/************************************************************************
*************************************************************************
@Name :         jScrollbar - jQuery Plugin
@Revison :  1.0
@Date :        21/03/2011
@Author:     ALPIXEL - http://www.myjqueryplugins.com - http://www.alpixel.fr
@License :       Open Source - MIT License : http://www.opensource.org/licenses/mit-license.php
**************************************************************************
*************************************************************************/
(function($) {
    $.fn.jScrollbar= function(op) {
        var defaults = {
            scrollStep : 10,
            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);