// Make a POST to the server 
// and pass on any data from browser
// via the XMLHTTPRequest
var lastPing = 0;
var url = "vehiclesxml.php";

function talkToServer(request, callBack)
{
	var req = newXMLHttpRequest();
	//register the callback handler function
  	var callbackHandler = getReadyStateHandler(req, callBack);
	req.onreadystatechange = callbackHandler;
	req.open("GET", "" + url + escape( encodeURI( request ) ), true);
  	req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
	req.send(null);	
} // talkToServer

function loadPage() {
	talkToServer("", loadVehicles);
}

// This is the callback functions that gets called
// for the response from the server with the XML data
function loadVehicles(testXML) {
	var res = testXML.getElementsByTagName("msg_box")[0];
	var num_images = res.getAttribute("entries");
	var timestamp = res.getAttribute("timestamp");

	if (timestamp > lastPing) {
		lastPing = timestamp;
		
		for(var i = 0; i < num_images; i++)	{
			vehicles[i + 1] = testXML.getElementsByTagName("vehicle")[i].firstChild.nodeValue;
		}
	} 
	loadVehicle(1);
}

function loadVehicle(id) {
		var disp = document.getElementById("vehicle_container");
		disp.innerHTML = vehicles[id]; 
}


//the following two functions are helper infrastructure to 
//craete a XMLHTTPRequest and register a listner callback function

function newXMLHttpRequest() {
	var xmlreq = false;
	if (window.XMLHttpRequest) {
		xmlreq = new XMLHttpRequest();
	} else if (window.ActiveXObject) {
    		// Try ActiveX
		try { 
			xmlreq = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e1) { 
			// first method failed 
			try {
				xmlreq = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e2) {
				 // both methods failed 
			} 
		}
 	}
   	return xmlreq;
} 

function getReadyStateHandler(req, responseXmlHandler) {
	return function () {
	if (req.readyState == 4) {
		if (req.status == 200) {
        		responseXmlHandler(req.responseXML);
		} else {
			//var hellomsg = document.getElementById("hellomsg");
			//hellomsg.innerHTML = "ERROR: "+ req.status;
			alert("ERROR: " + req.status);
      		}
    	}
 	}
} 

var vehicles = new Array();
if (window.addEventListener){
	window.addEventListener('load', loadPage, false); 
} else if (window.attachEvent){
	window.attachEvent("onload", loadPage);
}