/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* Copyright 2012 Mozilla Foundation
 *
 * 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.
 */

/** @license Copyright 2012 Mozilla Foundation 
 * Copyright 2013 Lu Wang <coolwanglu@gmail.com>
 * Apache License Version 2.0 
 */

'use strict';

// HTMLElement classList property
(function checkClassListProperty() {
  var div = document.createElement('div');
  if ('classList' in div)
    return; // classList property exists

  function changeList(element, itemName, add, remove) {
    var s = element.className || '';
    var list = s.split(/\s+/g);
    if (list[0] === '') list.shift();
    var index = list.indexOf(itemName);
    if (index < 0 && add)
      list.push(itemName);
    if (index >= 0 && remove)
      list.splice(index, 1);
    element.className = list.join(' ');
    return (index >= 0);
  }

  var classListPrototype = {
    add: function(name) {
      changeList(this.element, name, true, false);
    },
    contains: function(name) {
      return changeList(this.element, name, false, false);
    },
    remove: function(name) {
      changeList(this.element, name, false, true);
    },
    toggle: function(name) {
      changeList(this.element, name, true, true);
    }
  };

  Object.defineProperty(HTMLElement.prototype, 'classList', {
    get: function() {
      if (this['_classList'])
        return this['_classList'];

      var classList = Object.create(classListPrototype, {
        element: {
          value: this,
          writable: false,
          enumerable: true
        }
      });
      Object.defineProperty(this, '_classList', {
        value: classList,
        writable: false,
        enumerable: false
      });
      return classList;
    },
    enumerable: true
  });
})();