var Nav = {
	initialized : false,
	navItems : null,
	pageOn : null,
	sectionOn : null,

	initialize : function() {
		if (!this.initialized) {
			this.navItems = $('nav').getElementsBySelector('img');
			this._mouseOver = this.mouseOver.bindAsEventListener(this);
			this._mouseOut = this.mouseOut.bindAsEventListener(this);
			this.findSelected();
			for (var i=0; i<this.navItems.length; i++) {
				var n = this.navItems[i];
				var src = n.readAttribute('_src');
				var s = src.substring(0, src.lastIndexOf('.'));
				var e = src.substring(src.lastIndexOf('.'), src.length);
				n._osrc = s + '_over' + e;
				n._ssrc = s + '_over' + e;
				if (n.hasClassName('selected')) {
					n.src = n._ssrc;
				} else {
					n.observe('mouseover', this._mouseOver);
					n.observe('mouseout', this._mouseOut);
				}
			}
			this.initialized = true;
		}
	},

	findSelected : function() {
			for (var i=0; i<this.navItems.length; i++) {
				var j = this.navItems[i];
				if (j.up().href.indexOf(this.pageOn) != -1 || j.up().href.indexOf(this.sectionOn) != -1) {
					j.addClassName('selected');
				}
			}
		},

	mouseOver : function(event) {
		var img = Event.findElement(event, 'img');
		img.src = img._osrc;
	},

	mouseOut : function(event) {
		var img = Event.findElement(event, 'img');
		img.src = img.readAttribute('_src');
	}
}
Event.observe(window, 'load', function() {
	Nav.initialize();
});