// Requires an IMG ELEMENT called advert_holder
// Links must have a class of "popup"
// needs a folder called IMAGES with series of images called img(x).jpg

// When window loads prepare gallery
window.onload = initGallery;

function initGallery(){
	prepareGalleryLinks();	
	createLoadingHolder();
	createLoader();
}

// Create Hidden Holder to load images into 
function createLoadingHolder(){
	var newDiv	= document.createElement("div");
	newDiv.setAttribute("id","loadingHolderDiv");
	var newImage = document.createElement("img");
	newImage.setAttribute("id","loadingHolder");
	newImage.setAttribute("src","");
	newDiv.appendChild(newImage);
	newDiv.style.display="none";
	var galleryDiv = document.getElementById("advert_holder_div");
	galleryDiv.appendChild(newDiv);
}

// Create Loading Image
function createLoader(){
	var newLoad = document.createElement("div");
	newLoad.setAttribute("id","advertLoader");
	var newLoadImg = document.createElement("img");
	newLoadImg.setAttribute("src","images/site/loader.gif");
	newLoad.appendChild(newLoadImg);
	newLoad.style.display = "none"
	var galleryDiv = document.getElementById("advert_holder_div");
	galleryDiv.appendChild(newLoad);	
}



//Prepare UnObtrustive Links
function prepareGalleryLinks(){
	var links = document.getElementsByTagName("a");
	for (var i=0; i<links.length; i++){
		if (links[i].className == "popup"){
			links[i].onclick = function(){
				preLoadImage(this.getAttribute("href"));
				return false;
			}
		}
	}
}

//PreLoad the Image
function preLoadImage(url){
	var holder = document.getElementById("loadingHolder");
	var holderSource = holder.src;
	var image = document.getElementById("advert_holder");
	var imageSource = image.src;
	var imageSrc = imageSource.split("images/adverts/");
	var UrlSrc = url.split("images/adverts/");
	if (imageSrc[1] != UrlSrc[1]){
		var showLoader = document.getElementById("advertLoader");
		var hideHolder = document.getElementById("advert_holder");
		showLoader.style.display="block";
		hideHolder.style.display="none";
		holder.setAttribute("src",url);
		PreLoading = true;
		holder.onload = function(){
			imageLoaded(url);
			PreLoading = false;
		}
	}
}

// When Image Has Loaded
function imageLoaded(url){
	var loader = document.getElementById("advertLoader");
	var swapDiv = document.getElementById("advert_holder");
	swapDiv.setAttribute("src",url);
	var showDiv = document.getElementById("advert_holder");
	loader.style.display = "none";
	swapDiv.style.display = "block";
}