window.addEvent('domready', function(){

	initJS();

});

function initJS() {

	var items = $("sidebar").getElements("div.sidebar_item");
	var show_items = 4;

	i = (typeof i == "undefined") ? 0 : i;

	items.each(function(item, index) {
		if(item.id == "currentitem") i = index;
	});

	var sidebarScroll = new Fx.Scroll('sidebar', {
	    offset: {
	        'x': 0,
	        'y': 0
	    }
	}).toElement(items[i]);

	$$("div.top_navi").getElement("a").addEvent("click", function() {
		if(i > 0) {
			i = ( i - show_items < 0 ) ? 0 : i - show_items;
			sidebarScroll.toElement(items[i]);
		}
	});

	$$("div.down_navi").getElement("a").addEvent("click", function() {
		if(items.length > show_items && i + show_items < (items.length -1) ) {
			i = i + show_items;
			sidebarScroll.toElement(items[i]);
		}
	});
}