var request = null;

/* Wrapper function for constructing a request object.
	Parameters:
		reqType: The HTTP request type, such as GET or POST.
		url: The URL of the server program.
		asynch: Whether to send the request asynchronously or not.
		respHandle: The name of the function that will handle the response.
		Any fifth parameters, represented as arguments[4], are the data a
		POST request is designed to send. */
function httpRequest(reqType, url, asynch, respHandle)
{
	// Mozilla-based browsers
	if (window.XMLHttpRequest)
	{
		request = new XMLHttpRequest();
	}
	else if (window.ActiveXObject)
	{
		request = new ActiveXObject("Msxml2.XMLHTTP");
		if (!request)
		{
			request = new ActiveXObject("Microsoft.XMLHTTP");
		}
	}
	
	// very unlikely, but we test for a null request
	// if neither ActiveXObject was initialized
	if (request)
	{
		// if the reqType parameter is POST, then the
		// 5th argument to the function is the POSTed data
		if (reqType.toLowerCase() != "post")
		{
			initReq(reqType,url,asynch,respHandle);
		}
		else
		{
			// the POSTed data
			var args = arguments[4];
			if (args != null && args.length > 0)
			{
				initReq(reqType, url, asynch, respHandle, args);
			}
		}
	}
	else
	{
		alert("Your browse does not permit the use of all of this application's features!");
	}
}

/* Initialize a request object that is already constructed */
function initReq(reqType, url, bool, respHandle)
{
	try
	{
		/* Specify the function that will handle the HTTP response */
		//alert(respHandle);
		request.onreadystatechange=respHandle;
		request.open(reqType, url, bool);
		
		// if the reqType parameter is POST, then the
		// 5th argument to the function is the POSTed data
		if (reqType.toLowerCase() == "post")
		{
			request.setRequestHeader("Content-Type", "application/x-www-urlencoded; charset=UTF-8");
			request.send(arguments[4]);
		}
		else
		{
			request.send(null);
		}
	}
	catch (errv)
	{
		alert("The application cannot contact the server at the moment. Please try again in a few seconds.\nError detail: "+errv.message);
	}
}