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

/* 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 arguments.callee (child.parentNode, element);
}

Element.findChildren = function(element, onlyClasses, recursive, tagName) {		
	if(!element.hasChildNodes()) return null;
	var elements = [];
	$A(element.childNodes).each( function(e) {
    if(e.tagName && e.tagName==tagName &&
      (!onlyClasses || (Element.hasClassName(e, onlyClasses))))
        elements.push(e);
    if(recursive) {
      var grandchildren = Element.findChildren(e, onlyClasses, 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;
}

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 parentNode = element.parentNode;
		return drop._containers.detect(function(c) { return parentNode == 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) {
		var affected = Array();
		if(!this.drops.length) return;
		
		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) {
			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) {
		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.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);
			});
	},
	
	_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.prototype = {
	initialize: function(element) {
		var options = Object.extend({
			handle: false,
			starteffect: function(element) { 
				new Effect.Opacity(element, {duration:0.2, from:1.0, to:0.7}); 
			},
			reverteffect: function(element, top_offset, left_offset) {
				var dur = Math.sqrt(Math.abs(top_offset^2)+Math.abs(left_offset^2))*0.02;
				element._revert = new Effect.Move(element, { x: -left_offset, y: -top_offset, duration: dur});
			},
			endeffect: function(element) { 
				new Effect.Opacity(element, {duration:0.2, from:0.7, to:1.0}); 
			},
			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] }
		}, arguments[1] || {});

		this.element = $(element);
		
		if(options.handle && (typeof options.handle == 'string'))
			this.handle = Element.childrenWithClassName(this.element, options.handle)[0];	
		if(!this.handle) this.handle = $(options.handle);
		if(!this.handle) this.handle = this.element;
		
		if(options.scroll) options.scroll = $(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(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;
				
			if(this.element._revert) {
				this.element._revert.cancel();
				this.element._revert = null;
			}
			
			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) {
			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) {
			//if(this.scrollInterval) this.scroll();
			this.stopScrolling();
			var p = Position.page(this.options.scroll);
			p[0] += this.options.scroll.scrollLeft;
			p[1] += this.options.scroll.scrollTop;
			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);
		var d = this.currentDelta();
		pos[0] -= d[0]; pos[1] -= d[1];
		
		if(this.options.scroll) {
			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]);
			} 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;
		}
	},
	
	startScrolling: function(speed) {
		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;
		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);
		this.draw(Draggables._lastPointer);		
		
		if(this.options.change) this.options.change(this);
	}
}

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

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 = {
	sortables: {},
	
	_findRootElement: function(element) {

		while (element.tagName != "BODY") {	

			if (element.id && this.sortables[element.id] != null) 
				return element;
				
			element = element.parentNode;
		}
		
		return null;
	},
	
	setOptions: function(element, options) {
		this.sortables[element.id] = options;
	},

	options: function(element) {
		/* Optimized by Sammi Williams 15 Feb */
		element = Sortable._findRootElement($(element));
		if (element)
			return Sortable.sortables[element.id];
		return null;
	},
	
	destroy: function(element){
		/* Optimized by Sammi Williams 15 Feb */
		var s = Sortable.options(element);
		
		if (s != null) {
			Draggables.removeObserver(s.element);
			s.droppables.each(function(d){ Droppables.remove(d) });
			s.draggables.invoke('destroy');
			
			delete Sortable.sortables[element.id];
		}
	},
	
	create: function(element) {		
		element = $(element);
		var options = Object.extend({ 
			element:            element,
			tag:                'li',			 // assumes li children, override with tag: 'tagname'
			dropOnEmpty:	    false,
			tree:				false,
			treeTag:			'ul',
			overlap:			'vertical', // one of 'vertical', 'horizontal'
			constraint:		    'vertical', // one of 'vertical', 'horizontal', false
			containment: 	    element,		// also takes array of elements (or id's); or false
			handle:				false,			// or a CSS class
			only:				false,
			hoverclass:		    null,
			ghosting:			false,
			scroll:				false,
			format:				/^[^_]*_(.*)$/,
			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,
			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,
			hoverclass:		options.hoverclass,
			onHover:		 	Sortable.onHover,
			greedy:				!options.dropOnEmpty
		}

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

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

		// make it so
		var options_for_tree = {
			onHover:			Sortable.onEmptyHover,
			overlap:			options.overlap,
			containment:	options.containment,
			hoverclass:		options.hoverclass
		}

		// 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);
			options.droppables.push(e);			
		});

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

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

	/* Convenience functions - 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.toUpperCase());
	},

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

	onHover: function(element, dropon, overlap) {
		/* Cannot drop on itself - avoids some DOM exceptions */
		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});
			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);
	},

	sequence: function(element) {
		element = $(element);
		var sortableOptions = this.options(element);
		var options = Object.extend({
			tag:	sortableOptions.tag,
			only: sortableOptions.only,
			name: element.id,
			format: sortableOptions.format
		}, arguments[1] || {});
		return $(this.findElements(element, options) || []).map( function(item) {
			return item.id.match(options.format) ? item.id.match(options.format)[1] : '';
		});
	},

	_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)
				arguments.callee(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;
	},

	serialize: function(element) {
		element = $(element);
		var options = Sortable.options (element);
		
		if (options.tree) {
			return Sortable.tree(element, arguments[1]).children.map( function (item) {
				return [encodeURIComponent(element.id) + 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 encodeURIComponent(element.id) + "[]=" + encodeURIComponent(item);
			}).join('&');
		}
	}
}