var wikimap = (function (exports) {
  'use strict';

  var xhtml = "http://www.w3.org/1999/xhtml";

  var namespaces = {
    svg: "http://www.w3.org/2000/svg",
    xhtml: xhtml,
    xlink: "http://www.w3.org/1999/xlink",
    xml: "http://www.w3.org/XML/1998/namespace",
    xmlns: "http://www.w3.org/2000/xmlns/"
  };

  function namespace(name) {
    var prefix = name += "", i = prefix.indexOf(":");
    if (i >= 0 && (prefix = name.slice(0, i)) !== "xmlns") name = name.slice(i + 1);
    return namespaces.hasOwnProperty(prefix) ? {space: namespaces[prefix], local: name} : name;
  }

  function creatorInherit(name) {
    return function() {
      var document = this.ownerDocument,
          uri = this.namespaceURI;
      return uri === xhtml && document.documentElement.namespaceURI === xhtml
          ? document.createElement(name)
          : document.createElementNS(uri, name);
    };
  }

  function creatorFixed(fullname) {
    return function() {
      return this.ownerDocument.createElementNS(fullname.space, fullname.local);
    };
  }

  function creator(name) {
    var fullname = namespace(name);
    return (fullname.local
        ? creatorFixed
        : creatorInherit)(fullname);
  }

  function none() {}

  function selector(selector) {
    return selector == null ? none : function() {
      return this.querySelector(selector);
    };
  }

  function selection_select(select) {
    if (typeof select !== "function") select = selector(select);

    for (var groups = this._groups, m = groups.length, subgroups = new Array(m), j = 0; j < m; ++j) {
      for (var group = groups[j], n = group.length, subgroup = subgroups[j] = new Array(n), node, subnode, i = 0; i < n; ++i) {
        if ((node = group[i]) && (subnode = select.call(node, node.__data__, i, group))) {
          if ("__data__" in node) subnode.__data__ = node.__data__;
          subgroup[i] = subnode;
        }
      }
    }

    return new Selection(subgroups, this._parents);
  }

  function empty() {
    return [];
  }

  function selectorAll(selector) {
    return selector == null ? empty : function() {
      return this.querySelectorAll(selector);
    };
  }

  function selection_selectAll(select) {
    if (typeof select !== "function") select = selectorAll(select);

    for (var groups = this._groups, m = groups.length, subgroups = [], parents = [], j = 0; j < m; ++j) {
      for (var group = groups[j], n = group.length, node, i = 0; i < n; ++i) {
        if (node = group[i]) {
          subgroups.push(select.call(node, node.__data__, i, group));
          parents.push(node);
        }
      }
    }

    return new Selection(subgroups, parents);
  }

  function matcher(selector) {
    return function() {
      return this.matches(selector);
    };
  }

  function selection_filter(match) {
    if (typeof match !== "function") match = matcher(match);

    for (var groups = this._groups, m = groups.length, subgroups = new Array(m), j = 0; j < m; ++j) {
      for (var group = groups[j], n = group.length, subgroup = subgroups[j] = [], node, i = 0; i < n; ++i) {
        if ((node = group[i]) && match.call(node, node.__data__, i, group)) {
          subgroup.push(node);
        }
      }
    }

    return new Selection(subgroups, this._parents);
  }

  function sparse(update) {
    return new Array(update.length);
  }

  function selection_enter() {
    return new Selection(this._enter || this._groups.map(sparse), this._parents);
  }

  function EnterNode(parent, datum) {
    this.ownerDocument = parent.ownerDocument;
    this.namespaceURI = parent.namespaceURI;
    this._next = null;
    this._parent = parent;
    this.__data__ = datum;
  }

  EnterNode.prototype = {
    constructor: EnterNode,
    appendChild: function(child) { return this._parent.insertBefore(child, this._next); },
    insertBefore: function(child, next) { return this._parent.insertBefore(child, next); },
    querySelector: function(selector) { return this._parent.querySelector(selector); },
    querySelectorAll: function(selector) { return this._parent.querySelectorAll(selector); }
  };

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

  var keyPrefix = "$"; // Protect against keys like “__proto__”.

  function bindIndex(parent, group, enter, update, exit, data) {
    var i = 0,
        node,
        groupLength = group.length,
        dataLength = data.length;

    // Put any non-null nodes that fit into update.
    // Put any null nodes into enter.
    // Put any remaining data into enter.
    for (; i < dataLength; ++i) {
      if (node = group[i]) {
        node.__data__ = data[i];
        update[i] = node;
      } else {
        enter[i] = new EnterNode(parent, data[i]);
      }
    }

    // Put any non-null nodes that don’t fit into exit.
    for (; i < groupLength; ++i) {
      if (node = group[i]) {
        exit[i] = node;
      }
    }
  }

  function bindKey(parent, group, enter, update, exit, data, key) {
    var i,
        node,
        nodeByKeyValue = {},
        groupLength = group.length,
        dataLength = data.length,
        keyValues = new Array(groupLength),
        keyValue;

    // Compute the key for each node.
    // If multiple nodes have the same key, the duplicates are added to exit.
    for (i = 0; i < groupLength; ++i) {
      if (node = group[i]) {
        keyValues[i] = keyValue = keyPrefix + key.call(node, node.__data__, i, group);
        if (keyValue in nodeByKeyValue) {
          exit[i] = node;
        } else {
          nodeByKeyValue[keyValue] = node;
        }
      }
    }

    // Compute the key for each datum.
    // If there a node associated with this key, join and add it to update.
    // If there is not (or the key is a duplicate), add it to enter.
    for (i = 0; i < dataLength; ++i) {
      keyValue = keyPrefix + key.call(parent, data[i], i, data);
      if (node = nodeByKeyValue[keyValue]) {
        update[i] = node;
        node.__data__ = data[i];
        nodeByKeyValue[keyValue] = null;
      } else {
        enter[i] = new EnterNode(parent, data[i]);
      }
    }

    // Add any remaining nodes that were not bound to data to exit.
    for (i = 0; i < groupLength; ++i) {
      if ((node = group[i]) && (nodeByKeyValue[keyValues[i]] === node)) {
        exit[i] = node;
      }
    }
  }

  function selection_data(value, key) {
    if (!value) {
      data = new Array(this.size()), j = -1;
      this.each(function(d) { data[++j] = d; });
      return data;
    }

    var bind = key ? bindKey : bindIndex,
        parents = this._parents,
        groups = this._groups;

    if (typeof value !== "function") value = constant(value);

    for (var m = groups.length, update = new Array(m), enter = new Array(m), exit = new Array(m), j = 0; j < m; ++j) {
      var parent = parents[j],
          group = groups[j],
          groupLength = group.length,
          data = value.call(parent, parent && parent.__data__, j, parents),
          dataLength = data.length,
          enterGroup = enter[j] = new Array(dataLength),
          updateGroup = update[j] = new Array(dataLength),
          exitGroup = exit[j] = new Array(groupLength);

      bind(parent, group, enterGroup, updateGroup, exitGroup, data, key);

      // Now connect the enter nodes to their following update node, such that
      // appendChild can insert the materialized enter node before this node,
      // rather than at the end of the parent node.
      for (var i0 = 0, i1 = 0, previous, next; i0 < dataLength; ++i0) {
        if (previous = enterGroup[i0]) {
          if (i0 >= i1) i1 = i0 + 1;
          while (!(next = updateGroup[i1]) && ++i1 < dataLength);
          previous._next = next || null;
        }
      }
    }

    update = new Selection(update, parents);
    update._enter = enter;
    update._exit = exit;
    return update;
  }

  function selection_exit() {
    return new Selection(this._exit || this._groups.map(sparse), this._parents);
  }

  function selection_join(onenter, onupdate, onexit) {
    var enter = this.enter(), update = this, exit = this.exit();
    enter = typeof onenter === "function" ? onenter(enter) : enter.append(onenter + "");
    if (onupdate != null) update = onupdate(update);
    if (onexit == null) exit.remove(); else onexit(exit);
    return enter && update ? enter.merge(update).order() : update;
  }

  function selection_merge(selection) {

    for (var groups0 = this._groups, groups1 = selection._groups, m0 = groups0.length, m1 = groups1.length, m = Math.min(m0, m1), merges = new Array(m0), j = 0; j < m; ++j) {
      for (var group0 = groups0[j], group1 = groups1[j], n = group0.length, merge = merges[j] = new Array(n), node, i = 0; i < n; ++i) {
        if (node = group0[i] || group1[i]) {
          merge[i] = node;
        }
      }
    }

    for (; j < m0; ++j) {
      merges[j] = groups0[j];
    }

    return new Selection(merges, this._parents);
  }

  function selection_order() {

    for (var groups = this._groups, j = -1, m = groups.length; ++j < m;) {
      for (var group = groups[j], i = group.length - 1, next = group[i], node; --i >= 0;) {
        if (node = group[i]) {
          if (next && node.compareDocumentPosition(next) ^ 4) next.parentNode.insertBefore(node, next);
          next = node;
        }
      }
    }

    return this;
  }

  function selection_sort(compare) {
    if (!compare) compare = ascending;

    function compareNode(a, b) {
      return a && b ? compare(a.__data__, b.__data__) : !a - !b;
    }

    for (var groups = this._groups, m = groups.length, sortgroups = new Array(m), j = 0; j < m; ++j) {
      for (var group = groups[j], n = group.length, sortgroup = sortgroups[j] = new Array(n), node, i = 0; i < n; ++i) {
        if (node = group[i]) {
          sortgroup[i] = node;
        }
      }
      sortgroup.sort(compareNode);
    }

    return new Selection(sortgroups, this._parents).order();
  }

  function ascending(a, b) {
    return a < b ? -1 : a > b ? 1 : a >= b ? 0 : NaN;
  }

  function selection_call() {
    var callback = arguments[0];
    arguments[0] = this;
    callback.apply(null, arguments);
    return this;
  }

  function selection_nodes() {
    var nodes = new Array(this.size()), i = -1;
    this.each(function() { nodes[++i] = this; });
    return nodes;
  }

  function selection_node() {

    for (var groups = this._groups, j = 0, m = groups.length; j < m; ++j) {
      for (var group = groups[j], i = 0, n = group.length; i < n; ++i) {
        var node = group[i];
        if (node) return node;
      }
    }

    return null;
  }

  function selection_size() {
    var size = 0;
    this.each(function() { ++size; });
    return size;
  }

  function selection_empty() {
    return !this.node();
  }

  function selection_each(callback) {

    for (var groups = this._groups, j = 0, m = groups.length; j < m; ++j) {
      for (var group = groups[j], i = 0, n = group.length, node; i < n; ++i) {
        if (node = group[i]) callback.call(node, node.__data__, i, group);
      }
    }

    return this;
  }

  function attrRemove(name) {
    return function() {
      this.removeAttribute(name);
    };
  }

  function attrRemoveNS(fullname) {
    return function() {
      this.removeAttributeNS(fullname.space, fullname.local);
    };
  }

  function attrConstant(name, value) {
    return function() {
      this.setAttribute(name, value);
    };
  }

  function attrConstantNS(fullname, value) {
    return function() {
      this.setAttributeNS(fullname.space, fullname.local, value);
    };
  }

  function attrFunction(name, value) {
    return function() {
      var v = value.apply(this, arguments);
      if (v == null) this.removeAttribute(name);
      else this.setAttribute(name, v);
    };
  }

  function attrFunctionNS(fullname, value) {
    return function() {
      var v = value.apply(this, arguments);
      if (v == null) this.removeAttributeNS(fullname.space, fullname.local);
      else this.setAttributeNS(fullname.space, fullname.local, v);
    };
  }

  function selection_attr(name, value) {
    var fullname = namespace(name);

    if (arguments.length < 2) {
      var node = this.node();
      return fullname.local
          ? node.getAttributeNS(fullname.space, fullname.local)
          : node.getAttribute(fullname);
    }

    return this.each((value == null
        ? (fullname.local ? attrRemoveNS : attrRemove) : (typeof value === "function"
        ? (fullname.local ? attrFunctionNS : attrFunction)
        : (fullname.local ? attrConstantNS : attrConstant)))(fullname, value));
  }

  function defaultView(node) {
    return (node.ownerDocument && node.ownerDocument.defaultView) // node is a Node
        || (node.document && node) // node is a Window
        || node.defaultView; // node is a Document
  }

  function styleRemove(name) {
    return function() {
      this.style.removeProperty(name);
    };
  }

  function styleConstant(name, value, priority) {
    return function() {
      this.style.setProperty(name, value, priority);
    };
  }

  function styleFunction(name, value, priority) {
    return function() {
      var v = value.apply(this, arguments);
      if (v == null) this.style.removeProperty(name);
      else this.style.setProperty(name, v, priority);
    };
  }

  function selection_style(name, value, priority) {
    return arguments.length > 1
        ? this.each((value == null
              ? styleRemove : typeof value === "function"
              ? styleFunction
              : styleConstant)(name, value, priority == null ? "" : priority))
        : styleValue(this.node(), name);
  }

  function styleValue(node, name) {
    return node.style.getPropertyValue(name)
        || defaultView(node).getComputedStyle(node, null).getPropertyValue(name);
  }

  function propertyRemove(name) {
    return function() {
      delete this[name];
    };
  }

  function propertyConstant(name, value) {
    return function() {
      this[name] = value;
    };
  }

  function propertyFunction(name, value) {
    return function() {
      var v = value.apply(this, arguments);
      if (v == null) delete this[name];
      else this[name] = v;
    };
  }

  function selection_property(name, value) {
    return arguments.length > 1
        ? this.each((value == null
            ? propertyRemove : typeof value === "function"
            ? propertyFunction
            : propertyConstant)(name, value))
        : this.node()[name];
  }

  function classArray(string) {
    return string.trim().split(/^|\s+/);
  }

  function classList(node) {
    return node.classList || new ClassList(node);
  }

  function ClassList(node) {
    this._node = node;
    this._names = classArray(node.getAttribute("class") || "");
  }

  ClassList.prototype = {
    add: function(name) {
      var i = this._names.indexOf(name);
      if (i < 0) {
        this._names.push(name);
        this._node.setAttribute("class", this._names.join(" "));
      }
    },
    remove: function(name) {
      var i = this._names.indexOf(name);
      if (i >= 0) {
        this._names.splice(i, 1);
        this._node.setAttribute("class", this._names.join(" "));
      }
    },
    contains: function(name) {
      return this._names.indexOf(name) >= 0;
    }
  };

  function classedAdd(node, names) {
    var list = classList(node), i = -1, n = names.length;
    while (++i < n) list.add(names[i]);
  }

  function classedRemove(node, names) {
    var list = classList(node), i = -1, n = names.length;
    while (++i < n) list.remove(names[i]);
  }

  function classedTrue(names) {
    return function() {
      classedAdd(this, names);
    };
  }

  function classedFalse(names) {
    return function() {
      classedRemove(this, names);
    };
  }

  function classedFunction(names, value) {
    return function() {
      (value.apply(this, arguments) ? classedAdd : classedRemove)(this, names);
    };
  }

  function selection_classed(name, value) {
    var names = classArray(name + "");

    if (arguments.length < 2) {
      var list = classList(this.node()), i = -1, n = names.length;
      while (++i < n) if (!list.contains(names[i])) return false;
      return true;
    }

    return this.each((typeof value === "function"
        ? classedFunction : value
        ? classedTrue
        : classedFalse)(names, value));
  }

  function textRemove() {
    this.textContent = "";
  }

  function textConstant(value) {
    return function() {
      this.textContent = value;
    };
  }

  function textFunction(value) {
    return function() {
      var v = value.apply(this, arguments);
      this.textContent = v == null ? "" : v;
    };
  }

  function selection_text(value) {
    return arguments.length
        ? this.each(value == null
            ? textRemove : (typeof value === "function"
            ? textFunction
            : textConstant)(value))
        : this.node().textContent;
  }

  function htmlRemove() {
    this.innerHTML = "";
  }

  function htmlConstant(value) {
    return function() {
      this.innerHTML = value;
    };
  }

  function htmlFunction(value) {
    return function() {
      var v = value.apply(this, arguments);
      this.innerHTML = v == null ? "" : v;
    };
  }

  function selection_html(value) {
    return arguments.length
        ? this.each(value == null
            ? htmlRemove : (typeof value === "function"
            ? htmlFunction
            : htmlConstant)(value))
        : this.node().innerHTML;
  }

  function raise() {
    if (this.nextSibling) this.parentNode.appendChild(this);
  }

  function selection_raise() {
    return this.each(raise);
  }

  function lower() {
    if (this.previousSibling) this.parentNode.insertBefore(this, this.parentNode.firstChild);
  }

  function selection_lower() {
    return this.each(lower);
  }

  function selection_append(name) {
    var create = typeof name === "function" ? name : creator(name);
    return this.select(function() {
      return this.appendChild(create.apply(this, arguments));
    });
  }

  function constantNull() {
    return null;
  }

  function selection_insert(name, before) {
    var create = typeof name === "function" ? name : creator(name),
        select = before == null ? constantNull : typeof before === "function" ? before : selector(before);
    return this.select(function() {
      return this.insertBefore(create.apply(this, arguments), select.apply(this, arguments) || null);
    });
  }

  function remove() {
    var parent = this.parentNode;
    if (parent) parent.removeChild(this);
  }

  function selection_remove() {
    return this.each(remove);
  }

  function selection_cloneShallow() {
    return this.parentNode.insertBefore(this.cloneNode(false), this.nextSibling);
  }

  function selection_cloneDeep() {
    return this.parentNode.insertBefore(this.cloneNode(true), this.nextSibling);
  }

  function selection_clone(deep) {
    return this.select(deep ? selection_cloneDeep : selection_cloneShallow);
  }

  function selection_datum(value) {
    return arguments.length
        ? this.property("__data__", value)
        : this.node().__data__;
  }

  var filterEvents = {};

  var event = null;

  if (typeof document !== "undefined") {
    var element = document.documentElement;
    if (!("onmouseenter" in element)) {
      filterEvents = {mouseenter: "mouseover", mouseleave: "mouseout"};
    }
  }

  function filterContextListener(listener, index, group) {
    listener = contextListener(listener, index, group);
    return function(event) {
      var related = event.relatedTarget;
      if (!related || (related !== this && !(related.compareDocumentPosition(this) & 8))) {
        listener.call(this, event);
      }
    };
  }

  function contextListener(listener, index, group) {
    return function(event1) {
      var event0 = event; // Events can be reentrant (e.g., focus).
      event = event1;
      try {
        listener.call(this, this.__data__, index, group);
      } finally {
        event = event0;
      }
    };
  }

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

  function onRemove(typename) {
    return function() {
      var on = this.__on;
      if (!on) return;
      for (var j = 0, i = -1, m = on.length, o; j < m; ++j) {
        if (o = on[j], (!typename.type || o.type === typename.type) && o.name === typename.name) {
          this.removeEventListener(o.type, o.listener, o.capture);
        } else {
          on[++i] = o;
        }
      }
      if (++i) on.length = i;
      else delete this.__on;
    };
  }

  function onAdd(typename, value, capture) {
    var wrap = filterEvents.hasOwnProperty(typename.type) ? filterContextListener : contextListener;
    return function(d, i, group) {
      var on = this.__on, o, listener = wrap(value, i, group);
      if (on) for (var j = 0, m = on.length; j < m; ++j) {
        if ((o = on[j]).type === typename.type && o.name === typename.name) {
          this.removeEventListener(o.type, o.listener, o.capture);
          this.addEventListener(o.type, o.listener = listener, o.capture = capture);
          o.value = value;
          return;
        }
      }
      this.addEventListener(typename.type, listener, capture);
      o = {type: typename.type, name: typename.name, value: value, listener: listener, capture: capture};
      if (!on) this.__on = [o];
      else on.push(o);
    };
  }

  function selection_on(typename, value, capture) {
    var typenames = parseTypenames(typename + ""), i, n = typenames.length, t;

    if (arguments.length < 2) {
      var on = this.node().__on;
      if (on) for (var j = 0, m = on.length, o; j < m; ++j) {
        for (i = 0, o = on[j]; i < n; ++i) {
          if ((t = typenames[i]).type === o.type && t.name === o.name) {
            return o.value;
          }
        }
      }
      return;
    }

    on = value ? onAdd : onRemove;
    if (capture == null) capture = false;
    for (i = 0; i < n; ++i) this.each(on(typenames[i], value, capture));
    return this;
  }

  function customEvent(event1, listener, that, args) {
    var event0 = event;
    event1.sourceEvent = event;
    event = event1;
    try {
      return listener.apply(that, args);
    } finally {
      event = event0;
    }
  }

  function dispatchEvent(node, type, params) {
    var window = defaultView(node),
        event = window.CustomEvent;

    if (typeof event === "function") {
      event = new event(type, params);
    } else {
      event = window.document.createEvent("Event");
      if (params) event.initEvent(type, params.bubbles, params.cancelable), event.detail = params.detail;
      else event.initEvent(type, false, false);
    }

    node.dispatchEvent(event);
  }

  function dispatchConstant(type, params) {
    return function() {
      return dispatchEvent(this, type, params);
    };
  }

  function dispatchFunction(type, params) {
    return function() {
      return dispatchEvent(this, type, params.apply(this, arguments));
    };
  }

  function selection_dispatch(type, params) {
    return this.each((typeof params === "function"
        ? dispatchFunction
        : dispatchConstant)(type, params));
  }

  var root = [null];

  function Selection(groups, parents) {
    this._groups = groups;
    this._parents = parents;
  }

  function selection() {
    return new Selection([[document.documentElement]], root);
  }

  Selection.prototype = selection.prototype = {
    constructor: Selection,
    select: selection_select,
    selectAll: selection_selectAll,
    filter: selection_filter,
    data: selection_data,
    enter: selection_enter,
    exit: selection_exit,
    join: selection_join,
    merge: selection_merge,
    order: selection_order,
    sort: selection_sort,
    call: selection_call,
    nodes: selection_nodes,
    node: selection_node,
    size: selection_size,
    empty: selection_empty,
    each: selection_each,
    attr: selection_attr,
    style: selection_style,
    property: selection_property,
    classed: selection_classed,
    text: selection_text,
    html: selection_html,
    raise: selection_raise,
    lower: selection_lower,
    append: selection_append,
    insert: selection_insert,
    remove: selection_remove,
    clone: selection_clone,
    datum: selection_datum,
    on: selection_on,
    dispatch: selection_dispatch
  };

  function select(selector) {
    return typeof selector === "string"
        ? new Selection([[document.querySelector(selector)]], [document.documentElement])
        : new Selection([[selector]], root);
  }

  function sourceEvent() {
    var current = event, source;
    while (source = current.sourceEvent) current = source;
    return current;
  }

  function point(node, event) {
    var svg = node.ownerSVGElement || node;

    if (svg.createSVGPoint) {
      var point = svg.createSVGPoint();
      point.x = event.clientX, point.y = event.clientY;
      point = point.matrixTransform(node.getScreenCTM().inverse());
      return [point.x, point.y];
    }

    var rect = node.getBoundingClientRect();
    return [event.clientX - rect.left - node.clientLeft, event.clientY - rect.top - node.clientTop];
  }

  function mouse(node) {
    var event = sourceEvent();
    if (event.changedTouches) event = event.changedTouches[0];
    return point(node, event);
  }

  function touch(node, touches, identifier) {
    if (arguments.length < 3) identifier = touches, touches = sourceEvent().changedTouches;

    for (var i = 0, n = touches ? touches.length : 0, touch; i < n; ++i) {
      if ((touch = touches[i]).identifier === identifier) {
        return point(node, touch);
      }
    }

    return null;
  }

  var prefix = "$";

  function Map$1() {}

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

  function map(object, f) {
    var map = new Map$1;

    // Copy constructor.
    if (object instanceof Map$1) object.each(function(value, key) { map.set(key, value); });

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

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

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

    return map;
  }

  function Set() {}

  var proto = map.prototype;

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

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

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

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

    return set;
  }

  function values(map) {
    var values = [];
    for (var key in map) values.push(map[key]);
    return values;
  }

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

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

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

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

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

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

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

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

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

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

  function nopropagation() {
    event.stopImmediatePropagation();
  }

  function noevent() {
    event.preventDefault();
    event.stopImmediatePropagation();
  }

  function nodrag(view) {
    var root = view.document.documentElement,
        selection = select(view).on("dragstart.drag", noevent, true);
    if ("onselectstart" in root) {
      selection.on("selectstart.drag", noevent, true);
    } else {
      root.__noselect = root.style.MozUserSelect;
      root.style.MozUserSelect = "none";
    }
  }

  function yesdrag(view, noclick) {
    var root = view.document.documentElement,
        selection = select(view).on("dragstart.drag", null);
    if (noclick) {
      selection.on("click.drag", noevent, true);
      setTimeout(function() { selection.on("click.drag", null); }, 0);
    }
    if ("onselectstart" in root) {
      selection.on("selectstart.drag", null);
    } else {
      root.style.MozUserSelect = root.__noselect;
      delete root.__noselect;
    }
  }

  function constant$1(x) {
    return function() {
      return x;
    };
  }

  function DragEvent(target, type, subject, id, active, x, y, dx, dy, dispatch) {
    this.target = target;
    this.type = type;
    this.subject = subject;
    this.identifier = id;
    this.active = active;
    this.x = x;
    this.y = y;
    this.dx = dx;
    this.dy = dy;
    this._ = dispatch;
  }

  DragEvent.prototype.on = function() {
    var value = this._.on.apply(this._, arguments);
    return value === this._ ? this : value;
  };

  // Ignore right-click, since that should open the context menu.
  function defaultFilter() {
    return !event.button;
  }

  function defaultContainer() {
    return this.parentNode;
  }

  function defaultSubject(d) {
    return d == null ? {x: event.x, y: event.y} : d;
  }

  function defaultTouchable() {
    return "ontouchstart" in this;
  }

  function drag() {
    var filter = defaultFilter,
        container = defaultContainer,
        subject = defaultSubject,
        touchable = defaultTouchable,
        gestures = {},
        listeners = dispatch("start", "drag", "end"),
        active = 0,
        mousedownx,
        mousedowny,
        mousemoving,
        touchending,
        clickDistance2 = 0;

    function drag(selection) {
      selection
          .on("mousedown.drag", mousedowned)
        .filter(touchable)
          .on("touchstart.drag", touchstarted)
          .on("touchmove.drag", touchmoved)
          .on("touchend.drag touchcancel.drag", touchended)
          .style("touch-action", "none")
          .style("-webkit-tap-highlight-color", "rgba(0,0,0,0)");
    }

    function mousedowned() {
      if (touchending || !filter.apply(this, arguments)) return;
      var gesture = beforestart("mouse", container.apply(this, arguments), mouse, this, arguments);
      if (!gesture) return;
      select(event.view).on("mousemove.drag", mousemoved, true).on("mouseup.drag", mouseupped, true);
      nodrag(event.view);
      nopropagation();
      mousemoving = false;
      mousedownx = event.clientX;
      mousedowny = event.clientY;
      gesture("start");
    }

    function mousemoved() {
      noevent();
      if (!mousemoving) {
        var dx = event.clientX - mousedownx, dy = event.clientY - mousedowny;
        mousemoving = dx * dx + dy * dy > clickDistance2;
      }
      gestures.mouse("drag");
    }

    function mouseupped() {
      select(event.view).on("mousemove.drag mouseup.drag", null);
      yesdrag(event.view, mousemoving);
      noevent();
      gestures.mouse("end");
    }

    function touchstarted() {
      if (!filter.apply(this, arguments)) return;
      var touches = event.changedTouches,
          c = container.apply(this, arguments),
          n = touches.length, i, gesture;

      for (i = 0; i < n; ++i) {
        if (gesture = beforestart(touches[i].identifier, c, touch, this, arguments)) {
          nopropagation();
          gesture("start");
        }
      }
    }

    function touchmoved() {
      var touches = event.changedTouches,
          n = touches.length, i, gesture;

      for (i = 0; i < n; ++i) {
        if (gesture = gestures[touches[i].identifier]) {
          noevent();
          gesture("drag");
        }
      }
    }

    function touchended() {
      var touches = event.changedTouches,
          n = touches.length, i, gesture;

      if (touchending) clearTimeout(touchending);
      touchending = setTimeout(function() { touchending = null; }, 500); // Ghost clicks are delayed!
      for (i = 0; i < n; ++i) {
        if (gesture = gestures[touches[i].identifier]) {
          nopropagation();
          gesture("end");
        }
      }
    }

    function beforestart(id, container, point, that, args) {
      var p = point(container, id), s, dx, dy,
          sublisteners = listeners.copy();

      if (!customEvent(new DragEvent(drag, "beforestart", s, id, active, p[0], p[1], 0, 0, sublisteners), function() {
        if ((event.subject = s = subject.apply(that, args)) == null) return false;
        dx = s.x - p[0] || 0;
        dy = s.y - p[1] || 0;
        return true;
      })) return;

      return function gesture(type) {
        var p0 = p, n;
        switch (type) {
          case "start": gestures[id] = gesture, n = active++; break;
          case "end": delete gestures[id], --active; // nobreak
          case "drag": p = point(container, id), n = active; break;
        }
        customEvent(new DragEvent(drag, type, s, id, n, p[0] + dx, p[1] + dy, p[0] - p0[0], p[1] - p0[1], sublisteners), sublisteners.apply, sublisteners, [type, that, args]);
      };
    }

    drag.filter = function(_) {
      return arguments.length ? (filter = typeof _ === "function" ? _ : constant$1(!!_), drag) : filter;
    };

    drag.container = function(_) {
      return arguments.length ? (container = typeof _ === "function" ? _ : constant$1(_), drag) : container;
    };

    drag.subject = function(_) {
      return arguments.length ? (subject = typeof _ === "function" ? _ : constant$1(_), drag) : subject;
    };

    drag.touchable = function(_) {
      return arguments.length ? (touchable = typeof _ === "function" ? _ : constant$1(!!_), drag) : touchable;
    };

    drag.on = function() {
      var value = listeners.on.apply(listeners, arguments);
      return value === listeners ? drag : value;
    };

    drag.clickDistance = function(_) {
      return arguments.length ? (clickDistance2 = (_ = +_) * _, drag) : Math.sqrt(clickDistance2);
    };

    return drag;
  }

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

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

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

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

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

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

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

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

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

    // If there were no (valid) points, abort.
    if (x0 > x1 || y0 > y1) return this;

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

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

    return this;
  }

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

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

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

    // Otherwise, double repeatedly to cover.
    else {
      var z = x1 - x0,
          node = this._root,
          parent,
          i;

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

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

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

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

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

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

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

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

    while (q = quads.pop()) {

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

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

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

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

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

    return data;
  }

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

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

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

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

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

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

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

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

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

    return this;
  }

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

  function tree_root() {
    return this._root;
  }

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

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

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

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

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

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

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

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

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

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

  var treeProto = quadtree.prototype = Quadtree.prototype;

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

    if (!node) return copy;

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

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

    return copy;
  };

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

  function constant$2(x) {
    return function() {
      return x;
    };
  }

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

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

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

  function forceLink(links) {
    var id = index,
        strength = defaultStrength,
        strengths,
        distance = constant$2(30),
        distances,
        nodes,
        count,
        bias,
        iterations = 1;

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

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

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

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

      var i,
          n = nodes.length,
          m = links.length,
          nodeById = new Map(nodes.map((d, i) => [id(d, i, nodes), d])),
          link;

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

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

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

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

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

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

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

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

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

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

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

    force.strength = function(_) {
      return arguments.length ? (strength = typeof _ === "function" ? _ : constant$2(+_), initializeStrength(), force) : strength;
    };

    force.distance = function(_) {
      return arguments.length ? (distance = typeof _ === "function" ? _ : constant$2(+_), initializeDistance(), force) : distance;
    };

    return force;
  }

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

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

  function clearNow() {
    clockNow = 0;
  }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

      if (iterations === undefined) iterations = 1;

      for (var k = 0; k < iterations; ++k) {
        alpha += (alphaTarget - alpha) * alphaDecay;

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

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

      return simulation;
    }

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

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

    initializeNodes();

    return simulation = {
      tick: tick,

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

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

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

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

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

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

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

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

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

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

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

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

        return closest;
      },

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

  function forceManyBody() {
    var nodes,
        node,
        alpha,
        strength = constant$2(-30),
        strengths,
        distanceMin2 = 1,
        distanceMax2 = Infinity,
        theta2 = 0.81;

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

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

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

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

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

      quad.value = strength;
    }

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

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

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

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

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

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

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

    force.strength = function(_) {
      return arguments.length ? (strength = typeof _ === "function" ? _ : constant$2(+_), initialize(), force) : strength;
    };

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

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

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

    return force;
  }

  function forceRadial(radius, x, y) {
    var nodes,
        strength = constant$2(0.1),
        strengths,
        radiuses;

    if (typeof radius !== "function") radius = constant$2(+radius);
    if (x == null) x = 0;
    if (y == null) y = 0;

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

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

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

    force.strength = function(_) {
      return arguments.length ? (strength = typeof _ === "function" ? _ : constant$2(+_), initialize(), force) : strength;
    };

    force.radius = function(_) {
      return arguments.length ? (radius = typeof _ === "function" ? _ : constant$2(+_), initialize(), force) : radius;
    };

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

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

    return force;
  }

  var commonjsGlobal = typeof globalThis !== 'undefined' ? globalThis : typeof window !== 'undefined' ? window : typeof global !== 'undefined' ? global : typeof self !== 'undefined' ? self : {};

  function createCommonjsModule(fn, module) {
  	return module = { exports: {} }, fn(module, module.exports), module.exports;
  }

  var fetchJsonp = createCommonjsModule(function (module, exports) {
  (function (global, factory) {
    {
      factory(exports, module);
    }
  })(commonjsGlobal, function (exports, module) {

    var defaultOptions = {
      timeout: 5000,
      jsonpCallback: 'callback',
      jsonpCallbackFunction: null
    };

    function generateCallbackFunction() {
      return 'jsonp_' + Date.now() + '_' + Math.ceil(Math.random() * 100000);
    }

    function clearFunction(functionName) {
      // IE8 throws an exception when you try to delete a property on window
      // http://stackoverflow.com/a/1824228/751089
      try {
        delete window[functionName];
      } catch (e) {
        window[functionName] = undefined;
      }
    }

    function removeScript(scriptId) {
      var script = document.getElementById(scriptId);
      if (script) {
        document.getElementsByTagName('head')[0].removeChild(script);
      }
    }

    function fetchJsonp(_url) {
      var options = arguments.length <= 1 || arguments[1] === undefined ? {} : arguments[1];

      // to avoid param reassign
      var url = _url;
      var timeout = options.timeout || defaultOptions.timeout;
      var jsonpCallback = options.jsonpCallback || defaultOptions.jsonpCallback;

      var timeoutId = undefined;

      return new Promise(function (resolve, reject) {
        var callbackFunction = options.jsonpCallbackFunction || generateCallbackFunction();
        var scriptId = jsonpCallback + '_' + callbackFunction;

        window[callbackFunction] = function (response) {
          resolve({
            ok: true,
            // keep consistent with fetch API
            json: function json() {
              return Promise.resolve(response);
            }
          });

          if (timeoutId) clearTimeout(timeoutId);

          removeScript(scriptId);

          clearFunction(callbackFunction);
        };

        // Check if the user set their own params, and if not add a ? to start a list of params
        url += url.indexOf('?') === -1 ? '?' : '&';

        var jsonpScript = document.createElement('script');
        jsonpScript.setAttribute('src', '' + url + jsonpCallback + '=' + callbackFunction);
        if (options.charset) {
          jsonpScript.setAttribute('charset', options.charset);
        }
        jsonpScript.id = scriptId;
        document.getElementsByTagName('head')[0].appendChild(jsonpScript);

        timeoutId = setTimeout(function () {
          reject(new Error('JSONP request to ' + _url + ' timed out'));

          clearFunction(callbackFunction);
          removeScript(scriptId);
          window[callbackFunction] = function () {
            clearFunction(callbackFunction);
          };
        }, timeout);

        // Caught if got 404/500
        jsonpScript.onerror = function () {
          reject(new Error('JSONP request to ' + _url + ' failed'));

          clearFunction(callbackFunction);
          removeScript(scriptId);
          if (timeoutId) clearTimeout(timeoutId);
        };
      });
    }

    // export as global function
    /*
    let local;
    if (typeof global !== 'undefined') {
      local = global;
    } else if (typeof self !== 'undefined') {
      local = self;
    } else {
      try {
        local = Function('return this')();
      } catch (e) {
        throw new Error('polyfill failed because global object is unavailable in this environment');
      }
    }
    local.fetchJsonp = fetchJsonp;
    */

    module.exports = fetchJsonp;
  });
  });

  var NS = {
      main: 0,
      discussion: 1,
      template: 10,
      category: 14,
      news: 3106,
      web: 3116
  };

  class Wiki {
      constructor (apiurl) {
          this.apiurl = apiurl;
          this.pages_by_title = {};
          this.ns_names = {};
          for (var key in NS) {
              var nsid = NS[key];
              this.ns_names[nsid] = key;
          }
      }
      get_page_by_title (title) {
          var p = this.pages_by_title[title];
          if (p) {
              return p;
          } else {
              p = new Page(this, {title: title, ns: 0});
              this.pages_by_title[title] = p;
              return p; 
          }
      }
      page_for_object (n, merge_data) {
          if (merge_data === undefined) { merge_data = true; }
          var title = n.title,
              p = this.pages_by_title[title];
          if (p) {
              if (merge_data) { p.merge_data(n); }
              return p;
          } else {
              p = new Page(this, n);
              this.pages_by_title[title] = p;
              return p; 
          }
      }
      get_ns_classname (nsid) {
          // console.log("get_ns_classname", nsid, this.ns_names[nsid]);
          var ret = this.ns_names[nsid];
          console.log("classname", ret);
          if (ret === undefined) { console.log("warning classname undefined for ns", nsid); }
          return ret;
      }
      union (p1, p2) {
          var union = map(p1, d=>d.title);
          for (var i=0, l=p2.length; i<l; i++) {
              var x = p2[i];
              union.set(x.title, x);
          }
          return union.values();
      }
  }

  class Page {
      constructor (wiki, node) {
          this.wiki = wiki;
          this.merge_data(node);
      }
      url () {
          // return this.wiki.apiurl.replace("api.php", "index.php")+"/"+encodeURIComponent(this.title);
          return this.wiki.apiurl.replace("api.php", "index.php")+"/"+encodeURIComponent(this.title);
      }
      merge_data (node) {
          for (var key in node) {
              if (node.hasOwnProperty(key)) {
                  this[key] = node[key];
              }
          }        
      }

      // api.php?action=query&prop=categories&titles=Albert%20Einstein
      async get_prop (pname, prefix) {
          var ret = [];
          var url = this.wiki.apiurl+"?action=query&format=json&formatversion=2&prop="+pname+"&titles="+encodeURIComponent(this.title);
          while (true) {
              var data = await fetchJsonp(url);
              var json = await data.json();
              // console.log("BACKLINKS.RAW", json);
              // filter REDIRECTS + Discussion pages (ns==1)
              if (json.query.pages[0]) {
                  var p = json.query.pages[0];
                  // extract any missing page info
                  if (p.ns && !this.ns) { this.ns = p.ns; }
                  if (p.pageid && !this.pageid) { this.pageid = p.pageid; }
              }
              if (json.query.pages[0][pname]) {
                  ret.push.apply(ret, json.query.pages[0][pname]);
              }
              if (!json.continue) { break; }
              url = this.wiki.apiurl+"?action=query&format=json&formatversion=2&prop="+pname+"&"+prefix+"continue="+json.continue[prefix+"continue"]+"&titles="+encodeURIComponent(this.title);
          }
          ret = ret.map(x => this.wiki.page_for_object(x));
          // console.log("get_backlinks", ret);
          console.log("get_prop", pname, prefix, ret);
          return ret;
      }
      async get_links () {
          return await this.get_prop("links", "pl");
          // // http://localhost/mw/api.php?action=query&prop=links&titles=Bienvenue_%C3%A0_l%E2%80%99erg
          // var ret = [];
          // var url = this.wiki.apiurl+"?action=query&format=json&formatversion=2&prop=links&titles="+encodeURIComponent(this.title);
          // while (true) {
          //     var data = await fetchJsonp(url);
          //     var json = await data.json();
          //     // console.log("JSON", json);
          //     if (json.query.pages[0]) {
          //         var p = json.query.pages[0];
          //         // extract any missing page info
          //         if (p.ns && !this.ns) { this.ns = p.ns; }
          //         if (p.pageid && !this.pageid) { this.pageid = p.pageid; }
          //     }
          //     if (json.query.pages[0].links) {
          //         ret.push.apply(ret, json.query.pages[0].links);
          //     }
          //     if (!json.continue) { break; }
          //     url = this.wiki.apiurl+"?action=query&format=json&formatversion=2&prop=links&plcontinue="+json.continue.plcontinue+"&titles="+encodeURIComponent(this.title);
          // }
          // ret = ret.map(x => this.wiki.page_for_object(x));
          // // map these to page objects
          // return ret;
      }
      async get_linkshere () {
          return await this.get_prop("linkshere", "lh");
      }
      async get_list () {        
          // http://localhost/mw/api.php?action=query&prop=links&titles=Bienvenue_%C3%A0_l%E2%80%99erg
          var ret = [];
          var url = this.wiki.apiurl+"?action=query&format=json&formatversion=2&list=backlinks&bltitle="+encodeURIComponent(this.title);
          while (true) {
              var data = await fetchJsonp(url);
              var json = await data.json();
              // console.log("BACKLINKS.RAW", json);
              // filter REDIRECTS + Discussion pages (ns==1)
              var backlinks = json.query.backlinks;
              // backlink = backlinks.filter(x => (!x.redirect && x.ns != 1);
              ret.push.apply(ret, backlinks);
              if (!json.continue) { break; }
              url = this.wiki.apiurl+"?action=query&format=json&formatversion=2&list=backlinks&blcontinue="+json.continue.blcontinue+"&bltitle="+encodeURIComponent(this.title);
          }
          ret = ret.map(x => this.wiki.page_for_object(x));
          // console.log("get_backlinks", ret);
          return ret;
      }
  }

  var eventemitter3 = createCommonjsModule(function (module) {

  var has = Object.prototype.hasOwnProperty
    , prefix = '~';

  /**
   * Constructor to create a storage for our `EE` objects.
   * An `Events` instance is a plain object whose properties are event names.
   *
   * @constructor
   * @private
   */
  function Events() {}

  //
  // We try to not inherit from `Object.prototype`. In some engines creating an
  // instance in this way is faster than calling `Object.create(null)` directly.
  // If `Object.create(null)` is not supported we prefix the event names with a
  // character to make sure that the built-in object properties are not
  // overridden or used as an attack vector.
  //
  if (Object.create) {
    Events.prototype = Object.create(null);

    //
    // This hack is needed because the `__proto__` property is still inherited in
    // some old browsers like Android 4, iPhone 5.1, Opera 11 and Safari 5.
    //
    if (!new Events().__proto__) prefix = false;
  }

  /**
   * Representation of a single event listener.
   *
   * @param {Function} fn The listener function.
   * @param {*} context The context to invoke the listener with.
   * @param {Boolean} [once=false] Specify if the listener is a one-time listener.
   * @constructor
   * @private
   */
  function EE(fn, context, once) {
    this.fn = fn;
    this.context = context;
    this.once = once || false;
  }

  /**
   * Add a listener for a given event.
   *
   * @param {EventEmitter} emitter Reference to the `EventEmitter` instance.
   * @param {(String|Symbol)} event The event name.
   * @param {Function} fn The listener function.
   * @param {*} context The context to invoke the listener with.
   * @param {Boolean} once Specify if the listener is a one-time listener.
   * @returns {EventEmitter}
   * @private
   */
  function addListener(emitter, event, fn, context, once) {
    if (typeof fn !== 'function') {
      throw new TypeError('The listener must be a function');
    }

    var listener = new EE(fn, context || emitter, once)
      , evt = prefix ? prefix + event : event;

    if (!emitter._events[evt]) emitter._events[evt] = listener, emitter._eventsCount++;
    else if (!emitter._events[evt].fn) emitter._events[evt].push(listener);
    else emitter._events[evt] = [emitter._events[evt], listener];

    return emitter;
  }

  /**
   * Clear event by name.
   *
   * @param {EventEmitter} emitter Reference to the `EventEmitter` instance.
   * @param {(String|Symbol)} evt The Event name.
   * @private
   */
  function clearEvent(emitter, evt) {
    if (--emitter._eventsCount === 0) emitter._events = new Events();
    else delete emitter._events[evt];
  }

  /**
   * Minimal `EventEmitter` interface that is molded against the Node.js
   * `EventEmitter` interface.
   *
   * @constructor
   * @public
   */
  function EventEmitter() {
    this._events = new Events();
    this._eventsCount = 0;
  }

  /**
   * Return an array listing the events for which the emitter has registered
   * listeners.
   *
   * @returns {Array}
   * @public
   */
  EventEmitter.prototype.eventNames = function eventNames() {
    var names = []
      , events
      , name;

    if (this._eventsCount === 0) return names;

    for (name in (events = this._events)) {
      if (has.call(events, name)) names.push(prefix ? name.slice(1) : name);
    }

    if (Object.getOwnPropertySymbols) {
      return names.concat(Object.getOwnPropertySymbols(events));
    }

    return names;
  };

  /**
   * Return the listeners registered for a given event.
   *
   * @param {(String|Symbol)} event The event name.
   * @returns {Array} The registered listeners.
   * @public
   */
  EventEmitter.prototype.listeners = function listeners(event) {
    var evt = prefix ? prefix + event : event
      , handlers = this._events[evt];

    if (!handlers) return [];
    if (handlers.fn) return [handlers.fn];

    for (var i = 0, l = handlers.length, ee = new Array(l); i < l; i++) {
      ee[i] = handlers[i].fn;
    }

    return ee;
  };

  /**
   * Return the number of listeners listening to a given event.
   *
   * @param {(String|Symbol)} event The event name.
   * @returns {Number} The number of listeners.
   * @public
   */
  EventEmitter.prototype.listenerCount = function listenerCount(event) {
    var evt = prefix ? prefix + event : event
      , listeners = this._events[evt];

    if (!listeners) return 0;
    if (listeners.fn) return 1;
    return listeners.length;
  };

  /**
   * Calls each of the listeners registered for a given event.
   *
   * @param {(String|Symbol)} event The event name.
   * @returns {Boolean} `true` if the event had listeners, else `false`.
   * @public
   */
  EventEmitter.prototype.emit = function emit(event, a1, a2, a3, a4, a5) {
    var evt = prefix ? prefix + event : event;

    if (!this._events[evt]) return false;

    var listeners = this._events[evt]
      , len = arguments.length
      , args
      , i;

    if (listeners.fn) {
      if (listeners.once) this.removeListener(event, listeners.fn, undefined, true);

      switch (len) {
        case 1: return listeners.fn.call(listeners.context), true;
        case 2: return listeners.fn.call(listeners.context, a1), true;
        case 3: return listeners.fn.call(listeners.context, a1, a2), true;
        case 4: return listeners.fn.call(listeners.context, a1, a2, a3), true;
        case 5: return listeners.fn.call(listeners.context, a1, a2, a3, a4), true;
        case 6: return listeners.fn.call(listeners.context, a1, a2, a3, a4, a5), true;
      }

      for (i = 1, args = new Array(len -1); i < len; i++) {
        args[i - 1] = arguments[i];
      }

      listeners.fn.apply(listeners.context, args);
    } else {
      var length = listeners.length
        , j;

      for (i = 0; i < length; i++) {
        if (listeners[i].once) this.removeListener(event, listeners[i].fn, undefined, true);

        switch (len) {
          case 1: listeners[i].fn.call(listeners[i].context); break;
          case 2: listeners[i].fn.call(listeners[i].context, a1); break;
          case 3: listeners[i].fn.call(listeners[i].context, a1, a2); break;
          case 4: listeners[i].fn.call(listeners[i].context, a1, a2, a3); break;
          default:
            if (!args) for (j = 1, args = new Array(len -1); j < len; j++) {
              args[j - 1] = arguments[j];
            }

            listeners[i].fn.apply(listeners[i].context, args);
        }
      }
    }

    return true;
  };

  /**
   * Add a listener for a given event.
   *
   * @param {(String|Symbol)} event The event name.
   * @param {Function} fn The listener function.
   * @param {*} [context=this] The context to invoke the listener with.
   * @returns {EventEmitter} `this`.
   * @public
   */
  EventEmitter.prototype.on = function on(event, fn, context) {
    return addListener(this, event, fn, context, false);
  };

  /**
   * Add a one-time listener for a given event.
   *
   * @param {(String|Symbol)} event The event name.
   * @param {Function} fn The listener function.
   * @param {*} [context=this] The context to invoke the listener with.
   * @returns {EventEmitter} `this`.
   * @public
   */
  EventEmitter.prototype.once = function once(event, fn, context) {
    return addListener(this, event, fn, context, true);
  };

  /**
   * Remove the listeners of a given event.
   *
   * @param {(String|Symbol)} event The event name.
   * @param {Function} fn Only remove the listeners that match this function.
   * @param {*} context Only remove the listeners that have this context.
   * @param {Boolean} once Only remove one-time listeners.
   * @returns {EventEmitter} `this`.
   * @public
   */
  EventEmitter.prototype.removeListener = function removeListener(event, fn, context, once) {
    var evt = prefix ? prefix + event : event;

    if (!this._events[evt]) return this;
    if (!fn) {
      clearEvent(this, evt);
      return this;
    }

    var listeners = this._events[evt];

    if (listeners.fn) {
      if (
        listeners.fn === fn &&
        (!once || listeners.once) &&
        (!context || listeners.context === context)
      ) {
        clearEvent(this, evt);
      }
    } else {
      for (var i = 0, events = [], length = listeners.length; i < length; i++) {
        if (
          listeners[i].fn !== fn ||
          (once && !listeners[i].once) ||
          (context && listeners[i].context !== context)
        ) {
          events.push(listeners[i]);
        }
      }

      //
      // Reset the array, or remove it completely if we have no more listeners.
      //
      if (events.length) this._events[evt] = events.length === 1 ? events[0] : events;
      else clearEvent(this, evt);
    }

    return this;
  };

  /**
   * Remove all listeners, or those of the specified event.
   *
   * @param {(String|Symbol)} [event] The event name.
   * @returns {EventEmitter} `this`.
   * @public
   */
  EventEmitter.prototype.removeAllListeners = function removeAllListeners(event) {
    var evt;

    if (event) {
      evt = prefix ? prefix + event : event;
      if (this._events[evt]) clearEvent(this, evt);
    } else {
      this._events = new Events();
      this._eventsCount = 0;
    }

    return this;
  };

  //
  // Alias methods names because people roll like that.
  //
  EventEmitter.prototype.off = EventEmitter.prototype.removeListener;
  EventEmitter.prototype.addListener = EventEmitter.prototype.on;

  //
  // Expose the prefix.
  //
  EventEmitter.prefixed = prefix;

  //
  // Allow `EventEmitter` to be imported as module namespace.
  //
  EventEmitter.EventEmitter = EventEmitter;

  //
  // Expose the module.
  //
  {
    module.exports = EventEmitter;
  }
  });

  class Map$2 {

      constructor (apiurl) {
          var width = 600,
              height = 600;
          this.wiki = new Wiki(apiurl);
          this.events = new eventemitter3();
          this.active_page = null;
          // this.nodes = {};
          this.simulation = forceSimulation()
              .velocityDecay(0.1)
              .force("link", forceLink().id(d => d.title))
              .force("charge", forceManyBody())
              .force("radial", forceRadial(180, width/2, height/2));
              // .force("center", forceCenter(width / 2, height / 2));
          this.svg = null;
          this.historylinks = {};
      }

      on (message, callback, context) {
          this.events.on(message, callback, context);
      }

      init_svg (svg) {
          this.svg = select(svg || "svg");
          this.linksg = this.svg.append("g")
              .attr("class", "links");
          this.nodesg = this.svg.append("g")
              .attr("class", "nodes");
      }

      dragstarted (d) {
          if (!event.active) this.simulation.alphaTarget(0.3).restart();
          d.fx = d.x;
          d.fy = d.y;
      }

      dragged (d) {
          d.fx = event.x;
          d.fy = event.y;
      }

      dragended(d) {
          if (!event.active) this.simulation.alphaTarget(0);
          d.fx = null;
          d.fy = null;
      }

      update_graph (graph) {
          // console.log("UPDATE GRAPH", graph.nodes.length, graph.links.length);
          var that = this,
              link = this.linksg.selectAll("line")
                  .data(graph.links, function (d) { return that.link_key(d.source.title, d.target.title) });
          var link_enter = link.enter()
              .append("line");

          link.exit().each(d => {
              d.source.linked = false;
              d.target.linked = false;
          }).remove();
          
          link_enter.merge(link).each(d => {
                  d.source.linked = true;
                  d.target.linked = true;
              });

          var node = this.nodesg
              .selectAll("g.page")
              .data(graph.nodes, function (d) { return d.title });

          var node_enter = node.enter().append("g")
              .attr("class", d=>"page "+this.wiki.get_ns_classname(d.ns))
              .on("click", d => {
                  this.set_active_node(d.title);
              })
              .on("mouseover", function (d) {
                  // console.log("mouseover", this);
                  select(this).classed("mouse", true);
              })
              .on("mouseout", function (d) {
                  // console.log("mouseout", this);
                  select(this).classed("mouse", false);
              })
              .call(drag()
                  .on("start", this.dragstarted.bind(this))
                  .on("drag", this.dragged.bind(this))
                  .on("end", this.dragended.bind(this)));

          node_enter.append("circle")
              .attr("r", 6);

          node_enter.append("text")
              .text(d => d.title)
              .attr("x", 10);

          //node_enter.append("title")
          //   .text(function(d) { return d.title; });

          node = node_enter.merge(node);
          link = link_enter.merge(link);

          node.classed("active", d=>d.active);

          this.simulation
              .nodes(graph.nodes)
              .on("tick", ticked);

          this.simulation.force("link")
              .links(graph.links);

          this.simulation.force("radial").radius(d => d.linked ? null : 200);

          function ticked() {
              link
                  .attr("x1", function(d) { return d.source.x; })
                  .attr("y1", function(d) { return d.source.y; })
                  .attr("x2", function(d) { return d.target.x; })
                  .attr("y2", function(d) { return d.target.y; });

              // node
              //     .attr("cx", function(d) { return d.x; })
              //     .attr("cy", function(d) { return d.y; });
              node
                  .attr("transform", d => `translate(${d.x},${d.y})`);
          }
          this.simulation.alphaTarget(0.3).restart();
      }

      link_key (a, b) {
          return (a < b) ? ("link_"+a+"_"+b) : ("link_"+b+"_"+a);
      }

      walk (node, links) {
          var links_seen = {};
          // var node = this.ensure_node(nodename);
          node.all_links.forEach(x => {
              var link_key = this.link_key(node.title, x.title);
              if (!links_seen[link_key]) {
                  links.push({source: node, target: x});
                  links_seen[link_key] = true;
              }
          });
          return;
      }

      set_active_title (title) {
          this.set_active_node(title);
      }

      async set_active_node (page) {
          if (typeof(page) === "string") {
              page = this.wiki.get_page_by_title(page);
          }

          if (page === this.active_page) {
              // console.log("page is already the active page", page, this.active_page);
              return;
          }
          if (this.active_page) {
              this.active_page.active = false;
              var lkey = this.link_key(this.active_page.title, page.title),
                  source = (this.active_page.title < page.title) ? this.active_page : page,
                  target = (this.active_page.title < page.title) ? page : this.active_page;
              this.historylinks[lkey] = {source: source, target: target};
          }
          // n = this.ensure_node(pagetitle);
          
          this.active_page = page;
          this.active_page.active = true;
          this.load(this.active_page);
          this.events.emit("page", this.active_page.title);
      }

      async load (page) {
          console.log("loading", page.title);
          var links = await page.get_links(),
              backlinks = await page.get_linkshere(),
              alllinks = this.wiki.union(links, backlinks);

          page.all_links = alllinks;
          // console.log("alllinks", alllinks);
          var graph = {};

          graph.nodes = values(this.wiki.pages_by_title);
          graph.links = [];
          this.walk(page, graph.links);
          // activate historylinks
          values(this.historylinks).forEach(x => {
              graph.links.push(x);
          });
          // graph.links = titles.map(t => ({source: pagetitle, target: t}));
          this.update_graph(graph);
          // console.log("GOT DATA", titles);
          // return titles;
      }
  }



  // http://erg.activearchives.org/mw/api.php?action=query&prop=links&titles=Bienvenue_%C3%A0_l%E2%80%99erg
  // http://erg.activearchives.org/w/api.php?action=query&prop=info&titles=Main%20Page
  // Bienvenue_à_l’erg
  // http://erg.activearchives.org/mw/index.php/Bienvenue_%C3%A0_l%E2%80%99erg

  exports.Map = Map$2;

  return exports;

}({}));