// 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.

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

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) {
        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) {
                element._opacity = Element.getOpacity(element);
                new Effect.Opacity(element, {duration:0.2, from:element._opacity, 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) {
                var toOpacity = typeof element._opacity == 'number' ? element._opacity : 1.0
                new Effect.Opacity(element, {duration:0.2, from:0.7, to:toOpacity});
            },
            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')) {
            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);

        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) {
            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.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 && (this.options.scroll != window)) {
            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) {
        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);
        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 = {
    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 = $(element);
        var options = Object.extend({
            element:element,
            tag:'li', // assumes li children, override with tag: 'tagname'
            dropOnEmpty:false,
            tree:false,
            treeTag:'ul',
            overlap:'vertical', // one of 'vertical', 'horizontal'
            constraint:'vertical', // one of 'vertical', 'horizontal', false
            containment:element, // also takes array of elements (or id's); or false
            handle:false, // or a CSS class
            only:false,
            hoverclass:null,
            ghosting:false,
            scroll:false,
            scrollSensitivity:20,
            scrollSpeed:15,
            format:/^[^_]*_(.*)$/,
            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,
            scrollSpeed:options.scrollSpeed,
            scrollSensitivity:options.scrollSensitivity,
            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});
            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) + "=" +
                        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;
}