// declare a global  XMLHTTP Request object
var XmlHttpObj;

// create an instance of XMLHTTPRequest Object, varies with browser type, try for IE first then Mozilla
function CreateXmlHttpObj()
{
	// try creating for IE (note: we don't know the user's browser type here, just attempting IE first.)
	try
	{
		XmlHttpObj = new ActiveXObject("Msxml2.XMLHTTP");
	}
	catch(e)
	{
		try
		{
			XmlHttpObj = new ActiveXObject("Microsoft.XMLHTTP");
		} 
		catch(oc)
		{
			XmlHttpObj = null;
		}
	}
	// if unable to create using IE specific code then try creating for Mozilla (FireFox) 
	if(!XmlHttpObj && typeof XMLHttpRequest != "undefined") 
	{
		XmlHttpObj = new XMLHttpRequest();
	}
}

// called from onChange or onClick event of the ComputerFamily dropdown list
function ComputerFamilyListOnChange() 
{
    var ComputerFamilyList = document.getElementById("ComputerFamilyList");
    
    // get selected ComputerFamily from dropdown list
    var selectedComputerFamily = ComputerFamilyList.options[ComputerFamilyList.selectedIndex].value;
    
    // url of page that will send xml data back to client browser
    var requestUrl;
    // use the following line if using asp
    requestUrl = "/xml_product_data.asp" + "?filter=" + encodeURIComponent(selectedComputerFamily);
    
	CreateXmlHttpObj();
	
	// verify XmlHttpObj variable was successfully initialized
	if(XmlHttpObj)
	{
		XmlHttpObj.onreadystatechange = ComputerFamilyHandler;
		
		// define the iteraction with the server -- true for as asynchronous.
		XmlHttpObj.open("GET", requestUrl,  true);
		
		// send request to server, null arg  when using "GET"
		XmlHttpObj.send(null);		
	}
}


// called from onChange or onClick event of the ComputerModel dropdown list
function ComputerModelListOnChange() 
{
    var ComputerModelList = document.getElementById("ComputerModelList");
    
    // get selected ComputerModel from dropdown list
    var selectedComputerModel = ComputerModelList.options[ComputerModelList.selectedIndex].value;
    
    // url of page that will send xml data back to client browser
    var requestUrl;
    // use the following line if using asp
    requestUrl = "/xml_product_data2.asp" + "?model=" + encodeURIComponent(selectedComputerModel);
    
	CreateXmlHttpObj();
	
	// verify XmlHttpObj variable was successfully initialized
	if(XmlHttpObj)
	{
		XmlHttpObj.onreadystatechange = ComputerModelHandler;
		
		// define the iteraction with the server -- true for as asynchronous.
		XmlHttpObj.open("GET", requestUrl,  true);
		
		// send request to server, null arg  when using "GET"
		XmlHttpObj.send(null);		
	}
}



// this function called when state of  XmlHttpObj changes
// we're interested in the state that indicates data has been
// received from the server
function ComputerFamilyHandler()
{
	// state ==4 indicates receiving response data from server is completed
	if(XmlHttpObj.readyState == 4)
	{
		// To make sure valid response is received from the server, 200 means response received is OK
		if(XmlHttpObj.status == 200)
		{			
			PopulateComputerModelList(XmlHttpObj.responseXML.documentElement);
		}
		else
		{
			alert("problem retrieving data from the server, status code: "  + XmlHttpObj.status);
		}
	}
}


function ComputerModelHandler()
{
	// state ==4 indicates receiving response data from server is completed
	if(XmlHttpObj.readyState == 4)
	{
		// To make sure valid response is received from the server, 200 means response received is OK
		if(XmlHttpObj.status == 200)
		{			
			PopulateComputerChasisList(XmlHttpObj.responseXML.documentElement);
		}
		else
		{
			alert("problem retrieving data from the server, status code: "  + XmlHttpObj.status);
		}
	}
}

// populate the contents of the cmodel dropdown list
function PopulateComputerModelList(ComputermodelNode)
{
    var ComputerModelList = document.getElementById("ComputerModelList");
	// clear the cmodel list 
	for (var count = ComputerModelList.options.length-1; count >-1; count--)
	{
		ComputerModelList.options[count] = null;
	}

	var ComputermodelNodes = ComputermodelNode.getElementsByTagName('Computermodels');
	var idValue;
	var textValue; 
	var optionItem;
	// populate the dropdown list with data from the xml doc
	for (var count = 0; count < ComputermodelNodes.length; count++)
	{
   		textValue = GetInnerText(ComputermodelNodes[count]);
		idValue = ComputermodelNodes[count].getAttribute("id");
		optionItem = new Option( textValue, idValue,  false, false);
		ComputerModelList.options[ComputerModelList.length] = optionItem;
	}
}


// populate the contents of the cmodel dropdown list
function PopulateComputerChasisList(ComputerChasisNode)
{
    var ComputerChasisList = document.getElementById("ComputerChasisList");
	// clear the cmodel list 
	for (var count = ComputerChasisList.options.length-1; count >-1; count--)
	{
		ComputerChasisList.options[count] = null;
	}

	var ComputerChasisNodes = ComputerChasisNode.getElementsByTagName('ComputerChasis');
	var idValue;
	var textValue; 
	var optionItem;
	// populate the dropdown list with data from the xml doc
	for (var count = 0; count < ComputerChasisNodes.length; count++)
	{
   		textValue = GetInnerText(ComputerChasisNodes[count]);
		idValue = ComputerChasisNodes[count].getAttribute("id");
		optionItem = new Option( textValue, idValue,  false, false);
		ComputerChasisList.options[ComputerChasisList.length] = optionItem;
	}
}


// returns the node text value 
function GetInnerText (node)
{
	 return (node.textContent || node.innerText || node.text) ;
}