(function($) {
	$.fn.inavi_scroll = function(options){

		// default configuration properties
		var defaults = {
			prevId    : 'prevBtn',
			nextId    : 'nextBtn',
			viewSize : 4,
			size       : 1
		};

		var options = $.extend(defaults, options);
		var obj = this;
		var thisPostion = 0;
		var obj_li = $("li", obj);

		$("#"+options.nextId).click(function(){
			animate("next");
		});
		$("#"+options.prevId).click(function(){
			animate("prev");
		});

		function animate(status){
			if(status == 'prev' ){
				if (thisPostion > 0) thisPostion = thisPostion - options.size;
			}else{
				if (obj_li.length > parseInt(thisPostion + options.size)) thisPostion = thisPostion + options.size;
			}
			viewScroll(thisPostion);
		};

		function viewScroll(idx){
			var ckNum = 0;

			obj_li.each(function() {
				var objT = $(this);
				if (ckNum >= parseInt(idx) && ckNum < parseInt(idx + options.viewSize)){
					objT.show();
				}else{
					objT.hide();
				}
				ckNum ++;
			});
		};
		viewScroll(0);
	};

})(jQuery);