// 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();
	}
}

// functions to handle add/edit drop-downs

// called from onChange or onClick event of the market dropdown list
function CategoryListOnChange() 
{
    var catList = document.getElementById("eventcat");
    
    // get selected continent from dropdown list
    var selectedCat = catList.options[catList.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_data_provider.asp" + "?filter=" + encodeURIComponent(selectedContinent);
    // use the following line if using php
     requestUrl = "subcatxml.php" + "?cat=" + encodeURIComponent(selectedCat);
	//alert ("Requesting page: " + requestUrl);
    
	CreateXmlHttpObj();
	
	// verify XmlHttpObj variable was successfully initialized
	if(XmlHttpObj)
	{
        // assign the StateChangeHandler function ( defined below in this file)
        // to be called when the state of the XmlHttpObj changes
        // receiving data back from the server is one such change
		XmlHttpObj.onreadystatechange = CatStateChangeHandler;
		
		// 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 CatStateChangeHandler()
{
	// 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)
		{			
			//alert("XML status is 200");
			PopulateSubcatList(XmlHttpObj.responseXML.documentElement);
		}
		else
		{
			alert("There was a problem retrieving data from the server, status code: "  + XmlHttpObj.status);
		}
	}
}

// populate the contents of the project dropdown list
function PopulateSubcatList(subcatNode)
{
	//alert("Populating subcat list");
    var subcatList = document.getElementById("eventsubcat");
	// clear the subcat list 
	//alert("Clearing subcat list");
	for (var count = subcatList.options.length-1; count >-1; count--)
	{
		subcatList.options[count] = null;
	}

	var subcatNodes = subcatNode.getElementsByTagName('subcat');
	var idValue;
	var textValue; 
	var optionItem;
	// populate the dropdown list with data from the xml doc
	//alert("Populating subcat list");
	optionItem = new Option( 'All Subcategories', '',  false, false);
	subcatList.options[subcatList.length] = optionItem;
	for (var count = 0; count < subcatNodes.length; count++)
	{
   		textValue = GetInnerText(subcatNodes[count]);
		idValue = subcatNodes[count].getAttribute("id");
		optionItem = new Option( textValue, idValue,  false, false);
		subcatList.options[subcatList.length] = optionItem;
	}
}

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