var xmlHttp;


function addToCart(theATC){
	// theATC is formatted UPC~qty|UPC~qty|UPC~qty
	
	// read the cart
	// add product to cart, or alter qty
	// save cart
	// calculate new total
	
	xmlHttp = GetXmlHttpObject();
	
	if(xmlHttp == null){
		alert ("Browser does not support HTTP Request");
		return;
	}

	var url	= "cartAddXML.php";
	url		= url + "?atc=" + theATC;
	url		= url + "&sid=" + Math.random();
	xmlHttp.onreadystatechange = stateChangedAddToCart;
	xmlHttp.open("GET", url, true);
	xmlHttp.send(null);
}



function stateChangedAddToCart(){
	if(xmlHttp.readyState == 4 || xmlHttp.readyState == "complete"){
		xmlDoc = xmlHttp.responseXML;
		
		// affected will more than 0 if lines were changed.  0 if no lines changed.  
		if(xmlDoc.getElementsByTagName("shoppingCart")[0].hasChildNodes()){
			var myShoppingCart	= xmlDoc.getElementsByTagName("shoppingCart")[0].childNodes[0].nodeValue;
		}
		if(xmlDoc.getElementsByTagName("UPCs")[0].hasChildNodes()){
			var myUPCs			= xmlDoc.getElementsByTagName("UPCs")[0].childNodes[0].nodeValue;
			myUPCs = myUPCs.split("~");
		}
		if(xmlDoc.getElementsByTagName("QTYs")[0].hasChildNodes()){
			var myQTYs			= xmlDoc.getElementsByTagName("QTYs")[0].childNodes[0].nodeValue;
			myQTYs = myQTYs.split("~");
		}
		if(xmlDoc.getElementsByTagName("totalRetail")[0].hasChildNodes()){
			var myTotalRetail	= xmlDoc.getElementsByTagName("totalRetail")[0].childNodes[0].nodeValue;
		}
		if(xmlDoc.getElementsByTagName("lineCount")[0].hasChildNodes()){
			var myLineCount		= xmlDoc.getElementsByTagName("lineCount")[0].childNodes[0].nodeValue;
		}
		if(xmlDoc.getElementsByTagName("itemCount")[0].hasChildNodes()){
			var myItemCount		= xmlDoc.getElementsByTagName("itemCount")[0].childNodes[0].nodeValue;
		}
		if(xmlDoc.getElementsByTagName("inStockRetail")[0].hasChildNodes()){
			var myInStockRetail	= xmlDoc.getElementsByTagName("inStockRetail")[0].childNodes[0].nodeValue;
		}
		if(xmlDoc.getElementsByTagName("inStockLines")[0].hasChildNodes()){
			var myInStockLines	= xmlDoc.getElementsByTagName("inStockLines")[0].childNodes[0].nodeValue;
		}
		if(xmlDoc.getElementsByTagName("inStockItems")[0].hasChildNodes()){
			var myInStockItems	= xmlDoc.getElementsByTagName("inStockItems")[0].childNodes[0].nodeValue;
		}
		
		
		
		// update pricing/savings display
		// FOR EACH ITEM!
		for(var u in myUPCs){
			myUPC = myUPCs[u];
			myQTY = myQTYs[u];
			// alert(myUPC + " " + myShoppingCart);
			if(! myShoppingCart){
				// force the cart to be empty
				// alert("Shopping cart is now empty " + myQTY);
				myItemCount	= 0;
				myQTY		= 0;
			}
			showCartQTY	= document.getElementById('cartQTY_' + myUPC);
			document.LBcatalogProducts["atcQ_" + myUPC].value = ""; // clear out entry field
			showCartQTY.innerHTML = myQTY + " in <a href='shopcart.php'>cart<" + "/a> <a href='#' onClick=\"document.LBcatalogProducts.atcQ_" + myUPC + ".value='-" + myQTY + "'; listItem('LBcatalogProducts', '" + myUPC + "'); submitProduct(); return false;\"><img src='../catalog/images_S/trash12.gif' alt='remove' width='12' height='14' class='trash' /><" + "/a>";
			if(myQTY == 0) showCartQTY.innerHTML = ""; // do not show ZERO as 0
		}
		
		// update cart summary text
		showCartSummary	= document.getElementById('cartSummaryText');
		if(myItemCount > 0){
			showCartSummary.innerHTML = myItemCount + " items in your cart: $" + myTotalRetail;
		}else{
			showCartSummary.innerHTML = "Your cart is empty";
		}
		
		// clear out `atc` field ready for next item(s)
		document.LBcatalogProducts.atc.value = "";
	}
}



function GetXmlHttpObject(){
	var objXMLHttp=null;
	
	if(window.XMLHttpRequest){
		objXMLHttp=new XMLHttpRequest();
	}else if(window.ActiveXObject){
		objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP");
	}
	
	return objXMLHttp;
}