   */;
  _proto.hasDirectedEdge = function hasDirectedEdge(source, target) {
    // Early termination
    if (this.type === 'undirected') return false;
    if (arguments.length === 1) {
      var edge = '' + source;
      var edgeData = this._edges.get(edge);
      return !!edgeData && !edgeData.undirected;
    } else if (arguments.length === 2) {
      source = '' + source;
      target = '' + target;

      // If the node source or the target is not in the graph we break
      var nodeData = this._nodes.get(source);
      if (!nodeData) return false;

      // Is there a directed edge pointing toward target?
      return nodeData.out.hasOwnProperty(target);
    }
    throw new InvalidArgumentsGraphError("Graph.hasDirectedEdge: invalid arity (".concat(arguments.length, ", instead of 1 or 2). You can either ask for an edge id or for the existence of an edge between a source & a target."));
  }

  /**
   * Method returning whether the given undirected edge is found in the graph.
   *
   * Arity 1:
   * @param  {any}     edge - The edge's key.
   *
   * Arity 2:
   * @param  {any}     source - The edge's source.
   * @param  {any}     target - The edge's target.
   *
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the arguments are invalid.
   */;
  _proto.hasUndirectedEdge = function hasUndirectedEdge(source, target) {
    // Early termination
    if (this.type === 'directed') return false;
    if (arguments.length === 1) {
      var edge = '' + source;
      var edgeData = this._edges.get(edge);
      return !!edgeData && edgeData.undirected;
    } else if (arguments.length === 2) {
      source = '' + source;
      target = '' + target;

      // If the node source or the target is not in the graph we break
      var nodeData = this._nodes.get(source);
      if (!nodeData) return false;

      // Is there a directed edge pointing toward target?
      return nodeData.undirected.hasOwnProperty(target);
    }
    throw new InvalidArgumentsGraphError("Graph.hasDirectedEdge: invalid arity (".concat(arguments.length, ", instead of 1 or 2). You can either ask for an edge id or for the existence of an edge between a source & a target."));
  }

  /**
   * Method returning whether the given edge is found in the graph.
   *
   * Arity 1:
   * @param  {any}     edge - The edge's key.
   *
   * Arity 2:
   * @param  {any}     source - The edge's source.
   * @param  {any}     target - The edge's target.
   *
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the arguments are invalid.
   */;
  _proto.hasEdge = function hasEdge(source, target) {
    if (arguments.length === 1) {
      var edge = '' + source;
      return this._edges.has(edge);
    } else if (arguments.length === 2) {
      source = '' + source;
      target = '' + target;

      // If the node source or the target is not in the graph we break
      var nodeData = this._nodes.get(source);
      if (!nodeData) return false;

      // Is there a directed edge pointing toward target?
      return typeof nodeData.out !== 'undefined' && nodeData.out.hasOwnProperty(target) || typeof nodeData.undirected !== 'undefined' && nodeData.undirected.hasOwnProperty(target);
    }
    throw new InvalidArgumentsGraphError("Graph.hasEdge: invalid arity (".concat(arguments.length, ", instead of 1 or 2). You can either ask for an edge id or for the existence of an edge between a source & a target."));
  }

  /**
   * Method returning the edge matching source & target in a directed fashion.
   *
   * @param  {any} source - The edge's source.
   * @param  {any} target - The edge's target.
   *
   * @return {any|undefined}
   *
   * @throws {Error} - Will throw if the graph is multi.
   * @throws {Error} - Will throw if source or target doesn't exist.
   */;
  _proto.directedEdge = function directedEdge(source, target) {
    if (this.type === 'undirected') return;
    source = '' + source;
    target = '' + target;
    if (this.multi) throw new UsageGraphError('Graph.directedEdge: this method is irrelevant with multigraphs since there might be multiple edges between source & target. See #.directedEdges instead.');
    var sourceData = this._nodes.get(source);
    if (!sourceData) throw new NotFoundGraphError("Graph.directedEdge: could not find the \"".concat(source, "\" source node in the graph."));
    if (!this._nodes.has(target)) throw new NotFoundGraphError("Graph.directedEdge: could not find the \"".concat(target, "\" target node in the graph."));
    var edgeData = sourceData.out && sourceData.out[target] || undefined;
    if (edgeData) return edgeData.key;
  }

  /**
   * Method returning the edge matching source & target in a undirected fashion.
   *
   * @param  {any} source - The edge's source.
   * @param  {any} target - The edge's target.
   *
   * @return {any|undefined}
   *
   * @throws {Error} - Will throw if the graph is multi.
   * @throws {Error} - Will throw if source or target doesn't exist.
   */;
  _proto.undirectedEdge = function undirectedEdge(source, target) {
    if (this.type === 'directed') return;
    source = '' + source;
    target = '' + target;
    if (this.multi) throw new UsageGraphError('Graph.undirectedEdge: this method is irrelevant with multigraphs since there might be multiple edges between source & target. See #.undirectedEdges instead.');
    var sourceData = this._nodes.get(source);
    if (!sourceData) throw new NotFoundGraphError("Graph.undirectedEdge: could not find the \"".concat(source, "\" source node in the graph."));
    if (!this._nodes.has(target)) throw new NotFoundGraphError("Graph.undirectedEdge: could not find the \"".concat(target, "\" target node in the graph."));
    var edgeData = sourceData.undirected && sourceData.undirected[target] || undefined;
    if (edgeData) return edgeData.key;
  }

  /**
   * Method returning the edge matching source & target in a mixed fashion.
   *
   * @param  {any} source - The edge's source.
   * @param  {any} target - The edge's target.
   *
   * @return {any|undefined}
   *
   * @throws {Error} - Will throw if the graph is multi.
   * @throws {Error} - Will throw if source or target doesn't exist.
   */;
  _proto.edge = function edge(source, target) {
    if (this.multi) throw new UsageGraphError('Graph.edge: this method is irrelevant with multigraphs since there might be multiple edges between source & target. See #.edges instead.');
    source = '' + source;
    target = '' + target;
    var sourceData = this._nodes.get(source);
    if (!sourceData) throw new NotFoundGraphError("Graph.edge: could not find the \"".concat(source, "\" source node in the graph."));
    if (!this._nodes.has(target)) throw new NotFoundGraphError("Graph.edge: could not find the \"".concat(target, "\" target node in the graph."));
    var edgeData = sourceData.out && sourceData.out[target] || sourceData.undirected && sourceData.undirected[target] || undefined;
    if (edgeData) return edgeData.key;
  }

  /**
   * Method returning whether two nodes are directed neighbors.
   *
   * @param  {any}     node     - The node's key.
   * @param  {any}     neighbor - The neighbor's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.areDirectedNeighbors = function areDirectedNeighbors(node, neighbor) {
    node = '' + node;
    neighbor = '' + neighbor;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.areDirectedNeighbors: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return false;
    return neighbor in nodeData["in"] || neighbor in nodeData.out;
  }

  /**
   * Method returning whether two nodes are out neighbors.
   *
   * @param  {any}     node     - The node's key.
   * @param  {any}     neighbor - The neighbor's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.areOutNeighbors = function areOutNeighbors(node, neighbor) {
    node = '' + node;
    neighbor = '' + neighbor;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.areOutNeighbors: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return false;
    return neighbor in nodeData.out;
  }

  /**
   * Method returning whether two nodes are in neighbors.
   *
   * @param  {any}     node     - The node's key.
   * @param  {any}     neighbor - The neighbor's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.areInNeighbors = function areInNeighbors(node, neighbor) {
    node = '' + node;
    neighbor = '' + neighbor;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.areInNeighbors: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return false;
    return neighbor in nodeData["in"];
  }

  /**
   * Method returning whether two nodes are undirected neighbors.
   *
   * @param  {any}     node     - The node's key.
   * @param  {any}     neighbor - The neighbor's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.areUndirectedNeighbors = function areUndirectedNeighbors(node, neighbor) {
    node = '' + node;
    neighbor = '' + neighbor;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.areUndirectedNeighbors: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'directed') return false;
    return neighbor in nodeData.undirected;
  }

  /**
   * Method returning whether two nodes are neighbors.
   *
   * @param  {any}     node     - The node's key.
   * @param  {any}     neighbor - The neighbor's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.areNeighbors = function areNeighbors(node, neighbor) {
    node = '' + node;
    neighbor = '' + neighbor;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.areNeighbors: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type !== 'undirected') {
      if (neighbor in nodeData["in"] || neighbor in nodeData.out) return true;
    }
    if (this.type !== 'directed') {
      if (neighbor in nodeData.undirected) return true;
    }
    return false;
  }

  /**
   * Method returning whether two nodes are inbound neighbors.
   *
   * @param  {any}     node     - The node's key.
   * @param  {any}     neighbor - The neighbor's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.areInboundNeighbors = function areInboundNeighbors(node, neighbor) {
    node = '' + node;
    neighbor = '' + neighbor;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.areInboundNeighbors: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type !== 'undirected') {
      if (neighbor in nodeData["in"]) return true;
    }
    if (this.type !== 'directed') {
      if (neighbor in nodeData.undirected) return true;
    }
    return false;
  }

  /**
   * Method returning whether two nodes are outbound neighbors.
   *
   * @param  {any}     node     - The node's key.
   * @param  {any}     neighbor - The neighbor's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.areOutboundNeighbors = function areOutboundNeighbors(node, neighbor) {
    node = '' + node;
    neighbor = '' + neighbor;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.areOutboundNeighbors: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type !== 'undirected') {
      if (neighbor in nodeData.out) return true;
    }
    if (this.type !== 'directed') {
      if (neighbor in nodeData.undirected) return true;
    }
    return false;
  }

  /**
   * Method returning the given node's in degree.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's in degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.inDegree = function inDegree(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.inDegree: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return 0;
    return nodeData.inDegree;
  }

  /**
   * Method returning the given node's out degree.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's in degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.outDegree = function outDegree(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.outDegree: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return 0;
    return nodeData.outDegree;
  }

  /**
   * Method returning the given node's directed degree.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's in degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.directedDegree = function directedDegree(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.directedDegree: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return 0;
    return nodeData.inDegree + nodeData.outDegree;
  }

  /**
   * Method returning the given node's undirected degree.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's in degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.undirectedDegree = function undirectedDegree(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.undirectedDegree: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'directed') return 0;
    return nodeData.undirectedDegree;
  }

  /**
   * Method returning the given node's inbound degree.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's inbound degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.inboundDegree = function inboundDegree(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.inboundDegree: could not find the \"".concat(node, "\" node in the graph."));
    var degree = 0;
    if (this.type !== 'directed') {
      degree += nodeData.undirectedDegree;
    }
    if (this.type !== 'undirected') {
      degree += nodeData.inDegree;
    }
    return degree;
  }

  /**
   * Method returning the given node's outbound degree.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's outbound degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.outboundDegree = function outboundDegree(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.outboundDegree: could not find the \"".concat(node, "\" node in the graph."));
    var degree = 0;
    if (this.type !== 'directed') {
      degree += nodeData.undirectedDegree;
    }
    if (this.type !== 'undirected') {
      degree += nodeData.outDegree;
    }
    return degree;
  }

  /**
   * Method returning the given node's directed degree.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.degree = function degree(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.degree: could not find the \"".concat(node, "\" node in the graph."));
    var degree = 0;
    if (this.type !== 'directed') {
      degree += nodeData.undirectedDegree;
    }
    if (this.type !== 'undirected') {
      degree += nodeData.inDegree + nodeData.outDegree;
    }
    return degree;
  }

  /**
   * Method returning the given node's in degree without considering self loops.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's in degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.inDegreeWithoutSelfLoops = function inDegreeWithoutSelfLoops(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.inDegreeWithoutSelfLoops: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return 0;
    return nodeData.inDegree - nodeData.directedLoops;
  }

  /**
   * Method returning the given node's out degree without considering self loops.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's in degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.outDegreeWithoutSelfLoops = function outDegreeWithoutSelfLoops(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.outDegreeWithoutSelfLoops: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return 0;
    return nodeData.outDegree - nodeData.directedLoops;
  }

  /**
   * Method returning the given node's directed degree without considering self loops.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's in degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.directedDegreeWithoutSelfLoops = function directedDegreeWithoutSelfLoops(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.directedDegreeWithoutSelfLoops: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'undirected') return 0;
    return nodeData.inDegree + nodeData.outDegree - nodeData.directedLoops * 2;
  }

  /**
   * Method returning the given node's undirected degree without considering self loops.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's in degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.undirectedDegreeWithoutSelfLoops = function undirectedDegreeWithoutSelfLoops(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.undirectedDegreeWithoutSelfLoops: could not find the \"".concat(node, "\" node in the graph."));
    if (this.type === 'directed') return 0;
    return nodeData.undirectedDegree - nodeData.undirectedLoops * 2;
  }

  /**
   * Method returning the given node's inbound degree without considering self loops.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's inbound degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.inboundDegreeWithoutSelfLoops = function inboundDegreeWithoutSelfLoops(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.inboundDegreeWithoutSelfLoops: could not find the \"".concat(node, "\" node in the graph."));
    var degree = 0;
    var loops = 0;
    if (this.type !== 'directed') {
      degree += nodeData.undirectedDegree;
      loops += nodeData.undirectedLoops * 2;
    }
    if (this.type !== 'undirected') {
      degree += nodeData.inDegree;
      loops += nodeData.directedLoops;
    }
    return degree - loops;
  }

  /**
   * Method returning the given node's outbound degree without considering self loops.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's outbound degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.outboundDegreeWithoutSelfLoops = function outboundDegreeWithoutSelfLoops(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.outboundDegreeWithoutSelfLoops: could not find the \"".concat(node, "\" node in the graph."));
    var degree = 0;
    var loops = 0;
    if (this.type !== 'directed') {
      degree += nodeData.undirectedDegree;
      loops += nodeData.undirectedLoops * 2;
    }
    if (this.type !== 'undirected') {
      degree += nodeData.outDegree;
      loops += nodeData.directedLoops;
    }
    return degree - loops;
  }

  /**
   * Method returning the given node's directed degree without considering self loops.
   *
   * @param  {any}     node - The node's key.
   * @return {number}       - The node's degree.
   *
   * @throws {Error} - Will throw if the node isn't in the graph.
   */;
  _proto.degreeWithoutSelfLoops = function degreeWithoutSelfLoops(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.degreeWithoutSelfLoops: could not find the \"".concat(node, "\" node in the graph."));
    var degree = 0;
    var loops = 0;
    if (this.type !== 'directed') {
      degree += nodeData.undirectedDegree;
      loops += nodeData.undirectedLoops * 2;
    }
    if (this.type !== 'undirected') {
      degree += nodeData.inDegree + nodeData.outDegree;
      loops += nodeData.directedLoops * 2;
    }
    return degree - loops;
  }

  /**
   * Method returning the given edge's source.
   *
   * @param  {any} edge - The edge's key.
   * @return {any}      - The edge's source.
   *
   * @throws {Error} - Will throw if the edge isn't in the graph.
   */;
  _proto.source = function source(edge) {
    edge = '' + edge;
    var data = this._edges.get(edge);
    if (!data) throw new NotFoundGraphError("Graph.source: could not find the \"".concat(edge, "\" edge in the graph."));
    return data.source.key;
  }

  /**
   * Method returning the given edge's target.
   *
   * @param  {any} edge - The edge's key.
   * @return {any}      - The edge's target.
   *
   * @throws {Error} - Will throw if the edge isn't in the graph.
   */;
  _proto.target = function target(edge) {
    edge = '' + edge;
    var data = this._edges.get(edge);
    if (!data) throw new NotFoundGraphError("Graph.target: could not find the \"".concat(edge, "\" edge in the graph."));
    return data.target.key;
  }

  /**
   * Method returning the given edge's extremities.
   *
   * @param  {any}   edge - The edge's key.
   * @return {array}      - The edge's extremities.
   *
   * @throws {Error} - Will throw if the edge isn't in the graph.
   */;
  _proto.extremities = function extremities(edge) {
    edge = '' + edge;
    var edgeData = this._edges.get(edge);
    if (!edgeData) throw new NotFoundGraphError("Graph.extremities: could not find the \"".concat(edge, "\" edge in the graph."));
    return [edgeData.source.key, edgeData.target.key];
  }

  /**
   * Given a node & an edge, returns the other extremity of the edge.
   *
   * @param  {any}   node - The node's key.
   * @param  {any}   edge - The edge's key.
   * @return {any}        - The related node.
   *
   * @throws {Error} - Will throw if the edge isn't in the graph or if the
   *                   edge & node are not related.
   */;
  _proto.opposite = function opposite(node, edge) {
    node = '' + node;
    edge = '' + edge;
    var data = this._edges.get(edge);
    if (!data) throw new NotFoundGraphError("Graph.opposite: could not find the \"".concat(edge, "\" edge in the graph."));
    var source = data.source.key;
    var target = data.target.key;
    if (node === source) return target;
    if (node === target) return source;
    throw new NotFoundGraphError("Graph.opposite: the \"".concat(node, "\" node is not attached to the \"").concat(edge, "\" edge (").concat(source, ", ").concat(target, ")."));
  }

  /**
   * Returns whether the given edge has the given node as extremity.
   *
   * @param  {any}     edge - The edge's key.
   * @param  {any}     node - The node's key.
   * @return {boolean}      - The related node.
   *
   * @throws {Error} - Will throw if either the node or the edge isn't in the graph.
   */;
  _proto.hasExtremity = function hasExtremity(edge, node) {
    edge = '' + edge;
    node = '' + node;
    var data = this._edges.get(edge);
    if (!data) throw new NotFoundGraphError("Graph.hasExtremity: could not find the \"".concat(edge, "\" edge in the graph."));
    return data.source.key === node || data.target.key === node;
  }

  /**
   * Method returning whether the given edge is undirected.
   *
   * @param  {any}     edge - The edge's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the edge isn't in the graph.
   */;
  _proto.isUndirected = function isUndirected(edge) {
    edge = '' + edge;
    var data = this._edges.get(edge);
    if (!data) throw new NotFoundGraphError("Graph.isUndirected: could not find the \"".concat(edge, "\" edge in the graph."));
    return data.undirected;
  }

  /**
   * Method returning whether the given edge is directed.
   *
   * @param  {any}     edge - The edge's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the edge isn't in the graph.
   */;
  _proto.isDirected = function isDirected(edge) {
    edge = '' + edge;
    var data = this._edges.get(edge);
    if (!data) throw new NotFoundGraphError("Graph.isDirected: could not find the \"".concat(edge, "\" edge in the graph."));
    return !data.undirected;
  }

  /**
   * Method returning whether the given edge is a self loop.
   *
   * @param  {any}     edge - The edge's key.
   * @return {boolean}
   *
   * @throws {Error} - Will throw if the edge isn't in the graph.
   */;
  _proto.isSelfLoop = function isSelfLoop(edge) {
    edge = '' + edge;
    var data = this._edges.get(edge);
    if (!data) throw new NotFoundGraphError("Graph.isSelfLoop: could not find the \"".concat(edge, "\" edge in the graph."));
    return data.source === data.target;
  }

  /**---------------------------------------------------------------------------
   * Mutation
   **---------------------------------------------------------------------------
   */

  /**
   * Method used to add a node to the graph.
   *
   * @param  {any}    node         - The node.
   * @param  {object} [attributes] - Optional attributes.
   * @return {any}                 - The node.
   *
   * @throws {Error} - Will throw if the given node already exist.
   * @throws {Error} - Will throw if the given attributes are not an object.
   */;
  _proto.addNode = function addNode(node, attributes) {
    var nodeData = _addNode(this, node, attributes);
    return nodeData.key;
  }

  /**
   * Method used to merge a node into the graph.
   *
   * @param  {any}    node         - The node.
   * @param  {object} [attributes] - Optional attributes.
   * @return {any}                 - The node.
   */;
  _proto.mergeNode = function mergeNode(node, attributes) {
    if (attributes && !isPlainObject(attributes)) throw new InvalidArgumentsGraphError("Graph.mergeNode: invalid attributes. Expecting an object but got \"".concat(attributes, "\""));

    // String coercion
    node = '' + node;
    attributes = attributes || {};

    // If the node already exists, we merge the attributes
    var data = this._nodes.get(node);
    if (data) {
      if (attributes) {
        assign(data.attributes, attributes);
        this.emit('nodeAttributesUpdated', {
          type: 'merge',
          key: node,
          attributes: data.attributes,
          data: attributes
        });
      }
      return [node, false];
    }
    data = new this.NodeDataClass(node, attributes);

    // Adding the node to internal register
    this._nodes.set(node, data);

    // Emitting
    this.emit('nodeAdded', {
      key: node,
      attributes: attributes
    });
    return [node, true];
  }

  /**
   * Method used to add a node if it does not exist in the graph or else to
   * update its attributes using a function.
   *
   * @param  {any}      node      - The node.
   * @param  {function} [updater] - Optional updater function.
   * @return {any}                - The node.
   */;
  _proto.updateNode = function updateNode(node, updater) {
    if (updater && typeof updater !== 'function') throw new InvalidArgumentsGraphError("Graph.updateNode: invalid updater function. Expecting a function but got \"".concat(updater, "\""));

    // String coercion
    node = '' + node;

    // If the node already exists, we update the attributes
    var data = this._nodes.get(node);
    if (data) {
      if (updater) {
        var oldAttributes = data.attributes;
        data.attributes = updater(oldAttributes);
        this.emit('nodeAttributesUpdated', {
          type: 'replace',
          key: node,
          attributes: data.attributes
        });
      }
      return [node, false];
    }
    var attributes = updater ? updater({}) : {};
    data = new this.NodeDataClass(node, attributes);

    // Adding the node to internal register
    this._nodes.set(node, data);

    // Emitting
    this.emit('nodeAdded', {
      key: node,
      attributes: attributes
    });
    return [node, true];
  }

  /**
   * Method used to drop a single node & all its attached edges from the graph.
   *
   * @param  {any}    node - The node.
   * @return {Graph}
   *
   * @throws {Error} - Will throw if the node doesn't exist.
   */;
  _proto.dropNode = function dropNode(node) {
    node = '' + node;
    var nodeData = this._nodes.get(node);
    if (!nodeData) throw new NotFoundGraphError("Graph.dropNode: could not find the \"".concat(node, "\" node in the graph."));
    var edgeData;

    // Removing attached edges
    // NOTE: we could be faster here, but this is such a pain to maintain
    if (this.type !== 'undirected') {
      for (var neighbor in nodeData.out) {
        edgeData = nodeData.out[neighbor];
        do {
          dropEdgeFromData(this, edgeData);
          edgeData = edgeData.next;
        } while (edgeData);
      }
      for (var _neighbor in nodeData["in"]) {
        edgeData = nodeData["in"][_neighbor];
        do {
          dropEdgeFromData(this, edgeData);
          edgeData = edgeData.next;
        } while (edgeData);
      }
    }
    if (this.type !== 'directed') {
      for (var _neighbor2 in nodeData.undirected) {
        edgeData = nodeData.undirected[_neighbor2];
        do {
          dropEdgeFromData(this, edgeData);
          edgeData = edgeData.next;
        } while (edgeData);
      }
    }

    // Dropping the node from the register
    this._nodes["delete"](node);

    // Emitting
    this.emit('nodeDropped', {
      key: node,
      attributes: nodeData.attributes
    });
  }

  /**
   * Method used to drop a single edge from the graph.
   *
   * Arity 1:
   * @param  {any}    edge - The edge.
   *
   * Arity 2:
   * @param  {any}    source - Source node.
   * @param  {any}    target - Target node.
   *
   * @return {Graph}
   *
   * @throws {Error} - Will throw if the edge doesn't exist.
   */;
  _proto.dropEdge = function dropEdge(edge) {
    var edgeData;
    if (arguments.length > 1) {
      var source = '' + arguments[0];
      var target = '' + arguments[1];
      edgeData = getMatchingEdge(this, source, target, this.type);
      if (!edgeData) throw new NotFoundGraphError("Graph.dropEdge: could not find the \"".concat(source, "\" -> \"").concat(target, "\" edge in the graph."));
    } else {
      edge = '' + edge;
      edgeData = this._edges.get(edge);
      if (!edgeData) throw new NotFoundGraphError("Graph.dropEdge: could not find the \"".concat(edge, "\" edge in the graph."));
    }
    dropEdgeFromData(this, edgeData);
    return this;
  }

  /**
   * Method used to drop a single directed edge from the graph.
   *
   * @param  {any}    source - Source node.
   * @param  {any}    target - Target node.
   *
   * @return {Graph}
   *
   * @throws {Error} - Will throw if the edge doesn't exist.
   */;
  _proto.dropDirectedEdge = function dropDirectedEdge(source, target) {
    if (arguments.length < 2) throw new UsageGraphError('Graph.dropDirectedEdge: it does not make sense to try and drop a directed edge by key. What if the edge with this key is undirected? Use #.dropEdge for this purpose instead.');
    if (this.multi) throw new UsageGraphError('Graph.dropDirectedEdge: cannot use a {source,target} combo when dropping an edge in a MultiGraph since we cannot infer the one you want to delete as there could be multiple ones.');
    source = '' + source;
    target = '' + target;
    var edgeData = getMatchingEdge(this, source, target, 'directed');
    if (!edgeData) throw new NotFoundGraphError("Graph.dropDirectedEdge: could not find a \"".concat(source, "\" -> \"").concat(target, "\" edge in the graph."));
    dropEdgeFromData(this, edgeData);
    return this;
  }

  /**
   * Method used to drop a single undirected edge from the graph.
   *
   * @param  {any}    source - Source node.
   * @param  {any}    target - Target node.
   *
   * @return {Graph}
   *
   * @throws {Error} - Will throw if the edge doesn't exist.
   */;
  _proto.dropUndirectedEdge = function dropUndirectedEdge(source, target) {
    if (arguments.length < 2) throw new UsageGraphError('Graph.dropUndirectedEdge: it does not make sense to drop a directed edge by key. What if the edge with this key is undirected? Use #.dropEdge for this purpose instead.');
    if (this.multi) throw new UsageGraphError('Graph.dropUndirectedEdge: cannot use a {source,target} combo when dropping an edge in a MultiGraph since we cannot infer the one you want to delete as there could be multiple ones.');
    var edgeData = getMatchingEdge(this, source, target, 'undirected');
    if (!edgeData) throw new NotFoundGraphError("Graph.dropUndirectedEdge: could not find a \"".concat(source, "\" -> \"").concat(target, "\" edge in the graph."));
    dropEdgeFromData(this, edgeData);
    return this;
  }

  /**
   * Method used to remove every edge & every node from the graph.
   *
   * @return {Graph}
   */;
  _proto.clear = function clear() {
    // Clearing edges
    this._edges.clear();

    // Clearing nodes
    this._nodes.clear();

    // Reset counters
    this._resetInstanceCounters();

    // Emitting
    this.emit('cleared');
  }

  /**
   * Method used to remove every edge from the graph.
   *
   * @return {Graph}
   */;
  _proto.clearEdges = function clearEdges() {
    // Clearing structure index
    var iterator = this._nodes.values();
    var step;
    while (step = iterator.next(), step.done !== true) {
      step.value.clear();
    }

    // Clearing edges
    this._edges.clear();

    // Reset counters
    this._resetInstanceCounters();

    // Emitting
    this.emit('edgesCleared');
  }

  /**---------------------------------------------------------------------------
   * Attributes-related methods
   **---------------------------------------------------------------------------
   */

  /**
   * Method returning the desired graph's attribute.
   *
   * @param  {string} name - Name of the attribute.
   * @return {any}
   */;
  _proto.getAttribute = function getAttribute(name) {
    return this._attributes[name];
  }

  /**
   * Method returning the graph's attributes.
   *
   * @return {object}
   */;
  _proto.getAttributes = function getAttributes() {
    return this._attributes;
  }

  /**
   * Method returning whether the graph has the desired attribute.
   *
   * @param  {string}  name - Name of the attribute.
   * @return {boolean}
   */;
  _proto.hasAttribute = function hasAttribute(name) {
    return this._attributes.hasOwnProperty(name);
  }

  /**
   * Method setting a value for the desired graph's attribute.
   *
   * @param  {string}  name  - Name of the attribute.
   * @param  {any}     value - Value for the attribute.
   * @return {Graph}
   */;
  _proto.setAttribute = function setAttribute(name, value) {
    this._attributes[name] = value;

    // Emitting
    this.emit('attributesUpdated', {
      type: 'set',
      attributes: this._attributes,
      name: name
    });
    return this;
  }

  /**
   * Method using a function to update the desired graph's attribute's value.
   *
   * @param  {string}   name    - Name of the attribute.
   * @param  {function} updater - Function use to update the attribute's value.
   * @return {Graph}
   */;
  _proto.updateAttribute = function updateAttribute(name, updater) {
    if (typeof updater !== 'function') throw new InvalidArgumentsGraphError('Graph.updateAttribute: updater should be a function.');
    var value = this._attributes[name];
    this._attributes[name] = updater(value);

    // Emitting
    this.emit('attributesUpdated', {
      type: 'set',
      attributes: this._attributes,
      name: name
    });
    return this;
  }

  /**
   * Method removing the desired graph's attribute.
   *
   * @param  {string} name  - Name of the attribute.
   * @return {Graph}
   */;
  _proto.removeAttribute = function removeAttribute(name) {
    delete this._attributes[name];

    // Emitting
    this.emit('attributesUpdated', {
      type: 'remove',
      attributes: this._attributes,
      name: name
    });
    return this;
  }

  /**
   * Method replacing the graph's attributes.
   *
   * @param  {object} attributes - New attributes.
   * @return {Graph}
   *
   * @throws {Error} - Will throw if given attributes are not a plain object.
   */;
  _proto.replaceAttributes = function replaceAttributes(attributes) {
    if (!isPlainObject(attributes)) throw new InvalidArgumentsGraphError('Graph.replaceAttributes: provided attributes are not a plain object.');
    this._attributes = attributes;

    // Emitting
    this.emit('attributesUpdated', {
      type: 'replace',
      attributes: this._attributes
    });
    return this;
  }

  /**
   * Method merging the graph's attributes.
   *
   * @param  {object} attributes - Attributes to merge.
   * @return {Graph}
   *
   * @throws {Error} - Will throw if given attributes are not a plain object.
   */;
  _proto.mergeAttributes = function mergeAttributes(attributes) {
    if (!isPlainObject(attributes)) throw new InvalidArgumentsGraphError('Graph.mergeAttributes: provided attributes are not a plain object.');
    assign(this._attributes, attributes);

    // Emitting
    this.emit('attributesUpdated', {
      type: 'merge',
      attributes: this._attributes,
      data: attributes
    });
    return this;
  }

  /**
   * Method updating the graph's attributes.
   *
   * @param  {function} updater - Function used to update the attributes.
   * @return {Graph}
   *
   * @throws {Error} - Will throw if given updater is not a function.
   */;
  _proto.updateAttributes = function updateAttributes(updater) {
    if (typeof updater !== 'function') throw new InvalidArgumentsGraphError('Graph.updateAttributes: provided updater is not a function.');
    this._attributes = updater(this._attributes);

    // Emitting
    this.emit('attributesUpdated', {
      type: 'update',
      attributes: this._attributes
    });
    return this;
  }

  /**
   * Method used to update each node's attributes using the given function.
   *
   * @param {function}  updater - Updater function to use.
   * @param {object}    [hints] - Optional hints.
   */;
  _proto.updateEachNodeAttributes = function updateEachNodeAttributes(updater, hints) {
    if (typeof updater !== 'function') throw new InvalidArgumentsGraphError('Graph.updateEachNodeAttributes: expecting an updater function.');
    if (hints && !validateHints(hints)) throw new InvalidArgumentsGraphError('Graph.updateEachNodeAttributes: invalid hints. Expecting an object having the following shape: {attributes?: [string]}');
    var iterator = this._nodes.values();
    var step, nodeData;
    while (step = iterator.next(), step.done !== true) {
      nodeData = step.value;
      nodeData.attributes = updater(nodeData.key, nodeData.attributes);
    }
    this.emit('eachNodeAttributesUpdated', {
      hints: hints ? hints : null
    });
  }

  /**
   * Method used to update each edge's attributes using the given function.
   *
   * @param {function}  updater - Updater function to use.
   * @param {object}    [hints] - Optional hints.
   */;
  _proto.updateEachEdgeAttributes = function updateEachEdgeAttributes(updater, hints) {
    if (typeof updater !== 'function') throw new InvalidArgumentsGraphError('Graph.updateEachEdgeAttributes: expecting an updater function.');
    if (hints && !validateHints(hints)) throw new InvalidArgumentsGraphError('Graph.updateEachEdgeAttributes: invalid hints. Expecting an object having the following shape: {attributes?: [string]}');
    var iterator = this._edges.values();
    var step, edgeData, sourceData, targetData;
    while (step = iterator.next(), step.done !== true) {
      edgeData = step.value;
      sourceData = edgeData.source;
      targetData = edgeData.target;
      edgeData.attributes = updater(edgeData.key, edgeData.attributes, sourceData.key, targetData.key, sourceData.attributes, targetData.attributes, edgeData.undirected);
    }
    this.emit('eachEdgeAttributesUpdated', {
      hints: hints ? hints : null
    });
  }

  /**---------------------------------------------------------------------------
   * Iteration-related methods
   **---------------------------------------------------------------------------
   */

  /**
   * Method iterating over the graph's adjacency using the given callback.
   *
   * @param  {function}  callback - Callback to use.
   */;
  _proto.forEachAdjacencyEntry = function forEachAdjacencyEntry(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.forEachAdjacencyEntry: expecting a callback.');
    forEachAdjacency(false, false, false, this, callback);
  };
  _proto.forEachAdjacencyEntryWithOrphans = function forEachAdjacencyEntryWithOrphans(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.forEachAdjacencyEntryWithOrphans: expecting a callback.');
    forEachAdjacency(false, false, true, this, callback);
  }

  /**
   * Method iterating over the graph's assymetric adjacency using the given callback.
   *
   * @param  {function}  callback - Callback to use.
   */;
  _proto.forEachAssymetricAdjacencyEntry = function forEachAssymetricAdjacencyEntry(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.forEachAssymetricAdjacencyEntry: expecting a callback.');
    forEachAdjacency(false, true, false, this, callback);
  };
  _proto.forEachAssymetricAdjacencyEntryWithOrphans = function forEachAssymetricAdjacencyEntryWithOrphans(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.forEachAssymetricAdjacencyEntryWithOrphans: expecting a callback.');
    forEachAdjacency(false, true, true, this, callback);
  }

  /**
   * Method returning the list of the graph's nodes.
   *
   * @return {array} - The nodes.
   */;
  _proto.nodes = function nodes() {
    if (typeof Array.from === 'function') return Array.from(this._nodes.keys());
    return take__default["default"](this._nodes.keys(), this._nodes.size);
  }

  /**
   * Method iterating over the graph's nodes using the given callback.
   *
   * @param  {function}  callback - Callback (key, attributes, index).
   */;
  _proto.forEachNode = function forEachNode(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.forEachNode: expecting a callback.');
    var iterator = this._nodes.values();
    var step, nodeData;
    while (step = iterator.next(), step.done !== true) {
      nodeData = step.value;
      callback(nodeData.key, nodeData.attributes);
    }
  }

  /**
   * Method iterating attempting to find a node matching the given predicate
   * function.
   *
   * @param  {function}  callback - Callback (key, attributes).
   */;
  _proto.findNode = function findNode(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.findNode: expecting a callback.');
    var iterator = this._nodes.values();
    var step, nodeData;
    while (step = iterator.next(), step.done !== true) {
      nodeData = step.value;
      if (callback(nodeData.key, nodeData.attributes)) return nodeData.key;
    }
    return;
  }

  /**
   * Method mapping nodes.
   *
   * @param  {function}  callback - Callback (key, attributes).
   */;
  _proto.mapNodes = function mapNodes(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.mapNode: expecting a callback.');
    var iterator = this._nodes.values();
    var step, nodeData;
    var result = new Array(this.order);
    var i = 0;
    while (step = iterator.next(), step.done !== true) {
      nodeData = step.value;
      result[i++] = callback(nodeData.key, nodeData.attributes);
    }
    return result;
  }

  /**
   * Method returning whether some node verify the given predicate.
   *
   * @param  {function}  callback - Callback (key, attributes).
   */;
  _proto.someNode = function someNode(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.someNode: expecting a callback.');
    var iterator = this._nodes.values();
    var step, nodeData;
    while (step = iterator.next(), step.done !== true) {
      nodeData = step.value;
      if (callback(nodeData.key, nodeData.attributes)) return true;
    }
    return false;
  }

  /**
   * Method returning whether all node verify the given predicate.
   *
   * @param  {function}  callback - Callback (key, attributes).
   */;
  _proto.everyNode = function everyNode(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.everyNode: expecting a callback.');
    var iterator = this._nodes.values();
    var step, nodeData;
    while (step = iterator.next(), step.done !== true) {
      nodeData = step.value;
      if (!callback(nodeData.key, nodeData.attributes)) return false;
    }
    return true;
  }

  /**
   * Method filtering nodes.
   *
   * @param  {function}  callback - Callback (key, attributes).
   */;
  _proto.filterNodes = function filterNodes(callback) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.filterNodes: expecting a callback.');
    var iterator = this._nodes.values();
    var step, nodeData;
    var result = [];
    while (step = iterator.next(), step.done !== true) {
      nodeData = step.value;
      if (callback(nodeData.key, nodeData.attributes)) result.push(nodeData.key);
    }
    return result;
  }

  /**
   * Method reducing nodes.
   *
   * @param  {function}  callback - Callback (accumulator, key, attributes).
   */;
  _proto.reduceNodes = function reduceNodes(callback, initialValue) {
    if (typeof callback !== 'function') throw new InvalidArgumentsGraphError('Graph.reduceNodes: expecting a callback.');
    if (arguments.length < 2) throw new InvalidArgumentsGraphError('Graph.reduceNodes: missing initial value. You must provide it because the callback takes more than one argument and we cannot infer the initial value from the first iteration, as you could with a simple array.');
    var accumulator = initialValue;
    var iterator = this._nodes.values();
    var step, nodeData;
    while (step = iterator.next(), step.done !== true) {
      nodeData = step.value;
      accumulator = callback(accumulator, nodeData.key, nodeData.attributes);
    }
    return accumulator;
  }

  /**
   * Method returning an iterator over the graph's node entries.
   *
   * @return {Iterator}
   */;
  _proto.nodeEntries = function nodeEntries() {
    var iterator = this._nodes.values();
    return new Iterator__default["default"](function () {
      var step = iterator.next();
      if (step.done) return step;
      var data = step.value;
      return {
        value: {
          node: data.key,
          attributes: data.attributes
        },
        done: false
      };
    });
  }

  /**---------------------------------------------------------------------------
   * Serialization
   **---------------------------------------------------------------------------
   */

  /**
   * Method used to export the whole graph.
   *
   * @return {object} - The serialized graph.
   */;
  _proto["export"] = function _export() {
    var _this2 = this;
    var nodes = new Array(this._nodes.size);
    var i = 0;
    this._nodes.forEach(function (data, key) {
      nodes[i++] = serializeNode(key, data);
    });
    var edges = new Array(this._edges.size);
    i = 0;
    this._edges.forEach(function (data, key) {
      edges[i++] = serializeEdge(_this2.type, key, data);
    });
    return {
      options: {
        type: this.type,
        multi: this.multi,
        allowSelfLoops: this.allowSelfLoops
      },
      attributes: this.getAttributes(),
      nodes: nodes,
      edges: edges
    };
  }

  /**
   * Method used to import a serialized graph.
   *
   * @param  {object|Graph} data  - The serialized graph.
   * @param  {boolean}      merge - Whether to merge data.
   * @return {Graph}              - Returns itself for chaining.
   */;
  _proto["import"] = function _import(data) {
    var _this3 = this;
    var merge = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : false;
    // Importing a Graph instance directly
    if (data instanceof Graph) {
      // Nodes
      data.forEachNode(function (n, a) {
        if (merge) _this3.mergeNode(n, a);else _this3.addNode(n, a);
      });

      // Edges
      data.forEachEdge(function (e, a, s, t, _sa, _ta, u) {
        if (merge) {
          if (u) _this3.mergeUndirectedEdgeWithKey(e, s, t, a);else _this3.mergeDirectedEdgeWithKey(e, s, t, a);
        } else {
          if (u) _this3.addUndirectedEdgeWithKey(e, s, t, a);else _this3.addDirectedEdgeWithKey(e, s, t, a);
        }
      });
      return this;
    }

    // Importing a serialized graph
    if (!isPlainObject(data)) throw new InvalidArgumentsGraphError('Graph.import: invalid argument. Expecting a serialized graph or, alternatively, a Graph instance.');
    if (data.attributes) {
      if (!isPlainObject(data.attributes)) throw new InvalidArgumentsGraphError('Graph.import: invalid attributes. Expecting a plain object.');
      if (merge) this.mergeAttributes(data.attributes);else this.replaceAttributes(data.attributes);
    }
    var i, l, list, node, edge;
    if (data.nodes) {
      list = data.nodes;
      if (!Array.isArray(list)) throw new InvalidArgumentsGraphError('Graph.import: invalid nodes. Expecting an array.');
      for (i = 0, l = list.length; i < l; i++) {
        node = list[i];

        // Validating
        validateSerializedNode(node);

        // Adding the node
        var _node = node,
          key = _node.key,
          attributes = _node.attributes;
        if (merge) this.mergeNode(key, attributes);else this.addNode(key, attributes);
      }
    }
    if (data.edges) {
      var undirectedByDefault = false;
      if (this.type === 'undirected') {
        undirectedByDefault = true;
      }
      list = data.edges;
      if (!Array.isArray(list)) throw new InvalidArgumentsGraphError('Graph.import: invalid edges. Expecting an array.');
      for (i = 0, l = list.length; i < l; i++) {
        edge = list[i];

        // Validating
        validateSerializedEdge(edge);

        // Adding the edge
        var _edge = edge,
          source = _edge.source,
          target = _edge.target,
          _attributes = _edge.attributes,
          _edge$undirected = _edge.undirected,
          undirected = _edge$undirected === void 0 ? undirectedByDefault : _edge$undirected;
        var method = void 0;
        if ('key' in edge) {
          method = merge ? undirected ? this.mergeUndirectedEdgeWithKey : this.mergeDirectedEdgeWithKey : undirected ? this.addUndirectedEdgeWithKey : this.addDirectedEdgeWithKey;
          method.call(this, edge.key, source, target, _attributes);
        } else {
          method = merge ? undirected ? this.mergeUndirectedEdge : this.mergeDirectedEdge : undirected ? this.addUndirectedEdge : this.addDirectedEdge;
          method.call(this, source, target, _attributes);
        }
      }
    }
    return this;
  }

  /**---------------------------------------------------------------------------
   * Utils
   **---------------------------------------------------------------------------
   */

  /**
   * Method returning a null copy of the graph, i.e. a graph without nodes
   * & edges but with the exact same options.
   *
   * @param  {object} options - Options to merge with the current ones.
   * @return {Graph}          - The null copy.
   */;
  _proto.nullCopy = function nullCopy(options) {
    var graph = new Graph(assign({}, this._options, options));
    graph.replaceAttributes(assign({}, this.getAttributes()));
    return graph;
  }

  /**
   * Method returning an empty copy of the graph, i.e. a graph without edges but
   * with the exact same options.
   *
   * @param  {object} options - Options to merge with the current ones.
   * @return {Graph}          - The empty copy.
   */;
  _proto.emptyCopy = function emptyCopy(options) {
    var graph = this.nullCopy(options);
    this._nodes.forEach(function (nodeData, key) {
      var attributes = assign({}, nodeData.attributes);

      // NOTE: no need to emit events since user cannot access the instance yet
      nodeData = new graph.NodeDataClass(key, attributes);
      graph._nodes.set(key, nodeData);
    });
    return graph;
  }

  /**
   * Method returning an exact copy of the graph.
   *
   * @param  {object} options - Upgrade options.
   * @return {Graph}          - The copy.
   */;
  _proto.copy = function copy(options) {
    options = options || {};
    if (typeof options.type === 'string' && options.type !== this.type && options.type !== 'mixed') throw new UsageGraphError("Graph.copy: cannot create an incompatible copy from \"".concat(this.type, "\" type to \"").concat(options.type, "\" because this would mean losing information about the current graph."));
    if (typeof options.multi === 'boolean' && options.multi !== this.multi && options.multi !== true) throw new UsageGraphError('Graph.copy: cannot create an incompatible copy by downgrading a multi graph to a simple one because this would mean losing information about the current graph.');
    if (typeof options.allowSelfLoops === 'boolean' && options.allowSelfLoops !== this.allowSelfLoops && options.allowSelfLoops !== true) throw new UsageGraphError('Graph.copy: cannot create an incompatible copy from a graph allowing self loops to one that does not because this would mean losing information about the current graph.');
    var graph = this.emptyCopy(options);
    var iterator = this._edges.values();
    var step, edgeData;
    while (step = iterator.next(), step.done !== true) {
      edgeData = step.value;

      // NOTE: no need to emit events since user cannot access the instance yet
      addEdge(graph, 'copy', false, edgeData.undirected, edgeData.key, edgeData.source.key, edgeData.target.key, assign({}, edgeData.attributes));
    }
    return graph;
  }

  /**---------------------------------------------------------------------------
   * Known methods
   **---------------------------------------------------------------------------
   */

  /**
   * Method used by JavaScript to perform JSON serialization.
   *
   * @return {object} - The serialized graph.
   */;
  _proto.toJSON = function toJSON() {
    return this["export"]();
  }

  /**
   * Method returning [object Graph].
   */;
  _proto.toString = function toString() {
    return '[object Graph]';
  }

  /**
   * Method used internally by node's console to display a custom object.
   *
   * @return {object} - Formatted object representation of the graph.
   */;
  _proto.inspect = function inspect() {
    var _this4 = this;
    var nodes = {};
    this._nodes.forEach(function (data, key) {
      nodes[key] = data.attributes;
    });
    var edges = {},
      multiIndex = {};
    this._edges.forEach(function (data, key) {
      var direction = data.undirected ? '--' : '->';
      var label = '';
      var source = data.source.key;
      var target = data.target.key;
      var tmp;
      if (data.undirected && source > target) {
        tmp = source;
        source = target;
        target = tmp;
      }
      var desc = "(".concat(source, ")").concat(direction, "(").concat(target, ")");
      if (!key.startsWith('geid_')) {
        label += "[".concat(key, "]: ");
      } else if (_this4.multi) {
        if (typeof multiIndex[desc] === 'undefined') {
          multiIndex[desc] = 0;
        } else {
          multiIndex[desc]++;
        }
        label += "".concat(multiIndex[desc], ". ");
      }
      label += desc;
      edges[label] = data.attributes;
    });
    var dummy = {};
    for (var k in this) {
      if (this.hasOwnProperty(k) && !EMITTER_PROPS.has(k) && typeof this[k] !== 'function' && _typeof(k) !== 'symbol') dummy[k] = this[k];
    }
    dummy.attributes = this._attributes;
    dummy.nodes = nodes;
    dummy.edges = edges;
    privateProperty(dummy, 'constructor', this.constructor);
    return dummy;
  };
  return Graph;
}(events.EventEmitter);
if (typeof Symbol !== 'undefined') Graph.prototype[Symbol["for"]('nodejs.util.inspect.custom')] = Graph.prototype.inspect;

/**
 * Related to edge addition.
 */
EDGE_ADD_METHODS.forEach(function (method) {
  ['add', 'merge', 'update'].forEach(function (verb) {
    var name = method.name(verb);
    var fn = verb === 'add' ? addEdge : mergeEdge;
    if (method.generateKey) {
      Graph.prototype[name] = function (source, target, attributes) {
        return fn(this, name, true, (method.type || this.type) === 'undirected', null, source, target, attributes, verb === 'update');
      };
    } else {
      Graph.prototype[name] = function (edge, source, target, attributes) {
        return fn(this, name, false, (method.type || this.type) === 'undirected', edge, source, target, attributes, verb === 'update');
      };
    }
  });
});

/**
 * Attributes-related.
 */
attachNodeAttributesMethods(Graph);
attachEdgeAttributesMethods(Graph);

/**
 * Edge iteration-related.
 */
attachEdgeIterationMethods(Graph);

/**
 * Neighbor iteration-related.
 */
attachNeighborIterationMethods(Graph);

/**
 * Alternative constructors.
 */
var DirectedGraph = /*#__PURE__*/function (_Graph) {
  _inheritsLoose(DirectedGraph, _Graph);
  function DirectedGraph(options) {
    var finalOptions = assign({
      type: 'directed'
    }, options);
    if ('multi' in finalOptions && finalOptions.multi !== false) throw new InvalidArgumentsGraphError('DirectedGraph.from: inconsistent indication that the graph should be multi in given options!');
    if (finalOptions.type !== 'directed') throw new InvalidArgumentsGraphError('DirectedGraph.from: inconsistent "' + finalOptions.type + '" type in given options!');
    return _Graph.call(this, finalOptions) || this;
  }
  return DirectedGraph;
}(Graph);
var UndirectedGraph = /*#__PURE__*/function (_Graph2) {
  _inheritsLoose(UndirectedGraph, _Graph2);
  function UndirectedGraph(options) {
    var finalOptions = assign({
      type: 'undirected'
    }, options);
    if ('multi' in finalOptions && finalOptions.multi !== false) throw new InvalidArgumentsGraphError('UndirectedGraph.from: inconsistent indication that the graph should be multi in given options!');
    if (finalOptions.type !== 'undirected') throw new InvalidArgumentsGraphError('UndirectedGraph.from: inconsistent "' + finalOptions.type + '" type in given options!');
    return _Graph2.call(this, finalOptions) || this;
  }
  return UndirectedGraph;
}(Graph);
var MultiGraph = /*#__PURE__*/function (_Graph3) {
  _inheritsLoose(MultiGraph, _Graph3);
  function MultiGraph(options) {
    var finalOptions = assign({
      multi: true
    }, options);
    if ('multi' in finalOptions && finalOptions.multi !== true) throw new InvalidArgumentsGraphError('MultiGraph.from: inconsistent indication that the graph should be simple in given options!');
    return _Graph3.call(this, finalOptions) || this;
  }
  return MultiGraph;
}(Graph);
var MultiDirectedGraph = /*#__PURE__*/function (_Graph4) {
  _inheritsLoose(MultiDirectedGraph, _Graph4);
  function MultiDirectedGraph(options) {
    var finalOptions = assign({
      type: 'directed',
      multi: true
    }, options);
    if ('multi' in finalOptions && finalOptions.multi !== true) throw new InvalidArgumentsGraphError('MultiDirectedGraph.from: inconsistent indication that the graph should be simple in given options!');
    if (finalOptions.type !== 'directed') throw new InvalidArgumentsGraphError('MultiDirectedGraph.from: inconsistent "' + finalOptions.type + '" type in given options!');
    return _Graph4.call(this, finalOptions) || this;
  }
  return MultiDirectedGraph;
}(Graph);
var MultiUndirectedGraph = /*#__PURE__*/function (_Graph5) {
  _inheritsLoose(MultiUndirectedGraph, _Graph5);
  function MultiUndirectedGraph(options) {
    var finalOptions = assign({
      type: 'undirected',
      multi: true
    }, options);
    if ('multi' in finalOptions && finalOptions.multi !== true) throw new InvalidArgumentsGraphError('MultiUndirectedGraph.from: inconsistent indication that the graph should be simple in given options!');
    if (finalOptions.type !== 'undirected') throw new InvalidArgumentsGraphError('MultiUndirectedGraph.from: inconsistent "' + finalOptions.type + '" type in given options!');
    return _Graph5.call(this, finalOptions) || this;
  }
  return MultiUndirectedGraph;
}(Graph); /**
           * Attaching static #.from method to each of the constructors.
           */
function attachStaticFromMethod(Class) {
  /**
   * Builds a graph from serialized data or another graph's data.
   *
   * @param  {Graph|SerializedGraph} data      - Hydratation data.
   * @param  {object}                [options] - Options.
   * @return {Class}
   */
  Class.from = function (data, options) {
    // Merging given options with serialized ones
    var finalOptions = assign({}, data.options, options);
    var instance = new Class(finalOptions);
    instance["import"](data);
    return instance;
  };
}
attachStaticFromMethod(Graph);
attachStaticFromMethod(DirectedGraph);
attachStaticFromMethod(UndirectedGraph);
attachStaticFromMethod(MultiGraph);
attachStaticFromMethod(MultiDirectedGraph);
attachStaticFromMethod(MultiUndirectedGraph);
Graph.Graph = Graph;
Graph.DirectedGraph = DirectedGraph;
Graph.UndirectedGraph = UndirectedGraph;
Graph.MultiGraph = MultiGraph;
Graph.MultiDirectedGraph = MultiDirectedGraph;
Graph.MultiUndirectedGraph = MultiUndirectedGraph;
Graph.InvalidArgumentsGraphError = InvalidArgumentsGraphError;
Graph.NotFoundGraphError = NotFoundGraphError;
Graph.UsageGraphError = UsageGraphError;

/**
 * Graphology CommonJS Endoint
 * ============================
 *
 * Endpoint for CommonJS modules consumers.
 */

module.exports = Graph;
//# sourceMappingURL=graphology.cjs.js.map