/**
 * Written by Neil Crosby. 
 * http://www.workingwith.me.uk/
 *
 * Use this wherever you want, but please keep this comment at the top of this file.
 *
 * Copyright (c) 2006 Neil Crosby
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy 
 * of this software and associated documentation files (the "Software"), to deal 
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
 * copies of the Software, and to permit persons to whom the Software is 
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in 
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
 * SOFTWARE.
 **/
var css = {
   /**
    * Returns an array containing references to all elements
    * of a given tag type within a certain node which have a given class
    *
    * @param node    the node to start from 
    *             (e.g. document, 
    *                  getElementById('whateverStartpointYouWant')
    *             )
    * @param searchClass the class we're wanting
    *             (e.g. 'some_class')
    * @param tag      the tag that the found elements are allowed to be
    *             (e.g. '*', 'div', 'li')
    **/
   getElementsByClass : function(node, searchClass, tag) {
      var classElements = new Array();
      var els = node.getElementsByTagName(tag);
      var elsLen = els.length;
      var pattern = new RegExp("(^|\\s)"+searchClass+"(\\s|$)");
      
      for (var i = 0, j = 0; i < elsLen; i++) {
         if (this.elementHasClass(els[i], searchClass) ) {
            classElements[j] = els[i];
            j++;
         }
      }
      
      return classElements;
   },


   /**
    * PRIVATE.  Returns an array containing all the classes applied to this
    * element.
    *
    * Used internally by elementHasClass(), addClassToElement() and 
    * removeClassFromElement().
    **/
   privateGetClassArray: function(el) {
      return el.className.split(' '); 
   },

   /**
    * PRIVATE.  Creates a string from an array of class names which can be used 
    * by the className function.
    *
    * Used internally by addClassToElement().
    **/
   privateCreateClassString: function(classArray) {
      return classArray.join(' ');
   },

   /**
    * Returns true if the given element has been assigned the given class.
    **/
   elementHasClass: function(el, classString) {
      if (!el) {
         return false;
      }
      
      var regex = new RegExp('\\b'+classString+'\\b');
      if (el.className.match(regex)) {
         return true;
      }

      return false;
   },

   /**
    * Adds classString to the classes assigned to the element with id equal to
    * idString.
    **/
   addClassToId: function(idString, classString) {
      this.addClassToElement(document.getElementById(idString), classString);
   },

   /**
    * Adds classString to the classes assigned to the given element.
    * If the element already has the class which was to be added, then
    * it is not added again.
    **/
   addClassToElement: function(el, classString) {
      var classArray = this.privateGetClassArray(el);

      if (this.elementHasClass(el, classString)) {
         return; // already has element so don't need to add it
      }

      classArray.push(classString);

      el.className = this.privateCreateClassString(classArray);
   },

   /**
    * Removes the given classString from the list of classes assigned to the
    * element with id equal to idString
    **/
   removeClassFromId: function(idString, classString) {
      this.removeClassFromElement(document.getElementById(idString), classString);
   },

   /**
    * Removes the given classString from the list of classes assigned to the
    * given element.  If the element has the same class assigned to it twice, 
    * then only the first instance of that class is removed.
    **/
   removeClassFromElement: function(el, classString) {
      var classArray = this.privateGetClassArray(el);

      for (x in classArray) {
         if (classString == classArray[x]) {
            classArray[x] = '';
            break;
         }
      }

      el.className = this.privateCreateClassString(classArray);
   }
}