document.getElementsByClassName = function(className, parentElement) {
  var children = ($(parentElement) || document.body).getElementsByTagName('*');
  return $A(children).inject([], function(elements, child) {
    if (Element.hasClassName(child, className))
      elements.push(child);
    return elements;
  });
}

/*--------------------------------------------------------------------------*/

if (!window.Element) {
  var Element = new Object();
}

Object.extend(Element, {
  visible: function(element) {
    return $(element).style.display != 'none';
  },
  
  toggle: function() {
    for (var i = 0; i < arguments.length; i++) {
      var element = $(arguments[i]);
      Element[Element.visible(element) ? 'hide' : 'show'](element);
    }
  },

  hide: function() {
    for (var i = 0; i < arguments.length; i++) {
      var element = $(arguments[i]);
      element.style.display = 'none';
    }
  },
  
  show: function() {
    for (var i = 0; i < arguments.length; i++) {
      var element = $(arguments[i]);
      element.style.display = '';
    }
  },

  remove: function(element) {
    element = $(element);
    element.parentNode.removeChild(element);
  },
  
  getHeight: function(element) {
    element = $(element);
    return element.offsetHeight; 
  },
  
  classNames: function(element) {
    return new Element.ClassNames(element);
  },

  hasClassName: function(element, className) {
    if (!(element = $(element))) return;
    return Element.classNames(element).include(className);
  },

  addClassName: function(element, className) {
    if (!(element = $(element))) return;
    return Element.classNames(element).add(className);
  },

  removeClassName: function(element, className) {
    if (!(element = $(element))) return;
    return Element.classNames(element).remove(className);
  },
  
  // removes whitespace-only text node children
  cleanWhitespace: function(element) {
	if(undef(element) || isNull(element)) return;
    element = $(element);
    for (var i = 0; i < element.childNodes.length; i++) {
      var node = element.childNodes[i];
      if (node.nodeType == 3 && !/\S/.test(node.nodeValue)) 
       node.parentNode.removeChild(node);
    }
  },
  
  empty: function(element) {
    return $(element).innerHTML.match(/^\s*$/);
  },
  
  scrollTo: function(element) {
    element = $(element);
    var x = element.x ? element.x : element.offsetLeft,
        y = element.y ? element.y : element.offsetTop;
    window.scrollTo(x, y);
  },
  
  getStyle: function(element, style) {
    element = $(element);
    var value = element.style[style.camelize()];
    if (!value) {
      if (document.defaultView && document.defaultView.getComputedStyle) {
        var css = document.defaultView.getComputedStyle(element, null);
        value = css ? css.getPropertyValue(style) : null;
      } else if (element.currentStyle) {
        value = element.currentStyle[style.camelize()];
      }
    }

    if (window.opera && ['left', 'top', 'right', 'bottom'].include(style))
      if (Element.getStyle(element, 'position') == 'static') value = 'auto';

    return value == 'auto' ? null : value;
  },
  
  getDimensions: function(element) {
    element = $(element);
    if (Element.getStyle(element, 'display') != 'none')
      return {width: element.offsetWidth, height: element.offsetHeight};
    
    // All *Width and *Height properties give 0 on elements with display none,
    // so enable the element temporarily
    var els = element.style;
    var originalVisibility = els.visibility;
    var originalPosition = els.position;
    els.visibility = 'hidden';
    els.position = 'absolute';
    els.display = '';
    var originalWidth = element.clientWidth;
    var originalHeight = element.clientHeight;
    els.display = 'none';
    els.position = originalPosition;
    els.visibility = originalVisibility;
    return {width: originalWidth, height: originalHeight};    
  },
  
  makePositioned: function(element) {
    element = $(element);
    var pos = Element.getStyle(element, 'position');
    if (pos == 'static' || !pos) {
      element._madePositioned = true;
      element.style.position = 'relative';
      // Opera returns the offset relative to the positioning context, when an
      // element is position relative but top and left have not been defined
      if (window.opera) {
        element.style.top = 0;
        element.style.left = 0;
      }  
    }
  },

  undoPositioned: function(element) {
    element = $(element);
    if (element._madePositioned) {
      element._madePositioned = undefined;
      element.style.position =
        element.style.top =
        element.style.left =
        element.style.bottom =
        element.style.right = '';	  
    }
  },

  makeClipping: function(element) {
    element = $(element);
    if (element._overflow) return;
    element._overflow = element.style.overflow;
    if ((Element.getStyle(element, 'overflow') || 'visible') != 'hidden')
      element.style.overflow = 'hidden';
  },

  undoClipping: function(element) {
    element = $(element);
    if (element._overflow) return;
    element.style.overflow = element._overflow;
    element._overflow = undefined;
  }
});

var Toggle = new Object();
Toggle.display = Element.toggle;

/*--------------------------------------------------------------------------*/

Abstract.Insertion = function(adjacency) {
  this.adjacency = adjacency;
}

Abstract.Insertion.prototype = {
  initialize: function(element, content) {
    this.element = $(element);
    this.content = content;
    
    if (this.adjacency && this.element.insertAdjacentHTML) {
      try {
        this.element.insertAdjacentHTML(this.adjacency, this.content);
      } catch (e) {
        if (this.element.tagName.toLowerCase() == 'tbody') {
          this.insertContent(this.contentFromAnonymousTable());
        } else {
          throw e;
        }
      }
    } else {
      this.range = this.element.ownerDocument.createRange();
      if (this.initializeRange) this.initializeRange();
      this.insertContent([this.range.createContextualFragment(this.content)]);
    }
  },
  
  contentFromAnonymousTable: function() {
    var div = document.createElement('div');
    div.innerHTML = '<table><tbody>' + this.content + '</tbody></table>';
    return $A(div.childNodes[0].childNodes[0].childNodes);
  }
}

var Insertion = new Object();

Insertion.Before = Class.create();
Insertion.Before.prototype = Object.extend(new Abstract.Insertion('beforeBegin'), {
  initializeRange: function() {
    this.range.setStartBefore(this.element);
  },
  
  insertContent: function(fragments) {
    fragments.each((function(fragment) {
      this.element.parentNode.insertBefore(fragment, this.element);
    }).bind(this));
  }
});

Insertion.Top = Class.create();
Insertion.Top.prototype = Object.extend(new Abstract.Insertion('afterBegin'), {
  initializeRange: function() {
    this.range.selectNodeContents(this.element);
    this.range.collapse(true);
  },
  
  insertContent: function(fragments) {
    fragments.reverse().each((function(fragment) {
      this.element.insertBefore(fragment, this.element.firstChild);
    }).bind(this));
  }
});

Insertion.Bottom = Class.create();
Insertion.Bottom.prototype = Object.extend(new Abstract.Insertion('beforeEnd'), {
  initializeRange: function() {
    this.range.selectNodeContents(this.element);
    this.range.collapse(this.element);
  },
  
  insertContent: function(fragments) {
    fragments.each((function(fragment) {
      this.element.appendChild(fragment);
    }).bind(this));
  }
});

Insertion.After = Class.create();
Insertion.After.prototype = Object.extend(new Abstract.Insertion('afterEnd'), {
  initializeRange: function() {
    this.range.setStartAfter(this.element);
  },
  
  insertContent: function(fragments) {
    fragments.each((function(fragment) {
      this.element.parentNode.insertBefore(fragment, 
        this.element.nextSibling);
    }).bind(this));
  }
});

/*--------------------------------------------------------------------------*/

Element.ClassNames = Class.create();
Element.ClassNames.prototype = {
  initialize: function(element) {
    this.element = $(element);
  },

  _each: function(iterator) {
    this.element.className.split(/\s+/).select(function(name) {
      return name.length > 0;
    })._each(iterator);
  },
  
  set: function(className) {
    this.element.className = className;
  },
  
  add: function(classNameToAdd) {
    if (this.include(classNameToAdd)) return;
    this.set(this.toArray().concat(classNameToAdd).join(' '));
  },
  
  remove: function(classNameToRemove) {
    if (!this.include(classNameToRemove)) return;
    this.set(this.select(function(className) {
      return className != classNameToRemove;
    }));
  },
  
  toString: function() {
    return this.toArray().join(' ');
  }
}

Object.extend(Element.ClassNames.prototype, Enumerable);