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// Copyright 2005 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/**
 * @fileoverview An implementation of {@link goog.events.Listenable} that does
 * not need to be disposed.
 */

goog.provide('goog.labs.events.NonDisposableEventTarget');


goog.require('goog.array');
goog.require('goog.asserts');
goog.require('goog.events.Event');
goog.require('goog.events.Listenable');
goog.require('goog.events.ListenerMap');
goog.require('goog.object');



/**
 * An implementation of {@code goog.events.Listenable} with full W3C
 * EventTarget-like support (capture/bubble mechanism, stopping event
 * propagation, preventing default actions).
 *
 * You may subclass this class to turn your class into a Listenable.
 *
 * Unlike {@link goog.events.EventTarget}, this class does not implement
 * {@link goog.disposable.IDisposable}. Instances of this class that have had
 * It is not necessary to call {@link goog.dispose}
 * or {@link #removeAllListeners} in order for an instance of this class
 * to be garbage collected.
 *
 * Unless propagation is stopped, an event dispatched by an
 * EventTarget will bubble to the parent returned by
 * {@code getParentEventTarget}. To set the parent, call
 * {@code setParentEventTarget}. Subclasses that don't support
 * changing the parent can override the setter to throw an error.
 *
 * Example usage:
 *  *   var source = new goog.labs.events.NonDisposableEventTarget();
 *   function handleEvent(e) {
 *     alert('Type: ' + e.type + '; Target: ' + e.target);
 *   }
 *   source.listen('foo', handleEvent);
 *   source.dispatchEvent('foo'); // will call handleEvent
 * 
 *
 * TODO(chrishenry|johnlenz): Consider a more modern, less viral
 * (not based on inheritance) replacement of goog.Disposable, which will allow
 * goog.events.EventTarget to not be disposable.
 *
 * @constructor
 * @implements {goog.events.Listenable}
 * @final
 */
goog.labs.events.NonDisposableEventTarget = function() {
  /**
   * Maps of event type to an array of listeners.
   * @private {!goog.events.ListenerMap}
   */
  this.eventTargetListeners_ = new goog.events.ListenerMap(this);
};
goog.events.Listenable.addImplementation(
    goog.labs.events.NonDisposableEventTarget);


/**
 * An artificial cap on the number of ancestors you can have. This is mainly
 * for loop detection.
 * @const {number}
 * @private
 */
goog.labs.events.NonDisposableEventTarget.MAX_ANCESTORS_ = 1000;


/**
 * Parent event target, used during event bubbling.
 * @private {goog.events.Listenable}
 */
goog.labs.events.NonDisposableEventTarget.prototype.parentEventTarget_ = null;


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.getParentEventTarget =
    function() {
  return this.parentEventTarget_;
};


/**
 * Sets the parent of this event target to use for capture/bubble
 * mechanism.
 * @param {goog.events.Listenable} parent Parent listenable (null if none).
 */
goog.labs.events.NonDisposableEventTarget.prototype.setParentEventTarget =
    function(parent) {
  this.parentEventTarget_ = parent;
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.dispatchEvent = function(
    e) {
  this.assertInitialized_();
  var ancestorsTree, ancestor = this.getParentEventTarget();
  if (ancestor) {
    ancestorsTree = [];
    var ancestorCount = 1;
    for (; ancestor; ancestor = ancestor.getParentEventTarget()) {
      ancestorsTree.push(ancestor);
      goog.asserts.assert(
          (++ancestorCount <
           goog.labs.events.NonDisposableEventTarget.MAX_ANCESTORS_),
          'infinite loop');
    }
  }

  return goog.labs.events.NonDisposableEventTarget.dispatchEventInternal_(
      this, e, ancestorsTree);
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.listen = function(
    type, listener, opt_useCapture, opt_listenerScope) {
  this.assertInitialized_();
  return this.eventTargetListeners_.add(
      String(type), listener, false /* callOnce */, opt_useCapture,
      opt_listenerScope);
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.listenOnce = function(
    type, listener, opt_useCapture, opt_listenerScope) {
  return this.eventTargetListeners_.add(
      String(type), listener, true /* callOnce */, opt_useCapture,
      opt_listenerScope);
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.unlisten = function(
    type, listener, opt_useCapture, opt_listenerScope) {
  return this.eventTargetListeners_.remove(
      String(type), listener, opt_useCapture, opt_listenerScope);
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.unlistenByKey = function(
    key) {
  return this.eventTargetListeners_.removeByKey(key);
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.removeAllListeners =
    function(opt_type) {
  return this.eventTargetListeners_.removeAll(opt_type);
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.fireListeners = function(
    type, capture, eventObject) {
  // TODO(chrishenry): Original code avoids array creation when there
  // is no listener, so we do the same. If this optimization turns
  // out to be not required, we can replace this with
  // getListeners(type, capture) instead, which is simpler.
  var listenerArray = this.eventTargetListeners_.listeners[String(type)];
  if (!listenerArray) {
    return true;
  }
  listenerArray = goog.array.clone(listenerArray);

  var rv = true;
  for (var i = 0; i < listenerArray.length; ++i) {
    var listener = listenerArray[i];
    // We might not have a listener if the listener was removed.
    if (listener && !listener.removed && listener.capture == capture) {
      var listenerFn = listener.listener;
      var listenerHandler = listener.handler || listener.src;

      if (listener.callOnce) {
        this.unlistenByKey(listener);
      }
      rv = listenerFn.call(listenerHandler, eventObject) !== false && rv;
    }
  }

  return rv && eventObject.returnValue_ != false;
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.getListeners = function(
    type, capture) {
  return this.eventTargetListeners_.getListeners(String(type), capture);
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.getListener = function(
    type, listener, capture, opt_listenerScope) {
  return this.eventTargetListeners_.getListener(
      String(type), listener, capture, opt_listenerScope);
};


/** @override */
goog.labs.events.NonDisposableEventTarget.prototype.hasListener = function(
    opt_type, opt_capture) {
  var id = goog.isDef(opt_type) ? String(opt_type) : undefined;
  return this.eventTargetListeners_.hasListener(id, opt_capture);
};


/**
 * Asserts that the event target instance is initialized properly.
 * @private
 */
goog.labs.events.NonDisposableEventTarget.prototype.assertInitialized_ =
    function() {
  goog.asserts.assert(
      this.eventTargetListeners_,
      'Event target is not initialized. Did you call the superclass ' +
          '(goog.labs.events.NonDisposableEventTarget) constructor?');
};


/**
 * Dispatches the given event on the ancestorsTree.
 *
 * TODO(chrishenry): Look for a way to reuse this logic in
 * goog.events, if possible.
 *
 * @param {!Object} target The target to dispatch on.
 * @param {goog.events.Event|Object|string} e The event object.
 * @param {Array=} opt_ancestorsTree The ancestors
 *     tree of the target, in reverse order from the closest ancestor
 *     to the root event target. May be null if the target has no ancestor.
 * @return {boolean} If anyone called preventDefault on the event object (or
 *     if any of the listeners returns false) this will also return false.
 * @private
 */
goog.labs.events.NonDisposableEventTarget.dispatchEventInternal_ = function(
    target, e, opt_ancestorsTree) {
  var type = e.type || /** @type {string} */ (e);

  // If accepting a string or object, create a custom event object so that
  // preventDefault and stopPropagation work with the event.
  if (goog.isString(e)) {
    e = new goog.events.Event(e, target);
  } else if (!(e instanceof goog.events.Event)) {
    var oldEvent = e;
    e = new goog.events.Event(type, target);
    goog.object.extend(e, oldEvent);
  } else {
    e.target = e.target || target;
  }

  var rv = true, currentTarget;

  // Executes all capture listeners on the ancestors, if any.
  if (opt_ancestorsTree) {
    for (var i = opt_ancestorsTree.length - 1; !e.propagationStopped_ && i >= 0;
         i--) {
      currentTarget = e.currentTarget = opt_ancestorsTree[i];
      rv = currentTarget.fireListeners(type, true, e) && rv;
    }
  }

  // Executes capture and bubble listeners on the target.
  if (!e.propagationStopped_) {
    currentTarget = e.currentTarget = target;
    rv = currentTarget.fireListeners(type, true, e) && rv;
    if (!e.propagationStopped_) {
      rv = currentTarget.fireListeners(type, false, e) && rv;
    }
  }

  // Executes all bubble listeners on the ancestors, if any.
  if (opt_ancestorsTree) {
    for (i = 0; !e.propagationStopped_ && i < opt_ancestorsTree.length; i++) {
      currentTarget = e.currentTarget = opt_ancestorsTree[i];
      rv = currentTarget.fireListeners(type, false, e) && rv;
    }
  }

  return rv;
};