var photo_box = {};

function photo_box_init(id, urls) {
	photo_box[id] = {};
	photo_box[id].current = 0;
	photo_box[id].urls = urls;
}

function photo_box_show_next(id) {
	p = photo_box[id];
	p.current = (p.current + 1) % (p.urls.length);
	photo_box_update(id);
}

function photo_box_show_previous(id) {
	p = photo_box[id];
	p.current -= 1;
	if (p.current < 0)
		p.current = p.urls.length - 1;
	photo_box_update(id);
}

function photo_box_update(id) {
	p = photo_box[id];
	url = p.urls[p.current];

	img = document.getElementById("photo_box_" + id);
	preload = new Image();
	preload.onload = function() {
		document.getElementById("photo_loading_" + id).style.visibility = "hidden";
		img.src = url;
	}
	document.getElementById("photo_loading_" + id).style.visibility = "visible";
	preload.src = url;
}