// script.aculo.us dragdrop.js v1.6.4, Wed Sep 06 11:30:58 CEST 2006

// Copyright (c) 2005 Thomas Fuchs (http://script.aculo.us, http://mir.aculo.us)
//           (c) 2005 Sammi Williams (http://www.oriontransfer.co.nz, sammi@oriontransfer.co.nz)
//
// See scriptaculous.js for full license.

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

if(typeof Effect == 'undefined')
  throw("dragdrop.js requires including script.aculo.us' effects.js library");

var Droppables = {
  drops: [],

  remove: function(element) {
	this.drops = this.drops.reject(function(d) { return d.element==$(element) });
  },

  add: function(element) {
	element = $(element);
	var options = Object.extend({
	  greedy:     true,
	  hoverclass: null,
	  tree:       false
	}, arguments[1] || {});

	// cache containers
	if(options.containment) {
	  options._containers = [];
	  var containment = options.containment;
	  if((typeof containment == 'object') &&
		(containment.constructor == Array)) {
		containment.each( function(c) { options._containers.push($(c)) });
	  } else {
		options._containers.push($(containment));
	  }
	}

	if(options.accept) options.accept = [options.accept].flatten();

	Element.makePositioned(element); // fix IE
	options.element = element;

	this.drops.push(options);
  },

  findDeepestChild: function(drops) {
	deepest = drops[0];

	for (i = 1; i < drops.length; ++i)
	  if (Element.isParent(drops[i].element, deepest.element))
		deepest = drops[i];

	return deepest;
  },

  isContained: function(element, drop) {
	var containmentNode;
	if(drop.tree) {
	  containmentNode = element.treeNode;
	} else {
	  containmentNode = element.parentNode;
	}
	return drop._containers.detect(function(c) { return containmentNode == c });
  },

  isAffected: function(point, element, drop) {
	return (
	  (drop.element!=element) &&
	  ((!drop._containers) ||
		this.isContained(element, drop)) &&
	  ((!drop.accept) ||
		(Element.classNames(element).detect(
		  function(v) { return drop.accept.include(v) } ) )) &&
	  Position.within(drop.element, point[0], point[1]) );
  },

  deactivate: function(drop) {
	if(drop.hoverclass)
	  Element.removeClassName(drop.element, drop.hoverclass);
	this.last_active = null;
  },

  activate: function(drop) {
	if(drop.hoverclass)
	  Element.addClassName(drop.element, drop.hoverclass);
	this.last_active = drop;
  },

  show: function(point, element) {
	if(!this.drops.length) return;
	var affected = [];

	if(this.last_active) this.deactivate(this.last_active);
	this.drops.each( function(drop) {
	  if(Droppables.isAffected(point, element, drop))
		affected.push(drop);
	});

	if(affected.length>0) {
	  drop = Droppables.findDeepestChild(affected);
	  Position.within(drop.element, point[0], point[1]);
	  if(drop.onHover)
		drop.onHover(element, drop.element, Position.overlap(drop.overlap, drop.element));

	  Droppables.activate(drop);
	}
  },

  fire: function(event, element) {
	if(!this.last_active) return;
	Position.prepare();

	if (this.isAffected([Event.pointerX(event), Event.pointerY(event)], element, this.last_active))
	  if (this.last_active.onDrop)
		this.last_active.onDrop(element, this.last_active.element, event);
  },

  reset: function() {
	if(this.last_active)
	  this.deactivate(this.last_active);
  }
}

var Draggables = {
  drags: [],
  observers: [],

  register: function(draggable) {
	if(this.drags.length == 0) {
	  this.eventMouseUp   = this.endDrag.bindAsEventListener(this);
	  this.eventMouseMove = this.updateDrag.bindAsEventListener(this);
	  this.eventKeypress  = this.keyPress.bindAsEventListener(this);

	  Event.observe(document, "mouseup", this.eventMouseUp);
	  Event.observe(document, "mousemove", this.eventMouseMove);
	  Event.observe(document, "keypress", this.eventKeypress);
	}
	this.drags.push(draggable);
  },

  unregister: function(draggable) {
	this.drags = this.drags.reject(function(d) { return d==draggable });
	if(this.drags.length == 0) {
	  Event.stopObserving(document, "mouseup", this.eventMouseUp);
	  Event.stopObserving(document, "mousemove", this.eventMouseMove);
	  Event.stopObserving(document, "keypress", this.eventKeypress);
	}
  },

  activate: function(draggable) {
	if(draggable.options.delay) {
	  this._timeout = setTimeout(function() {
		Draggables._timeout = null;
		window.focus();
		Draggables.activeDraggable = draggable;
	  }.bind(this), draggable.options.delay);
	} else {
	  window.focus(); // allows keypress events if window isn't currently focused, fails for Safari
	  this.activeDraggable = draggable;
	}
  },

  deactivate: function() {
	this.activeDraggable = null;
  },

  updateDrag: function(event) {
	if(!this.activeDraggable) return;
	var pointer = [Event.pointerX(event), Event.pointerY(event)];
	// Mozilla-based browsers fire successive mousemove events with
	// the same coordinates, prevent needless redrawing (moz bug?)
	if(this._lastPointer && (this._lastPointer.inspect() == pointer.inspect())) return;
	this._lastPointer = pointer;

	this.activeDraggable.updateDrag(event, pointer);
  },

  endDrag: function(event) {
	if(this._timeout) {
	  clearTimeout(this._timeout);
	  this._timeout = null;
	}
	if(!this.activeDraggable) return;
	this._lastPointer = null;
	this.activeDraggable.endDrag(event);
	this.activeDraggable = null;
  },

  keyPress: function(event) {
	if(this.activeDraggable)
	  this.activeDraggable.keyPress(event);
  },

  addObserver: function(observer) {
	this.observers.push(observer);
	this._cacheObserverCallbacks();
  },

  removeObserver: function(element) {  // element instead of observer fixes mem leaks
	this.observers = this.observers.reject( function(o) { return o.element==element });
	this._cacheObserverCallbacks();
  },

  notify: function(eventName, draggable, event) {  // 'onStart', 'onEnd', 'onDrag'
	if(this[eventName+'Count'] > 0)
	  this.observers.each( function(o) {
		if(o[eventName]) o[eventName](eventName, draggable, event);
	  });
	if(draggable.options[eventName]) draggable.options[eventName](draggable, event);
  },

  _cacheObserverCallbacks: function() {
	['onStart','onEnd','onDrag'].each( function(eventName) {
	  Draggables[eventName+'Count'] = Draggables.observers.select(
		function(o) { return o[eventName]; }
	  ).length;
	});
  }
}

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

var Draggable = Class.create();
Draggable._dragging    = {};

Draggable.prototype = {
  initialize: function(element) {
	var defaults = {
	  handle: false,
	  reverteffect: function(element, top_offset, left_offset) {
		var dur = Math.sqrt(Math.abs(top_offset^2)+Math.abs(left_offset^2))*0.02;
		new Effect.Move(element, { x: -left_offset, y: -top_offset, duration: dur,
		  queue: {scope:'_draggable', position:'end'}
		});
	  },
	  endeffect: function(element) {
		var toOpacity = typeof element._opacity == 'number' ? element._opacity : 1.0;
		new Effect.Opacity(element, {duration:0.2, from:0.7, to:toOpacity,
		  queue: {scope:'_draggable', position:'end'},
		  afterFinish: function(){
			Draggable._dragging[element] = false
		  }
		});
	  },
	  zindex: 1000,
	  revert: false,
	  scroll: false,
	  scrollSensitivity: 20,
	  scrollSpeed: 15,
	  snap: false,  // false, or xy or [x,y] or function(x,y){ return [x,y] }
	  delay: 0
	};

	if(arguments[1] && typeof arguments[1].endeffect == 'undefined')
	  Object.extend(defaults, {
		starteffect: function(element) {
		  element._opacity = Element.getOpacity(element);
		  Draggable._dragging[element] = true;
		  new Effect.Opacity(element, {duration:0.2, from:element._opacity, to:0.7});
		}
	  });

	var options = Object.extend(defaults, arguments[1] || {});

	this.element = $(element);

	if(options.handle && (typeof options.handle == 'string')) {
	  var h = Element.childrenWithClassName(this.element, options.handle, true);
	  if(h.length>0) this.handle = h[0];
	}
	if(!this.handle) this.handle = $(options.handle);
	if(!this.handle) this.handle = this.element;

	if(options.scroll && !options.scroll.scrollTo && !options.scroll.outerHTML) {
	  options.scroll = $(options.scroll);
	  this._isScrollChild = Element.childOf(this.element, options.scroll);
	}

	Element.makePositioned(this.element); // fix IE

	this.delta    = this.currentDelta();
	this.options  = options;
	this.dragging = false;

	this.eventMouseDown = this.initDrag.bindAsEventListener(this);
	Event.observe(this.handle, "mousedown", this.eventMouseDown);

	Draggables.register(this);
  },

  destroy: function() {
	Event.stopObserving(this.handle, "mousedown", this.eventMouseDown);
	Draggables.unregister(this);
  },

  currentDelta: function() {
	return([
	  parseInt(Element.getStyle(this.element,'left') || '0'),
	  parseInt(Element.getStyle(this.element,'top') || '0')]);
  },

  initDrag: function(event) {
	if(typeof Draggable._dragging[this.element] != 'undefined' &&
	  Draggable._dragging[this.element]) return;
	if(Event.isLeftClick(event)) {
	  // abort on form elements, fixes a Firefox issue
	  var src = Event.element(event);
	  if(src.tagName && (
		src.tagName=='INPUT' ||
		src.tagName=='SELECT' ||
		src.tagName=='OPTION' ||
		src.tagName=='BUTTON' ||
		src.tagName=='TEXTAREA')) return;

	  var pointer = [Event.pointerX(event), Event.pointerY(event)];
	  var pos     = Position.cumulativeOffset(this.element);
	  this.offset = [0,1].map( function(i) { return (pointer[i] - pos[i]) });

	  Draggables.activate(this);
	  Event.stop(event);
	}
  },

  startDrag: function(event) {
	this.dragging = true;

	if(this.options.zindex) {
	  this.originalZ = parseInt(Element.getStyle(this.element,'z-index') || 0);
	  this.element.style.zIndex = this.options.zindex;
	}

	if(this.options.ghosting) {
	  this._clone = this.element.cloneNode(true);
	  Position.absolutize(this.element);
	  this.element.parentNode.insertBefore(this._clone, this.element);
	}

	if(this.options.scroll) {
	  if (this.options.scroll == window) {
		var where = this._getWindowScroll(this.options.scroll);
		this.originalScrollLeft = where.left;
		this.originalScrollTop = where.top;
	  } else {
		this.originalScrollLeft = this.options.scroll.scrollLeft;
		this.originalScrollTop = this.options.scroll.scrollTop;
	  }
	}

	Draggables.notify('onStart', this, event);

	if(this.options.starteffect) this.options.starteffect(this.element);
  },

  updateDrag: function(event, pointer) {
	if(!this.dragging) this.startDrag(event);
	Position.prepare();
	Droppables.show(pointer, this.element);
	Draggables.notify('onDrag', this, event);

	this.draw(pointer);
	if(this.options.change) this.options.change(this);

	if(this.options.scroll) {
	  this.stopScrolling();

	  var p;
	  if (this.options.scroll == window) {
		with(this._getWindowScroll(this.options.scroll)) { p = [ left, top, left+width, top+height ]; }
	  } else {
		p = Position.page(this.options.scroll);
		p[0] += this.options.scroll.scrollLeft;
		p[1] += this.options.scroll.scrollTop;

		p[0] += (window.pageXOffset || document.documentElement.scrollLeft || document.body.scrollLeft || 0);
		p[1] += (window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0);

		p.push(p[0]+this.options.scroll.offsetWidth);
		p.push(p[1]+this.options.scroll.offsetHeight);
	  }
	  var speed = [0,0];
	  if(pointer[0] < (p[0]+this.options.scrollSensitivity)) speed[0] = pointer[0]-(p[0]+this.options.scrollSensitivity);
	  if(pointer[1] < (p[1]+this.options.scrollSensitivity)) speed[1] = pointer[1]-(p[1]+this.options.scrollSensitivity);
	  if(pointer[0] > (p[2]-this.options.scrollSensitivity)) speed[0] = pointer[0]-(p[2]-this.options.scrollSensitivity);
	  if(pointer[1] > (p[3]-this.options.scrollSensitivity)) speed[1] = pointer[1]-(p[3]-this.options.scrollSensitivity);
	  this.startScrolling(speed);
	}

	// fix AppleWebKit rendering
	if(navigator.appVersion.indexOf('AppleWebKit')>0) window.scrollBy(0,0);

	Event.stop(event);
  },

  finishDrag: function(event, success) {
	this.dragging = false;

	if(this.options.ghosting) {
	  Position.relativize(this.element);
	  Element.remove(this._clone);
	  this._clone = null;
	}

	if(success) Droppables.fire(event, this.element);
	Draggables.notify('onEnd', this, event);

	var revert = this.options.revert;
	if(revert && typeof revert == 'function') revert = revert(this.element);

	var d = this.currentDelta();
	if(revert && this.options.reverteffect) {
	  this.options.reverteffect(this.element,
		d[1]-this.delta[1], d[0]-this.delta[0]);
	} else {
	  this.delta = d;
	}

	if(this.options.zindex)
	  this.element.style.zIndex = this.originalZ;

	if(this.options.endeffect)
	  this.options.endeffect(this.element);

	Draggables.deactivate(this);
	Droppables.reset();
  },

  keyPress: function(event) {
	if(event.keyCode!=Event.KEY_ESC) return;
	this.finishDrag(event, false);
	Event.stop(event);
  },

  endDrag: function(event) {
	if(!this.dragging) return;
	this.stopScrolling();
	this.finishDrag(event, true);
	Event.stop(event);
  },

  draw: function(point) {
	var pos = Position.cumulativeOffset(this.element);
	if(this.options.ghosting) {
	  var r   = Position.realOffset(this.element);
	  window.status = r.inspect();
	  pos[0] += r[0] - Position.deltaX; pos[1] += r[1] - Position.deltaY;
	}

	var d = this.currentDelta();
	pos[0] -= d[0]; pos[1] -= d[1];

	if(this.options.scroll && (this.options.scroll != window && this._isScrollChild)) {
	  pos[0] -= this.options.scroll.scrollLeft-this.originalScrollLeft;
	  pos[1] -= this.options.scroll.scrollTop-this.originalScrollTop;
	}

	var p = [0,1].map(function(i){
	  return (point[i]-pos[i]-this.offset[i])
	}.bind(this));

	if(this.options.snap) {
	  if(typeof this.options.snap == 'function') {
		p = this.options.snap(p[0],p[1],this);
	  } else {
	  if(this.options.snap instanceof Array) {
		p = p.map( function(v, i) {
		  return Math.round(v/this.options.snap[i])*this.options.snap[i] }.bind(this))
	  } else {
		p = p.map( function(v) {
		  return Math.round(v/this.options.snap)*this.options.snap }.bind(this))
	  }
	}}

	var style = this.element.style;
	if((!this.options.constraint) || (this.options.constraint=='horizontal'))
	  style.left = p[0] + "px";
	if((!this.options.constraint) || (this.options.constraint=='vertical'))
	  style.top  = p[1] + "px";

	if(style.visibility=="hidden") style.visibility = ""; // fix gecko rendering
  },

  stopScrolling: function() {
	if(this.scrollInterval) {
	  clearInterval(this.scrollInterval);
	  this.scrollInterval = null;
	  Draggables._lastScrollPointer = null;
	}
  },

  startScrolling: function(speed) {
	if(!(speed[0] || speed[1])) return;
	this.scrollSpeed = [speed[0]*this.options.scrollSpeed,speed[1]*this.options.scrollSpeed];
	this.lastScrolled = new Date();
	this.scrollInterval = setInterval(this.scroll.bind(this), 10);
  },

  scroll: function() {
	var current = new Date();
	var delta = current - this.lastScrolled;
	this.lastScrolled = current;
	if(this.options.scroll == window) {
	  with (this._getWindowScroll(this.options.scroll)) {
		if (this.scrollSpeed[0] || this.scrollSpeed[1]) {
		  var d = delta / 1000;
		  this.options.scroll.scrollTo( left + d*this.scrollSpeed[0], top + d*this.scrollSpeed[1] );
		}
	  }
	} else {
	  this.options.scroll.scrollLeft += this.scrollSpeed[0] * delta / 1000;
	  this.options.scroll.scrollTop  += this.scrollSpeed[1] * delta / 1000;
	}

	Position.prepare();
	Droppables.show(Draggables._lastPointer, this.element);
	Draggables.notify('onDrag', this);
	if (this._isScrollChild) {
	  Draggables._lastScrollPointer = Draggables._lastScrollPointer || $A(Draggables._lastPointer);
	  Draggables._lastScrollPointer[0] += this.scrollSpeed[0] * delta / 1000;
	  Draggables._lastScrollPointer[1] += this.scrollSpeed[1] * delta / 1000;
	  if (Draggables._lastScrollPointer[0] < 0)
		Draggables._lastScrollPointer[0] = 0;
	  if (Draggables._lastScrollPointer[1] < 0)
		Draggables._lastScrollPointer[1] = 0;
	  this.draw(Draggables._lastScrollPointer);
	}

	if(this.options.change) this.options.change(this);
  },

  _getWindowScroll: function(w) {
	var T, L, W, H;
	with (w.document) {
	  if (w.document.documentElement && documentElement.scrollTop) {
		T = documentElement.scrollTop;
		L = documentElement.scrollLeft;
	  } else if (w.document.body) {
		T = body.scrollTop;
		L = body.scrollLeft;
	  }
	  if (w.innerWidth) {
		W = w.innerWidth;
		H = w.innerHeight;
	  } else if (w.document.documentElement && documentElement.clientWidth) {
		W = documentElement.clientWidth;
		H = documentElement.clientHeight;
	  } else {
		W = body.offsetWidth;
		H = body.offsetHeight
	  }
	}
	return { top: T, left: L, width: W, height: H };
  }
}

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

var SortableObserver = Class.create();
SortableObserver.prototype = {
  initialize: function(element, observer) {
	this.element   = $(element);
	this.observer  = observer;
	this.lastValue = Sortable.serialize(this.element);
  },

  onStart: function() {
	this.lastValue = Sortable.serialize(this.element);
  },

  onEnd: function() {
	Sortable.unmark();
	if(this.lastValue != Sortable.serialize(this.element))
	  this.observer(this.element)
  }
}

var Sortable = {
  SERIALIZE_RULE: /^[^_\-](?:[A-Za-z0-9\-\_]*)[_](.*)$/,

  sortables: {},

  _findRootElement: function(element) {
	while (element.tagName != "BODY") {
	  if(element.id && Sortable.sortables[element.id]) return element;
	  element = element.parentNode;
	}
  },

  options: function(element) {
	element = Sortable._findRootElement($(element));
	if(!element) return;
	return Sortable.sortables[element.id];
  },

  destroy: function(element){
	var s = Sortable.options(element);

	if(s) {
	  Draggables.removeObserver(s.element);
	  s.droppables.each(function(d){ Droppables.remove(d) });
	  s.draggables.invoke('destroy');

	  delete Sortable.sortables[s.element.id];
	}
  },

  create: function(element) {
	element = $(element);
	var options = Object.extend({
	  element:     element,
	  tag:         'li',       // assumes li children, override with tag: 'tagname'
	  dropOnEmpty: false,
	  tree:        false,
	  treeTag:     'ul',
	  overlap:     'vertical', // one of 'vertical', 'horizontal'
	  constraint:  'vertical', // one of 'vertical', 'horizontal', false
	  containment: element,    // also takes array of elements (or id's); or false
	  handle:      false,      // or a CSS class
	  only:        false,
	  delay:       0,
	  hoverclass:  null,
	  ghosting:    false,
	  scroll:      false,
	  scrollSensitivity: 20,
	  scrollSpeed: 15,
	  format:      this.SERIALIZE_RULE,
	  onChange:    Prototype.emptyFunction,
	  onUpdate:    Prototype.emptyFunction
	}, arguments[1] || {});

	// clear any old sortable with same element
	this.destroy(element);

	// build options for the draggables
	var options_for_draggable = {
	  revert:      true,
	  scroll:      options.scroll,
	  scrollSpeed: options.scrollSpeed,
	  scrollSensitivity: options.scrollSensitivity,
	  delay:       options.delay,
	  ghosting:    options.ghosting,
	  constraint:  options.constraint,
	  handle:      options.handle };

	if(options.starteffect)
	  options_for_draggable.starteffect = options.starteffect;

	if(options.reverteffect)
	  options_for_draggable.reverteffect = options.reverteffect;
	else
	  if(options.ghosting) options_for_draggable.reverteffect = function(element) {
		element.style.top  = 0;
		element.style.left = 0;
	  };

	if(options.endeffect)
	  options_for_draggable.endeffect = options.endeffect;

	if(options.zindex)
	  options_for_draggable.zindex = options.zindex;

	// build options for the droppables
	var options_for_droppable = {
	  overlap:     options.overlap,
	  containment: options.containment,
	  tree:        options.tree,
	  hoverclass:  options.hoverclass,
	  onHover:     Sortable.onHover
	  //greedy:      !options.dropOnEmpty
	}

	var options_for_tree = {
	  onHover:      Sortable.onEmptyHover,
	  overlap:      options.overlap,
	  containment:  options.containment,
	  hoverclass:   options.hoverclass
	}

	// fix for gecko engine
	Element.cleanWhitespace(element);

	options.draggables = [];
	options.droppables = [];

	// drop on empty handling
	if(options.dropOnEmpty || options.tree) {
	  Droppables.add(element, options_for_tree);
	  options.droppables.push(element);
	}

	(this.findElements(element, options) || []).each( function(e) {
	  // handles are per-draggable
	  var handle = options.handle ?
		Element.childrenWithClassName(e, options.handle)[0] : e;
	  options.draggables.push(
		new Draggable(e, Object.extend(options_for_draggable, { handle: handle })));
	  Droppables.add(e, options_for_droppable);
	  if(options.tree) e.treeNode = element;
	  options.droppables.push(e);
	});

	if(options.tree) {
	  (Sortable.findTreeElements(element, options) || []).each( function(e) {
		Droppables.add(e, options_for_tree);
		e.treeNode = element;
		options.droppables.push(e);
	  });
	}

	// keep reference
	this.sortables[element.id] = options;

	// for onupdate
	Draggables.addObserver(new SortableObserver(element, options.onUpdate));

  },

  // return all suitable-for-sortable elements in a guaranteed order
  findElements: function(element, options) {
	return Element.findChildren(
	  element, options.only, options.tree ? true : false, options.tag);
  },

  findTreeElements: function(element, options) {
	return Element.findChildren(
	  element, options.only, options.tree ? true : false, options.treeTag);
  },

  onHover: function(element, dropon, overlap) {
	if(Element.isParent(dropon, element)) return;

	if(overlap > .33 && overlap < .66 && Sortable.options(dropon).tree) {
	  return;
	} else if(overlap>0.5) {
	  Sortable.mark(dropon, 'before');
	  if(dropon.previousSibling != element) {
		var oldParentNode = element.parentNode;
		element.style.visibility = "hidden"; // fix gecko rendering
		dropon.parentNode.insertBefore(element, dropon);
		if(dropon.parentNode!=oldParentNode)
		  Sortable.options(oldParentNode).onChange(element);
		Sortable.options(dropon.parentNode).onChange(element);
	  }
	} else {
	  Sortable.mark(dropon, 'after');
	  var nextElement = dropon.nextSibling || null;
	  if(nextElement != element) {
		var oldParentNode = element.parentNode;
		element.style.visibility = "hidden"; // fix gecko rendering
		dropon.parentNode.insertBefore(element, nextElement);
		if(dropon.parentNode!=oldParentNode)
		  Sortable.options(oldParentNode).onChange(element);
		Sortable.options(dropon.parentNode).onChange(element);
	  }
	}
  },

  onEmptyHover: function(element, dropon, overlap) {
	var oldParentNode = element.parentNode;
	var droponOptions = Sortable.options(dropon);

	if(!Element.isParent(dropon, element)) {
	  var index;

	  var children = Sortable.findElements(dropon, {tag: droponOptions.tag, only: droponOptions.only});
	  var child = null;

	  if(children) {
		var offset = Element.offsetSize(dropon, droponOptions.overlap) * (1.0 - overlap);

		for (index = 0; index < children.length; index += 1) {
		  if (offset - Element.offsetSize (children[index], droponOptions.overlap) >= 0) {
			offset -= Element.offsetSize (children[index], droponOptions.overlap);
		  } else if (offset - (Element.offsetSize (children[index], droponOptions.overlap) / 2) >= 0) {
			child = index + 1 < children.length ? children[index + 1] : null;
			break;
		  } else {
			child = children[index];
			break;
		  }
		}
	  }

	  dropon.insertBefore(element, child);

	  Sortable.options(oldParentNode).onChange(element);
	  droponOptions.onChange(element);
	}
  },

  unmark: function() {
	if(Sortable._marker) Element.hide(Sortable._marker);
  },

  mark: function(dropon, position) {
	// mark on ghosting only
	var sortable = Sortable.options(dropon.parentNode);
	if(sortable && !sortable.ghosting) return;

	if(!Sortable._marker) {
	  Sortable._marker = $('dropmarker') || document.createElement('DIV');
	  Element.hide(Sortable._marker);
	  Element.addClassName(Sortable._marker, 'dropmarker');
	  Sortable._marker.style.position = 'absolute';
	  document.getElementsByTagName("body").item(0).appendChild(Sortable._marker);
	}
	var offsets = Position.cumulativeOffset(dropon);
	Sortable._marker.style.left = offsets[0] + 'px';
	Sortable._marker.style.top = offsets[1] + 'px';

	if(position=='after')
	  if(sortable.overlap == 'horizontal')
		Sortable._marker.style.left = (offsets[0]+dropon.clientWidth) + 'px';
	  else
		Sortable._marker.style.top = (offsets[1]+dropon.clientHeight) + 'px';

	Element.show(Sortable._marker);
  },

  _tree: function(element, options, parent) {
	var children = Sortable.findElements(element, options) || [];

	for (var i = 0; i < children.length; ++i) {
	  var match = children[i].id.match(options.format);

	  if (!match) continue;

	  var child = {
		id: encodeURIComponent(match ? match[1] : null),
		element: element,
		parent: parent,
		children: new Array,
		position: parent.children.length,
		container: Sortable._findChildrenElement(children[i], options.treeTag.toUpperCase())
	  }

	  /* Get the element containing the children and recurse over it */
	  if (child.container)
		this._tree(child.container, options, child)

	  parent.children.push (child);
	}

	return parent;
  },

  /* Finds the first element of the given tag type within a parent element.
	Used for finding the first LI[ST] within a L[IST]I[TEM].*/
  _findChildrenElement: function (element, containerTag) {
	if (element && element.hasChildNodes)
	  for (var i = 0; i < element.childNodes.length; ++i)
		if (element.childNodes[i].tagName == containerTag)
		  return element.childNodes[i];

	return null;
  },

  tree: function(element) {
	element = $(element);
	var sortableOptions = this.options(element);
	var options = Object.extend({
	  tag: sortableOptions.tag,
	  treeTag: sortableOptions.treeTag,
	  only: sortableOptions.only,
	  name: element.id,
	  format: sortableOptions.format
	}, arguments[1] || {});

	var root = {
	  id: null,
	  parent: null,
	  children: new Array,
	  container: element,
	  position: 0
	}

	return Sortable._tree (element, options, root);
  },

  /* Construct a [i] index for a particular node */
  _constructIndex: function(node) {
	var index = '';
	do {
	  if (node.id) index = '[' + node.position + ']' + index;
	} while ((node = node.parent) != null);
	return index;
  },

  sequence: function(element) {
	element = $(element);
	var options = Object.extend(this.options(element), arguments[1] || {});

	return $(this.findElements(element, options) || []).map( function(item) {
	  return item.id.match(options.format) ? item.id.match(options.format)[1] : '';
	});
  },

  setSequence: function(element, new_sequence) {
	element = $(element);
	var options = Object.extend(this.options(element), arguments[2] || {});

	var nodeMap = {};
	this.findElements(element, options).each( function(n) {
		if (n.id.match(options.format))
			nodeMap[n.id.match(options.format)[1]] = [n, n.parentNode];
		n.parentNode.removeChild(n);
	});

	new_sequence.each(function(ident) {
	  var n = nodeMap[ident];
	  if (n) {
		n[1].appendChild(n[0]);
		delete nodeMap[ident];
	  }
	});
  },

  serialize: function(element) {
	element = $(element);
	var options = Object.extend(Sortable.options(element), arguments[1] || {});
	var name = encodeURIComponent(
	  (arguments[1] && arguments[1].name) ? arguments[1].name : element.id);

	if (options.tree) {
	  return Sortable.tree(element, arguments[1]).children.map( function (item) {
		return [name + Sortable._constructIndex(item) + "[id]=" +
				encodeURIComponent(item.id)].concat(item.children.map(arguments.callee));
	  }).flatten().join('&');
	} else {
	  return Sortable.sequence(element, arguments[1]).map( function(item) {
		return name + "[]=" + encodeURIComponent(item);
	  }).join('&');
	}
  }
}

/* Returns true if child is contained within element */
Element.isParent = function(child, element) {
  if (!child.parentNode || child == element) return false;

  if (child.parentNode == element) return true;

  return Element.isParent(child.parentNode, element);
}

Element.findChildren = function(element, only, recursive, tagName) {
  if(!element.hasChildNodes()) return null;
  tagName = tagName.toUpperCase();
  if(only) only = [only].flatten();
  var elements = [];
  $A(element.childNodes).each( function(e) {
	if(e.tagName && e.tagName.toUpperCase()==tagName &&
	  (!only || (Element.classNames(e).detect(function(v) { return only.include(v) }))))
		elements.push(e);
	if(recursive) {
	  var grandchildren = Element.findChildren(e, only, recursive, tagName);
	  if(grandchildren) elements.push(grandchildren);
	}
  });

  return (elements.length>0 ? elements.flatten() : []);
}

Element.offsetSize = function (element, type) {
  if (type == 'vertical' || type == 'height')
	return element.offsetHeight;
  else
	return element.offsetWidth;
}