(function($) {
	$.fn.jScrollbar= function(op) {
        var defaults = {
			scrollStep : 20,
			allowMouseWheel : true
        };
		
		if(this.length>0)
		return this.each(function() {
			
			/*
			// Vars
			*/
			var 
				$this = $(this),
				opts = $.extend(defaults, op),
				js_mask = $this.find('.jScrollbar_mask'),
				js_drag = $this.find('.jScrollbar_draggable a.draggable'),
				js_Parentdrag = $this.find('.jScrollbar_draggable'),
				diff = parseInt(js_mask.innerHeight()) - parseInt($this.height());
			
			/** if mask container is heighter than the main container **/
			if(diff > 0)
			{
				js_Parentdrag.show();
				var pxDraggable = parseInt(js_Parentdrag.height()) - parseInt(js_drag.height());;
				var pxUpWhenScrollMove = opts.scrollStep;
				var pxUpWhenMaskMove = pxUpWhenScrollMove * (diff/pxDraggable);
				
				js_drag
				.click(function(e){e.preventDefault();})
				.draggable({
					axis:'y',
					containment: js_Parentdrag,
					scroll: false,
					drag: function(event, ui){
						js_mask.css('top','-'+(ui.position.top * (diff/pxDraggable))+'px');
					}
				});
				
				
				/** if mousewheel allowed **/
				if(opts.allowMouseWheel)
				$this.mousewheel(function(objEvent, intDelta) {
					// mousewheel up (first if)  and mousewheel down (second if)
					if (intDelta > 0 && parseInt(js_mask.css('top')) < 0){
						js_drag.stop(true, true).animate({top:'-='+pxUpWhenScrollMove+'px'}, 100);
						js_mask.stop(true, true).animate({top:'+='+pxUpWhenMaskMove+'px'},100,function(){
							RelativeTop = parseInt(js_mask.css('top'));
							if(RelativeTop > 0 ) {
								js_drag.animate({top:'0px'},150);
								js_mask.css({top:0});
							}
						});
					}
					else if (intDelta < 00 && parseInt(js_mask.css('top')) > -diff) {
						js_drag.stop(true, true).animate({top:'+='+pxUpWhenScrollMove+'px'}, 100);
						js_mask.stop(true, true).animate({top:'-='+pxUpWhenMaskMove+'px'},100,function(){
							RelativeTop = parseInt(js_mask.css('top'));
							if(RelativeTop < -diff)
							{
								js_mask.css({top:-diff});
								js_drag.animate({top:pxDraggable},150);
							}
						});
					}
				});
			}
		});

	}
})(jQuery);