/**
 * Copyright 2013-2014, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ReactTransitionEvents
 */

"use strict";

var ExecutionEnvironment = require('ExecutionEnvironment');

/**
 * EVENT_NAME_MAP is used to determine which event fired when a
 * transition/animation ends, based on the style property used to
 * define that event.
 */
var EVENT_NAME_MAP = {
  transitionend: {
    'transition': 'transitionend',
    'WebkitTransition': 'webkitTransitionEnd',
    'MozTransition': 'mozTransitionEnd',
    'OTransition': 'oTransitionEnd',
    'msTransition': 'MSTransitionEnd'
  },

  animationend: {
    'animation': 'animationend',
    'WebkitAnimation': 'webkitAnimationEnd',
    'MozAnimation': 'mozAnimationEnd',
    'OAnimation': 'oAnimationEnd',
    'msAnimation': 'MSAnimationEnd'
  }
};

var endEvents = [];

function detectEvents() {
  var testEl = document.createElement('div');
  var style = testEl.style;

  // On some platforms, in particular some releases of Android 4.x,
  // the un-prefixed "animation" and "transition" properties are defined on the
  // style object but the events that fire will still be prefixed, so we need
  // to check if the un-prefixed events are useable, and if not remove them
  // from the map
  if (!('AnimationEvent' in window)) {
    delete EVENT_NAME_MAP.animationend.animation;
  }

  if (!('TransitionEvent' in window)) {
    delete EVENT_NAME_MAP.transitionend.transition;
  }

  for (var baseEventName in EVENT_NAME_MAP) {
    var baseEvents = EVENT_NAME_MAP[baseEventName];
    for (var styleName in baseEvents) {
      if (styleName in style) {
        endEvents.push(baseEvents[styleName]);
        break;
      }
    }
  }
}

if (ExecutionEnvironment.canUseDOM) {
  detectEvents();
}

// We use the raw {add|remove}EventListener() call because EventListener
// does not know how to remove event listeners and we really should
// clean up. Also, these events are not triggered in older browsers
// so we should be A-OK here.

function addEventListener(node, eventName, eventListener) {
  node.addEventListener(eventName, eventListener, false);
}

function removeEventListener(node, eventName, eventListener) {
  node.removeEventListener(eventName, eventListener, false);
}

var ReactTransitionEvents = {
  addEndEventListener: function(node, eventListener) {
    if (endEvents.length === 0) {
      // If CSS transitions are not supported, trigger an "end animation"
      // event immediately.
      window.setTimeout(eventListener, 0);
      return;
    }
    endEvents.forEach(function(endEvent) {
      addEventListener(node, endEvent, eventListener);
    });
  },

  removeEndEventListener: function(node, eventListener) {
    if (endEvents.length === 0) {
      return;
    }
    endEvents.forEach(function(endEvent) {
      removeEventListener(node, endEvent, eventListener);
    });
  }
};

module.exports = ReactTransitionEvents;
