function AccordionExtClass( extendsArg ) {
    this.Extends = extendsArg;

	this.options = {
		onActive: Class.empty,
		onBackground: Class.empty,
		display: 0,
		show: false,
		height: true,
		width: false,
		opacity: true,
		fixedHeight: false,
		fixedWidth: false,
		wait: false,
		alwaysHide: false
	};

	this.initialize = function(){
		var options, togglers, elements, container;
		$each(arguments, function(argument, i){
			switch($type(argument)){
				case 'object': options = argument; break;
				case 'element': container = $(argument); break;
				default:
					var temp = $$(argument);
					if (!togglers) togglers = temp;
					else elements = temp;
			}
		});
		this.togglers = togglers || [];
		this.elements = elements || [];
		this.container = $(container);
		this.setOptions(options);
		this.previous = -1;
		if (this.options.alwaysHide) this.options.wait = true;
		if ($chk(this.options.show)){
			this.options.display = false;
			this.previous = this.options.show;
		}
		if (this.options.start){
			this.options.display = false;
			this.options.show = false;
		}
		this.effects = {};
		if (this.options.opacity) this.effects.opacity = 'fullOpacity';
		if (this.options.width) this.effects.width = this.options.fixedWidth ? 'fullWidth' : 'offsetWidth';
		if (this.options.height) this.effects.height = this.options.fixedHeight ? 'fullHeight' : 'scrollHeight';
		for (var i = 0, l = this.togglers.length; i < l; i++) this.addSection(this.togglers[i], this.elements[i]);
		this.elements.each(function(el, i){
			if (this.options.show === i || this.togglers[i].hasClass('fullopen')){
				this.fireEvent('onActive', [this.togglers[i], el]);
				this.previous = i;
			} else {
				for (var fx in this.effects) el.setStyle(fx, 0);
			}
		}, this);
		this.parent(this.elements);
		//if ($chk(this.options.display)) this.display(this.options.display);
	};

	/*
	Property: addSection
		Dynamically adds a new section into the accordion at the specified position.

	Arguments:
		toggler - (dom element) the element that toggles the accordion section open.
		element - (dom element) the element that stretches open when the toggler is clicked.
		pos - (integer) the index where these objects are to be inserted within the accordion.
	*/

	this.addSection = function(toggler, element, pos){
		toggler = $(toggler);
		element = $(element);
		var test = this.togglers.contains(toggler);
		var len = this.togglers.length;
		this.togglers.include(toggler);
		this.elements.include(element);
		if (len && (!test || pos)){
			pos = $pick(pos, len - 1);
			toggler.injectBefore(this.togglers[pos]);
			element.injectAfter(toggler);
		} else if (this.container && !test){
			toggler.inject(this.container);
			element.inject(this.container);
		}
		var idx = this.togglers.indexOf(toggler);
		toggler.addEvent('click', this.display.bind(this, idx));
		if (this.options.height) element.setStyles({'padding-top': 0, 'border-top': 'none', 'padding-bottom': 0, 'border-bottom': 'none'});
		if (this.options.width) element.setStyles({'padding-left': 0, 'border-left': 'none', 'padding-right': 0, 'border-right': 'none'});
		element.fullOpacity = 1;
		if (this.options.fixedWidth) element.fullWidth = this.options.fixedWidth;
		if (this.options.fixedHeight) element.fullHeight = this.options.fixedHeight;
		element.setStyle('overflow', 'hidden');
		if (!test){
			for (var fx in this.effects) element.setStyle(fx, 0);
		}
		return this;
	};

	/*
	Property: display
		Shows a specific section and hides all others. Useful when triggering an accordion from outside.

	Arguments:
		index - integer, the index of the item to show, or the actual element to show.
	*/

	this.display = function(index){
		index = ($type(index) == 'element') ? this.elements.indexOf(index) : index;
		if ((this.timer && this.options.wait) || (index === this.previous && !this.options.alwaysHide)) return this;
		this.previous = index;
		var obj = {};
		this.elements.each(function(el, i){
			obj[i] = {};
			var hide = (i != index) || (this.options.alwaysHide && (el.offsetHeight > 0));
			this.fireEvent(hide ? 'onBackground' : 'onActive', [this.togglers[i], el]);
			for (var fx in this.effects) obj[i][fx] = hide ? 0 : el[this.effects[fx]];
		}, this);
		return this.start(obj);
	};

	this.showThisHideOpen = function(index){return this.display(index);};

};


var AccordionExt = '';
if( MooTools.version < "1.2" ) {
    AccordionExt = Fx.Elements.extend( new AccordionExtClass( '' ) );    // backward compatibility for MooTools 1.1x; Thanks for Alexander Rohra
} else {
    AccordionExt = new Class( new AccordionExtClass( Fx.Elements ) );
}