jQuery.fn.extend({
        // nextUntil is necessary, would be nice to have this in jQuery core
        nextUntil: function(expr) {
            var match = [];

            // We need to figure out which elements to push onto the array
            this.each(function(){
                // Traverse through the sibling nodes
                for( var i = this.nextSibling; i; i = i.nextSibling ) {
                    // Make sure that we're only dealing with elements
                    if ( i.nodeType != 1 ) continue;

                    // If we find a match then we need to stop
                    if ( jQuery.filter( expr, [i] ).r.length ) break;

                    // Otherwise, add it on to the stack
                    match.push( i );
                }
            });

            return this.pushStack( match );
        },
        // the plugin method itself
        Accordion: function(settings) {
                // setup configuration
                settings = jQuery.extend({}, jQuery.Accordion.defaults, {
                        // define context defaults
                        header: jQuery(':first-child', this)[0].tagName // take first childs tagName as header
                }, settings);

                // calculate active if not specified, using the first header
                var container = this,
                        active = settings.active
                                ? jQuery(settings.active, this)
                                : settings.active === false
                                        ? jQuery("<div>")
                                        : jQuery(settings.header, this).eq(0),
                        running = 0;

                container.find(settings.header)
                        .not(active || "")
                        .nextUntil(settings.header)
                        .hide();
                active.addClass(settings.selectedClass);

                function clickHandler(event) {
                        // get the click target
                        var clicked = jQuery(event.target);

                        // due to the event delegation model, we have to check if one
                        // of the parent elements is our actual header, and find that
                        if ( clicked.parents(settings.header).length ) {
                                while ( !clicked.is(settings.header) ) {
                                        clicked = clicked.parent();
                                }
                        }

                        var clickedActive = clicked[0] == active[0];

                        // if animations are still active, or the active header is the target, ignore click
                        if(running || (settings.alwaysOpen && clickedActive) || !clicked.is(settings.header))
                                return;

                        // switch classes
                        active.toggleClass(settings.selectedClass);
                        if ( !clickedActive ) {
                                clicked.addClass(settings.selectedClass);
                        }

                        // find elements to show and hide
                        var toShow = clicked.nextUntil(settings.header),
                                toHide = active.nextUntil(settings.header),
                                data = [clicked, active, toShow, toHide];
                        active = clickedActive ? jQuery([]) : clicked;
                        // count elements to animate
                        running = toHide.size() + toShow.size();
                        var finished = function(cancel) {
                                running = cancel ? 0 : --running;
                                if ( running )
                                        return;

                                // trigger custom change event
                                container.trigger("change", data);
                        };
                        // TODO if hideSpeed is set to zero, animations are crappy
                        // workaround: use hide instead
                        // solution: animate should check for speed of 0 and do something about it
                        if ( settings.animated ) {
                                if ( !settings.alwaysOpen && clickedActive ) {
                                        toShow.slideToggle(settings.showSpeed);
                                        finished(true);
                                } else {
                                        toHide.filter(":hidden").each(finished).end().filter(":visible").slideUp(settings.hideSpeed, finished);
                                        toShow.slideDown(settings.showSpeed, finished);
                                }
                        } else {
                                if ( !settings.alwaysOpen && clickedActive ) {
                                        toShow.toggle();
                                } else {
                                        toHide.hide();
                                        toShow.show();
                                }
                                finished(true);
                        }

                        return false;
                };
                function activateHandlder(event, index) {
                        // call clickHandler with custom event
                        clickHandler({
                                target: jQuery(settings.header, this)[index]
                        });
                };

                return container
                        .bind(settings.event, clickHandler)
                        .bind("activate", activateHandlder);
        },
        // programmatic triggering
        activate: function(index) {
                return this.trigger('activate', [index || 0]);
        }
});

jQuery.Accordion = {};
jQuery.extend(jQuery.Accordion, {
        defaults: {
                selectedClass: "selected",
                showSpeed: 'slow',
                hideSpeed: 'fast',
                alwaysOpen: true,
                animated: true,
                event: "click"
        },
        setDefaults: function(settings) {
                jQuery.extend(jQuery.Accordion.defaults, settings);
        }
});