var numberOfImages = 5;
var timer;

window.onload=function(){

	$('hpimage').src = "/common/images/header/"+getNewImage();
	timer = new PeriodicalExecuter(changeImage,10);	
}

function changeImage(){

	timer.stop();
	var picId = 'hpimage';
	var oldSrc = $(picId).src;
	var src="/common/images/header/"+getNewImage();
	while (isSameImage(oldSrc,src)){
		src="/common/images/header/"+getNewImage();
	}
	var img = new Image();
	img.name=picId
	img.onload=function(img){
	
		var img=this;
		var id = "hpimage";
		var hide =  new Effect.Fade(id, {duration: 1.0, from:1.0, to:0.01, queue: { scope: id, position: 'front' }, afterFinish: function(effect) {
			$(id).src=effect.img.src;
			$(id).name=effect.img.name;
			new Effect.Appear(id, { duration: 1.0, from:0.01, to:1.0, queue: { scope: id, position: 'front' }});
			timer = new PeriodicalExecuter(changeImage,10);
		}});
		hide.img=img;
	};
	img.src=src;
}

function getNewImage(){

	var num = Math.floor(Math.random()*numberOfImages)+1;
	return "header-right-"+num+".jpg";
}

function isSameImage(oldSrc,newSrc){
	return getImageName(oldSrc)==getImageName(newSrc);
}

function getImageName(src){
	var lastSlash = src.lastIndexOf("/");
	return src.substring(lastSlash,src.length);
}