xref: /external/chromium-trace/trace-viewer/tracing/third_party/components/polymer/polymer.js

/**
 * @license
 * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */
// @version 0.5.5
window.PolymerGestures = {};

(function(scope) {
  var hasFullPath = false;

  // test for full event path support
  var pathTest = document.createElement('meta');
  if (pathTest.createShadowRoot) {
    var sr = pathTest.createShadowRoot();
    var s = document.createElement('span');
    sr.appendChild(s);
    pathTest.addEventListener('testpath', function(ev) {
      if (ev.path) {
        // if the span is in the event path, then path[0] is the real source for all events
        hasFullPath = ev.path[0] === s;
      }
      ev.stopPropagation();
    });
    var ev = new CustomEvent('testpath', {bubbles: true});
    // must add node to DOM to trigger event listener
    document.head.appendChild(pathTest);
    s.dispatchEvent(ev);
    pathTest.parentNode.removeChild(pathTest);
    sr = s = null;
  }
  pathTest = null;

  var target = {
    shadow: function(inEl) {
      if (inEl) {
        return inEl.shadowRoot || inEl.webkitShadowRoot;
      }
    },
    canTarget: function(shadow) {
      return shadow && Boolean(shadow.elementFromPoint);
    },
    targetingShadow: function(inEl) {
      var s = this.shadow(inEl);
      if (this.canTarget(s)) {
        return s;
      }
    },
    olderShadow: function(shadow) {
      var os = shadow.olderShadowRoot;
      if (!os) {
        var se = shadow.querySelector('shadow');
        if (se) {
          os = se.olderShadowRoot;
        }
      }
      return os;
    },
    allShadows: function(element) {
      var shadows = [], s = this.shadow(element);
      while(s) {
        shadows.push(s);
        s = this.olderShadow(s);
      }
      return shadows;
    },
    searchRoot: function(inRoot, x, y) {
      var t, st, sr, os;
      if (inRoot) {
        t = inRoot.elementFromPoint(x, y);
        if (t) {
          // found element, check if it has a ShadowRoot
          sr = this.targetingShadow(t);
        } else if (inRoot !== document) {
          // check for sibling roots
          sr = this.olderShadow(inRoot);
        }
        // search other roots, fall back to light dom element
        return this.searchRoot(sr, x, y) || t;
      }
    },
    owner: function(element) {
      if (!element) {
        return document;
      }
      var s = element;
      // walk up until you hit the shadow root or document
      while (s.parentNode) {
        s = s.parentNode;
      }
      // the owner element is expected to be a Document or ShadowRoot
      if (s.nodeType != Node.DOCUMENT_NODE && s.nodeType != Node.DOCUMENT_FRAGMENT_NODE) {
        s = document;
      }
      return s;
    },
    findTarget: function(inEvent) {
      if (hasFullPath && inEvent.path && inEvent.path.length) {
        return inEvent.path[0];
      }
      var x = inEvent.clientX, y = inEvent.clientY;
      // if the listener is in the shadow root, it is much faster to start there
      var s = this.owner(inEvent.target);
      // if x, y is not in this root, fall back to document search
      if (!s.elementFromPoint(x, y)) {
        s = document;
      }
      return this.searchRoot(s, x, y);
    },
    findTouchAction: function(inEvent) {
      var n;
      if (hasFullPath && inEvent.path && inEvent.path.length) {
        var path = inEvent.path;
        for (var i = 0; i < path.length; i++) {
          n = path[i];
          if (n.nodeType === Node.ELEMENT_NODE && n.hasAttribute('touch-action')) {
            return n.getAttribute('touch-action');
          }
        }
      } else {
        n = inEvent.target;
        while(n) {
          if (n.nodeType === Node.ELEMENT_NODE && n.hasAttribute('touch-action')) {
            return n.getAttribute('touch-action');
          }
          n = n.parentNode || n.host;
        }
      }
      // auto is default
      return "auto";
    },
    LCA: function(a, b) {
      if (a === b) {
        return a;
      }
      if (a && !b) {
        return a;
      }
      if (b && !a) {
        return b;
      }
      if (!b && !a) {
        return document;
      }
      // fast case, a is a direct descendant of b or vice versa
      if (a.contains && a.contains(b)) {
        return a;
      }
      if (b.contains && b.contains(a)) {
        return b;
      }
      var adepth = this.depth(a);
      var bdepth = this.depth(b);
      var d = adepth - bdepth;
      if (d >= 0) {
        a = this.walk(a, d);
      } else {
        b = this.walk(b, -d);
      }
      while (a && b && a !== b) {
        a = a.parentNode || a.host;
        b = b.parentNode || b.host;
      }
      return a;
    },
    walk: function(n, u) {
      for (var i = 0; n && (i < u); i++) {
        n = n.parentNode || n.host;
      }
      return n;
    },
    depth: function(n) {
      var d = 0;
      while(n) {
        d++;
        n = n.parentNode || n.host;
      }
      return d;
    },
    deepContains: function(a, b) {
      var common = this.LCA(a, b);
      // if a is the common ancestor, it must "deeply" contain b
      return common === a;
    },
    insideNode: function(node, x, y) {
      var rect = node.getBoundingClientRect();
      return (rect.left <= x) && (x <= rect.right) && (rect.top <= y) && (y <= rect.bottom);
    },
    path: function(event) {
      var p;
      if (hasFullPath && event.path && event.path.length) {
        p = event.path;
      } else {
        p = [];
        var n = this.findTarget(event);
        while (n) {
          p.push(n);
          n = n.parentNode || n.host;
        }
      }
      return p;
    }
  };
  scope.targetFinding = target;
  /**
   * Given an event, finds the "deepest" node that could have been the original target before ShadowDOM retargetting
   *
   * @param {Event} Event An event object with clientX and clientY properties
   * @return {Element} The probable event origninator
   */
  scope.findTarget = target.findTarget.bind(target);
  /**
   * Determines if the "container" node deeply contains the "containee" node, including situations where the "containee" is contained by one or more ShadowDOM
   * roots.
   *
   * @param {Node} container
   * @param {Node} containee
   * @return {Boolean}
   */
  scope.deepContains = target.deepContains.bind(target);

  /**
   * Determines if the x/y position is inside the given node.
   *
   * Example:
   *
   *     function upHandler(event) {
   *       var innode = PolymerGestures.insideNode(event.target, event.clientX, event.clientY);
   *       if (innode) {
   *         // wait for tap?
   *       } else {
   *         // tap will never happen
   *       }
   *     }
   *
   * @param {Node} node
   * @param {Number} x Screen X position
   * @param {Number} y screen Y position
   * @return {Boolean}
   */
  scope.insideNode = target.insideNode;

})(window.PolymerGestures);

(function() {
  function shadowSelector(v) {
    return 'html /deep/ ' + selector(v);
  }
  function selector(v) {
    return '[touch-action="' + v + '"]';
  }
  function rule(v) {
    return '{ -ms-touch-action: ' + v + '; touch-action: ' + v + ';}';
  }
  var attrib2css = [
    'none',
    'auto',
    'pan-x',
    'pan-y',
    {
      rule: 'pan-x pan-y',
      selectors: [
        'pan-x pan-y',
        'pan-y pan-x'
      ]
    },
    'manipulation'
  ];
  var styles = '';
  // only install stylesheet if the browser has touch action support
  var hasTouchAction = typeof document.head.style.touchAction === 'string';
  // only add shadow selectors if shadowdom is supported
  var hasShadowRoot = !window.ShadowDOMPolyfill && document.head.createShadowRoot;

  if (hasTouchAction) {
    attrib2css.forEach(function(r) {
      if (String(r) === r) {
        styles += selector(r) + rule(r) + '\n';
        if (hasShadowRoot) {
          styles += shadowSelector(r) + rule(r) + '\n';
        }
      } else {
        styles += r.selectors.map(selector) + rule(r.rule) + '\n';
        if (hasShadowRoot) {
          styles += r.selectors.map(shadowSelector) + rule(r.rule) + '\n';
        }
      }
    });

    var el = document.createElement('style');
    el.textContent = styles;
    document.head.appendChild(el);
  }
})();

/**
 * This is the constructor for new PointerEvents.
 *
 * New Pointer Events must be given a type, and an optional dictionary of
 * initialization properties.
 *
 * Due to certain platform requirements, events returned from the constructor
 * identify as MouseEvents.
 *
 * @constructor
 * @param {String} inType The type of the event to create.
 * @param {Object} [inDict] An optional dictionary of initial event properties.
 * @return {Event} A new PointerEvent of type `inType` and initialized with properties from `inDict`.
 */
(function(scope) {

  var MOUSE_PROPS = [
    'bubbles',
    'cancelable',
    'view',
    'detail',
    'screenX',
    'screenY',
    'clientX',
    'clientY',
    'ctrlKey',
    'altKey',
    'shiftKey',
    'metaKey',
    'button',
    'relatedTarget',
    'pageX',
    'pageY'
  ];

  var MOUSE_DEFAULTS = [
    false,
    false,
    null,
    null,
    0,
    0,
    0,
    0,
    false,
    false,
    false,
    false,
    0,
    null,
    0,
    0
  ];

  var NOP_FACTORY = function(){ return function(){}; };

  var eventFactory = {
    // TODO(dfreedm): this is overridden by tap recognizer, needs review
    preventTap: NOP_FACTORY,
    makeBaseEvent: function(inType, inDict) {
      var e = document.createEvent('Event');
      e.initEvent(inType, inDict.bubbles || false, inDict.cancelable || false);
      e.preventTap = eventFactory.preventTap(e);
      return e;
    },
    makeGestureEvent: function(inType, inDict) {
      inDict = inDict || Object.create(null);

      var e = this.makeBaseEvent(inType, inDict);
      for (var i = 0, keys = Object.keys(inDict), k; i < keys.length; i++) {
        k = keys[i];
        if( k !== 'bubbles' && k !== 'cancelable' ) {
           e[k] = inDict[k];
        }
      }
      return e;
    },
    makePointerEvent: function(inType, inDict) {
      inDict = inDict || Object.create(null);

      var e = this.makeBaseEvent(inType, inDict);
      // define inherited MouseEvent properties
      for(var i = 2, p; i < MOUSE_PROPS.length; i++) {
        p = MOUSE_PROPS[i];
        e[p] = inDict[p] || MOUSE_DEFAULTS[i];
      }
      e.buttons = inDict.buttons || 0;

      // Spec requires that pointers without pressure specified use 0.5 for down
      // state and 0 for up state.
      var pressure = 0;
      if (inDict.pressure) {
        pressure = inDict.pressure;
      } else {
        pressure = e.buttons ? 0.5 : 0;
      }

      // add x/y properties aliased to clientX/Y
      e.x = e.clientX;
      e.y = e.clientY;

      // define the properties of the PointerEvent interface
      e.pointerId = inDict.pointerId || 0;
      e.width = inDict.width || 0;
      e.height = inDict.height || 0;
      e.pressure = pressure;
      e.tiltX = inDict.tiltX || 0;
      e.tiltY = inDict.tiltY || 0;
      e.pointerType = inDict.pointerType || '';
      e.hwTimestamp = inDict.hwTimestamp || 0;
      e.isPrimary = inDict.isPrimary || false;
      e._source = inDict._source || '';
      return e;
    }
  };

  scope.eventFactory = eventFactory;
})(window.PolymerGestures);

/**
 * This module implements an map of pointer states
 */
(function(scope) {
  var USE_MAP = window.Map && window.Map.prototype.forEach;
  var POINTERS_FN = function(){ return this.size; };
  function PointerMap() {
    if (USE_MAP) {
      var m = new Map();
      m.pointers = POINTERS_FN;
      return m;
    } else {
      this.keys = [];
      this.values = [];
    }
  }

  PointerMap.prototype = {
    set: function(inId, inEvent) {
      var i = this.keys.indexOf(inId);
      if (i > -1) {
        this.values[i] = inEvent;
      } else {
        this.keys.push(inId);
        this.values.push(inEvent);
      }
    },
    has: function(inId) {
      return this.keys.indexOf(inId) > -1;
    },
    'delete': function(inId) {
      var i = this.keys.indexOf(inId);
      if (i > -1) {
        this.keys.splice(i, 1);
        this.values.splice(i, 1);
      }
    },
    get: function(inId) {
      var i = this.keys.indexOf(inId);
      return this.values[i];
    },
    clear: function() {
      this.keys.length = 0;
      this.values.length = 0;
    },
    // return value, key, map
    forEach: function(callback, thisArg) {
      this.values.forEach(function(v, i) {
        callback.call(thisArg, v, this.keys[i], this);
      }, this);
    },
    pointers: function() {
      return this.keys.length;
    }
  };

  scope.PointerMap = PointerMap;
})(window.PolymerGestures);

(function(scope) {
  var CLONE_PROPS = [
    // MouseEvent
    'bubbles',
    'cancelable',
    'view',
    'detail',
    'screenX',
    'screenY',
    'clientX',
    'clientY',
    'ctrlKey',
    'altKey',
    'shiftKey',
    'metaKey',
    'button',
    'relatedTarget',
    // DOM Level 3
    'buttons',
    // PointerEvent
    'pointerId',
    'width',
    'height',
    'pressure',
    'tiltX',
    'tiltY',
    'pointerType',
    'hwTimestamp',
    'isPrimary',
    // event instance
    'type',
    'target',
    'currentTarget',
    'which',
    'pageX',
    'pageY',
    'timeStamp',
    // gesture addons
    'preventTap',
    'tapPrevented',
    '_source'
  ];

  var CLONE_DEFAULTS = [
    // MouseEvent
    false,
    false,
    null,
    null,
    0,
    0,
    0,
    0,
    false,
    false,
    false,
    false,
    0,
    null,
    // DOM Level 3
    0,
    // PointerEvent
    0,
    0,
    0,
    0,
    0,
    0,
    '',
    0,
    false,
    // event instance
    '',
    null,
    null,
    0,
    0,
    0,
    0,
    function(){},
    false
  ];

  var HAS_SVG_INSTANCE = (typeof SVGElementInstance !== 'undefined');

  var eventFactory = scope.eventFactory;

  // set of recognizers to run for the currently handled event
  var currentGestures;

  /**
   * This module is for normalizing events. Mouse and Touch events will be
   * collected here, and fire PointerEvents that have the same semantics, no
   * matter the source.
   * Events fired:
   *   - pointerdown: a pointing is added
   *   - pointerup: a pointer is removed
   *   - pointermove: a pointer is moved
   *   - pointerover: a pointer crosses into an element
   *   - pointerout: a pointer leaves an element
   *   - pointercancel: a pointer will no longer generate events
   */
  var dispatcher = {
    IS_IOS: false,
    pointermap: new scope.PointerMap(),
    requiredGestures: new scope.PointerMap(),
    eventMap: Object.create(null),
    // Scope objects for native events.
    // This exists for ease of testing.
    eventSources: Object.create(null),
    eventSourceList: [],
    gestures: [],
    // map gesture event -> {listeners: int, index: gestures[int]}
    dependencyMap: {
      // make sure down and up are in the map to trigger "register"
      down: {listeners: 0, index: -1},
      up: {listeners: 0, index: -1}
    },
    gestureQueue: [],
    /**
     * Add a new event source that will generate pointer events.
     *
     * `inSource` must contain an array of event names named `events`, and
     * functions with the names specified in the `events` array.
     * @param {string} name A name for the event source
     * @param {Object} source A new source of platform events.
     */
    registerSource: function(name, source) {
      var s = source;
      var newEvents = s.events;
      if (newEvents) {
        newEvents.forEach(function(e) {
          if (s[e]) {
            this.eventMap[e] = s[e].bind(s);
          }
        }, this);
        this.eventSources[name] = s;
        this.eventSourceList.push(s);
      }
    },
    registerGesture: function(name, source) {
      var obj = Object.create(null);
      obj.listeners = 0;
      obj.index = this.gestures.length;
      for (var i = 0, g; i < source.exposes.length; i++) {
        g = source.exposes[i].toLowerCase();
        this.dependencyMap[g] = obj;
      }
      this.gestures.push(source);
    },
    register: function(element, initial) {
      var l = this.eventSourceList.length;
      for (var i = 0, es; (i < l) && (es = this.eventSourceList[i]); i++) {
        // call eventsource register
        es.register.call(es, element, initial);
      }
    },
    unregister: function(element) {
      var l = this.eventSourceList.length;
      for (var i = 0, es; (i < l) && (es = this.eventSourceList[i]); i++) {
        // call eventsource register
        es.unregister.call(es, element);
      }
    },
    // EVENTS
    down: function(inEvent) {
      this.requiredGestures.set(inEvent.pointerId, currentGestures);
      this.fireEvent('down', inEvent);
    },
    move: function(inEvent) {
      // pipe move events into gesture queue directly
      inEvent.type = 'move';
      this.fillGestureQueue(inEvent);
    },
    up: function(inEvent) {
      this.fireEvent('up', inEvent);
      this.requiredGestures.delete(inEvent.pointerId);
    },
    cancel: function(inEvent) {
      inEvent.tapPrevented = true;
      this.fireEvent('up', inEvent);
      this.requiredGestures.delete(inEvent.pointerId);
    },
    addGestureDependency: function(node, currentGestures) {
      var gesturesWanted = node._pgEvents;
      if (gesturesWanted && currentGestures) {
        var gk = Object.keys(gesturesWanted);
        for (var i = 0, r, ri, g; i < gk.length; i++) {
          // gesture
          g = gk[i];
          if (gesturesWanted[g] > 0) {
            // lookup gesture recognizer
            r = this.dependencyMap[g];
            // recognizer index
            ri = r ? r.index : -1;
            currentGestures[ri] = true;
          }
        }
      }
    },
    // LISTENER LOGIC
    eventHandler: function(inEvent) {
      // This is used to prevent multiple dispatch of events from
      // platform events. This can happen when two elements in different scopes
      // are set up to create pointer events, which is relevant to Shadow DOM.

      var type = inEvent.type;

      // only generate the list of desired events on "down"
      if (type === 'touchstart' || type === 'mousedown' || type === 'pointerdown' || type === 'MSPointerDown') {
        if (!inEvent._handledByPG) {
          currentGestures = {};
        }

        // in IOS mode, there is only a listener on the document, so this is not re-entrant
        if (this.IS_IOS) {
          var ev = inEvent;
          if (type === 'touchstart') {
            var ct = inEvent.changedTouches[0];
            // set up a fake event to give to the path builder
            ev = {target: inEvent.target, clientX: ct.clientX, clientY: ct.clientY, path: inEvent.path};
          }
          // use event path if available, otherwise build a path from target finding
          var nodes = inEvent.path || scope.targetFinding.path(ev);
          for (var i = 0, n; i < nodes.length; i++) {
            n = nodes[i];
            this.addGestureDependency(n, currentGestures);
          }
        } else {
          this.addGestureDependency(inEvent.currentTarget, currentGestures);
        }
      }

      if (inEvent._handledByPG) {
        return;
      }
      var fn = this.eventMap && this.eventMap[type];
      if (fn) {
        fn(inEvent);
      }
      inEvent._handledByPG = true;
    },
    // set up event listeners
    listen: function(target, events) {
      for (var i = 0, l = events.length, e; (i < l) && (e = events[i]); i++) {
        this.addEvent(target, e);
      }
    },
    // remove event listeners
    unlisten: function(target, events) {
      for (var i = 0, l = events.length, e; (i < l) && (e = events[i]); i++) {
        this.removeEvent(target, e);
      }
    },
    addEvent: function(target, eventName) {
      target.addEventListener(eventName, this.boundHandler);
    },
    removeEvent: function(target, eventName) {
      target.removeEventListener(eventName, this.boundHandler);
    },
    // EVENT CREATION AND TRACKING
    /**
     * Creates a new Event of type `inType`, based on the information in
     * `inEvent`.
     *
     * @param {string} inType A string representing the type of event to create
     * @param {Event} inEvent A platform event with a target
     * @return {Event} A PointerEvent of type `inType`
     */
    makeEvent: function(inType, inEvent) {
      var e = eventFactory.makePointerEvent(inType, inEvent);
      e.preventDefault = inEvent.preventDefault;
      e.tapPrevented = inEvent.tapPrevented;
      e._target = e._target || inEvent.target;
      return e;
    },
    // make and dispatch an event in one call
    fireEvent: function(inType, inEvent) {
      var e = this.makeEvent(inType, inEvent);
      return this.dispatchEvent(e);
    },
    /**
     * Returns a snapshot of inEvent, with writable properties.
     *
     * @param {Event} inEvent An event that contains properties to copy.
     * @return {Object} An object containing shallow copies of `inEvent`'s
     *    properties.
     */
    cloneEvent: function(inEvent) {
      var eventCopy = Object.create(null), p;
      for (var i = 0; i < CLONE_PROPS.length; i++) {
        p = CLONE_PROPS[i];
        eventCopy[p] = inEvent[p] || CLONE_DEFAULTS[i];
        // Work around SVGInstanceElement shadow tree
        // Return the <use> element that is represented by the instance for Safari, Chrome, IE.
        // This is the behavior implemented by Firefox.
        if (p === 'target' || p === 'relatedTarget') {
          if (HAS_SVG_INSTANCE && eventCopy[p] instanceof SVGElementInstance) {
            eventCopy[p] = eventCopy[p].correspondingUseElement;
          }
        }
      }
      // keep the semantics of preventDefault
      eventCopy.preventDefault = function() {
        inEvent.preventDefault();
      };
      return eventCopy;
    },
    /**
     * Dispatches the event to its target.
     *
     * @param {Event} inEvent The event to be dispatched.
     * @return {Boolean} True if an event handler returns true, false otherwise.
     */
    dispatchEvent: function(inEvent) {
      var t = inEvent._target;
      if (t) {
        t.dispatchEvent(inEvent);
        // clone the event for the gesture system to process
        // clone after dispatch to pick up gesture prevention code
        var clone = this.cloneEvent(inEvent);
        clone.target = t;
        this.fillGestureQueue(clone);
      }
    },
    gestureTrigger: function() {
      // process the gesture queue
      for (var i = 0, e, rg; i < this.gestureQueue.length; i++) {
        e = this.gestureQueue[i];
        rg = e._requiredGestures;
        if (rg) {
          for (var j = 0, g, fn; j < this.gestures.length; j++) {
            // only run recognizer if an element in the source event's path is listening for those gestures
            if (rg[j]) {
              g = this.gestures[j];
              fn = g[e.type];
              if (fn) {
                fn.call(g, e);
              }
            }
          }
        }
      }
      this.gestureQueue.length = 0;
    },
    fillGestureQueue: function(ev) {
      // only trigger the gesture queue once
      if (!this.gestureQueue.length) {
        requestAnimationFrame(this.boundGestureTrigger);
      }
      ev._requiredGestures = this.requiredGestures.get(ev.pointerId);
      this.gestureQueue.push(ev);
    }
  };
  dispatcher.boundHandler = dispatcher.eventHandler.bind(dispatcher);
  dispatcher.boundGestureTrigger = dispatcher.gestureTrigger.bind(dispatcher);
  scope.dispatcher = dispatcher;

  /**
   * Listen for `gesture` on `node` with the `handler` function
   *
   * If `handler` is the first listener for `gesture`, the underlying gesture recognizer is then enabled.
   *
   * @param {Element} node
   * @param {string} gesture
   * @return Boolean `gesture` is a valid gesture
   */
  scope.activateGesture = function(node, gesture) {
    var g = gesture.toLowerCase();
    var dep = dispatcher.dependencyMap[g];
    if (dep) {
      var recognizer = dispatcher.gestures[dep.index];
      if (!node._pgListeners) {
        dispatcher.register(node);
        node._pgListeners = 0;
      }
      // TODO(dfreedm): re-evaluate bookkeeping to avoid using attributes
      if (recognizer) {
        var touchAction = recognizer.defaultActions && recognizer.defaultActions[g];
        var actionNode;
        switch(node.nodeType) {
          case Node.ELEMENT_NODE:
            actionNode = node;
          break;
          case Node.DOCUMENT_FRAGMENT_NODE:
            actionNode = node.host;
          break;
          default:
            actionNode = null;
          break;
        }
        if (touchAction && actionNode && !actionNode.hasAttribute('touch-action')) {
          actionNode.setAttribute('touch-action', touchAction);
        }
      }
      if (!node._pgEvents) {
        node._pgEvents = {};
      }
      node._pgEvents[g] = (node._pgEvents[g] || 0) + 1;
      node._pgListeners++;
    }
    return Boolean(dep);
  };

  /**
   *
   * Listen for `gesture` from `node` with `handler` function.
   *
   * @param {Element} node
   * @param {string} gesture
   * @param {Function} handler
   * @param {Boolean} capture
   */
  scope.addEventListener = function(node, gesture, handler, capture) {
    if (handler) {
      scope.activateGesture(node, gesture);
      node.addEventListener(gesture, handler, capture);
    }
  };

  /**
   * Tears down the gesture configuration for `node`
   *
   * If `handler` is the last listener for `gesture`, the underlying gesture recognizer is disabled.
   *
   * @param {Element} node
   * @param {string} gesture
   * @return Boolean `gesture` is a valid gesture
   */
  scope.deactivateGesture = function(node, gesture) {
    var g = gesture.toLowerCase();
    var dep = dispatcher.dependencyMap[g];
    if (dep) {
      if (node._pgListeners > 0) {
        node._pgListeners--;
      }
      if (node._pgListeners === 0) {
        dispatcher.unregister(node);
      }
      if (node._pgEvents) {
        if (node._pgEvents[g] > 0) {
          node._pgEvents[g]--;
        } else {
          node._pgEvents[g] = 0;
        }
      }
    }
    return Boolean(dep);
  };

  /**
   * Stop listening for `gesture` from `node` with `handler` function.
   *
   * @param {Element} node
   * @param {string} gesture
   * @param {Function} handler
   * @param {Boolean} capture
   */
  scope.removeEventListener = function(node, gesture, handler, capture) {
    if (handler) {
      scope.deactivateGesture(node, gesture);
      node.removeEventListener(gesture, handler, capture);
    }
  };
})(window.PolymerGestures);

(function(scope) {
  var dispatcher = scope.dispatcher;
  var pointermap = dispatcher.pointermap;
  // radius around touchend that swallows mouse events
  var DEDUP_DIST = 25;

  var WHICH_TO_BUTTONS = [0, 1, 4, 2];

  var currentButtons = 0;

  var FIREFOX_LINUX = /Linux.*Firefox\//i;

  var HAS_BUTTONS = (function() {
    // firefox on linux returns spec-incorrect values for mouseup.buttons
    // https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent.buttons#See_also
    // https://codereview.chromium.org/727593003/#msg16
    if (FIREFOX_LINUX.test(navigator.userAgent)) {
      return false;
    }
    try {
      return new MouseEvent('test', {buttons: 1}).buttons === 1;
    } catch (e) {
      return false;
    }
  })();

  // handler block for native mouse events
  var mouseEvents = {
    POINTER_ID: 1,
    POINTER_TYPE: 'mouse',
    events: [
      'mousedown',
      'mousemove',
      'mouseup'
    ],
    exposes: [
      'down',
      'up',
      'move'
    ],
    register: function(target) {
      dispatcher.listen(target, this.events);
    },
    unregister: function(target) {
      if (target.nodeType === Node.DOCUMENT_NODE) {
        return;
      }
      dispatcher.unlisten(target, this.events);
    },
    lastTouches: [],
    // collide with the global mouse listener
    isEventSimulatedFromTouch: function(inEvent) {
      var lts = this.lastTouches;
      var x = inEvent.clientX, y = inEvent.clientY;
      for (var i = 0, l = lts.length, t; i < l && (t = lts[i]); i++) {
        // simulated mouse events will be swallowed near a primary touchend
        var dx = Math.abs(x - t.x), dy = Math.abs(y - t.y);
        if (dx <= DEDUP_DIST && dy <= DEDUP_DIST) {
          return true;
        }
      }
    },
    prepareEvent: function(inEvent) {
      var e = dispatcher.cloneEvent(inEvent);
      e.pointerId = this.POINTER_ID;
      e.isPrimary = true;
      e.pointerType = this.POINTER_TYPE;
      e._source = 'mouse';
      if (!HAS_BUTTONS) {
        var type = inEvent.type;
        var bit = WHICH_TO_BUTTONS[inEvent.which] || 0;
        if (type === 'mousedown') {
          currentButtons |= bit;
        } else if (type === 'mouseup') {
          currentButtons &= ~bit;
        }
        e.buttons = currentButtons;
      }
      return e;
    },
    mousedown: function(inEvent) {
      if (!this.isEventSimulatedFromTouch(inEvent)) {
        var p = pointermap.has(this.POINTER_ID);
        var e = this.prepareEvent(inEvent);
        e.target = scope.findTarget(inEvent);
        pointermap.set(this.POINTER_ID, e.target);
        dispatcher.down(e);
      }
    },
    mousemove: function(inEvent) {
      if (!this.isEventSimulatedFromTouch(inEvent)) {
        var target = pointermap.get(this.POINTER_ID);
        if (target) {
          var e = this.prepareEvent(inEvent);
          e.target = target;
          // handle case where we missed a mouseup
          if ((HAS_BUTTONS ? e.buttons : e.which) === 0) {
            if (!HAS_BUTTONS) {
              currentButtons = e.buttons = 0;
            }
            dispatcher.cancel(e);
            this.cleanupMouse(e.buttons);
          } else {
            dispatcher.move(e);
          }
        }
      }
    },
    mouseup: function(inEvent) {
      if (!this.isEventSimulatedFromTouch(inEvent)) {
        var e = this.prepareEvent(inEvent);
        e.relatedTarget = scope.findTarget(inEvent);
        e.target = pointermap.get(this.POINTER_ID);
        dispatcher.up(e);
        this.cleanupMouse(e.buttons);
      }
    },
    cleanupMouse: function(buttons) {
      if (buttons === 0) {
        pointermap.delete(this.POINTER_ID);
      }
    }
  };

  scope.mouseEvents = mouseEvents;
})(window.PolymerGestures);

(function(scope) {
  var dispatcher = scope.dispatcher;
  var allShadows = scope.targetFinding.allShadows.bind(scope.targetFinding);
  var pointermap = dispatcher.pointermap;
  var touchMap = Array.prototype.map.call.bind(Array.prototype.map);
  // This should be long enough to ignore compat mouse events made by touch
  var DEDUP_TIMEOUT = 2500;
  var DEDUP_DIST = 25;
  var CLICK_COUNT_TIMEOUT = 200;
  var HYSTERESIS = 20;
  var ATTRIB = 'touch-action';
  // TODO(dfreedm): disable until http://crbug.com/399765 is resolved
  // var HAS_TOUCH_ACTION = ATTRIB in document.head.style;
  var HAS_TOUCH_ACTION = false;

  // handler block for native touch events
  var touchEvents = {
    IS_IOS: false,
    events: [
      'touchstart',
      'touchmove',
      'touchend',
      'touchcancel'
    ],
    exposes: [
      'down',
      'up',
      'move'
    ],
    register: function(target, initial) {
      if (this.IS_IOS ? initial : !initial) {
        dispatcher.listen(target, this.events);
      }
    },
    unregister: function(target) {
      if (!this.IS_IOS) {
        dispatcher.unlisten(target, this.events);
      }
    },
    scrollTypes: {
      EMITTER: 'none',
      XSCROLLER: 'pan-x',
      YSCROLLER: 'pan-y',
    },
    touchActionToScrollType: function(touchAction) {
      var t = touchAction;
      var st = this.scrollTypes;
      if (t === st.EMITTER) {
        return 'none';
      } else if (t === st.XSCROLLER) {
        return 'X';
      } else if (t === st.YSCROLLER) {
        return 'Y';
      } else {
        return 'XY';
      }
    },
    POINTER_TYPE: 'touch',
    firstTouch: null,
    isPrimaryTouch: function(inTouch) {
      return this.firstTouch === inTouch.identifier;
    },
    setPrimaryTouch: function(inTouch) {
      // set primary touch if there no pointers, or the only pointer is the mouse
      if (pointermap.pointers() === 0 || (pointermap.pointers() === 1 && pointermap.has(1))) {
        this.firstTouch = inTouch.identifier;
        this.firstXY = {X: inTouch.clientX, Y: inTouch.clientY};
        this.firstTarget = inTouch.target;
        this.scrolling = null;
        this.cancelResetClickCount();
      }
    },
    removePrimaryPointer: function(inPointer) {
      if (inPointer.isPrimary) {
        this.firstTouch = null;
        this.firstXY = null;
        this.resetClickCount();
      }
    },
    clickCount: 0,
    resetId: null,
    resetClickCount: function() {
      var fn = function() {
        this.clickCount = 0;
        this.resetId = null;
      }.bind(this);
      this.resetId = setTimeout(fn, CLICK_COUNT_TIMEOUT);
    },
    cancelResetClickCount: function() {
      if (this.resetId) {
        clearTimeout(this.resetId);
      }
    },
    typeToButtons: function(type) {
      var ret = 0;
      if (type === 'touchstart' || type === 'touchmove') {
        ret = 1;
      }
      return ret;
    },
    findTarget: function(touch, id) {
      if (this.currentTouchEvent.type === 'touchstart') {
        if (this.isPrimaryTouch(touch)) {
          var fastPath = {
            clientX: touch.clientX,
            clientY: touch.clientY,
            path: this.currentTouchEvent.path,
            target: this.currentTouchEvent.target
          };
          return scope.findTarget(fastPath);
        } else {
          return scope.findTarget(touch);
        }
      }
      // reuse target we found in touchstart
      return pointermap.get(id);
    },
    touchToPointer: function(inTouch) {
      var cte = this.currentTouchEvent;
      var e = dispatcher.cloneEvent(inTouch);
      // Spec specifies that pointerId 1 is reserved for Mouse.
      // Touch identifiers can start at 0.
      // Add 2 to the touch identifier for compatibility.
      var id = e.pointerId = inTouch.identifier + 2;
      e.target = this.findTarget(inTouch, id);
      e.bubbles = true;
      e.cancelable = true;
      e.detail = this.clickCount;
      e.buttons = this.typeToButtons(cte.type);
      e.width = inTouch.webkitRadiusX || inTouch.radiusX || 0;
      e.height = inTouch.webkitRadiusY || inTouch.radiusY || 0;
      e.pressure = inTouch.webkitForce || inTouch.force || 0.5;
      e.isPrimary = this.isPrimaryTouch(inTouch);
      e.pointerType = this.POINTER_TYPE;
      e._source = 'touch';
      // forward touch preventDefaults
      var self = this;
      e.preventDefault = function() {
        self.scrolling = false;
        self.firstXY = null;
        cte.preventDefault();
      };
      return e;
    },
    processTouches: function(inEvent, inFunction) {
      var tl = inEvent.changedTouches;
      this.currentTouchEvent = inEvent;
      for (var i = 0, t, p; i < tl.length; i++) {
        t = tl[i];
        p = this.touchToPointer(t);
        if (inEvent.type === 'touchstart') {
          pointermap.set(p.pointerId, p.target);
        }
        if (pointermap.has(p.pointerId)) {
          inFunction.call(this, p);
        }
        if (inEvent.type === 'touchend' || inEvent._cancel) {
          this.cleanUpPointer(p);
        }
      }
    },
    // For single axis scrollers, determines whether the element should emit
    // pointer events or behave as a scroller
    shouldScroll: function(inEvent) {
      if (this.firstXY) {
        var ret;
        var touchAction = scope.targetFinding.findTouchAction(inEvent);
        var scrollAxis = this.touchActionToScrollType(touchAction);
        if (scrollAxis === 'none') {
          // this element is a touch-action: none, should never scroll
          ret = false;
        } else if (scrollAxis === 'XY') {
          // this element should always scroll
          ret = true;
        } else {
          var t = inEvent.changedTouches[0];
          // check the intended scroll axis, and other axis
          var a = scrollAxis;
          var oa = scrollAxis === 'Y' ? 'X' : 'Y';
          var da = Math.abs(t['client' + a] - this.firstXY[a]);
          var doa = Math.abs(t['client' + oa] - this.firstXY[oa]);
          // if delta in the scroll axis > delta other axis, scroll instead of
          // making events
          ret = da >= doa;
        }
        return ret;
      }
    },
    findTouch: function(inTL, inId) {
      for (var i = 0, l = inTL.length, t; i < l && (t = inTL[i]); i++) {
        if (t.identifier === inId) {
          return true;
        }
      }
    },
    // In some instances, a touchstart can happen without a touchend. This
    // leaves the pointermap in a broken state.
    // Therefore, on every touchstart, we remove the touches that did not fire a
    // touchend event.
    // To keep state globally consistent, we fire a
    // pointercancel for this "abandoned" touch
    vacuumTouches: function(inEvent) {
      var tl = inEvent.touches;
      // pointermap.pointers() should be < tl.length here, as the touchstart has not
      // been processed yet.
      if (pointermap.pointers() >= tl.length) {
        var d = [];
        pointermap.forEach(function(value, key) {
          // Never remove pointerId == 1, which is mouse.
          // Touch identifiers are 2 smaller than their pointerId, which is the
          // index in pointermap.
          if (key !== 1 && !this.findTouch(tl, key - 2)) {
            var p = value;
            d.push(p);
          }
        }, this);
        d.forEach(function(p) {
          this.cancel(p);
          pointermap.delete(p.pointerId);
        }, this);
      }
    },
    touchstart: function(inEvent) {
      this.vacuumTouches(inEvent);
      this.setPrimaryTouch(inEvent.changedTouches[0]);
      this.dedupSynthMouse(inEvent);
      if (!this.scrolling) {
        this.clickCount++;
        this.processTouches(inEvent, this.down);
      }
    },
    down: function(inPointer) {
      dispatcher.down(inPointer);
    },
    touchmove: function(inEvent) {
      if (HAS_TOUCH_ACTION) {
        // touchevent.cancelable == false is sent when the page is scrolling under native Touch Action in Chrome 36
        // https://groups.google.com/a/chromium.org/d/msg/input-dev/wHnyukcYBcA/b9kmtwM1jJQJ
        if (inEvent.cancelable) {
          this.processTouches(inEvent, this.move);
        }
      } else {
        if (!this.scrolling) {
          if (this.scrolling === null && this.shouldScroll(inEvent)) {
            this.scrolling = true;
          } else {
            this.scrolling = false;
            inEvent.preventDefault();
            this.processTouches(inEvent, this.move);
          }
        } else if (this.firstXY) {
          var t = inEvent.changedTouches[0];
          var dx = t.clientX - this.firstXY.X;
          var dy = t.clientY - this.firstXY.Y;
          var dd = Math.sqrt(dx * dx + dy * dy);
          if (dd >= HYSTERESIS) {
            this.touchcancel(inEvent);
            this.scrolling = true;
            this.firstXY = null;
          }
        }
      }
    },
    move: function(inPointer) {
      dispatcher.move(inPointer);
    },
    touchend: function(inEvent) {
      this.dedupSynthMouse(inEvent);
      this.processTouches(inEvent, this.up);
    },
    up: function(inPointer) {
      inPointer.relatedTarget = scope.findTarget(inPointer);
      dispatcher.up(inPointer);
    },
    cancel: function(inPointer) {
      dispatcher.cancel(inPointer);
    },
    touchcancel: function(inEvent) {
      inEvent._cancel = true;
      this.processTouches(inEvent, this.cancel);
    },
    cleanUpPointer: function(inPointer) {
      pointermap['delete'](inPointer.pointerId);
      this.removePrimaryPointer(inPointer);
    },
    // prevent synth mouse events from creating pointer events
    dedupSynthMouse: function(inEvent) {
      var lts = scope.mouseEvents.lastTouches;
      var t = inEvent.changedTouches[0];
      // only the primary finger will synth mouse events
      if (this.isPrimaryTouch(t)) {
        // remember x/y of last touch
        var lt = {x: t.clientX, y: t.clientY};
        lts.push(lt);
        var fn = (function(lts, lt){
          var i = lts.indexOf(lt);
          if (i > -1) {
            lts.splice(i, 1);
          }
        }).bind(null, lts, lt);
        setTimeout(fn, DEDUP_TIMEOUT);
      }
    }
  };

  // prevent "ghost clicks" that come from elements that were removed in a touch handler
  var STOP_PROP_FN = Event.prototype.stopImmediatePropagation || Event.prototype.stopPropagation;
  document.addEventListener('click', function(ev) {
    var x = ev.clientX, y = ev.clientY;
    // check if a click is within DEDUP_DIST px radius of the touchstart
    var closeTo = function(touch) {
      var dx = Math.abs(x - touch.x), dy = Math.abs(y - touch.y);
      return (dx <= DEDUP_DIST && dy <= DEDUP_DIST);
    };
    // if click coordinates are close to touch coordinates, assume the click came from a touch
    var wasTouched = scope.mouseEvents.lastTouches.some(closeTo);
    // if the click came from touch, and the touchstart target is not in the path of the click event,
    // then the touchstart target was probably removed, and the click should be "busted"
    var path = scope.targetFinding.path(ev);
    if (wasTouched) {
      for (var i = 0; i < path.length; i++) {
        if (path[i] === touchEvents.firstTarget) {
          return;
        }
      }
      ev.preventDefault();
      STOP_PROP_FN.call(ev);
    }
  }, true);

  scope.touchEvents = touchEvents;
})(window.PolymerGestures);

(function(scope) {
  var dispatcher = scope.dispatcher;
  var pointermap = dispatcher.pointermap;
  var HAS_BITMAP_TYPE = window.MSPointerEvent && typeof window.MSPointerEvent.MSPOINTER_TYPE_MOUSE === 'number';
  var msEvents = {
    events: [
      'MSPointerDown',
      'MSPointerMove',
      'MSPointerUp',
      'MSPointerCancel',
    ],
    register: function(target) {
      dispatcher.listen(target, this.events);
    },
    unregister: function(target) {
      if (target.nodeType === Node.DOCUMENT_NODE) {
        return;
      }
      dispatcher.unlisten(target, this.events);
    },
    POINTER_TYPES: [
      '',
      'unavailable',
      'touch',
      'pen',
      'mouse'
    ],
    prepareEvent: function(inEvent) {
      var e = inEvent;
      e = dispatcher.cloneEvent(inEvent);
      if (HAS_BITMAP_TYPE) {
        e.pointerType = this.POINTER_TYPES[inEvent.pointerType];
      }
      e._source = 'ms';
      return e;
    },
    cleanup: function(id) {
      pointermap['delete'](id);
    },
    MSPointerDown: function(inEvent) {
      var e = this.prepareEvent(inEvent);
      e.target = scope.findTarget(inEvent);
      pointermap.set(inEvent.pointerId, e.target);
      dispatcher.down(e);
    },
    MSPointerMove: function(inEvent) {
      var target = pointermap.get(inEvent.pointerId);
      if (target) {
        var e = this.prepareEvent(inEvent);
        e.target = target;
        dispatcher.move(e);
      }
    },
    MSPointerUp: function(inEvent) {
      var e = this.prepareEvent(inEvent);
      e.relatedTarget = scope.findTarget(inEvent);
      e.target = pointermap.get(e.pointerId);
      dispatcher.up(e);
      this.cleanup(inEvent.pointerId);
    },
    MSPointerCancel: function(inEvent) {
      var e = this.prepareEvent(inEvent);
      e.relatedTarget = scope.findTarget(inEvent);
      e.target = pointermap.get(e.pointerId);
      dispatcher.cancel(e);
      this.cleanup(inEvent.pointerId);
    }
  };

  scope.msEvents = msEvents;
})(window.PolymerGestures);

(function(scope) {
  var dispatcher = scope.dispatcher;
  var pointermap = dispatcher.pointermap;
  var pointerEvents = {
    events: [
      'pointerdown',
      'pointermove',
      'pointerup',
      'pointercancel'
    ],
    prepareEvent: function(inEvent) {
      var e = dispatcher.cloneEvent(inEvent);
      e._source = 'pointer';
      return e;
    },
    register: function(target) {
      dispatcher.listen(target, this.events);
    },
    unregister: function(target) {
      if (target.nodeType === Node.DOCUMENT_NODE) {
        return;
      }
      dispatcher.unlisten(target, this.events);
    },
    cleanup: function(id) {
      pointermap['delete'](id);
    },
    pointerdown: function(inEvent) {
      var e = this.prepareEvent(inEvent);
      e.target = scope.findTarget(inEvent);
      pointermap.set(e.pointerId, e.target);
      dispatcher.down(e);
    },
    pointermove: function(inEvent) {
      var target = pointermap.get(inEvent.pointerId);
      if (target) {
        var e = this.prepareEvent(inEvent);
        e.target = target;
        dispatcher.move(e);
      }
    },
    pointerup: function(inEvent) {
      var e = this.prepareEvent(inEvent);
      e.relatedTarget = scope.findTarget(inEvent);
      e.target = pointermap.get(e.pointerId);
      dispatcher.up(e);
      this.cleanup(inEvent.pointerId);
    },
    pointercancel: function(inEvent) {
      var e = this.prepareEvent(inEvent);
      e.relatedTarget = scope.findTarget(inEvent);
      e.target = pointermap.get(e.pointerId);
      dispatcher.cancel(e);
      this.cleanup(inEvent.pointerId);
    }
  };

  scope.pointerEvents = pointerEvents;
})(window.PolymerGestures);

/**
 * This module contains the handlers for native platform events.
 * From here, the dispatcher is called to create unified pointer events.
 * Included are touch events (v1), mouse events, and MSPointerEvents.
 */
(function(scope) {

  var dispatcher = scope.dispatcher;
  var nav = window.navigator;

  if (window.PointerEvent) {
    dispatcher.registerSource('pointer', scope.pointerEvents);
  } else if (nav.msPointerEnabled) {
    dispatcher.registerSource('ms', scope.msEvents);
  } else {
    dispatcher.registerSource('mouse', scope.mouseEvents);
    if (window.ontouchstart !== undefined) {
      dispatcher.registerSource('touch', scope.touchEvents);
    }
  }

  // Work around iOS bugs https://bugs.webkit.org/show_bug.cgi?id=135628 and https://bugs.webkit.org/show_bug.cgi?id=136506
  var ua = navigator.userAgent;
  var IS_IOS = ua.match(/iPad|iPhone|iPod/) && 'ontouchstart' in window;

  dispatcher.IS_IOS = IS_IOS;
  scope.touchEvents.IS_IOS = IS_IOS;

  dispatcher.register(document, true);
})(window.PolymerGestures);

/**
 * This event denotes the beginning of a series of tracking events.
 *
 * @module PointerGestures
 * @submodule Events
 * @class trackstart
 */
/**
 * Pixels moved in the x direction since trackstart.
 * @type Number
 * @property dx
 */
/**
 * Pixes moved in the y direction since trackstart.
 * @type Number
 * @property dy
 */
/**
 * Pixels moved in the x direction since the last track.
 * @type Number
 * @property ddx
 */
/**
 * Pixles moved in the y direction since the last track.
 * @type Number
 * @property ddy
 */
/**
 * The clientX position of the track gesture.
 * @type Number
 * @property clientX
 */
/**
 * The clientY position of the track gesture.
 * @type Number
 * @property clientY
 */
/**
 * The pageX position of the track gesture.
 * @type Number
 * @property pageX
 */
/**
 * The pageY position of the track gesture.
 * @type Number
 * @property pageY
 */
/**
 * The screenX position of the track gesture.
 * @type Number
 * @property screenX
 */
/**
 * The screenY position of the track gesture.
 * @type Number
 * @property screenY
 */
/**
 * The last x axis direction of the pointer.
 * @type Number
 * @property xDirection
 */
/**
 * The last y axis direction of the pointer.
 * @type Number
 * @property yDirection
 */
/**
 * A shared object between all tracking events.
 * @type Object
 * @property trackInfo
 */
/**
 * The element currently under the pointer.
 * @type Element
 * @property relatedTarget
 */
/**
 * The type of pointer that make the track gesture.
 * @type String
 * @property pointerType
 */
/**
 *
 * This event fires for all pointer movement being tracked.
 *
 * @class track
 * @extends trackstart
 */
/**
 * This event fires when the pointer is no longer being tracked.
 *
 * @class trackend
 * @extends trackstart
 */

 (function(scope) {
   var dispatcher = scope.dispatcher;
   var eventFactory = scope.eventFactory;
   var pointermap = new scope.PointerMap();
   var track = {
     events: [
       'down',
       'move',
       'up',
     ],
     exposes: [
      'trackstart',
      'track',
      'trackx',
      'tracky',
      'trackend'
     ],
     defaultActions: {
       'track': 'none',
       'trackx': 'pan-y',
       'tracky': 'pan-x'
     },
     WIGGLE_THRESHOLD: 4,
     clampDir: function(inDelta) {
       return inDelta > 0 ? 1 : -1;
     },
     calcPositionDelta: function(inA, inB) {
       var x = 0, y = 0;
       if (inA && inB) {
         x = inB.pageX - inA.pageX;
         y = inB.pageY - inA.pageY;
       }
       return {x: x, y: y};
     },
     fireTrack: function(inType, inEvent, inTrackingData) {
       var t = inTrackingData;
       var d = this.calcPositionDelta(t.downEvent, inEvent);
       var dd = this.calcPositionDelta(t.lastMoveEvent, inEvent);
       if (dd.x) {
         t.xDirection = this.clampDir(dd.x);
       } else if (inType === 'trackx') {
         return;
       }
       if (dd.y) {
         t.yDirection = this.clampDir(dd.y);
       } else if (inType === 'tracky') {
         return;
       }
       var gestureProto = {
         bubbles: true,
         cancelable: true,
         trackInfo: t.trackInfo,
         relatedTarget: inEvent.relatedTarget,
         pointerType: inEvent.pointerType,
         pointerId: inEvent.pointerId,
         _source: 'track'
       };
       if (inType !== 'tracky') {
         gestureProto.x = inEvent.x;
         gestureProto.dx = d.x;
         gestureProto.ddx = dd.x;
         gestureProto.clientX = inEvent.clientX;
         gestureProto.pageX = inEvent.pageX;
         gestureProto.screenX = inEvent.screenX;
         gestureProto.xDirection = t.xDirection;
       }
       if (inType !== 'trackx') {
         gestureProto.dy = d.y;
         gestureProto.ddy = dd.y;
         gestureProto.y = inEvent.y;
         gestureProto.clientY = inEvent.clientY;
         gestureProto.pageY = inEvent.pageY;
         gestureProto.screenY = inEvent.screenY;
         gestureProto.yDirection = t.yDirection;
       }
       var e = eventFactory.makeGestureEvent(inType, gestureProto);
       t.downTarget.dispatchEvent(e);
     },
     down: function(inEvent) {
       if (inEvent.isPrimary && (inEvent.pointerType === 'mouse' ? inEvent.buttons === 1 : true)) {
         var p = {
           downEvent: inEvent,
           downTarget: inEvent.target,
           trackInfo: {},
           lastMoveEvent: null,
           xDirection: 0,
           yDirection: 0,
           tracking: false
         };
         pointermap.set(inEvent.pointerId, p);
       }
     },
     move: function(inEvent) {
       var p = pointermap.get(inEvent.pointerId);
       if (p) {
         if (!p.tracking) {
           var d = this.calcPositionDelta(p.downEvent, inEvent);
           var move = d.x * d.x + d.y * d.y;
           // start tracking only if finger moves more than WIGGLE_THRESHOLD
           if (move > this.WIGGLE_THRESHOLD) {
             p.tracking = true;
             p.lastMoveEvent = p.downEvent;
             this.fireTrack('trackstart', inEvent, p);
           }
         }
         if (p.tracking) {
           this.fireTrack('track', inEvent, p);
           this.fireTrack('trackx', inEvent, p);
           this.fireTrack('tracky', inEvent, p);
         }
         p.lastMoveEvent = inEvent;
       }
     },
     up: function(inEvent) {
       var p = pointermap.get(inEvent.pointerId);
       if (p) {
         if (p.tracking) {
           this.fireTrack('trackend', inEvent, p);
         }
         pointermap.delete(inEvent.pointerId);
       }
     }
   };
   dispatcher.registerGesture('track', track);
 })(window.PolymerGestures);

/**
 * This event is fired when a pointer is held down for 200ms.
 *
 * @module PointerGestures
 * @submodule Events
 * @class hold
 */
/**
 * Type of pointer that made the holding event.
 * @type String
 * @property pointerType
 */
/**
 * Screen X axis position of the held pointer
 * @type Number
 * @property clientX
 */
/**
 * Screen Y axis position of the held pointer
 * @type Number
 * @property clientY
 */
/**
 * Type of pointer that made the holding event.
 * @type String
 * @property pointerType
 */
/**
 * This event is fired every 200ms while a pointer is held down.
 *
 * @class holdpulse
 * @extends hold
 */
/**
 * Milliseconds pointer has been held down.
 * @type Number
 * @property holdTime
 */
/**
 * This event is fired when a held pointer is released or moved.
 *
 * @class release
 */

(function(scope) {
  var dispatcher = scope.dispatcher;
  var eventFactory = scope.eventFactory;
  var hold = {
    // wait at least HOLD_DELAY ms between hold and pulse events
    HOLD_DELAY: 200,
    // pointer can move WIGGLE_THRESHOLD pixels before not counting as a hold
    WIGGLE_THRESHOLD: 16,
    events: [
      'down',
      'move',
      'up',
    ],
    exposes: [
      'hold',
      'holdpulse',
      'release'
    ],
    heldPointer: null,
    holdJob: null,
    pulse: function() {
      var hold = Date.now() - this.heldPointer.timeStamp;
      var type = this.held ? 'holdpulse' : 'hold';
      this.fireHold(type, hold);
      this.held = true;
    },
    cancel: function() {
      clearInterval(this.holdJob);
      if (this.held) {
        this.fireHold('release');
      }
      this.held = false;
      this.heldPointer = null;
      this.target = null;
      this.holdJob = null;
    },
    down: function(inEvent) {
      if (inEvent.isPrimary && !this.heldPointer) {
        this.heldPointer = inEvent;
        this.target = inEvent.target;
        this.holdJob = setInterval(this.pulse.bind(this), this.HOLD_DELAY);
      }
    },
    up: function(inEvent) {
      if (this.heldPointer && this.heldPointer.pointerId === inEvent.pointerId) {
        this.cancel();
      }
    },
    move: function(inEvent) {
      if (this.heldPointer && this.heldPointer.pointerId === inEvent.pointerId) {
        var x = inEvent.clientX - this.heldPointer.clientX;
        var y = inEvent.clientY - this.heldPointer.clientY;
        if ((x * x + y * y) > this.WIGGLE_THRESHOLD) {
          this.cancel();
        }
      }
    },
    fireHold: function(inType, inHoldTime) {
      var p = {
        bubbles: true,
        cancelable: true,
        pointerType: this.heldPointer.pointerType,
        pointerId: this.heldPointer.pointerId,
        x: this.heldPointer.clientX,
        y: this.heldPointer.clientY,
        _source: 'hold'
      };
      if (inHoldTime) {
        p.holdTime = inHoldTime;
      }
      var e = eventFactory.makeGestureEvent(inType, p);
      this.target.dispatchEvent(e);
    }
  };
  dispatcher.registerGesture('hold', hold);
})(window.PolymerGestures);

/**
 * This event is fired when a pointer quickly goes down and up, and is used to
 * denote activation.
 *
 * Any gesture event can prevent the tap event from being created by calling
 * `event.preventTap`.
 *
 * Any pointer event can prevent the tap by setting the `tapPrevented` property
 * on itself.
 *
 * @module PointerGestures
 * @submodule Events
 * @class tap
 */
/**
 * X axis position of the tap.
 * @property x
 * @type Number
 */
/**
 * Y axis position of the tap.
 * @property y
 * @type Number
 */
/**
 * Type of the pointer that made the tap.
 * @property pointerType
 * @type String
 */
(function(scope) {
  var dispatcher = scope.dispatcher;
  var eventFactory = scope.eventFactory;
  var pointermap = new scope.PointerMap();
  var tap = {
    events: [
      'down',
      'up'
    ],
    exposes: [
      'tap'
    ],
    down: function(inEvent) {
      if (inEvent.isPrimary && !inEvent.tapPrevented) {
        pointermap.set(inEvent.pointerId, {
          target: inEvent.target,
          buttons: inEvent.buttons,
          x: inEvent.clientX,
          y: inEvent.clientY
        });
      }
    },
    shouldTap: function(e, downState) {
      var tap = true;
      if (e.pointerType === 'mouse') {
        // only allow left click to tap for mouse
        tap = (e.buttons ^ 1) && (downState.buttons & 1);
      }
      return tap && !e.tapPrevented;
    },
    up: function(inEvent) {
      var start = pointermap.get(inEvent.pointerId);
      if (start && this.shouldTap(inEvent, start)) {
        // up.relatedTarget is target currently under finger
        var t = scope.targetFinding.LCA(start.target, inEvent.relatedTarget);
        if (t) {
          var e = eventFactory.makeGestureEvent('tap', {
            bubbles: true,
            cancelable: true,
            x: inEvent.clientX,
            y: inEvent.clientY,
            detail: inEvent.detail,
            pointerType: inEvent.pointerType,
            pointerId: inEvent.pointerId,
            altKey: inEvent.altKey,
            ctrlKey: inEvent.ctrlKey,
            metaKey: inEvent.metaKey,
            shiftKey: inEvent.shiftKey,
            _source: 'tap'
          });
          t.dispatchEvent(e);
        }
      }
      pointermap.delete(inEvent.pointerId);
    }
  };
  // patch eventFactory to remove id from tap's pointermap for preventTap calls
  eventFactory.preventTap = function(e) {
    return function() {
      e.tapPrevented = true;
      pointermap.delete(e.pointerId);
    };
  };
  dispatcher.registerGesture('tap', tap);
})(window.PolymerGestures);

/*
 * Basic strategy: find the farthest apart points, use as diameter of circle
 * react to size change and rotation of the chord
 */

/**
 * @module pointer-gestures
 * @submodule Events
 * @class pinch
 */
/**
 * Scale of the pinch zoom gesture
 * @property scale
 * @type Number
 */
/**
 * Center X position of pointers causing pinch
 * @property centerX
 * @type Number
 */
/**
 * Center Y position of pointers causing pinch
 * @property centerY
 * @type Number
 */

/**
 * @module pointer-gestures
 * @submodule Events
 * @class rotate
 */
/**
 * Angle (in degrees) of rotation. Measured from starting positions of pointers.
 * @property angle
 * @type Number
 */
/**
 * Center X position of pointers causing rotation
 * @property centerX
 * @type Number
 */
/**
 * Center Y position of pointers causing rotation
 * @property centerY
 * @type Number
 */
(function(scope) {
  var dispatcher = scope.dispatcher;
  var eventFactory = scope.eventFactory;
  var pointermap = new scope.PointerMap();
  var RAD_TO_DEG = 180 / Math.PI;
  var pinch = {
    events: [
      'down',
      'up',
      'move',
      'cancel'
    ],
    exposes: [
      'pinchstart',
      'pinch',
      'pinchend',
      'rotate'
    ],
    defaultActions: {
      'pinch': 'none',
      'rotate': 'none'
    },
    reference: {},
    down: function(inEvent) {
      pointermap.set(inEvent.pointerId, inEvent);
      if (pointermap.pointers() == 2) {
        var points = this.calcChord();
        var angle = this.calcAngle(points);
        this.reference = {
          angle: angle,
          diameter: points.diameter,
          target: scope.targetFinding.LCA(points.a.target, points.b.target)
        };

        this.firePinch('pinchstart', points.diameter, points);
      }
    },
    up: function(inEvent) {
      var p = pointermap.get(inEvent.pointerId);
      var num = pointermap.pointers();
      if (p) {
        if (num === 2) {
          // fire 'pinchend' before deleting pointer
          var points = this.calcChord();
          this.firePinch('pinchend', points.diameter, points);
        }
        pointermap.delete(inEvent.pointerId);
      }
    },
    move: function(inEvent) {
      if (pointermap.has(inEvent.pointerId)) {
        pointermap.set(inEvent.pointerId, inEvent);
        if (pointermap.pointers() > 1) {
          this.calcPinchRotate();
        }
      }
    },
    cancel: function(inEvent) {
        this.up(inEvent);
    },
    firePinch: function(type, diameter, points) {
      var zoom = diameter / this.reference.diameter;
      var e = eventFactory.makeGestureEvent(type, {
        bubbles: true,
        cancelable: true,
        scale: zoom,
        centerX: points.center.x,
        centerY: points.center.y,
        _source: 'pinch'
      });
      this.reference.target.dispatchEvent(e);
    },
    fireRotate: function(angle, points) {
      var diff = Math.round((angle - this.reference.angle) % 360);
      var e = eventFactory.makeGestureEvent('rotate', {
        bubbles: true,
        cancelable: true,
        angle: diff,
        centerX: points.center.x,
        centerY: points.center.y,
        _source: 'pinch'
      });
      this.reference.target.dispatchEvent(e);
    },
    calcPinchRotate: function() {
      var points = this.calcChord();
      var diameter = points.diameter;
      var angle = this.calcAngle(points);
      if (diameter != this.reference.diameter) {
        this.firePinch('pinch', diameter, points);
      }
      if (angle != this.reference.angle) {
        this.fireRotate(angle, points);
      }
    },
    calcChord: function() {
      var pointers = [];
      pointermap.forEach(function(p) {
        pointers.push(p);
      });
      var dist = 0;
      // start with at least two pointers
      var points = {a: pointers[0], b: pointers[1]};
      var x, y, d;
      for (var i = 0; i < pointers.length; i++) {
        var a = pointers[i];
        for (var j = i + 1; j < pointers.length; j++) {
          var b = pointers[j];
          x = Math.abs(a.clientX - b.clientX);
          y = Math.abs(a.clientY - b.clientY);
          d = x + y;
          if (d > dist) {
            dist = d;
            points = {a: a, b: b};
          }
        }
      }
      x = Math.abs(points.a.clientX + points.b.clientX) / 2;
      y = Math.abs(points.a.clientY + points.b.clientY) / 2;
      points.center = { x: x, y: y };
      points.diameter = dist;
      return points;
    },
    calcAngle: function(points) {
      var x = points.a.clientX - points.b.clientX;
      var y = points.a.clientY - points.b.clientY;
      return (360 + Math.atan2(y, x) * RAD_TO_DEG) % 360;
    }
  };
  dispatcher.registerGesture('pinch', pinch);
})(window.PolymerGestures);

(function (global) {
    'use strict';

    var Token,
        TokenName,
        Syntax,
        Messages,
        source,
        index,
        length,
        delegate,
        lookahead,
        state;

    Token = {
        BooleanLiteral: 1,
        EOF: 2,
        Identifier: 3,
        Keyword: 4,
        NullLiteral: 5,
        NumericLiteral: 6,
        Punctuator: 7,
        StringLiteral: 8
    };

    TokenName = {};
    TokenName[Token.BooleanLiteral] = 'Boolean';
    TokenName[Token.EOF] = '<end>';
    TokenName[Token.Identifier] = 'Identifier';
    TokenName[Token.Keyword] = 'Keyword';
    TokenName[Token.NullLiteral] = 'Null';
    TokenName[Token.NumericLiteral] = 'Numeric';
    TokenName[Token.Punctuator] = 'Punctuator';
    TokenName[Token.StringLiteral] = 'String';

    Syntax = {
        ArrayExpression: 'ArrayExpression',
        BinaryExpression: 'BinaryExpression',
        CallExpression: 'CallExpression',
        ConditionalExpression: 'ConditionalExpression',
        EmptyStatement: 'EmptyStatement',
        ExpressionStatement: 'ExpressionStatement',
        Identifier: 'Identifier',
        Literal: 'Literal',
        LabeledStatement: 'LabeledStatement',
        LogicalExpression: 'LogicalExpression',
        MemberExpression: 'MemberExpression',
        ObjectExpression: 'ObjectExpression',
        Program: 'Program',
        Property: 'Property',
        ThisExpression: 'ThisExpression',
        UnaryExpression: 'UnaryExpression'
    };

    // Error messages should be identical to V8.
    Messages = {
        UnexpectedToken:  'Unexpected token %0',
        UnknownLabel: 'Undefined label \'%0\'',
        Redeclaration: '%0 \'%1\' has already been declared'
    };

    // Ensure the condition is true, otherwise throw an error.
    // This is only to have a better contract semantic, i.e. another safety net
    // to catch a logic error. The condition shall be fulfilled in normal case.
    // Do NOT use this to enforce a certain condition on any user input.

    function assert(condition, message) {
        if (!condition) {
            throw new Error('ASSERT: ' + message);
        }
    }

    function isDecimalDigit(ch) {
        return (ch >= 48 && ch <= 57);   // 0..9
    }


    // 7.2 White Space

    function isWhiteSpace(ch) {
        return (ch === 32) ||  // space
            (ch === 9) ||      // tab
            (ch === 0xB) ||
            (ch === 0xC) ||
            (ch === 0xA0) ||
            (ch >= 0x1680 && '\u1680\u180E\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u202F\u205F\u3000\uFEFF'.indexOf(String.fromCharCode(ch)) > 0);
    }

    // 7.3 Line Terminators

    function isLineTerminator(ch) {
        return (ch === 10) || (ch === 13) || (ch === 0x2028) || (ch === 0x2029);
    }

    // 7.6 Identifier Names and Identifiers

    function isIdentifierStart(ch) {
        return (ch === 36) || (ch === 95) ||  // $ (dollar) and _ (underscore)
            (ch >= 65 && ch <= 90) ||         // A..Z
            (ch >= 97 && ch <= 122);          // a..z
    }

    function isIdentifierPart(ch) {
        return (ch === 36) || (ch === 95) ||  // $ (dollar) and _ (underscore)
            (ch >= 65 && ch <= 90) ||         // A..Z
            (ch >= 97 && ch <= 122) ||        // a..z
            (ch >= 48 && ch <= 57);           // 0..9
    }

    // 7.6.1.1 Keywords

    function isKeyword(id) {
        return (id === 'this')
    }

    // 7.4 Comments

    function skipWhitespace() {
        while (index < length && isWhiteSpace(source.charCodeAt(index))) {
           ++index;
        }
    }

    function getIdentifier() {
        var start, ch;

        start = index++;
        while (index < length) {
            ch = source.charCodeAt(index);
            if (isIdentifierPart(ch)) {
                ++index;
            } else {
                break;
            }
        }

        return source.slice(start, index);
    }

    function scanIdentifier() {
        var start, id, type;

        start = index;

        id = getIdentifier();

        // There is no keyword or literal with only one character.
        // Thus, it must be an identifier.
        if (id.length === 1) {
            type = Token.Identifier;
        } else if (isKeyword(id)) {
            type = Token.Keyword;
        } else if (id === 'null') {
            type = Token.NullLiteral;
        } else if (id === 'true' || id === 'false') {
            type = Token.BooleanLiteral;
        } else {
            type = Token.Identifier;
        }

        return {
            type: type,
            value: id,
            range: [start, index]
        };
    }


    // 7.7 Punctuators

    function scanPunctuator() {
        var start = index,
            code = source.charCodeAt(index),
            code2,
            ch1 = source[index],
            ch2;

        switch (code) {

        // Check for most common single-character punctuators.
        case 46:   // . dot
        case 40:   // ( open bracket
        case 41:   // ) close bracket
        case 59:   // ; semicolon
        case 44:   // , comma
        case 123:  // { open curly brace
        case 125:  // } close curly brace
        case 91:   // [
        case 93:   // ]
        case 58:   // :
        case 63:   // ?
            ++index;
            return {
                type: Token.Punctuator,
                value: String.fromCharCode(code),
                range: [start, index]
            };

        default:
            code2 = source.charCodeAt(index + 1);

            // '=' (char #61) marks an assignment or comparison operator.
            if (code2 === 61) {
                switch (code) {
                case 37:  // %
                case 38:  // &
                case 42:  // *:
                case 43:  // +
                case 45:  // -
                case 47:  // /
                case 60:  // <
                case 62:  // >
                case 124: // |
                    index += 2;
                    return {
                        type: Token.Punctuator,
                        value: String.fromCharCode(code) + String.fromCharCode(code2),
                        range: [start, index]
                    };

                case 33: // !
                case 61: // =
                    index += 2;

                    // !== and ===
                    if (source.charCodeAt(index) === 61) {
                        ++index;
                    }
                    return {
                        type: Token.Punctuator,
                        value: source.slice(start, index),
                        range: [start, index]
                    };
                default:
                    break;
                }
            }
            break;
        }

        // Peek more characters.

        ch2 = source[index + 1];

        // Other 2-character punctuators: && ||

        if (ch1 === ch2 && ('&|'.indexOf(ch1) >= 0)) {
            index += 2;
            return {
                type: Token.Punctuator,
                value: ch1 + ch2,
                range: [start, index]
            };
        }

        if ('<>=!+-*%&|^/'.indexOf(ch1) >= 0) {
            ++index;
            return {
                type: Token.Punctuator,
                value: ch1,
                range: [start, index]
            };
        }

        throwError({}, Messages.UnexpectedToken, 'ILLEGAL');
    }

    // 7.8.3 Numeric Literals
    function scanNumericLiteral() {
        var number, start, ch;

        ch = source[index];
        assert(isDecimalDigit(ch.charCodeAt(0)) || (ch === '.'),
            'Numeric literal must start with a decimal digit or a decimal point');

        start = index;
        number = '';
        if (ch !== '.') {
            number = source[index++];
            ch = source[index];

            // Hex number starts with '0x'.
            // Octal number starts with '0'.
            if (number === '0') {
                // decimal number starts with '0' such as '09' is illegal.
                if (ch && isDecimalDigit(ch.charCodeAt(0))) {
                    throwError({}, Messages.UnexpectedToken, 'ILLEGAL');
                }
            }

            while (isDecimalDigit(source.charCodeAt(index))) {
                number += source[index++];
            }
            ch = source[index];
        }

        if (ch === '.') {
            number += source[index++];
            while (isDecimalDigit(source.charCodeAt(index))) {
                number += source[index++];
            }
            ch = source[index];
        }

        if (ch === 'e' || ch === 'E') {
            number += source[index++];

            ch = source[index];
            if (ch === '+' || ch === '-') {
                number += source[index++];
            }
            if (isDecimalDigit(source.charCodeAt(index))) {
                while (isDecimalDigit(source.charCodeAt(index))) {
                    number += source[index++];
                }
            } else {
                throwError({}, Messages.UnexpectedToken, 'ILLEGAL');
            }
        }

        if (isIdentifierStart(source.charCodeAt(index))) {
            throwError({}, Messages.UnexpectedToken, 'ILLEGAL');
        }

        return {
            type: Token.NumericLiteral,
            value: parseFloat(number),
            range: [start, index]
        };
    }

    // 7.8.4 String Literals

    function scanStringLiteral() {
        var str = '', quote, start, ch, octal = false;

        quote = source[index];
        assert((quote === '\'' || quote === '"'),
            'String literal must starts with a quote');

        start = index;
        ++index;

        while (index < length) {
            ch = source[index++];

            if (ch === quote) {
                quote = '';
                break;
            } else if (ch === '\\') {
                ch = source[index++];
                if (!ch || !isLineTerminator(ch.charCodeAt(0))) {
                    switch (ch) {
                    case 'n':
                        str += '\n';
                        break;
                    case 'r':
                        str += '\r';
                        break;
                    case 't':
                        str += '\t';
                        break;
                    case 'b':
                        str += '\b';
                        break;
                    case 'f':
                        str += '\f';
                        break;
                    case 'v':
                        str += '\x0B';
                        break;

                    default:
                        str += ch;
                        break;
                    }
                } else {
                    if (ch ===  '\r' && source[index] === '\n') {
                        ++index;
                    }
                }
            } else if (isLineTerminator(ch.charCodeAt(0))) {
                break;
            } else {
                str += ch;
            }
        }

        if (quote !== '') {
            throwError({}, Messages.UnexpectedToken, 'ILLEGAL');
        }

        return {
            type: Token.StringLiteral,
            value: str,
            octal: octal,
            range: [start, index]
        };
    }

    function isIdentifierName(token) {
        return token.type === Token.Identifier ||
            token.type === Token.Keyword ||
            token.type === Token.BooleanLiteral ||
            token.type === Token.NullLiteral;
    }

    function advance() {
        var ch;

        skipWhitespace();

        if (index >= length) {
            return {
                type: Token.EOF,
                range: [index, index]
            };
        }

        ch = source.charCodeAt(index);

        // Very common: ( and ) and ;
        if (ch === 40 || ch === 41 || ch === 58) {
            return scanPunctuator();
        }

        // String literal starts with single quote (#39) or double quote (#34).
        if (ch === 39 || ch === 34) {
            return scanStringLiteral();
        }

        if (isIdentifierStart(ch)) {
            return scanIdentifier();
        }

        // Dot (.) char #46 can also start a floating-point number, hence the need
        // to check the next character.
        if (ch === 46) {
            if (isDecimalDigit(source.charCodeAt(index + 1))) {
                return scanNumericLiteral();
            }
            return scanPunctuator();
        }

        if (isDecimalDigit(ch)) {
            return scanNumericLiteral();
        }

        return scanPunctuator();
    }

    function lex() {
        var token;

        token = lookahead;
        index = token.range[1];

        lookahead = advance();

        index = token.range[1];

        return token;
    }

    function peek() {
        var pos;

        pos = index;
        lookahead = advance();
        index = pos;
    }

    // Throw an exception

    function throwError(token, messageFormat) {
        var error,
            args = Array.prototype.slice.call(arguments, 2),
            msg = messageFormat.replace(
                /%(\d)/g,
                function (whole, index) {
                    assert(index < args.length, 'Message reference must be in range');
                    return args[index];
                }
            );

        error = new Error(msg);
        error.index = index;
        error.description = msg;
        throw error;
    }

    // Throw an exception because of the token.

    function throwUnexpected(token) {
        throwError(token, Messages.UnexpectedToken, token.value);
    }

    // Expect the next token to match the specified punctuator.
    // If not, an exception will be thrown.

    function expect(value) {
        var token = lex();
        if (token.type !== Token.Punctuator || token.value !== value) {
            throwUnexpected(token);
        }
    }

    // Return true if the next token matches the specified punctuator.

    function match(value) {
        return lookahead.type === Token.Punctuator && lookahead.value === value;
    }

    // Return true if the next token matches the specified keyword

    function matchKeyword(keyword) {
        return lookahead.type === Token.Keyword && lookahead.value === keyword;
    }

    function consumeSemicolon() {
        // Catch the very common case first: immediately a semicolon (char #59).
        if (source.charCodeAt(index) === 59) {
            lex();
            return;
        }

        skipWhitespace();

        if (match(';')) {
            lex();
            return;
        }

        if (lookahead.type !== Token.EOF && !match('}')) {
            throwUnexpected(lookahead);
        }
    }

    // 11.1.4 Array Initialiser

    function parseArrayInitialiser() {
        var elements = [];

        expect('[');

        while (!match(']')) {
            if (match(',')) {
                lex();
                elements.push(null);
            } else {
                elements.push(parseExpression());

                if (!match(']')) {
                    expect(',');
                }
            }
        }

        expect(']');

        return delegate.createArrayExpression(elements);
    }

    // 11.1.5 Object Initialiser

    function parseObjectPropertyKey() {
        var token;

        skipWhitespace();
        token = lex();

        // Note: This function is called only from parseObjectProperty(), where
        // EOF and Punctuator tokens are already filtered out.
        if (token.type === Token.StringLiteral || token.type === Token.NumericLiteral) {
            return delegate.createLiteral(token);
        }

        return delegate.createIdentifier(token.value);
    }

    function parseObjectProperty() {
        var token, key;

        token = lookahead;
        skipWhitespace();

        if (token.type === Token.EOF || token.type === Token.Punctuator) {
            throwUnexpected(token);
        }

        key = parseObjectPropertyKey();
        expect(':');
        return delegate.createProperty('init', key, parseExpression());
    }

    function parseObjectInitialiser() {
        var properties = [];

        expect('{');

        while (!match('}')) {
            properties.push(parseObjectProperty());

            if (!match('}')) {
                expect(',');
            }
        }

        expect('}');

        return delegate.createObjectExpression(properties);
    }

    // 11.1.6 The Grouping Operator

    function parseGroupExpression() {
        var expr;

        expect('(');

        expr = parseExpression();

        expect(')');

        return expr;
    }


    // 11.1 Primary Expressions

    function parsePrimaryExpression() {
        var type, token, expr;

        if (match('(')) {
            return parseGroupExpression();
        }

        type = lookahead.type;

        if (type === Token.Identifier) {
            expr = delegate.createIdentifier(lex().value);
        } else if (type === Token.StringLiteral || type === Token.NumericLiteral) {
            expr = delegate.createLiteral(lex());
        } else if (type === Token.Keyword) {
            if (matchKeyword('this')) {
                lex();
                expr = delegate.createThisExpression();
            }
        } else if (type === Token.BooleanLiteral) {
            token = lex();
            token.value = (token.value === 'true');
            expr = delegate.createLiteral(token);
        } else if (type === Token.NullLiteral) {
            token = lex();
            token.value = null;
            expr = delegate.createLiteral(token);
        } else if (match('[')) {
            expr = parseArrayInitialiser();
        } else if (match('{')) {
            expr = parseObjectInitialiser();
        }

        if (expr) {
            return expr;
        }

        throwUnexpected(lex());
    }

    // 11.2 Left-Hand-Side Expressions

    function parseArguments() {
        var args = [];

        expect('(');

        if (!match(')')) {
            while (index < length) {
                args.push(parseExpression());
                if (match(')')) {
                    break;
                }
                expect(',');
            }
        }

        expect(')');

        return args;
    }

    function parseNonComputedProperty() {
        var token;

        token = lex();

        if (!isIdentifierName(token)) {
            throwUnexpected(token);
        }

        return delegate.createIdentifier(token.value);
    }

    function parseNonComputedMember() {
        expect('.');

        return parseNonComputedProperty();
    }

    function parseComputedMember() {
        var expr;

        expect('[');

        expr = parseExpression();

        expect(']');

        return expr;
    }

    function parseLeftHandSideExpression() {
        var expr, args, property;

        expr = parsePrimaryExpression();

        while (true) {
            if (match('[')) {
                property = parseComputedMember();
                expr = delegate.createMemberExpression('[', expr, property);
            } else if (match('.')) {
                property = parseNonComputedMember();
                expr = delegate.createMemberExpression('.', expr, property);
            } else if (match('(')) {
                args = parseArguments();
                expr = delegate.createCallExpression(expr, args);
            } else {
                break;
            }
        }

        return expr;
    }

    // 11.3 Postfix Expressions

    var parsePostfixExpression = parseLeftHandSideExpression;

    // 11.4 Unary Operators

    function parseUnaryExpression() {
        var token, expr;

        if (lookahead.type !== Token.Punctuator && lookahead.type !== Token.Keyword) {
            expr = parsePostfixExpression();
        } else if (match('+') || match('-') || match('!')) {
            token = lex();
            expr = parseUnaryExpression();
            expr = delegate.createUnaryExpression(token.value, expr);
        } else if (matchKeyword('delete') || matchKeyword('void') || matchKeyword('typeof')) {
            throwError({}, Messages.UnexpectedToken);
        } else {
            expr = parsePostfixExpression();
        }

        return expr;
    }

    function binaryPrecedence(token) {
        var prec = 0;

        if (token.type !== Token.Punctuator && token.type !== Token.Keyword) {
            return 0;
        }

        switch (token.value) {
        case '||':
            prec = 1;
            break;

        case '&&':
            prec = 2;
            break;

        case '==':
        case '!=':
        case '===':
        case '!==':
            prec = 6;
            break;

        case '<':
        case '>':
        case '<=':
        case '>=':
        case 'instanceof':
            prec = 7;
            break;

        case 'in':
            prec = 7;
            break;

        case '+':
        case '-':
            prec = 9;
            break;

        case '*':
        case '/':
        case '%':
            prec = 11;
            break;

        default:
            break;
        }

        return prec;
    }

    // 11.5 Multiplicative Operators
    // 11.6 Additive Operators
    // 11.7 Bitwise Shift Operators
    // 11.8 Relational Operators
    // 11.9 Equality Operators
    // 11.10 Binary Bitwise Operators
    // 11.11 Binary Logical Operators

    function parseBinaryExpression() {
        var expr, token, prec, stack, right, operator, left, i;

        left = parseUnaryExpression();

        token = lookahead;
        prec = binaryPrecedence(token);
        if (prec === 0) {
            return left;
        }
        token.prec = prec;
        lex();

        right = parseUnaryExpression();

        stack = [left, token, right];

        while ((prec = binaryPrecedence(lookahead)) > 0) {

            // Reduce: make a binary expression from the three topmost entries.
            while ((stack.length > 2) && (prec <= stack[stack.length - 2].prec)) {
                right = stack.pop();
                operator = stack.pop().value;
                left = stack.pop();
                expr = delegate.createBinaryExpression(operator, left, right);
                stack.push(expr);
            }

            // Shift.
            token = lex();
            token.prec = prec;
            stack.push(token);
            expr = parseUnaryExpression();
            stack.push(expr);
        }

        // Final reduce to clean-up the stack.
        i = stack.length - 1;
        expr = stack[i];
        while (i > 1) {
            expr = delegate.createBinaryExpression(stack[i - 1].value, stack[i - 2], expr);
            i -= 2;
        }

        return expr;
    }


    // 11.12 Conditional Operator

    function parseConditionalExpression() {
        var expr, consequent, alternate;

        expr = parseBinaryExpression();

        if (match('?')) {
            lex();
            consequent = parseConditionalExpression();
            expect(':');
            alternate = parseConditionalExpression();

            expr = delegate.createConditionalExpression(expr, consequent, alternate);
        }

        return expr;
    }

    // Simplification since we do not support AssignmentExpression.
    var parseExpression = parseConditionalExpression;

    // Polymer Syntax extensions

    // Filter ::
    //   Identifier
    //   Identifier "(" ")"
    //   Identifier "(" FilterArguments ")"

    function parseFilter() {
        var identifier, args;

        identifier = lex();

        if (identifier.type !== Token.Identifier) {
            throwUnexpected(identifier);
        }

        args = match('(') ? parseArguments() : [];

        return delegate.createFilter(identifier.value, args);
    }

    // Filters ::
    //   "|" Filter
    //   Filters "|" Filter

    function parseFilters() {
        while (match('|')) {
            lex();
            parseFilter();
        }
    }

    // TopLevel ::
    //   LabelledExpressions
    //   AsExpression
    //   InExpression
    //   FilterExpression

    // AsExpression ::
    //   FilterExpression as Identifier

    // InExpression ::
    //   Identifier, Identifier in FilterExpression
    //   Identifier in FilterExpression

    // FilterExpression ::
    //   Expression
    //   Expression Filters

    function parseTopLevel() {
        skipWhitespace();
        peek();

        var expr = parseExpression();
        if (expr) {
            if (lookahead.value === ',' || lookahead.value == 'in' &&
                       expr.type === Syntax.Identifier) {
                parseInExpression(expr);
            } else {
                parseFilters();
                if (lookahead.value === 'as') {
                    parseAsExpression(expr);
                } else {
                    delegate.createTopLevel(expr);
                }
            }
        }

        if (lookahead.type !== Token.EOF) {
            throwUnexpected(lookahead);
        }
    }

    function parseAsExpression(expr) {
        lex();  // as
        var identifier = lex().value;
        delegate.createAsExpression(expr, identifier);
    }

    function parseInExpression(identifier) {
        var indexName;
        if (lookahead.value === ',') {
            lex();
            if (lookahead.type !== Token.Identifier)
                throwUnexpected(lookahead);
            indexName = lex().value;
        }

        lex();  // in
        var expr = parseExpression();
        parseFilters();
        delegate.createInExpression(identifier.name, indexName, expr);
    }

    function parse(code, inDelegate) {
        delegate = inDelegate;
        source = code;
        index = 0;
        length = source.length;
        lookahead = null;
        state = {
            labelSet: {}
        };

        return parseTopLevel();
    }

    global.esprima = {
        parse: parse
    };
})(this);

// Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
// This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
// The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
// The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
// Code distributed by Google as part of the polymer project is also
// subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt

(function (global) {
  'use strict';

  function prepareBinding(expressionText, name, node, filterRegistry) {
    var expression;
    try {
      expression = getExpression(expressionText);
      if (expression.scopeIdent &&
          (node.nodeType !== Node.ELEMENT_NODE ||
           node.tagName !== 'TEMPLATE' ||
           (name !== 'bind' && name !== 'repeat'))) {
        throw Error('as and in can only be used within <template bind/repeat>');
      }
    } catch (ex) {
      console.error('Invalid expression syntax: ' + expressionText, ex);
      return;
    }

    return function(model, node, oneTime) {
      var binding = expression.getBinding(model, filterRegistry, oneTime);
      if (expression.scopeIdent && binding) {
        node.polymerExpressionScopeIdent_ = expression.scopeIdent;
        if (expression.indexIdent)
          node.polymerExpressionIndexIdent_ = expression.indexIdent;
      }

      return binding;
    }
  }

  // TODO(rafaelw): Implement simple LRU.
  var expressionParseCache = Object.create(null);

  function getExpression(expressionText) {
    var expression = expressionParseCache[expressionText];
    if (!expression) {
      var delegate = new ASTDelegate();
      esprima.parse(expressionText, delegate);
      expression = new Expression(delegate);
      expressionParseCache[expressionText] = expression;
    }
    return expression;
  }

  function Literal(value) {
    this.value = value;
    this.valueFn_ = undefined;
  }

  Literal.prototype = {
    valueFn: function() {
      if (!this.valueFn_) {
        var value = this.value;
        this.valueFn_ = function() {
          return value;
        }
      }

      return this.valueFn_;
    }
  }

  function IdentPath(name) {
    this.name = name;
    this.path = Path.get(name);
  }

  IdentPath.prototype = {
    valueFn: function() {
      if (!this.valueFn_) {
        var name = this.name;
        var path = this.path;
        this.valueFn_ = function(model, observer) {
          if (observer)
            observer.addPath(model, path);

          return path.getValueFrom(model);
        }
      }

      return this.valueFn_;
    },

    setValue: function(model, newValue) {
      if (this.path.length == 1)
        model = findScope(model, this.path[0]);

      return this.path.setValueFrom(model, newValue);
    }
  };

  function MemberExpression(object, property, accessor) {
    this.computed = accessor == '[';

    this.dynamicDeps = typeof object == 'function' ||
                       object.dynamicDeps ||
                       (this.computed && !(property instanceof Literal));

    this.simplePath =
        !this.dynamicDeps &&
        (property instanceof IdentPath || property instanceof Literal) &&
        (object instanceof MemberExpression || object instanceof IdentPath);

    this.object = this.simplePath ? object : getFn(object);
    this.property = !this.computed || this.simplePath ?
        property : getFn(property);
  }

  MemberExpression.prototype = {
    get fullPath() {
      if (!this.fullPath_) {

        var parts = this.object instanceof MemberExpression ?
            this.object.fullPath.slice() : [this.object.name];
        parts.push(this.property instanceof IdentPath ?
            this.property.name : this.property.value);
        this.fullPath_ = Path.get(parts);
      }

      return this.fullPath_;
    },

    valueFn: function() {
      if (!this.valueFn_) {
        var object = this.object;

        if (this.simplePath) {
          var path = this.fullPath;

          this.valueFn_ = function(model, observer) {
            if (observer)
              observer.addPath(model, path);

            return path.getValueFrom(model);
          };
        } else if (!this.computed) {
          var path = Path.get(this.property.name);

          this.valueFn_ = function(model, observer, filterRegistry) {
            var context = object(model, observer, filterRegistry);

            if (observer)
              observer.addPath(context, path);

            return path.getValueFrom(context);
          }
        } else {
          // Computed property.
          var property = this.property;

          this.valueFn_ = function(model, observer, filterRegistry) {
            var context = object(model, observer, filterRegistry);
            var propName = property(model, observer, filterRegistry);
            if (observer)
              observer.addPath(context, [propName]);

            return context ? context[propName] : undefined;
          };
        }
      }
      return this.valueFn_;
    },

    setValue: function(model, newValue) {
      if (this.simplePath) {
        this.fullPath.setValueFrom(model, newValue);
        return newValue;
      }

      var object = this.object(model);
      var propName = this.property instanceof IdentPath ? this.property.name :
          this.property(model);
      return object[propName] = newValue;
    }
  };

  function Filter(name, args) {
    this.name = name;
    this.args = [];
    for (var i = 0; i < args.length; i++) {
      this.args[i] = getFn(args[i]);
    }
  }

  Filter.prototype = {
    transform: function(model, observer, filterRegistry, toModelDirection,
                        initialArgs) {
      var context = model;
      var fn = context[this.name];

      if (!fn) {
        fn = filterRegistry[this.name];
        if (!fn) {
          console.error('Cannot find function or filter: ' + this.name);
          return;
        }
      }

      // If toModelDirection is falsey, then the "normal" (dom-bound) direction
      // is used. Otherwise, it looks for a 'toModel' property function on the
      // object.
      if (toModelDirection) {
        fn = fn.toModel;
      } else if (typeof fn.toDOM == 'function') {
        fn = fn.toDOM;
      }

      if (typeof fn != 'function') {
        console.error('Cannot find function or filter: ' + this.name);
        return;
      }

      var args = initialArgs || [];
      for (var i = 0; i < this.args.length; i++) {
        args.push(getFn(this.args[i])(model, observer, filterRegistry));
      }

      return fn.apply(context, args);
    }
  };

  function notImplemented() { throw Error('Not Implemented'); }

  var unaryOperators = {
    '+': function(v) { return +v; },
    '-': function(v) { return -v; },
    '!': function(v) { return !v; }
  };

  var binaryOperators = {
    '+': function(l, r) { return l+r; },
    '-': function(l, r) { return l-r; },
    '*': function(l, r) { return l*r; },
    '/': function(l, r) { return l/r; },
    '%': function(l, r) { return l%r; },
    '<': function(l, r) { return l<r; },
    '>': function(l, r) { return l>r; },
    '<=': function(l, r) { return l<=r; },
    '>=': function(l, r) { return l>=r; },
    '==': function(l, r) { return l==r; },
    '!=': function(l, r) { return l!=r; },
    '===': function(l, r) { return l===r; },
    '!==': function(l, r) { return l!==r; },
    '&&': function(l, r) { return l&&r; },
    '||': function(l, r) { return l||r; },
  };

  function getFn(arg) {
    return typeof arg == 'function' ? arg : arg.valueFn();
  }

  function ASTDelegate() {
    this.expression = null;
    this.filters = [];
    this.deps = {};
    this.currentPath = undefined;
    this.scopeIdent = undefined;
    this.indexIdent = undefined;
    this.dynamicDeps = false;
  }

  ASTDelegate.prototype = {
    createUnaryExpression: function(op, argument) {
      if (!unaryOperators[op])
        throw Error('Disallowed operator: ' + op);

      argument = getFn(argument);

      return function(model, observer, filterRegistry) {
        return unaryOperators[op](argument(model, observer, filterRegistry));
      };
    },

    createBinaryExpression: function(op, left, right) {
      if (!binaryOperators[op])
        throw Error('Disallowed operator: ' + op);

      left = getFn(left);
      right = getFn(right);

      switch (op) {
        case '||':
          this.dynamicDeps = true;
          return function(model, observer, filterRegistry) {
            return left(model, observer, filterRegistry) ||
                right(model, observer, filterRegistry);
          };
        case '&&':
          this.dynamicDeps = true;
          return function(model, observer, filterRegistry) {
            return left(model, observer, filterRegistry) &&
                right(model, observer, filterRegistry);
          };
      }

      return function(model, observer, filterRegistry) {
        return binaryOperators[op](left(model, observer, filterRegistry),
                                   right(model, observer, filterRegistry));
      };
    },

    createConditionalExpression: function(test, consequent, alternate) {
      test = getFn(test);
      consequent = getFn(consequent);
      alternate = getFn(alternate);

      this.dynamicDeps = true;

      return function(model, observer, filterRegistry) {
        return test(model, observer, filterRegistry) ?
            consequent(model, observer, filterRegistry) :
            alternate(model, observer, filterRegistry);
      }
    },

    createIdentifier: function(name) {
      var ident = new IdentPath(name);
      ident.type = 'Identifier';
      return ident;
    },

    createMemberExpression: function(accessor, object, property) {
      var ex = new MemberExpression(object, property, accessor);
      if (ex.dynamicDeps)
        this.dynamicDeps = true;
      return ex;
    },

    createCallExpression: function(expression, args) {
      if (!(expression instanceof IdentPath))
        throw Error('Only identifier function invocations are allowed');

      var filter = new Filter(expression.name, args);

      return function(model, observer, filterRegistry) {
        return filter.transform(model, observer, filterRegistry, false);
      };
    },

    createLiteral: function(token) {
      return new Literal(token.value);
    },

    createArrayExpression: function(elements) {
      for (var i = 0; i < elements.length; i++)
        elements[i] = getFn(elements[i]);

      return function(model, observer, filterRegistry) {
        var arr = []
        for (var i = 0; i < elements.length; i++)
          arr.push(elements[i](model, observer, filterRegistry));
        return arr;
      }
    },

    createProperty: function(kind, key, value) {
      return {
        key: key instanceof IdentPath ? key.name : key.value,
        value: value
      };
    },

    createObjectExpression: function(properties) {
      for (var i = 0; i < properties.length; i++)
        properties[i].value = getFn(properties[i].value);

      return function(model, observer, filterRegistry) {
        var obj = {};
        for (var i = 0; i < properties.length; i++)
          obj[properties[i].key] =
              properties[i].value(model, observer, filterRegistry);
        return obj;
      }
    },

    createFilter: function(name, args) {
      this.filters.push(new Filter(name, args));
    },

    createAsExpression: function(expression, scopeIdent) {
      this.expression = expression;
      this.scopeIdent = scopeIdent;
    },

    createInExpression: function(scopeIdent, indexIdent, expression) {
      this.expression = expression;
      this.scopeIdent = scopeIdent;
      this.indexIdent = indexIdent;
    },

    createTopLevel: function(expression) {
      this.expression = expression;
    },

    createThisExpression: notImplemented
  }

  function ConstantObservable(value) {
    this.value_ = value;
  }

  ConstantObservable.prototype = {
    open: function() { return this.value_; },
    discardChanges: function() { return this.value_; },
    deliver: function() {},
    close: function() {},
  }

  function Expression(delegate) {
    this.scopeIdent = delegate.scopeIdent;
    this.indexIdent = delegate.indexIdent;

    if (!delegate.expression)
      throw Error('No expression found.');

    this.expression = delegate.expression;
    getFn(this.expression); // forces enumeration of path dependencies

    this.filters = delegate.filters;
    this.dynamicDeps = delegate.dynamicDeps;
  }

  Expression.prototype = {
    getBinding: function(model, filterRegistry, oneTime) {
      if (oneTime)
        return this.getValue(model, undefined, filterRegistry);

      var observer = new CompoundObserver();
      // captures deps.
      var firstValue = this.getValue(model, observer, filterRegistry);
      var firstTime = true;
      var self = this;

      function valueFn() {
        // deps cannot have changed on first value retrieval.
        if (firstTime) {
          firstTime = false;
          return firstValue;
        }

        if (self.dynamicDeps)
          observer.startReset();

        var value = self.getValue(model,
                                  self.dynamicDeps ? observer : undefined,
                                  filterRegistry);
        if (self.dynamicDeps)
          observer.finishReset();

        return value;
      }

      function setValueFn(newValue) {
        self.setValue(model, newValue, filterRegistry);
        return newValue;
      }

      return new ObserverTransform(observer, valueFn, setValueFn, true);
    },

    getValue: function(model, observer, filterRegistry) {
      var value = getFn(this.expression)(model, observer, filterRegistry);
      for (var i = 0; i < this.filters.length; i++) {
        value = this.filters[i].transform(model, observer, filterRegistry,
            false, [value]);
      }

      return value;
    },

    setValue: function(model, newValue, filterRegistry) {
      var count = this.filters ? this.filters.length : 0;
      while (count-- > 0) {
        newValue = this.filters[count].transform(model, undefined,
            filterRegistry, true, [newValue]);
      }

      if (this.expression.setValue)
        return this.expression.setValue(model, newValue);
    }
  }

  /**
   * Converts a style property name to a css property name. For example:
   * "WebkitUserSelect" to "-webkit-user-select"
   */
  function convertStylePropertyName(name) {
    return String(name).replace(/[A-Z]/g, function(c) {
      return '-' + c.toLowerCase();
    });
  }

  var parentScopeName = '@' + Math.random().toString(36).slice(2);

  // Single ident paths must bind directly to the appropriate scope object.
  // I.e. Pushed values in two-bindings need to be assigned to the actual model
  // object.
  function findScope(model, prop) {
    while (model[parentScopeName] &&
           !Object.prototype.hasOwnProperty.call(model, prop)) {
      model = model[parentScopeName];
    }

    return model;
  }

  function isLiteralExpression(pathString) {
    switch (pathString) {
      case '':
        return false;

      case 'false':
      case 'null':
      case 'true':
        return true;
    }

    if (!isNaN(Number(pathString)))
      return true;

    return false;
  };

  function PolymerExpressions() {}

  PolymerExpressions.prototype = {
    // "built-in" filters
    styleObject: function(value) {
      var parts = [];
      for (var key in value) {
        parts.push(convertStylePropertyName(key) + ': ' + value[key]);
      }
      return parts.join('; ');
    },

    tokenList: function(value) {
      var tokens = [];
      for (var key in value) {
        if (value[key])
          tokens.push(key);
      }
      return tokens.join(' ');
    },

    // binding delegate API
    prepareInstancePositionChanged: function(template) {
      var indexIdent = template.polymerExpressionIndexIdent_;
      if (!indexIdent)
        return;

      return function(templateInstance, index) {
        templateInstance.model[indexIdent] = index;
      };
    },

    prepareBinding: function(pathString, name, node) {
      var path = Path.get(pathString);

      if (!isLiteralExpression(pathString) && path.valid) {
        if (path.length == 1) {
          return function(model, node, oneTime) {
            if (oneTime)
              return path.getValueFrom(model);

            var scope = findScope(model, path[0]);
            return new PathObserver(scope, path);
          };
        }
        return; // bail out early if pathString is simple path.
      }

      return prepareBinding(pathString, name, node, this);
    },

    prepareInstanceModel: function(template) {
      var scopeName = template.polymerExpressionScopeIdent_;
      if (!scopeName)
        return;

      var parentScope = template.templateInstance ?
          template.templateInstance.model :
          template.model;

      var indexName = template.polymerExpressionIndexIdent_;

      return function(model) {
        return createScopeObject(parentScope, model, scopeName, indexName);
      };
    }
  };

  var createScopeObject = ('__proto__' in {}) ?
    function(parentScope, model, scopeName, indexName) {
      var scope = {};
      scope[scopeName] = model;
      scope[indexName] = undefined;
      scope[parentScopeName] = parentScope;
      scope.__proto__ = parentScope;
      return scope;
    } :
    function(parentScope, model, scopeName, indexName) {
      var scope = Object.create(parentScope);
      Object.defineProperty(scope, scopeName,
          { value: model, configurable: true, writable: true });
      Object.defineProperty(scope, indexName,
          { value: undefined, configurable: true, writable: true });
      Object.defineProperty(scope, parentScopeName,
          { value: parentScope, configurable: true, writable: true });
      return scope;
    };

  global.PolymerExpressions = PolymerExpressions;
  PolymerExpressions.getExpression = getExpression;
})(this);

Polymer = {
  version: '0.5.5'
};

// TODO(sorvell): this ensures Polymer is an object and not a function
// Platform is currently defining it as a function to allow for async loading
// of polymer; once we refine the loading process this likely goes away.
if (typeof window.Polymer === 'function') {
  Polymer = {};
}


(function(scope) {

  function withDependencies(task, depends) {
    depends = depends || [];
    if (!depends.map) {
      depends = [depends];
    }
    return task.apply(this, depends.map(marshal));
  }

  function module(name, dependsOrFactory, moduleFactory) {
    var module;
    switch (arguments.length) {
      case 0:
        return;
      case 1:
        module = null;
        break;
      case 2:
        // dependsOrFactory is `factory` in this case
        module = dependsOrFactory.apply(this);
        break;
      default:
        // dependsOrFactory is `depends` in this case
        module = withDependencies(moduleFactory, dependsOrFactory);
        break;
    }
    modules[name] = module;
  };

  function marshal(name) {
    return modules[name];
  }

  var modules = {};

  function using(depends, task) {
    HTMLImports.whenImportsReady(function() {
      withDependencies(task, depends);
    });
  };

  // exports

  scope.marshal = marshal;
  // `module` confuses commonjs detectors
  scope.modularize = module;
  scope.using = using;

})(window);

/*
	Build only script.

  Ensures scripts needed for basic x-platform compatibility
  will be run when platform.js is not loaded.
 */
if (!window.WebComponents) {

/*
	On supported platforms, platform.js is not needed. To retain compatibility
	with the polyfills, we stub out minimal functionality.
 */
if (!window.WebComponents) {

  WebComponents = {
  	flush: function() {},
    flags: {log: {}}
  };

  Platform = WebComponents;

  CustomElements = {
  	useNative: true,
    ready: true,
    takeRecords: function() {},
    instanceof: function(obj, base) {
      return obj instanceof base;
    }
  };

  HTMLImports = {
  	useNative: true
  };


  addEventListener('HTMLImportsLoaded', function() {
    document.dispatchEvent(
      new CustomEvent('WebComponentsReady', {bubbles: true})
    );
  });


  // ShadowDOM
  ShadowDOMPolyfill = null;
  wrap = unwrap = function(n){
    return n;
  };

}

/*
  Create polyfill scope and feature detect native support.
*/
window.HTMLImports = window.HTMLImports || {flags:{}};

(function(scope) {

/**
  Basic setup and simple module executer. We collect modules and then execute
  the code later, only if it's necessary for polyfilling.
*/
var IMPORT_LINK_TYPE = 'import';
var useNative = Boolean(IMPORT_LINK_TYPE in document.createElement('link'));

/**
  Support `currentScript` on all browsers as `document._currentScript.`

  NOTE: We cannot polyfill `document.currentScript` because it's not possible
  both to override and maintain the ability to capture the native value.
  Therefore we choose to expose `_currentScript` both when native imports
  and the polyfill are in use.
*/
// NOTE: ShadowDOMPolyfill intrusion.
var hasShadowDOMPolyfill = Boolean(window.ShadowDOMPolyfill);
var wrap = function(node) {
  return hasShadowDOMPolyfill ? ShadowDOMPolyfill.wrapIfNeeded(node) : node;
};
var rootDocument = wrap(document);

var currentScriptDescriptor = {
  get: function() {
    var script = HTMLImports.currentScript || document.currentScript ||
        // NOTE: only works when called in synchronously executing code.
        // readyState should check if `loading` but IE10 is
        // interactive when scripts run so we cheat.
        (document.readyState !== 'complete' ?
        document.scripts[document.scripts.length - 1] : null);
    return wrap(script);
  },
  configurable: true
};

Object.defineProperty(document, '_currentScript', currentScriptDescriptor);
Object.defineProperty(rootDocument, '_currentScript', currentScriptDescriptor);

/**
  Add support for the `HTMLImportsLoaded` event and the `HTMLImports.whenReady`
  method. This api is necessary because unlike the native implementation,
  script elements do not force imports to resolve. Instead, users should wrap
  code in either an `HTMLImportsLoaded` hander or after load time in an
  `HTMLImports.whenReady(callback)` call.

  NOTE: This module also supports these apis under the native implementation.
  Therefore, if this file is loaded, the same code can be used under both
  the polyfill and native implementation.
 */

var isIE = /Trident/.test(navigator.userAgent);

// call a callback when all HTMLImports in the document at call time
// (or at least document ready) have loaded.
// 1. ensure the document is in a ready state (has dom), then
// 2. watch for loading of imports and call callback when done
function whenReady(callback, doc) {
  doc = doc || rootDocument;
  // if document is loading, wait and try again
  whenDocumentReady(function() {
    watchImportsLoad(callback, doc);
  }, doc);
}

// call the callback when the document is in a ready state (has dom)
var requiredReadyState = isIE ? 'complete' : 'interactive';
var READY_EVENT = 'readystatechange';
function isDocumentReady(doc) {
  return (doc.readyState === 'complete' ||
      doc.readyState === requiredReadyState);
}

// call <callback> when we ensure the document is in a ready state
function whenDocumentReady(callback, doc) {
  if (!isDocumentReady(doc)) {
    var checkReady = function() {
      if (doc.readyState === 'complete' ||
          doc.readyState === requiredReadyState) {
        doc.removeEventListener(READY_EVENT, checkReady);
        whenDocumentReady(callback, doc);
      }
    };
    doc.addEventListener(READY_EVENT, checkReady);
  } else if (callback) {
    callback();
  }
}

function markTargetLoaded(event) {
  event.target.__loaded = true;
}

// call <callback> when we ensure all imports have loaded
function watchImportsLoad(callback, doc) {
  var imports = doc.querySelectorAll('link[rel=import]');
  var loaded = 0, l = imports.length;
  function checkDone(d) {
    if ((loaded == l) && callback) {
       callback();
    }
  }
  function loadedImport(e) {
    markTargetLoaded(e);
    loaded++;
    checkDone();
  }
  if (l) {
    for (var i=0, imp; (i<l) && (imp=imports[i]); i++) {
      if (isImportLoaded(imp)) {
        loadedImport.call(imp, {target: imp});
      } else {
        imp.addEventListener('load', loadedImport);
        imp.addEventListener('error', loadedImport);
      }
    }
  } else {
    checkDone();
  }
}

// NOTE: test for native imports loading is based on explicitly watching
// all imports (see below).
// However, we cannot rely on this entirely without watching the entire document
// for import links. For perf reasons, currently only head is watched.
// Instead, we fallback to checking if the import property is available
// and the document is not itself loading.
function isImportLoaded(link) {
  return useNative ? link.__loaded ||
      (link.import && link.import.readyState !== 'loading') :
      link.__importParsed;
}

// TODO(sorvell): Workaround for
// https://www.w3.org/Bugs/Public/show_bug.cgi?id=25007, should be removed when
// this bug is addressed.
// (1) Install a mutation observer to see when HTMLImports have loaded
// (2) if this script is run during document load it will watch any existing
// imports for loading.
//
// NOTE: The workaround has restricted functionality: (1) it's only compatible
// with imports that are added to document.head since the mutation observer
// watches only head for perf reasons, (2) it requires this script
// to run before any imports have completed loading.
if (useNative) {
  new MutationObserver(function(mxns) {
    for (var i=0, l=mxns.length, m; (i < l) && (m=mxns[i]); i++) {
      if (m.addedNodes) {
        handleImports(m.addedNodes);
      }
    }
  }).observe(document.head, {childList: true});

  function handleImports(nodes) {
    for (var i=0, l=nodes.length, n; (i<l) && (n=nodes[i]); i++) {
      if (isImport(n)) {
        handleImport(n);
      }
    }
  }

  function isImport(element) {
    return element.localName === 'link' && element.rel === 'import';
  }

  function handleImport(element) {
    var loaded = element.import;
    if (loaded) {
      markTargetLoaded({target: element});
    } else {
      element.addEventListener('load', markTargetLoaded);
      element.addEventListener('error', markTargetLoaded);
    }
  }

  // make sure to catch any imports that are in the process of loading
  // when this script is run.
  (function() {
    if (document.readyState === 'loading') {
      var imports = document.querySelectorAll('link[rel=import]');
      for (var i=0, l=imports.length, imp; (i<l) && (imp=imports[i]); i++) {
        handleImport(imp);
      }
    }
  })();

}

// Fire the 'HTMLImportsLoaded' event when imports in document at load time
// have loaded. This event is required to simulate the script blocking
// behavior of native imports. A main document script that needs to be sure
// imports have loaded should wait for this event.
whenReady(function() {
  HTMLImports.ready = true;
  HTMLImports.readyTime = new Date().getTime();
  rootDocument.dispatchEvent(
    new CustomEvent('HTMLImportsLoaded', {bubbles: true})
  );
});

// exports
scope.IMPORT_LINK_TYPE = IMPORT_LINK_TYPE;
scope.useNative = useNative;
scope.rootDocument = rootDocument;
scope.whenReady = whenReady;
scope.isIE = isIE;

})(HTMLImports);

(function(scope) {

  // TODO(sorvell): It's desireable to provide a default stylesheet
  // that's convenient for styling unresolved elements, but
  // it's cumbersome to have to include this manually in every page.
  // It would make sense to put inside some HTMLImport but
  // the HTMLImports polyfill does not allow loading of stylesheets
  // that block rendering. Therefore this injection is tolerated here.
  var style = document.createElement('style');
  style.textContent = ''
      + 'body {'
      + 'transition: opacity ease-in 0.2s;'
      + ' } \n'
      + 'body[unresolved] {'
      + 'opacity: 0; display: block; overflow: hidden;'
      + ' } \n'
      ;
  var head = document.querySelector('head');
  head.insertBefore(style, head.firstChild);

})(Platform);

/*
	Build only script.

  Ensures scripts needed for basic x-platform compatibility
  will be run when platform.js is not loaded.
 */
}
(function(global) {
  'use strict';

  var testingExposeCycleCount = global.testingExposeCycleCount;

  // Detect and do basic sanity checking on Object/Array.observe.
  function detectObjectObserve() {
    if (typeof Object.observe !== 'function' ||
        typeof Array.observe !== 'function') {
      return false;
    }

    var records = [];

    function callback(recs) {
      records = recs;
    }

    var test = {};
    var arr = [];
    Object.observe(test, callback);
    Array.observe(arr, callback);
    test.id = 1;
    test.id = 2;
    delete test.id;
    arr.push(1, 2);
    arr.length = 0;

    Object.deliverChangeRecords(callback);
    if (records.length !== 5)
      return false;

    if (records[0].type != 'add' ||
        records[1].type != 'update' ||
        records[2].type != 'delete' ||
        records[3].type != 'splice' ||
        records[4].type != 'splice') {
      return false;
    }

    Object.unobserve(test, callback);
    Array.unobserve(arr, callback);

    return true;
  }

  var hasObserve = detectObjectObserve();

  function detectEval() {
    // Don't test for eval if we're running in a Chrome App environment.
    // We check for APIs set that only exist in a Chrome App context.
    if (typeof chrome !== 'undefined' && chrome.app && chrome.app.runtime) {
      return false;
    }

    // Firefox OS Apps do not allow eval. This feature detection is very hacky
    // but even if some other platform adds support for this function this code
    // will continue to work.
    if (typeof navigator != 'undefined' && navigator.getDeviceStorage) {
      return false;
    }

    try {
      var f = new Function('', 'return true;');
      return f();
    } catch (ex) {
      return false;
    }
  }

  var hasEval = detectEval();

  function isIndex(s) {
    return +s === s >>> 0 && s !== '';
  }

  function toNumber(s) {
    return +s;
  }

  function isObject(obj) {
    return obj === Object(obj);
  }

  var numberIsNaN = global.Number.isNaN || function(value) {
    return typeof value === 'number' && global.isNaN(value);
  }

  function areSameValue(left, right) {
    if (left === right)
      return left !== 0 || 1 / left === 1 / right;
    if (numberIsNaN(left) && numberIsNaN(right))
      return true;

    return left !== left && right !== right;
  }

  var createObject = ('__proto__' in {}) ?
    function(obj) { return obj; } :
    function(obj) {
      var proto = obj.__proto__;
      if (!proto)
        return obj;
      var newObject = Object.create(proto);
      Object.getOwnPropertyNames(obj).forEach(function(name) {
        Object.defineProperty(newObject, name,
                             Object.getOwnPropertyDescriptor(obj, name));
      });
      return newObject;
    };

  var identStart = '[\$_a-zA-Z]';
  var identPart = '[\$_a-zA-Z0-9]';
  var identRegExp = new RegExp('^' + identStart + '+' + identPart + '*' + '$');

  function getPathCharType(char) {
    if (char === undefined)
      return 'eof';

    var code = char.charCodeAt(0);

    switch(code) {
      case 0x5B: // [
      case 0x5D: // ]
      case 0x2E: // .
      case 0x22: // "
      case 0x27: // '
      case 0x30: // 0
        return char;

      case 0x5F: // _
      case 0x24: // $
        return 'ident';

      case 0x20: // Space
      case 0x09: // Tab
      case 0x0A: // Newline
      case 0x0D: // Return
      case 0xA0:  // No-break space
      case 0xFEFF:  // Byte Order Mark
      case 0x2028:  // Line Separator
      case 0x2029:  // Paragraph Separator
        return 'ws';
    }

    // a-z, A-Z
    if ((0x61 <= code && code <= 0x7A) || (0x41 <= code && code <= 0x5A))
      return 'ident';

    // 1-9
    if (0x31 <= code && code <= 0x39)
      return 'number';

    return 'else';
  }

  var pathStateMachine = {
    'beforePath': {
      'ws': ['beforePath'],
      'ident': ['inIdent', 'append'],
      '[': ['beforeElement'],
      'eof': ['afterPath']
    },

    'inPath': {
      'ws': ['inPath'],
      '.': ['beforeIdent'],
      '[': ['beforeElement'],
      'eof': ['afterPath']
    },

    'beforeIdent': {
      'ws': ['beforeIdent'],
      'ident': ['inIdent', 'append']
    },

    'inIdent': {
      'ident': ['inIdent', 'append'],
      '0': ['inIdent', 'append'],
      'number': ['inIdent', 'append'],
      'ws': ['inPath', 'push'],
      '.': ['beforeIdent', 'push'],
      '[': ['beforeElement', 'push'],
      'eof': ['afterPath', 'push']
    },

    'beforeElement': {
      'ws': ['beforeElement'],
      '0': ['afterZero', 'append'],
      'number': ['inIndex', 'append'],
      "'": ['inSingleQuote', 'append', ''],
      '"': ['inDoubleQuote', 'append', '']
    },

    'afterZero': {
      'ws': ['afterElement', 'push'],
      ']': ['inPath', 'push']
    },

    'inIndex': {
      '0': ['inIndex', 'append'],
      'number': ['inIndex', 'append'],
      'ws': ['afterElement'],
      ']': ['inPath', 'push']
    },

    'inSingleQuote': {
      "'": ['afterElement'],
      'eof': ['error'],
      'else': ['inSingleQuote', 'append']
    },

    'inDoubleQuote': {
      '"': ['afterElement'],
      'eof': ['error'],
      'else': ['inDoubleQuote', 'append']
    },

    'afterElement': {
      'ws': ['afterElement'],
      ']': ['inPath', 'push']
    }
  }

  function noop() {}

  function parsePath(path) {
    var keys = [];
    var index = -1;
    var c, newChar, key, type, transition, action, typeMap, mode = 'beforePath';

    var actions = {
      push: function() {
        if (key === undefined)
          return;

        keys.push(key);
        key = undefined;
      },

      append: function() {
        if (key === undefined)
          key = newChar
        else
          key += newChar;
      }
    };

    function maybeUnescapeQuote() {
      if (index >= path.length)
        return;

      var nextChar = path[index + 1];
      if ((mode == 'inSingleQuote' && nextChar == "'") ||
          (mode == 'inDoubleQuote' && nextChar == '"')) {
        index++;
        newChar = nextChar;
        actions.append();
        return true;
      }
    }

    while (mode) {
      index++;
      c = path[index];

      if (c == '\\' && maybeUnescapeQuote(mode))
        continue;

      type = getPathCharType(c);
      typeMap = pathStateMachine[mode];
      transition = typeMap[type] || typeMap['else'] || 'error';

      if (transition == 'error')
        return; // parse error;

      mode = transition[0];
      action = actions[transition[1]] || noop;
      newChar = transition[2] === undefined ? c : transition[2];
      action();

      if (mode === 'afterPath') {
        return keys;
      }
    }

    return; // parse error
  }

  function isIdent(s) {
    return identRegExp.test(s);
  }

  var constructorIsPrivate = {};

  function Path(parts, privateToken) {
    if (privateToken !== constructorIsPrivate)
      throw Error('Use Path.get to retrieve path objects');

    for (var i = 0; i < parts.length; i++) {
      this.push(String(parts[i]));
    }

    if (hasEval && this.length) {
      this.getValueFrom = this.compiledGetValueFromFn();
    }
  }

  // TODO(rafaelw): Make simple LRU cache
  var pathCache = {};

  function getPath(pathString) {
    if (pathString instanceof Path)
      return pathString;

    if (pathString == null || pathString.length == 0)
      pathString = '';

    if (typeof pathString != 'string') {
      if (isIndex(pathString.length)) {
        // Constructed with array-like (pre-parsed) keys
        return new Path(pathString, constructorIsPrivate);
      }

      pathString = String(pathString);
    }

    var path = pathCache[pathString];
    if (path)
      return path;

    var parts = parsePath(pathString);
    if (!parts)
      return invalidPath;

    var path = new Path(parts, constructorIsPrivate);
    pathCache[pathString] = path;
    return path;
  }

  Path.get = getPath;

  function formatAccessor(key) {
    if (isIndex(key)) {
      return '[' + key + ']';
    } else {
      return '["' + key.replace(/"/g, '\\"') + '"]';
    }
  }

  Path.prototype = createObject({
    __proto__: [],
    valid: true,

    toString: function() {
      var pathString = '';
      for (var i = 0; i < this.length; i++) {
        var key = this[i];
        if (isIdent(key)) {
          pathString += i ? '.' + key : key;
        } else {
          pathString += formatAccessor(key);
        }
      }

      return pathString;
    },

    getValueFrom: function(obj, directObserver) {
      for (var i = 0; i < this.length; i++) {
        if (obj == null)
          return;
        obj = obj[this[i]];
      }
      return obj;
    },

    iterateObjects: function(obj, observe) {
      for (var i = 0; i < this.length; i++) {
        if (i)
          obj = obj[this[i - 1]];
        if (!isObject(obj))
          return;
        observe(obj, this[i]);
      }
    },

    compiledGetValueFromFn: function() {
      var str = '';
      var pathString = 'obj';
      str += 'if (obj != null';
      var i = 0;
      var key;
      for (; i < (this.length - 1); i++) {
        key = this[i];
        pathString += isIdent(key) ? '.' + key : formatAccessor(key);
        str += ' &&\n     ' + pathString + ' != null';
      }
      str += ')\n';

      var key = this[i];
      pathString += isIdent(key) ? '.' + key : formatAccessor(key);

      str += '  return ' + pathString + ';\nelse\n  return undefined;';
      return new Function('obj', str);
    },

    setValueFrom: function(obj, value) {
      if (!this.length)
        return false;

      for (var i = 0; i < this.length - 1; i++) {
        if (!isObject(obj))
          return false;
        obj = obj[this[i]];
      }

      if (!isObject(obj))
        return false;

      obj[this[i]] = value;
      return true;
    }
  });

  var invalidPath = new Path('', constructorIsPrivate);
  invalidPath.valid = false;
  invalidPath.getValueFrom = invalidPath.setValueFrom = function() {};

  var MAX_DIRTY_CHECK_CYCLES = 1000;

  function dirtyCheck(observer) {
    var cycles = 0;
    while (cycles < MAX_DIRTY_CHECK_CYCLES && observer.check_()) {
      cycles++;
    }
    if (testingExposeCycleCount)
      global.dirtyCheckCycleCount = cycles;

    return cycles > 0;
  }

  function objectIsEmpty(object) {
    for (var prop in object)
      return false;
    return true;
  }

  function diffIsEmpty(diff) {
    return objectIsEmpty(diff.added) &&
           objectIsEmpty(diff.removed) &&
           objectIsEmpty(diff.changed);
  }

  function diffObjectFromOldObject(object, oldObject) {
    var added = {};
    var removed = {};
    var changed = {};

    for (var prop in oldObject) {
      var newValue = object[prop];

      if (newValue !== undefined && newValue === oldObject[prop])
        continue;

      if (!(prop in object)) {
        removed[prop] = undefined;
        continue;
      }

      if (newValue !== oldObject[prop])
        changed[prop] = newValue;
    }

    for (var prop in object) {
      if (prop in oldObject)
        continue;

      added[prop] = object[prop];
    }

    if (Array.isArray(object) && object.length !== oldObject.length)
      changed.length = object.length;

    return {
      added: added,
      removed: removed,
      changed: changed
    };
  }

  var eomTasks = [];
  function runEOMTasks() {
    if (!eomTasks.length)
      return false;

    for (var i = 0; i < eomTasks.length; i++) {
      eomTasks[i]();
    }
    eomTasks.length = 0;
    return true;
  }

  var runEOM = hasObserve ? (function(){
    return function(fn) {
      return Promise.resolve().then(fn);
    }
  })() :
  (function() {
    return function(fn) {
      eomTasks.push(fn);
    };
  })();

  var observedObjectCache = [];

  function newObservedObject() {
    var observer;
    var object;
    var discardRecords = false;
    var first = true;

    function callback(records) {
      if (observer && observer.state_ === OPENED && !discardRecords)
        observer.check_(records);
    }

    return {
      open: function(obs) {
        if (observer)
          throw Error('ObservedObject in use');

        if (!first)
          Object.deliverChangeRecords(callback);

        observer = obs;
        first = false;
      },
      observe: function(obj, arrayObserve) {
        object = obj;
        if (arrayObserve)
          Array.observe(object, callback);
        else
          Object.observe(object, callback);
      },
      deliver: function(discard) {
        discardRecords = discard;
        Object.deliverChangeRecords(callback);
        discardRecords = false;
      },
      close: function() {
        observer = undefined;
        Object.unobserve(object, callback);
        observedObjectCache.push(this);
      }
    };
  }

  /*
   * The observedSet abstraction is a perf optimization which reduces the total
   * number of Object.observe observations of a set of objects. The idea is that
   * groups of Observers will have some object dependencies in common and this
   * observed set ensures that each object in the transitive closure of
   * dependencies is only observed once. The observedSet acts as a write barrier
   * such that whenever any change comes through, all Observers are checked for
   * changed values.
   *
   * Note that this optimization is explicitly moving work from setup-time to
   * change-time.
   *
   * TODO(rafaelw): Implement "garbage collection". In order to move work off
   * the critical path, when Observers are closed, their observed objects are
   * not Object.unobserve(d). As a result, it's possible that if the observedSet
   * is kept open, but some Observers have been closed, it could cause "leaks"
   * (prevent otherwise collectable objects from being collected). At some
   * point, we should implement incremental "gc" which keeps a list of
   * observedSets which may need clean-up and does small amounts of cleanup on a
   * timeout until all is clean.
   */

  function getObservedObject(observer, object, arrayObserve) {
    var dir = observedObjectCache.pop() || newObservedObject();
    dir.open(observer);
    dir.observe(object, arrayObserve);
    return dir;
  }

  var observedSetCache = [];

  function newObservedSet() {
    var observerCount = 0;
    var observers = [];
    var objects = [];
    var rootObj;
    var rootObjProps;

    function observe(obj, prop) {
      if (!obj)
        return;

      if (obj === rootObj)
        rootObjProps[prop] = true;

      if (objects.indexOf(obj) < 0) {
        objects.push(obj);
        Object.observe(obj, callback);
      }

      observe(Object.getPrototypeOf(obj), prop);
    }

    function allRootObjNonObservedProps(recs) {
      for (var i = 0; i < recs.length; i++) {
        var rec = recs[i];
        if (rec.object !== rootObj ||
            rootObjProps[rec.name] ||
            rec.type === 'setPrototype') {
          return false;
        }
      }
      return true;
    }

    function callback(recs) {
      if (allRootObjNonObservedProps(recs))
        return;

      var observer;
      for (var i = 0; i < observers.length; i++) {
        observer = observers[i];
        if (observer.state_ == OPENED) {
          observer.iterateObjects_(observe);
        }
      }

      for (var i = 0; i < observers.length; i++) {
        observer = observers[i];
        if (observer.state_ == OPENED) {
          observer.check_();
        }
      }
    }

    var record = {
      objects: objects,
      get rootObject() { return rootObj; },
      set rootObject(value) {
        rootObj = value;
        rootObjProps = {};
      },
      open: function(obs, object) {
        observers.push(obs);
        observerCount++;
        obs.iterateObjects_(observe);
      },
      close: function(obs) {
        observerCount--;
        if (observerCount > 0) {
          return;
        }

        for (var i = 0; i < objects.length; i++) {
          Object.unobserve(objects[i], callback);
          Observer.unobservedCount++;
        }

        observers.length = 0;
        objects.length = 0;
        rootObj = undefined;
        rootObjProps = undefined;
        observedSetCache.push(this);
        if (lastObservedSet === this)
          lastObservedSet = null;
      },
    };

    return record;
  }

  var lastObservedSet;

  function getObservedSet(observer, obj) {
    if (!lastObservedSet || lastObservedSet.rootObject !== obj) {
      lastObservedSet = observedSetCache.pop() || newObservedSet();
      lastObservedSet.rootObject = obj;
    }
    lastObservedSet.open(observer, obj);
    return lastObservedSet;
  }

  var UNOPENED = 0;
  var OPENED = 1;
  var CLOSED = 2;
  var RESETTING = 3;

  var nextObserverId = 1;

  function Observer() {
    this.state_ = UNOPENED;
    this.callback_ = undefined;
    this.target_ = undefined; // TODO(rafaelw): Should be WeakRef
    this.directObserver_ = undefined;
    this.value_ = undefined;
    this.id_ = nextObserverId++;
  }

  Observer.prototype = {
    open: function(callback, target) {
      if (this.state_ != UNOPENED)
        throw Error('Observer has already been opened.');

      addToAll(this);
      this.callback_ = callback;
      this.target_ = target;
      this.connect_();
      this.state_ = OPENED;
      return this.value_;
    },

    close: function() {
      if (this.state_ != OPENED)
        return;

      removeFromAll(this);
      this.disconnect_();
      this.value_ = undefined;
      this.callback_ = undefined;
      this.target_ = undefined;
      this.state_ = CLOSED;
    },

    deliver: function() {
      if (this.state_ != OPENED)
        return;

      dirtyCheck(this);
    },

    report_: function(changes) {
      try {
        this.callback_.apply(this.target_, changes);
      } catch (ex) {
        Observer._errorThrownDuringCallback = true;
        console.error('Exception caught during observer callback: ' +
                       (ex.stack || ex));
      }
    },

    discardChanges: function() {
      this.check_(undefined, true);
      return this.value_;
    }
  }

  var collectObservers = !hasObserve;
  var allObservers;
  Observer._allObserversCount = 0;

  if (collectObservers) {
    allObservers = [];
  }

  function addToAll(observer) {
    Observer._allObserversCount++;
    if (!collectObservers)
      return;

    allObservers.push(observer);
  }

  function removeFromAll(observer) {
    Observer._allObserversCount--;
  }

  var runningMicrotaskCheckpoint = false;

  global.Platform = global.Platform || {};

  global.Platform.performMicrotaskCheckpoint = function() {
    if (runningMicrotaskCheckpoint)
      return;

    if (!collectObservers)
      return;

    runningMicrotaskCheckpoint = true;

    var cycles = 0;
    var anyChanged, toCheck;

    do {
      cycles++;
      toCheck = allObservers;
      allObservers = [];
      anyChanged = false;

      for (var i = 0; i < toCheck.length; i++) {
        var observer = toCheck[i];
        if (observer.state_ != OPENED)
          continue;

        if (observer.check_())
          anyChanged = true;

        allObservers.push(observer);
      }
      if (runEOMTasks())
        anyChanged = true;
    } while (cycles < MAX_DIRTY_CHECK_CYCLES && anyChanged);

    if (testingExposeCycleCount)
      global.dirtyCheckCycleCount = cycles;

    runningMicrotaskCheckpoint = false;
  };

  if (collectObservers) {
    global.Platform.clearObservers = function() {
      allObservers = [];
    };
  }

  function ObjectObserver(object) {
    Observer.call(this);
    this.value_ = object;
    this.oldObject_ = undefined;
  }

  ObjectObserver.prototype = createObject({
    __proto__: Observer.prototype,

    arrayObserve: false,

    connect_: function(callback, target) {
      if (hasObserve) {
        this.directObserver_ = getObservedObject(this, this.value_,
                                                 this.arrayObserve);
      } else {
        this.oldObject_ = this.copyObject(this.value_);
      }

    },

    copyObject: function(object) {
      var copy = Array.isArray(object) ? [] : {};
      for (var prop in object) {
        copy[prop] = object[prop];
      };
      if (Array.isArray(object))
        copy.length = object.length;
      return copy;
    },

    check_: function(changeRecords, skipChanges) {
      var diff;
      var oldValues;
      if (hasObserve) {
        if (!changeRecords)
          return false;

        oldValues = {};
        diff = diffObjectFromChangeRecords(this.value_, changeRecords,
                                           oldValues);
      } else {
        oldValues = this.oldObject_;
        diff = diffObjectFromOldObject(this.value_, this.oldObject_);
      }

      if (diffIsEmpty(diff))
        return false;

      if (!hasObserve)
        this.oldObject_ = this.copyObject(this.value_);

      this.report_([
        diff.added || {},
        diff.removed || {},
        diff.changed || {},
        function(property) {
          return oldValues[property];
        }
      ]);

      return true;
    },

    disconnect_: function() {
      if (hasObserve) {
        this.directObserver_.close();
        this.directObserver_ = undefined;
      } else {
        this.oldObject_ = undefined;
      }
    },

    deliver: function() {
      if (this.state_ != OPENED)
        return;

      if (hasObserve)
        this.directObserver_.deliver(false);
      else
        dirtyCheck(this);
    },

    discardChanges: function() {
      if (this.directObserver_)
        this.directObserver_.deliver(true);
      else
        this.oldObject_ = this.copyObject(this.value_);

      return this.value_;
    }
  });

  function ArrayObserver(array) {
    if (!Array.isArray(array))
      throw Error('Provided object is not an Array');
    ObjectObserver.call(this, array);
  }

  ArrayObserver.prototype = createObject({

    __proto__: ObjectObserver.prototype,

    arrayObserve: true,

    copyObject: function(arr) {
      return arr.slice();
    },

    check_: function(changeRecords) {
      var splices;
      if (hasObserve) {
        if (!changeRecords)
          return false;
        splices = projectArraySplices(this.value_, changeRecords);
      } else {
        splices = calcSplices(this.value_, 0, this.value_.length,
                              this.oldObject_, 0, this.oldObject_.length);
      }

      if (!splices || !splices.length)
        return false;

      if (!hasObserve)
        this.oldObject_ = this.copyObject(this.value_);

      this.report_([splices]);
      return true;
    }
  });

  ArrayObserver.applySplices = function(previous, current, splices) {
    splices.forEach(function(splice) {
      var spliceArgs = [splice.index, splice.removed.length];
      var addIndex = splice.index;
      while (addIndex < splice.index + splice.addedCount) {
        spliceArgs.push(current[addIndex]);
        addIndex++;
      }

      Array.prototype.splice.apply(previous, spliceArgs);
    });
  };

  function PathObserver(object, path) {
    Observer.call(this);

    this.object_ = object;
    this.path_ = getPath(path);
    this.directObserver_ = undefined;
  }

  PathObserver.prototype = createObject({
    __proto__: Observer.prototype,

    get path() {
      return this.path_;
    },

    connect_: function() {
      if (hasObserve)
        this.directObserver_ = getObservedSet(this, this.object_);

      this.check_(undefined, true);
    },

    disconnect_: function() {
      this.value_ = undefined;

      if (this.directObserver_) {
        this.directObserver_.close(this);
        this.directObserver_ = undefined;
      }
    },

    iterateObjects_: function(observe) {
      this.path_.iterateObjects(this.object_, observe);
    },

    check_: function(changeRecords, skipChanges) {
      var oldValue = this.value_;
      this.value_ = this.path_.getValueFrom(this.object_);
      if (skipChanges || areSameValue(this.value_, oldValue))
        return false;

      this.report_([this.value_, oldValue, this]);
      return true;
    },

    setValue: function(newValue) {
      if (this.path_)
        this.path_.setValueFrom(this.object_, newValue);
    }
  });

  function CompoundObserver(reportChangesOnOpen) {
    Observer.call(this);

    this.reportChangesOnOpen_ = reportChangesOnOpen;
    this.value_ = [];
    this.directObserver_ = undefined;
    this.observed_ = [];
  }

  var observerSentinel = {};

  CompoundObserver.prototype = createObject({
    __proto__: Observer.prototype,

    connect_: function() {
      if (hasObserve) {
        var object;
        var needsDirectObserver = false;
        for (var i = 0; i < this.observed_.length; i += 2) {
          object = this.observed_[i]
          if (object !== observerSentinel) {
            needsDirectObserver = true;
            break;
          }
        }

        if (needsDirectObserver)
          this.directObserver_ = getObservedSet(this, object);
      }

      this.check_(undefined, !this.reportChangesOnOpen_);
    },

    disconnect_: function() {
      for (var i = 0; i < this.observed_.length; i += 2) {
        if (this.observed_[i] === observerSentinel)
          this.observed_[i + 1].close();
      }
      this.observed_.length = 0;
      this.value_.length = 0;

      if (this.directObserver_) {
        this.directObserver_.close(this);
        this.directObserver_ = undefined;
      }
    },

    addPath: function(object, path) {
      if (this.state_ != UNOPENED && this.state_ != RESETTING)
        throw Error('Cannot add paths once started.');

      var path = getPath(path);
      this.observed_.push(object, path);
      if (!this.reportChangesOnOpen_)
        return;
      var index = this.observed_.length / 2 - 1;
      this.value_[index] = path.getValueFrom(object);
    },

    addObserver: function(observer) {
      if (this.state_ != UNOPENED && this.state_ != RESETTING)
        throw Error('Cannot add observers once started.');

      this.observed_.push(observerSentinel, observer);
      if (!this.reportChangesOnOpen_)
        return;
      var index = this.observed_.length / 2 - 1;
      this.value_[index] = observer.open(this.deliver, this);
    },

    startReset: function() {
      if (this.state_ != OPENED)
        throw Error('Can only reset while open');

      this.state_ = RESETTING;
      this.disconnect_();
    },

    finishReset: function() {
      if (this.state_ != RESETTING)
        throw Error('Can only finishReset after startReset');
      this.state_ = OPENED;
      this.connect_();

      return this.value_;
    },

    iterateObjects_: function(observe) {
      var object;
      for (var i = 0; i < this.observed_.length; i += 2) {
        object = this.observed_[i]
        if (object !== observerSentinel)
          this.observed_[i + 1].iterateObjects(object, observe)
      }
    },

    check_: function(changeRecords, skipChanges) {
      var oldValues;
      for (var i = 0; i < this.observed_.length; i += 2) {
        var object = this.observed_[i];
        var path = this.observed_[i+1];
        var value;
        if (object === observerSentinel) {
          var observable = path;
          value = this.state_ === UNOPENED ?
              observable.open(this.deliver, this) :
              observable.discardChanges();
        } else {
          value = path.getValueFrom(object);
        }

        if (skipChanges) {
          this.value_[i / 2] = value;
          continue;
        }

        if (areSameValue(value, this.value_[i / 2]))
          continue;

        oldValues = oldValues || [];
        oldValues[i / 2] = this.value_[i / 2];
        this.value_[i / 2] = value;
      }

      if (!oldValues)
        return false;

      // TODO(rafaelw): Having observed_ as the third callback arg here is
      // pretty lame API. Fix.
      this.report_([this.value_, oldValues, this.observed_]);
      return true;
    }
  });

  function identFn(value) { return value; }

  function ObserverTransform(observable, getValueFn, setValueFn,
                             dontPassThroughSet) {
    this.callback_ = undefined;
    this.target_ = undefined;
    this.value_ = undefined;
    this.observable_ = observable;
    this.getValueFn_ = getValueFn || identFn;
    this.setValueFn_ = setValueFn || identFn;
    // TODO(rafaelw): This is a temporary hack. PolymerExpressions needs this
    // at the moment because of a bug in it's dependency tracking.
    this.dontPassThroughSet_ = dontPassThroughSet;
  }

  ObserverTransform.prototype = {
    open: function(callback, target) {
      this.callback_ = callback;
      this.target_ = target;
      this.value_ =
          this.getValueFn_(this.observable_.open(this.observedCallback_, this));
      return this.value_;
    },

    observedCallback_: function(value) {
      value = this.getValueFn_(value);
      if (areSameValue(value, this.value_))
        return;
      var oldValue = this.value_;
      this.value_ = value;
      this.callback_.call(this.target_, this.value_, oldValue);
    },

    discardChanges: function() {
      this.value_ = this.getValueFn_(this.observable_.discardChanges());
      return this.value_;
    },

    deliver: function() {
      return this.observable_.deliver();
    },

    setValue: function(value) {
      value = this.setValueFn_(value);
      if (!this.dontPassThroughSet_ && this.observable_.setValue)
        return this.observable_.setValue(value);
    },

    close: function() {
      if (this.observable_)
        this.observable_.close();
      this.callback_ = undefined;
      this.target_ = undefined;
      this.observable_ = undefined;
      this.value_ = undefined;
      this.getValueFn_ = undefined;
      this.setValueFn_ = undefined;
    }
  }

  var expectedRecordTypes = {
    add: true,
    update: true,
    delete: true
  };

  function diffObjectFromChangeRecords(object, changeRecords, oldValues) {
    var added = {};
    var removed = {};

    for (var i = 0; i < changeRecords.length; i++) {
      var record = changeRecords[i];
      if (!expectedRecordTypes[record.type]) {
        console.error('Unknown changeRecord type: ' + record.type);
        console.error(record);
        continue;
      }

      if (!(record.name in oldValues))
        oldValues[record.name] = record.oldValue;

      if (record.type == 'update')
        continue;

      if (record.type == 'add') {
        if (record.name in removed)
          delete removed[record.name];
        else
          added[record.name] = true;

        continue;
      }

      // type = 'delete'
      if (record.name in added) {
        delete added[record.name];
        delete oldValues[record.name];
      } else {
        removed[record.name] = true;
      }
    }

    for (var prop in added)
      added[prop] = object[prop];

    for (var prop in removed)
      removed[prop] = undefined;

    var changed = {};
    for (var prop in oldValues) {
      if (prop in added || prop in removed)
        continue;

      var newValue = object[prop];
      if (oldValues[prop] !== newValue)
        changed[prop] = newValue;
    }

    return {
      added: added,
      removed: removed,
      changed: changed
    };
  }

  function newSplice(index, removed, addedCount) {
    return {
      index: index,
      removed: removed,
      addedCount: addedCount
    };
  }

  var EDIT_LEAVE = 0;
  var EDIT_UPDATE = 1;
  var EDIT_ADD = 2;
  var EDIT_DELETE = 3;

  function ArraySplice() {}

  ArraySplice.prototype = {

    // Note: This function is *based* on the computation of the Levenshtein
    // "edit" distance. The one change is that "updates" are treated as two
    // edits - not one. With Array splices, an update is really a delete
    // followed by an add. By retaining this, we optimize for "keeping" the
    // maximum array items in the original array. For example:
    //
    //   'xxxx123' -> '123yyyy'
    //
    // With 1-edit updates, the shortest path would be just to update all seven
    // characters. With 2-edit updates, we delete 4, leave 3, and add 4. This
    // leaves the substring '123' intact.
    calcEditDistances: function(current, currentStart, currentEnd,
                                old, oldStart, oldEnd) {
      // "Deletion" columns
      var rowCount = oldEnd - oldStart + 1;
      var columnCount = currentEnd - currentStart + 1;
      var distances = new Array(rowCount);

      // "Addition" rows. Initialize null column.
      for (var i = 0; i < rowCount; i++) {
        distances[i] = new Array(columnCount);
        distances[i][0] = i;
      }

      // Initialize null row
      for (var j = 0; j < columnCount; j++)
        distances[0][j] = j;

      for (var i = 1; i < rowCount; i++) {
        for (var j = 1; j < columnCount; j++) {
          if (this.equals(current[currentStart + j - 1], old[oldStart + i - 1]))
            distances[i][j] = distances[i - 1][j - 1];
          else {
            var north = distances[i - 1][j] + 1;
            var west = distances[i][j - 1] + 1;
            distances[i][j] = north < west ? north : west;
          }
        }
      }

      return distances;
    },

    // This starts at the final weight, and walks "backward" by finding
    // the minimum previous weight recursively until the origin of the weight
    // matrix.
    spliceOperationsFromEditDistances: function(distances) {
      var i = distances.length - 1;
      var j = distances[0].length - 1;
      var current = distances[i][j];
      var edits = [];
      while (i > 0 || j > 0) {
        if (i == 0) {
          edits.push(EDIT_ADD);
          j--;
          continue;
        }
        if (j == 0) {
          edits.push(EDIT_DELETE);
          i--;
          continue;
        }
        var northWest = distances[i - 1][j - 1];
        var west = distances[i - 1][j];
        var north = distances[i][j - 1];

        var min;
        if (west < north)
          min = west < northWest ? west : northWest;
        else
          min = north < northWest ? north : northWest;

        if (min == northWest) {
          if (northWest == current) {
            edits.push(EDIT_LEAVE);
          } else {
            edits.push(EDIT_UPDATE);
            current = northWest;
          }
          i--;
          j--;
        } else if (min == west) {
          edits.push(EDIT_DELETE);
          i--;
          current = west;
        } else {
          edits.push(EDIT_ADD);
          j--;
          current = north;
        }
      }

      edits.reverse();
      return edits;
    },

    /**
     * Splice Projection functions:
     *
     * A splice map is a representation of how a previous array of items
     * was transformed into a new array of items. Conceptually it is a list of
     * tuples of
     *
     *   <index, removed, addedCount>
     *
     * which are kept in ascending index order of. The tuple represents that at
     * the |index|, |removed| sequence of items were removed, and counting forward
     * from |index|, |addedCount| items were added.
     */

    /**
     * Lacking individual splice mutation information, the minimal set of
     * splices can be synthesized given the previous state and final state of an
     * array. The basic approach is to calculate the edit distance matrix and
     * choose the shortest path through it.
     *
     * Complexity: O(l * p)
     *   l: The length of the current array
     *   p: The length of the old array
     */
    calcSplices: function(current, currentStart, currentEnd,
                          old, oldStart, oldEnd) {
      var prefixCount = 0;
      var suffixCount = 0;

      var minLength = Math.min(currentEnd - currentStart, oldEnd - oldStart);
      if (currentStart == 0 && oldStart == 0)
        prefixCount = this.sharedPrefix(current, old, minLength);

      if (currentEnd == current.length && oldEnd == old.length)
        suffixCount = this.sharedSuffix(current, old, minLength - prefixCount);

      currentStart += prefixCount;
      oldStart += prefixCount;
      currentEnd -= suffixCount;
      oldEnd -= suffixCount;

      if (currentEnd - currentStart == 0 && oldEnd - oldStart == 0)
        return [];

      if (currentStart == currentEnd) {
        var splice = newSplice(currentStart, [], 0);
        while (oldStart < oldEnd)
          splice.removed.push(old[oldStart++]);

        return [ splice ];
      } else if (oldStart == oldEnd)
        return [ newSplice(currentStart, [], currentEnd - currentStart) ];

      var ops = this.spliceOperationsFromEditDistances(
          this.calcEditDistances(current, currentStart, currentEnd,
                                 old, oldStart, oldEnd));

      var splice = undefined;
      var splices = [];
      var index = currentStart;
      var oldIndex = oldStart;
      for (var i = 0; i < ops.length; i++) {
        switch(ops[i]) {
          case EDIT_LEAVE:
            if (splice) {
              splices.push(splice);
              splice = undefined;
            }

            index++;
            oldIndex++;
            break;
          case EDIT_UPDATE:
            if (!splice)
              splice = newSplice(index, [], 0);

            splice.addedCount++;
            index++;

            splice.removed.push(old[oldIndex]);
            oldIndex++;
            break;
          case EDIT_ADD:
            if (!splice)
              splice = newSplice(index, [], 0);

            splice.addedCount++;
            index++;
            break;
          case EDIT_DELETE:
            if (!splice)
              splice = newSplice(index, [], 0);

            splice.removed.push(old[oldIndex]);
            oldIndex++;
            break;
        }
      }

      if (splice) {
        splices.push(splice);
      }
      return splices;
    },

    sharedPrefix: function(current, old, searchLength) {
      for (var i = 0; i < searchLength; i++)
        if (!this.equals(current[i], old[i]))
          return i;
      return searchLength;
    },

    sharedSuffix: function(current, old, searchLength) {
      var index1 = current.length;
      var index2 = old.length;
      var count = 0;
      while (count < searchLength && this.equals(current[--index1], old[--index2]))
        count++;

      return count;
    },

    calculateSplices: function(current, previous) {
      return this.calcSplices(current, 0, current.length, previous, 0,
                              previous.length);
    },

    equals: function(currentValue, previousValue) {
      return currentValue === previousValue;
    }
  };

  var arraySplice = new ArraySplice();

  function calcSplices(current, currentStart, currentEnd,
                       old, oldStart, oldEnd) {
    return arraySplice.calcSplices(current, currentStart, currentEnd,
                                   old, oldStart, oldEnd);
  }

  function intersect(start1, end1, start2, end2) {
    // Disjoint
    if (end1 < start2 || end2 < start1)
      return -1;

    // Adjacent
    if (end1 == start2 || end2 == start1)
      return 0;

    // Non-zero intersect, span1 first
    if (start1 < start2) {
      if (end1 < end2)
        return end1 - start2; // Overlap
      else
        return end2 - start2; // Contained
    } else {
      // Non-zero intersect, span2 first
      if (end2 < end1)
        return end2 - start1; // Overlap
      else
        return end1 - start1; // Contained
    }
  }

  function mergeSplice(splices, index, removed, addedCount) {

    var splice = newSplice(index, removed, addedCount);

    var inserted = false;
    var insertionOffset = 0;

    for (var i = 0; i < splices.length; i++) {
      var current = splices[i];
      current.index += insertionOffset;

      if (inserted)
        continue;

      var intersectCount = intersect(splice.index,
                                     splice.index + splice.removed.length,
                                     current.index,
                                     current.index + current.addedCount);

      if (intersectCount >= 0) {
        // Merge the two splices

        splices.splice(i, 1);
        i--;

        insertionOffset -= current.addedCount - current.removed.length;

        splice.addedCount += current.addedCount - intersectCount;
        var deleteCount = splice.removed.length +
                          current.removed.length - intersectCount;

        if (!splice.addedCount && !deleteCount) {
          // merged splice is a noop. discard.
          inserted = true;
        } else {
          var removed = current.removed;

          if (splice.index < current.index) {
            // some prefix of splice.removed is prepended to current.removed.
            var prepend = splice.removed.slice(0, current.index - splice.index);
            Array.prototype.push.apply(prepend, removed);
            removed = prepend;
          }

          if (splice.index + splice.removed.length > current.index + current.addedCount) {
            // some suffix of splice.removed is appended to current.removed.
            var append = splice.removed.slice(current.index + current.addedCount - splice.index);
            Array.prototype.push.apply(removed, append);
          }

          splice.removed = removed;
          if (current.index < splice.index) {
            splice.index = current.index;
          }
        }
      } else if (splice.index < current.index) {
        // Insert splice here.

        inserted = true;

        splices.splice(i, 0, splice);
        i++;

        var offset = splice.addedCount - splice.removed.length
        current.index += offset;
        insertionOffset += offset;
      }
    }

    if (!inserted)
      splices.push(splice);
  }

  function createInitialSplices(array, changeRecords) {
    var splices = [];

    for (var i = 0; i < changeRecords.length; i++) {
      var record = changeRecords[i];
      switch(record.type) {
        case 'splice':
          mergeSplice(splices, record.index, record.removed.slice(), record.addedCount);
          break;
        case 'add':
        case 'update':
        case 'delete':
          if (!isIndex(record.name))
            continue;
          var index = toNumber(record.name);
          if (index < 0)
            continue;
          mergeSplice(splices, index, [record.oldValue], 1);
          break;
        default:
          console.error('Unexpected record type: ' + JSON.stringify(record));
          break;
      }
    }

    return splices;
  }

  function projectArraySplices(array, changeRecords) {
    var splices = [];

    createInitialSplices(array, changeRecords).forEach(function(splice) {
      if (splice.addedCount == 1 && splice.removed.length == 1) {
        if (splice.removed[0] !== array[splice.index])
          splices.push(splice);

        return
      };

      splices = splices.concat(calcSplices(array, splice.index, splice.index + splice.addedCount,
                                           splice.removed, 0, splice.removed.length));
    });

    return splices;
  }

  // Export the observe-js object for **Node.js**, with backwards-compatibility
  // for the old `require()` API. Also ensure `exports` is not a DOM Element.
  // If we're in the browser, export as a global object.

  var expose = global;

  if (typeof exports !== 'undefined' && !exports.nodeType) {
    if (typeof module !== 'undefined' && module.exports) {
      exports = module.exports;
    }
    expose = exports;
  }

  expose.Observer = Observer;
  expose.Observer.runEOM_ = runEOM;
  expose.Observer.observerSentinel_ = observerSentinel; // for testing.
  expose.Observer.hasObjectObserve = hasObserve;
  expose.ArrayObserver = ArrayObserver;
  expose.ArrayObserver.calculateSplices = function(current, previous) {
    return arraySplice.calculateSplices(current, previous);
  };

  expose.ArraySplice = ArraySplice;
  expose.ObjectObserver = ObjectObserver;
  expose.PathObserver = PathObserver;
  expose.CompoundObserver = CompoundObserver;
  expose.Path = Path;
  expose.ObserverTransform = ObserverTransform;

})(typeof global !== 'undefined' && global && typeof module !== 'undefined' && module ? global : this || window);

// Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
// This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
// The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
// The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
// Code distributed by Google as part of the polymer project is also
// subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt

(function(global) {
  'use strict';

  var filter = Array.prototype.filter.call.bind(Array.prototype.filter);

  function getTreeScope(node) {
    while (node.parentNode) {
      node = node.parentNode;
    }

    return typeof node.getElementById === 'function' ? node : null;
  }

  Node.prototype.bind = function(name, observable) {
    console.error('Unhandled binding to Node: ', this, name, observable);
  };

  Node.prototype.bindFinished = function() {};

  function updateBindings(node, name, binding) {
    var bindings = node.bindings_;
    if (!bindings)
      bindings = node.bindings_ = {};

    if (bindings[name])
      binding[name].close();

    return bindings[name] = binding;
  }

  function returnBinding(node, name, binding) {
    return binding;
  }

  function sanitizeValue(value) {
    return value == null ? '' : value;
  }

  function updateText(node, value) {
    node.data = sanitizeValue(value);
  }

  function textBinding(node) {
    return function(value) {
      return updateText(node, value);
    };
  }

  var maybeUpdateBindings = returnBinding;

  Object.defineProperty(Platform, 'enableBindingsReflection', {
    get: function() {
      return maybeUpdateBindings === updateBindings;
    },
    set: function(enable) {
      maybeUpdateBindings = enable ? updateBindings : returnBinding;
      return enable;
    },
    configurable: true
  });

  Text.prototype.bind = function(name, value, oneTime) {
    if (name !== 'textContent')
      return Node.prototype.bind.call(this, name, value, oneTime);

    if (oneTime)
      return updateText(this, value);

    var observable = value;
    updateText(this, observable.open(textBinding(this)));
    return maybeUpdateBindings(this, name, observable);
  }

  function updateAttribute(el, name, conditional, value) {
    if (conditional) {
      if (value)
        el.setAttribute(name, '');
      else
        el.removeAttribute(name);
      return;
    }

    el.setAttribute(name, sanitizeValue(value));
  }

  function attributeBinding(el, name, conditional) {
    return function(value) {
      updateAttribute(el, name, conditional, value);
    };
  }

  Element.prototype.bind = function(name, value, oneTime) {
    var conditional = name[name.length - 1] == '?';
    if (conditional) {
      this.removeAttribute(name);
      name = name.slice(0, -1);
    }

    if (oneTime)
      return updateAttribute(this, name, conditional, value);


    var observable = value;
    updateAttribute(this, name, conditional,
        observable.open(attributeBinding(this, name, conditional)));

    return maybeUpdateBindings(this, name, observable);
  };

  var checkboxEventType;
  (function() {
    // Attempt to feature-detect which event (change or click) is fired first
    // for checkboxes.
    var div = document.createElement('div');
    var checkbox = div.appendChild(document.createElement('input'));
    checkbox.setAttribute('type', 'checkbox');
    var first;
    var count = 0;
    checkbox.addEventListener('click', function(e) {
      count++;
      first = first || 'click';
    });
    checkbox.addEventListener('change', function() {
      count++;
      first = first || 'change';
    });

    var event = document.createEvent('MouseEvent');
    event.initMouseEvent("click", true, true, window, 0, 0, 0, 0, 0, false,
        false, false, false, 0, null);
    checkbox.dispatchEvent(event);
    // WebKit/Blink don't fire the change event if the element is outside the
    // document, so assume 'change' for that case.
    checkboxEventType = count == 1 ? 'change' : first;
  })();

  function getEventForInputType(element) {
    switch (element.type) {
      case 'checkbox':
        return checkboxEventType;
      case 'radio':
      case 'select-multiple':
      case 'select-one':
        return 'change';
      case 'range':
        if (/Trident|MSIE/.test(navigator.userAgent))
          return 'change';
      default:
        return 'input';
    }
  }

  function updateInput(input, property, value, santizeFn) {
    input[property] = (santizeFn || sanitizeValue)(value);
  }

  function inputBinding(input, property, santizeFn) {
    return function(value) {
      return updateInput(input, property, value, santizeFn);
    }
  }

  function noop() {}

  function bindInputEvent(input, property, observable, postEventFn) {
    var eventType = getEventForInputType(input);

    function eventHandler() {
      var isNum = property == 'value' && input.type == 'number';
      observable.setValue(isNum ? input.valueAsNumber : input[property]);
      observable.discardChanges();
      (postEventFn || noop)(input);
      Platform.performMicrotaskCheckpoint();
    }
    input.addEventListener(eventType, eventHandler);

    return {
      close: function() {
        input.removeEventListener(eventType, eventHandler);
        observable.close();
      },

      observable_: observable
    }
  }

  function booleanSanitize(value) {
    return Boolean(value);
  }

  // |element| is assumed to be an HTMLInputElement with |type| == 'radio'.
  // Returns an array containing all radio buttons other than |element| that
  // have the same |name|, either in the form that |element| belongs to or,
  // if no form, in the document tree to which |element| belongs.
  //
  // This implementation is based upon the HTML spec definition of a
  // "radio button group":
  //   http://www.whatwg.org/specs/web-apps/current-work/multipage/number-state.html#radio-button-group
  //
  function getAssociatedRadioButtons(element) {
    if (element.form) {
      return filter(element.form.elements, function(el) {
        return el != element &&
            el.tagName == 'INPUT' &&
            el.type == 'radio' &&
            el.name == element.name;
      });
    } else {
      var treeScope = getTreeScope(element);
      if (!treeScope)
        return [];
      var radios = treeScope.querySelectorAll(
          'input[type="radio"][name="' + element.name + '"]');
      return filter(radios, function(el) {
        return el != element && !el.form;
      });
    }
  }

  function checkedPostEvent(input) {
    // Only the radio button that is getting checked gets an event. We
    // therefore find all the associated radio buttons and update their
    // check binding manually.
    if (input.tagName === 'INPUT' &&
        input.type === 'radio') {
      getAssociatedRadioButtons(input).forEach(function(radio) {
        var checkedBinding = radio.bindings_.checked;
        if (checkedBinding) {
          // Set the value directly to avoid an infinite call stack.
          checkedBinding.observable_.setValue(false);
        }
      });
    }
  }

  HTMLInputElement.prototype.bind = function(name, value, oneTime) {
    if (name !== 'value' && name !== 'checked')
      return HTMLElement.prototype.bind.call(this, name, value, oneTime);

    this.removeAttribute(name);
    var sanitizeFn = name == 'checked' ? booleanSanitize : sanitizeValue;
    var postEventFn = name == 'checked' ? checkedPostEvent : noop;

    if (oneTime)
      return updateInput(this, name, value, sanitizeFn);


    var observable = value;
    var binding = bindInputEvent(this, name, observable, postEventFn);
    updateInput(this, name,
                observable.open(inputBinding(this, name, sanitizeFn)),
                sanitizeFn);

    // Checkboxes may need to update bindings of other checkboxes.
    return updateBindings(this, name, binding);
  }

  HTMLTextAreaElement.prototype.bind = function(name, value, oneTime) {
    if (name !== 'value')
      return HTMLElement.prototype.bind.call(this, name, value, oneTime);

    this.removeAttribute('value');

    if (oneTime)
      return updateInput(this, 'value', value);

    var observable = value;
    var binding = bindInputEvent(this, 'value', observable);
    updateInput(this, 'value',
                observable.open(inputBinding(this, 'value', sanitizeValue)));
    return maybeUpdateBindings(this, name, binding);
  }

  function updateOption(option, value) {
    var parentNode = option.parentNode;;
    var select;
    var selectBinding;
    var oldValue;
    if (parentNode instanceof HTMLSelectElement &&
        parentNode.bindings_ &&
        parentNode.bindings_.value) {
      select = parentNode;
      selectBinding = select.bindings_.value;
      oldValue = select.value;
    }

    option.value = sanitizeValue(value);

    if (select && select.value != oldValue) {
      selectBinding.observable_.setValue(select.value);
      selectBinding.observable_.discardChanges();
      Platform.performMicrotaskCheckpoint();
    }
  }

  function optionBinding(option) {
    return function(value) {
      updateOption(option, value);
    }
  }

  HTMLOptionElement.prototype.bind = function(name, value, oneTime) {
    if (name !== 'value')
      return HTMLElement.prototype.bind.call(this, name, value, oneTime);

    this.removeAttribute('value');

    if (oneTime)
      return updateOption(this, value);

    var observable = value;
    var binding = bindInputEvent(this, 'value', observable);
    updateOption(this, observable.open(optionBinding(this)));
    return maybeUpdateBindings(this, name, binding);
  }

  HTMLSelectElement.prototype.bind = function(name, value, oneTime) {
    if (name === 'selectedindex')
      name = 'selectedIndex';

    if (name !== 'selectedIndex' && name !== 'value')
      return HTMLElement.prototype.bind.call(this, name, value, oneTime);

    this.removeAttribute(name);

    if (oneTime)
      return updateInput(this, name, value);

    var observable = value;
    var binding = bindInputEvent(this, name, observable);
    updateInput(this, name,
                observable.open(inputBinding(this, name)));

    // Option update events may need to access select bindings.
    return updateBindings(this, name, binding);
  }
})(this);

// Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
// This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
// The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
// The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
// Code distributed by Google as part of the polymer project is also
// subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt

(function(global) {
  'use strict';

  function assert(v) {
    if (!v)
      throw new Error('Assertion failed');
  }

  var forEach = Array.prototype.forEach.call.bind(Array.prototype.forEach);

  function getFragmentRoot(node) {
    var p;
    while (p = node.parentNode) {
      node = p;
    }

    return node;
  }

  function searchRefId(node, id) {
    if (!id)
      return;

    var ref;
    var selector = '#' + id;
    while (!ref) {
      node = getFragmentRoot(node);

      if (node.protoContent_)
        ref = node.protoContent_.querySelector(selector);
      else if (node.getElementById)
        ref = node.getElementById(id);

      if (ref || !node.templateCreator_)
        break

      node = node.templateCreator_;
    }

    return ref;
  }

  function getInstanceRoot(node) {
    while (node.parentNode) {
      node = node.parentNode;
    }
    return node.templateCreator_ ? node : null;
  }

  var Map;
  if (global.Map && typeof global.Map.prototype.forEach === 'function') {
    Map = global.Map;
  } else {
    Map = function() {
      this.keys = [];
      this.values = [];
    };

    Map.prototype = {
      set: function(key, value) {
        var index = this.keys.indexOf(key);
        if (index < 0) {
          this.keys.push(key);
          this.values.push(value);
        } else {
          this.values[index] = value;
        }
      },

      get: function(key) {
        var index = this.keys.indexOf(key);
        if (index < 0)
          return;

        return this.values[index];
      },

      delete: function(key, value) {
        var index = this.keys.indexOf(key);
        if (index < 0)
          return false;

        this.keys.splice(index, 1);
        this.values.splice(index, 1);
        return true;
      },

      forEach: function(f, opt_this) {
        for (var i = 0; i < this.keys.length; i++)
          f.call(opt_this || this, this.values[i], this.keys[i], this);
      }
    };
  }

  // JScript does not have __proto__. We wrap all object literals with
  // createObject which uses Object.create, Object.defineProperty and
  // Object.getOwnPropertyDescriptor to create a new object that does the exact
  // same thing. The main downside to this solution is that we have to extract
  // all those property descriptors for IE.
  var createObject = ('__proto__' in {}) ?
      function(obj) { return obj; } :
      function(obj) {
        var proto = obj.__proto__;
        if (!proto)
          return obj;
        var newObject = Object.create(proto);
        Object.getOwnPropertyNames(obj).forEach(function(name) {
          Object.defineProperty(newObject, name,
                               Object.getOwnPropertyDescriptor(obj, name));
        });
        return newObject;
      };

  // IE does not support have Document.prototype.contains.
  if (typeof document.contains != 'function') {
    Document.prototype.contains = function(node) {
      if (node === this || node.parentNode === this)
        return true;
      return this.documentElement.contains(node);
    }
  }

  var BIND = 'bind';
  var REPEAT = 'repeat';
  var IF = 'if';

  var templateAttributeDirectives = {
    'template': true,
    'repeat': true,
    'bind': true,
    'ref': true,
    'if': true
  };

  var semanticTemplateElements = {
    'THEAD': true,
    'TBODY': true,
    'TFOOT': true,
    'TH': true,
    'TR': true,
    'TD': true,
    'COLGROUP': true,
    'COL': true,
    'CAPTION': true,
    'OPTION': true,
    'OPTGROUP': true
  };

  var hasTemplateElement = typeof HTMLTemplateElement !== 'undefined';
  if (hasTemplateElement) {
    // TODO(rafaelw): Remove when fix for
    // https://codereview.chromium.org/164803002/
    // makes it to Chrome release.
    (function() {
      var t = document.createElement('template');
      var d = t.content.ownerDocument;
      var html = d.appendChild(d.createElement('html'));
      var head = html.appendChild(d.createElement('head'));
      var base = d.createElement('base');
      base.href = document.baseURI;
      head.appendChild(base);
    })();
  }

  var allTemplatesSelectors = 'template, ' +
      Object.keys(semanticTemplateElements).map(function(tagName) {
        return tagName.toLowerCase() + '[template]';
      }).join(', ');

  function isSVGTemplate(el) {
    return el.tagName == 'template' &&
           el.namespaceURI == 'http://www.w3.org/2000/svg';
  }

  function isHTMLTemplate(el) {
    return el.tagName == 'TEMPLATE' &&
           el.namespaceURI == 'http://www.w3.org/1999/xhtml';
  }

  function isAttributeTemplate(el) {
    return Boolean(semanticTemplateElements[el.tagName] &&
                   el.hasAttribute('template'));
  }

  function isTemplate(el) {
    if (el.isTemplate_ === undefined)
      el.isTemplate_ = el.tagName == 'TEMPLATE' || isAttributeTemplate(el);

    return el.isTemplate_;
  }

  // FIXME: Observe templates being added/removed from documents
  // FIXME: Expose imperative API to decorate and observe templates in
  // "disconnected tress" (e.g. ShadowRoot)
  document.addEventListener('DOMContentLoaded', function(e) {
    bootstrapTemplatesRecursivelyFrom(document);
    // FIXME: Is this needed? Seems like it shouldn't be.
    Platform.performMicrotaskCheckpoint();
  }, false);

  function forAllTemplatesFrom(node, fn) {
    var subTemplates = node.querySelectorAll(allTemplatesSelectors);

    if (isTemplate(node))
      fn(node)
    forEach(subTemplates, fn);
  }

  function bootstrapTemplatesRecursivelyFrom(node) {
    function bootstrap(template) {
      if (!HTMLTemplateElement.decorate(template))
        bootstrapTemplatesRecursivelyFrom(template.content);
    }

    forAllTemplatesFrom(node, bootstrap);
  }

  if (!hasTemplateElement) {
    /**
     * This represents a <template> element.
     * @constructor
     * @extends {HTMLElement}
     */
    global.HTMLTemplateElement = function() {
      throw TypeError('Illegal constructor');
    };
  }

  var hasProto = '__proto__' in {};

  function mixin(to, from) {
    Object.getOwnPropertyNames(from).forEach(function(name) {
      Object.defineProperty(to, name,
                            Object.getOwnPropertyDescriptor(from, name));
    });
  }

  // http://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/templates/index.html#dfn-template-contents-owner
  function getOrCreateTemplateContentsOwner(template) {
    var doc = template.ownerDocument
    if (!doc.defaultView)
      return doc;
    var d = doc.templateContentsOwner_;
    if (!d) {
      // TODO(arv): This should either be a Document or HTMLDocument depending
      // on doc.
      d = doc.implementation.createHTMLDocument('');
      while (d.lastChild) {
        d.removeChild(d.lastChild);
      }
      doc.templateContentsOwner_ = d;
    }
    return d;
  }

  function getTemplateStagingDocument(template) {
    if (!template.stagingDocument_) {
      var owner = template.ownerDocument;
      if (!owner.stagingDocument_) {
        owner.stagingDocument_ = owner.implementation.createHTMLDocument('');
        owner.stagingDocument_.isStagingDocument = true;
        // TODO(rafaelw): Remove when fix for
        // https://codereview.chromium.org/164803002/
        // makes it to Chrome release.
        var base = owner.stagingDocument_.createElement('base');
        base.href = document.baseURI;
        owner.stagingDocument_.head.appendChild(base);

        owner.stagingDocument_.stagingDocument_ = owner.stagingDocument_;
      }

      template.stagingDocument_ = owner.stagingDocument_;
    }

    return template.stagingDocument_;
  }

  // For non-template browsers, the parser will disallow <template> in certain
  // locations, so we allow "attribute templates" which combine the template
  // element with the top-level container node of the content, e.g.
  //
  //   <tr template repeat="{{ foo }}"" class="bar"><td>Bar</td></tr>
  //
  // becomes
  //
  //   <template repeat="{{ foo }}">
  //   + #document-fragment
  //     + <tr class="bar">
  //       + <td>Bar</td>
  //
  function extractTemplateFromAttributeTemplate(el) {
    var template = el.ownerDocument.createElement('template');
    el.parentNode.insertBefore(template, el);

    var attribs = el.attributes;
    var count = attribs.length;
    while (count-- > 0) {
      var attrib = attribs[count];
      if (templateAttributeDirectives[attrib.name]) {
        if (attrib.name !== 'template')
          template.setAttribute(attrib.name, attrib.value);
        el.removeAttribute(attrib.name);
      }
    }

    return template;
  }

  function extractTemplateFromSVGTemplate(el) {
    var template = el.ownerDocument.createElement('template');
    el.parentNode.insertBefore(template, el);

    var attribs = el.attributes;
    var count = attribs.length;
    while (count-- > 0) {
      var attrib = attribs[count];
      template.setAttribute(attrib.name, attrib.value);
      el.removeAttribute(attrib.name);
    }

    el.parentNode.removeChild(el);
    return template;
  }

  function liftNonNativeTemplateChildrenIntoContent(template, el, useRoot) {
    var content = template.content;
    if (useRoot) {
      content.appendChild(el);
      return;
    }

    var child;
    while (child = el.firstChild) {
      content.appendChild(child);
    }
  }

  var templateObserver;
  if (typeof MutationObserver == 'function') {
    templateObserver = new MutationObserver(function(records) {
      for (var i = 0; i < records.length; i++) {
        records[i].target.refChanged_();
      }
    });
  }

  /**
   * Ensures proper API and content model for template elements.
   * @param {HTMLTemplateElement} opt_instanceRef The template element which
   *     |el| template element will return as the value of its ref(), and whose
   *     content will be used as source when createInstance() is invoked.
   */
  HTMLTemplateElement.decorate = function(el, opt_instanceRef) {
    if (el.templateIsDecorated_)
      return false;

    var templateElement = el;
    templateElement.templateIsDecorated_ = true;

    var isNativeHTMLTemplate = isHTMLTemplate(templateElement) &&
                               hasTemplateElement;
    var bootstrapContents = isNativeHTMLTemplate;
    var liftContents = !isNativeHTMLTemplate;
    var liftRoot = false;

    if (!isNativeHTMLTemplate) {
      if (isAttributeTemplate(templateElement)) {
        assert(!opt_instanceRef);
        templateElement = extractTemplateFromAttributeTemplate(el);
        templateElement.templateIsDecorated_ = true;
        isNativeHTMLTemplate = hasTemplateElement;
        liftRoot = true;
      } else if (isSVGTemplate(templateElement)) {
        templateElement = extractTemplateFromSVGTemplate(el);
        templateElement.templateIsDecorated_ = true;
        isNativeHTMLTemplate = hasTemplateElement;
      }
    }

    if (!isNativeHTMLTemplate) {
      fixTemplateElementPrototype(templateElement);
      var doc = getOrCreateTemplateContentsOwner(templateElement);
      templateElement.content_ = doc.createDocumentFragment();
    }

    if (opt_instanceRef) {
      // template is contained within an instance, its direct content must be
      // empty
      templateElement.instanceRef_ = opt_instanceRef;
    } else if (liftContents) {
      liftNonNativeTemplateChildrenIntoContent(templateElement,
                                               el,
                                               liftRoot);
    } else if (bootstrapContents) {
      bootstrapTemplatesRecursivelyFrom(templateElement.content);
    }

    return true;
  };

  // TODO(rafaelw): This used to decorate recursively all templates from a given
  // node. This happens by default on 'DOMContentLoaded', but may be needed
  // in subtrees not descendent from document (e.g. ShadowRoot).
  // Review whether this is the right public API.
  HTMLTemplateElement.bootstrap = bootstrapTemplatesRecursivelyFrom;

  var htmlElement = global.HTMLUnknownElement || HTMLElement;

  var contentDescriptor = {
    get: function() {
      return this.content_;
    },
    enumerable: true,
    configurable: true
  };

  if (!hasTemplateElement) {
    // Gecko is more picky with the prototype than WebKit. Make sure to use the
    // same prototype as created in the constructor.
    HTMLTemplateElement.prototype = Object.create(htmlElement.prototype);

    Object.defineProperty(HTMLTemplateElement.prototype, 'content',
                          contentDescriptor);
  }

  function fixTemplateElementPrototype(el) {
    if (hasProto)
      el.__proto__ = HTMLTemplateElement.prototype;
    else
      mixin(el, HTMLTemplateElement.prototype);
  }

  function ensureSetModelScheduled(template) {
    if (!template.setModelFn_) {
      template.setModelFn_ = function() {
        template.setModelFnScheduled_ = false;
        var map = getBindings(template,
            template.delegate_ && template.delegate_.prepareBinding);
        processBindings(template, map, template.model_);
      };
    }

    if (!template.setModelFnScheduled_) {
      template.setModelFnScheduled_ = true;
      Observer.runEOM_(template.setModelFn_);
    }
  }

  mixin(HTMLTemplateElement.prototype, {
    bind: function(name, value, oneTime) {
      if (name != 'ref')
        return Element.prototype.bind.call(this, name, value, oneTime);

      var self = this;
      var ref = oneTime ? value : value.open(function(ref) {
        self.setAttribute('ref', ref);
        self.refChanged_();
      });

      this.setAttribute('ref', ref);
      this.refChanged_();
      if (oneTime)
        return;

      if (!this.bindings_) {
        this.bindings_ = { ref: value };
      } else {
        this.bindings_.ref = value;
      }

      return value;
    },

    processBindingDirectives_: function(directives) {
      if (this.iterator_)
        this.iterator_.closeDeps();

      if (!directives.if && !directives.bind && !directives.repeat) {
        if (this.iterator_) {
          this.iterator_.close();
          this.iterator_ = undefined;
        }

        return;
      }

      if (!this.iterator_) {
        this.iterator_ = new TemplateIterator(this);
      }

      this.iterator_.updateDependencies(directives, this.model_);

      if (templateObserver) {
        templateObserver.observe(this, { attributes: true,
                                         attributeFilter: ['ref'] });
      }

      return this.iterator_;
    },

    createInstance: function(model, bindingDelegate, delegate_) {
      if (bindingDelegate)
        delegate_ = this.newDelegate_(bindingDelegate);
      else if (!delegate_)
        delegate_ = this.delegate_;

      if (!this.refContent_)
        this.refContent_ = this.ref_.content;
      var content = this.refContent_;
      if (content.firstChild === null)
        return emptyInstance;

      var map = getInstanceBindingMap(content, delegate_);
      var stagingDocument = getTemplateStagingDocument(this);
      var instance = stagingDocument.createDocumentFragment();
      instance.templateCreator_ = this;
      instance.protoContent_ = content;
      instance.bindings_ = [];
      instance.terminator_ = null;
      var instanceRecord = instance.templateInstance_ = {
        firstNode: null,
        lastNode: null,
        model: model
      };

      var i = 0;
      var collectTerminator = false;
      for (var child = content.firstChild; child; child = child.nextSibling) {
        // The terminator of the instance is the clone of the last child of the
        // content. If the last child is an active template, it may produce
        // instances as a result of production, so simply collecting the last
        // child of the instance after it has finished producing may be wrong.
        if (child.nextSibling === null)
          collectTerminator = true;

        var clone = cloneAndBindInstance(child, instance, stagingDocument,
                                         map.children[i++],
                                         model,
                                         delegate_,
                                         instance.bindings_);
        clone.templateInstance_ = instanceRecord;
        if (collectTerminator)
          instance.terminator_ = clone;
      }

      instanceRecord.firstNode = instance.firstChild;
      instanceRecord.lastNode = instance.lastChild;
      instance.templateCreator_ = undefined;
      instance.protoContent_ = undefined;
      return instance;
    },

    get model() {
      return this.model_;
    },

    set model(model) {
      this.model_ = model;
      ensureSetModelScheduled(this);
    },

    get bindingDelegate() {
      return this.delegate_ && this.delegate_.raw;
    },

    refChanged_: function() {
      if (!this.iterator_ || this.refContent_ === this.ref_.content)
        return;

      this.refContent_ = undefined;
      this.iterator_.valueChanged();
      this.iterator_.updateIteratedValue(this.iterator_.getUpdatedValue());
    },

    clear: function() {
      this.model_ = undefined;
      this.delegate_ = undefined;
      if (this.bindings_ && this.bindings_.ref)
        this.bindings_.ref.close()
      this.refContent_ = undefined;
      if (!this.iterator_)
        return;
      this.iterator_.valueChanged();
      this.iterator_.close()
      this.iterator_ = undefined;
    },

    setDelegate_: function(delegate) {
      this.delegate_ = delegate;
      this.bindingMap_ = undefined;
      if (this.iterator_) {
        this.iterator_.instancePositionChangedFn_ = undefined;
        this.iterator_.instanceModelFn_ = undefined;
      }
    },

    newDelegate_: function(bindingDelegate) {
      if (!bindingDelegate)
        return;

      function delegateFn(name) {
        var fn = bindingDelegate && bindingDelegate[name];
        if (typeof fn != 'function')
          return;

        return function() {
          return fn.apply(bindingDelegate, arguments);
        };
      }

      return {
        bindingMaps: {},
        raw: bindingDelegate,
        prepareBinding: delegateFn('prepareBinding'),
        prepareInstanceModel: delegateFn('prepareInstanceModel'),
        prepareInstancePositionChanged:
            delegateFn('prepareInstancePositionChanged')
      };
    },

    set bindingDelegate(bindingDelegate) {
      if (this.delegate_) {
        throw Error('Template must be cleared before a new bindingDelegate ' +
                    'can be assigned');
      }

      this.setDelegate_(this.newDelegate_(bindingDelegate));
    },

    get ref_() {
      var ref = searchRefId(this, this.getAttribute('ref'));
      if (!ref)
        ref = this.instanceRef_;

      if (!ref)
        return this;

      var nextRef = ref.ref_;
      return nextRef ? nextRef : ref;
    }
  });

  // Returns
  //   a) undefined if there are no mustaches.
  //   b) [TEXT, (ONE_TIME?, PATH, DELEGATE_FN, TEXT)+] if there is at least one mustache.
  function parseMustaches(s, name, node, prepareBindingFn) {
    if (!s || !s.length)
      return;

    var tokens;
    var length = s.length;
    var startIndex = 0, lastIndex = 0, endIndex = 0;
    var onlyOneTime = true;
    while (lastIndex < length) {
      var startIndex = s.indexOf('{{', lastIndex);
      var oneTimeStart = s.indexOf('[[', lastIndex);
      var oneTime = false;
      var terminator = '}}';

      if (oneTimeStart >= 0 &&
          (startIndex < 0 || oneTimeStart < startIndex)) {
        startIndex = oneTimeStart;
        oneTime = true;
        terminator = ']]';
      }

      endIndex = startIndex < 0 ? -1 : s.indexOf(terminator, startIndex + 2);

      if (endIndex < 0) {
        if (!tokens)
          return;

        tokens.push(s.slice(lastIndex)); // TEXT
        break;
      }

      tokens = tokens || [];
      tokens.push(s.slice(lastIndex, startIndex)); // TEXT
      var pathString = s.slice(startIndex + 2, endIndex).trim();
      tokens.push(oneTime); // ONE_TIME?
      onlyOneTime = onlyOneTime && oneTime;
      var delegateFn = prepareBindingFn &&
                       prepareBindingFn(pathString, name, node);
      // Don't try to parse the expression if there's a prepareBinding function
      if (delegateFn == null) {
        tokens.push(Path.get(pathString)); // PATH
      } else {
        tokens.push(null);
      }
      tokens.push(delegateFn); // DELEGATE_FN
      lastIndex = endIndex + 2;
    }

    if (lastIndex === length)
      tokens.push(''); // TEXT

    tokens.hasOnePath = tokens.length === 5;
    tokens.isSimplePath = tokens.hasOnePath &&
                          tokens[0] == '' &&
                          tokens[4] == '';
    tokens.onlyOneTime = onlyOneTime;

    tokens.combinator = function(values) {
      var newValue = tokens[0];

      for (var i = 1; i < tokens.length; i += 4) {
        var value = tokens.hasOnePath ? values : values[(i - 1) / 4];
        if (value !== undefined)
          newValue += value;
        newValue += tokens[i + 3];
      }

      return newValue;
    }

    return tokens;
  };

  function processOneTimeBinding(name, tokens, node, model) {
    if (tokens.hasOnePath) {
      var delegateFn = tokens[3];
      var value = delegateFn ? delegateFn(model, node, true) :
                               tokens[2].getValueFrom(model);
      return tokens.isSimplePath ? value : tokens.combinator(value);
    }

    var values = [];
    for (var i = 1; i < tokens.length; i += 4) {
      var delegateFn = tokens[i + 2];
      values[(i - 1) / 4] = delegateFn ? delegateFn(model, node) :
          tokens[i + 1].getValueFrom(model);
    }

    return tokens.combinator(values);
  }

  function processSinglePathBinding(name, tokens, node, model) {
    var delegateFn = tokens[3];
    var observer = delegateFn ? delegateFn(model, node, false) :
        new PathObserver(model, tokens[2]);

    return tokens.isSimplePath ? observer :
        new ObserverTransform(observer, tokens.combinator);
  }

  function processBinding(name, tokens, node, model) {
    if (tokens.onlyOneTime)
      return processOneTimeBinding(name, tokens, node, model);

    if (tokens.hasOnePath)
      return processSinglePathBinding(name, tokens, node, model);

    var observer = new CompoundObserver();

    for (var i = 1; i < tokens.length; i += 4) {
      var oneTime = tokens[i];
      var delegateFn = tokens[i + 2];

      if (delegateFn) {
        var value = delegateFn(model, node, oneTime);
        if (oneTime)
          observer.addPath(value)
        else
          observer.addObserver(value);
        continue;
      }

      var path = tokens[i + 1];
      if (oneTime)
        observer.addPath(path.getValueFrom(model))
      else
        observer.addPath(model, path);
    }

    return new ObserverTransform(observer, tokens.combinator);
  }

  function processBindings(node, bindings, model, instanceBindings) {
    for (var i = 0; i < bindings.length; i += 2) {
      var name = bindings[i]
      var tokens = bindings[i + 1];
      var value = processBinding(name, tokens, node, model);
      var binding = node.bind(name, value, tokens.onlyOneTime);
      if (binding && instanceBindings)
        instanceBindings.push(binding);
    }

    node.bindFinished();
    if (!bindings.isTemplate)
      return;

    node.model_ = model;
    var iter = node.processBindingDirectives_(bindings);
    if (instanceBindings && iter)
      instanceBindings.push(iter);
  }

  function parseWithDefault(el, name, prepareBindingFn) {
    var v = el.getAttribute(name);
    return parseMustaches(v == '' ? '{{}}' : v, name, el, prepareBindingFn);
  }

  function parseAttributeBindings(element, prepareBindingFn) {
    assert(element);

    var bindings = [];
    var ifFound = false;
    var bindFound = false;

    for (var i = 0; i < element.attributes.length; i++) {
      var attr = element.attributes[i];
      var name = attr.name;
      var value = attr.value;

      // Allow bindings expressed in attributes to be prefixed with underbars.
      // We do this to allow correct semantics for browsers that don't implement
      // <template> where certain attributes might trigger side-effects -- and
      // for IE which sanitizes certain attributes, disallowing mustache
      // replacements in their text.
      while (name[0] === '_') {
        name = name.substring(1);
      }

      if (isTemplate(element) &&
          (name === IF || name === BIND || name === REPEAT)) {
        continue;
      }

      var tokens = parseMustaches(value, name, element,
                                  prepareBindingFn);
      if (!tokens)
        continue;

      bindings.push(name, tokens);
    }

    if (isTemplate(element)) {
      bindings.isTemplate = true;
      bindings.if = parseWithDefault(element, IF, prepareBindingFn);
      bindings.bind = parseWithDefault(element, BIND, prepareBindingFn);
      bindings.repeat = parseWithDefault(element, REPEAT, prepareBindingFn);

      if (bindings.if && !bindings.bind && !bindings.repeat)
        bindings.bind = parseMustaches('{{}}', BIND, element, prepareBindingFn);
    }

    return bindings;
  }

  function getBindings(node, prepareBindingFn) {
    if (node.nodeType === Node.ELEMENT_NODE)
      return parseAttributeBindings(node, prepareBindingFn);

    if (node.nodeType === Node.TEXT_NODE) {
      var tokens = parseMustaches(node.data, 'textContent', node,
                                  prepareBindingFn);
      if (tokens)
        return ['textContent', tokens];
    }

    return [];
  }

  function cloneAndBindInstance(node, parent, stagingDocument, bindings, model,
                                delegate,
                                instanceBindings,
                                instanceRecord) {
    var clone = parent.appendChild(stagingDocument.importNode(node, false));

    var i = 0;
    for (var child = node.firstChild; child; child = child.nextSibling) {
      cloneAndBindInstance(child, clone, stagingDocument,
                            bindings.children[i++],
                            model,
                            delegate,
                            instanceBindings);
    }

    if (bindings.isTemplate) {
      HTMLTemplateElement.decorate(clone, node);
      if (delegate)
        clone.setDelegate_(delegate);
    }

    processBindings(clone, bindings, model, instanceBindings);
    return clone;
  }

  function createInstanceBindingMap(node, prepareBindingFn) {
    var map = getBindings(node, prepareBindingFn);
    map.children = {};
    var index = 0;
    for (var child = node.firstChild; child; child = child.nextSibling) {
      map.children[index++] = createInstanceBindingMap(child, prepareBindingFn);
    }

    return map;
  }

  var contentUidCounter = 1;

  // TODO(rafaelw): Setup a MutationObserver on content which clears the id
  // so that bindingMaps regenerate when the template.content changes.
  function getContentUid(content) {
    var id = content.id_;
    if (!id)
      id = content.id_ = contentUidCounter++;
    return id;
  }

  // Each delegate is associated with a set of bindingMaps, one for each
  // content which may be used by a template. The intent is that each binding
  // delegate gets the opportunity to prepare the instance (via the prepare*
  // delegate calls) once across all uses.
  // TODO(rafaelw): Separate out the parse map from the binding map. In the
  // current implementation, if two delegates need a binding map for the same
  // content, the second will have to reparse.
  function getInstanceBindingMap(content, delegate_) {
    var contentId = getContentUid(content);
    if (delegate_) {
      var map = delegate_.bindingMaps[contentId];
      if (!map) {
        map = delegate_.bindingMaps[contentId] =
            createInstanceBindingMap(content, delegate_.prepareBinding) || [];
      }
      return map;
    }

    var map = content.bindingMap_;
    if (!map) {
      map = content.bindingMap_ =
          createInstanceBindingMap(content, undefined) || [];
    }
    return map;
  }

  Object.defineProperty(Node.prototype, 'templateInstance', {
    get: function() {
      var instance = this.templateInstance_;
      return instance ? instance :
          (this.parentNode ? this.parentNode.templateInstance : undefined);
    }
  });

  var emptyInstance = document.createDocumentFragment();
  emptyInstance.bindings_ = [];
  emptyInstance.terminator_ = null;

  function TemplateIterator(templateElement) {
    this.closed = false;
    this.templateElement_ = templateElement;
    this.instances = [];
    this.deps = undefined;
    this.iteratedValue = [];
    this.presentValue = undefined;
    this.arrayObserver = undefined;
  }

  TemplateIterator.prototype = {
    closeDeps: function() {
      var deps = this.deps;
      if (deps) {
        if (deps.ifOneTime === false)
          deps.ifValue.close();
        if (deps.oneTime === false)
          deps.value.close();
      }
    },

    updateDependencies: function(directives, model) {
      this.closeDeps();

      var deps = this.deps = {};
      var template = this.templateElement_;

      var ifValue = true;
      if (directives.if) {
        deps.hasIf = true;
        deps.ifOneTime = directives.if.onlyOneTime;
        deps.ifValue = processBinding(IF, directives.if, template, model);

        ifValue = deps.ifValue;

        // oneTime if & predicate is false. nothing else to do.
        if (deps.ifOneTime && !ifValue) {
          this.valueChanged();
          return;
        }

        if (!deps.ifOneTime)
          ifValue = ifValue.open(this.updateIfValue, this);
      }

      if (directives.repeat) {
        deps.repeat = true;
        deps.oneTime = directives.repeat.onlyOneTime;
        deps.value = processBinding(REPEAT, directives.repeat, template, model);
      } else {
        deps.repeat = false;
        deps.oneTime = directives.bind.onlyOneTime;
        deps.value = processBinding(BIND, directives.bind, template, model);
      }

      var value = deps.value;
      if (!deps.oneTime)
        value = value.open(this.updateIteratedValue, this);

      if (!ifValue) {
        this.valueChanged();
        return;
      }

      this.updateValue(value);
    },

    /**
     * Gets the updated value of the bind/repeat. This can potentially call
     * user code (if a bindingDelegate is set up) so we try to avoid it if we
     * already have the value in hand (from Observer.open).
     */
    getUpdatedValue: function() {
      var value = this.deps.value;
      if (!this.deps.oneTime)
        value = value.discardChanges();
      return value;
    },

    updateIfValue: function(ifValue) {
      if (!ifValue) {
        this.valueChanged();
        return;
      }

      this.updateValue(this.getUpdatedValue());
    },

    updateIteratedValue: function(value) {
      if (this.deps.hasIf) {
        var ifValue = this.deps.ifValue;
        if (!this.deps.ifOneTime)
          ifValue = ifValue.discardChanges();
        if (!ifValue) {
          this.valueChanged();
          return;
        }
      }

      this.updateValue(value);
    },

    updateValue: function(value) {
      if (!this.deps.repeat)
        value = [value];
      var observe = this.deps.repeat &&
                    !this.deps.oneTime &&
                    Array.isArray(value);
      this.valueChanged(value, observe);
    },

    valueChanged: function(value, observeValue) {
      if (!Array.isArray(value))
        value = [];

      if (value === this.iteratedValue)
        return;

      this.unobserve();
      this.presentValue = value;
      if (observeValue) {
        this.arrayObserver = new ArrayObserver(this.presentValue);
        this.arrayObserver.open(this.handleSplices, this);
      }

      this.handleSplices(ArrayObserver.calculateSplices(this.presentValue,
                                                        this.iteratedValue));
    },

    getLastInstanceNode: function(index) {
      if (index == -1)
        return this.templateElement_;
      var instance = this.instances[index];
      var terminator = instance.terminator_;
      if (!terminator)
        return this.getLastInstanceNode(index - 1);

      if (terminator.nodeType !== Node.ELEMENT_NODE ||
          this.templateElement_ === terminator) {
        return terminator;
      }

      var subtemplateIterator = terminator.iterator_;
      if (!subtemplateIterator)
        return terminator;

      return subtemplateIterator.getLastTemplateNode();
    },

    getLastTemplateNode: function() {
      return this.getLastInstanceNode(this.instances.length - 1);
    },

    insertInstanceAt: function(index, fragment) {
      var previousInstanceLast = this.getLastInstanceNode(index - 1);
      var parent = this.templateElement_.parentNode;
      this.instances.splice(index, 0, fragment);

      parent.insertBefore(fragment, previousInstanceLast.nextSibling);
    },

    extractInstanceAt: function(index) {
      var previousInstanceLast = this.getLastInstanceNode(index - 1);
      var lastNode = this.getLastInstanceNode(index);
      var parent = this.templateElement_.parentNode;
      var instance = this.instances.splice(index, 1)[0];

      while (lastNode !== previousInstanceLast) {
        var node = previousInstanceLast.nextSibling;
        if (node == lastNode)
          lastNode = previousInstanceLast;

        instance.appendChild(parent.removeChild(node));
      }

      return instance;
    },

    getDelegateFn: function(fn) {
      fn = fn && fn(this.templateElement_);
      return typeof fn === 'function' ? fn : null;
    },

    handleSplices: function(splices) {
      if (this.closed || !splices.length)
        return;

      var template = this.templateElement_;

      if (!template.parentNode) {
        this.close();
        return;
      }

      ArrayObserver.applySplices(this.iteratedValue, this.presentValue,
                                 splices);

      var delegate = template.delegate_;
      if (this.instanceModelFn_ === undefined) {
        this.instanceModelFn_ =
            this.getDelegateFn(delegate && delegate.prepareInstanceModel);
      }

      if (this.instancePositionChangedFn_ === undefined) {
        this.instancePositionChangedFn_ =
            this.getDelegateFn(delegate &&
                               delegate.prepareInstancePositionChanged);
      }

      // Instance Removals
      var instanceCache = new Map;
      var removeDelta = 0;
      for (var i = 0; i < splices.length; i++) {
        var splice = splices[i];
        var removed = splice.removed;
        for (var j = 0; j < removed.length; j++) {
          var model = removed[j];
          var instance = this.extractInstanceAt(splice.index + removeDelta);
          if (instance !== emptyInstance) {
            instanceCache.set(model, instance);
          }
        }

        removeDelta -= splice.addedCount;
      }

      // Instance Insertions
      for (var i = 0; i < splices.length; i++) {
        var splice = splices[i];
        var addIndex = splice.index;
        for (; addIndex < splice.index + splice.addedCount; addIndex++) {