/*
* Returns a new XMLHttpRequest object, or false if this browser
* doesn't support it
*/
function newXMLHttpRequest() {

    var xmlreq = false;

    if (window.XMLHttpRequest) {

        // Create XMLHttpRequest object in non-Microsoft browsers
        xmlreq = new XMLHttpRequest();

    } else if (window.ActiveXObject) {

        // Create XMLHttpRequest via MS ActiveX
        try {
            // Try to create XMLHttpRequest in later versions
            // of Internet Explorer

            xmlreq = new ActiveXObject("Msxml2.XMLHTTP");

        } catch (e1) {

            // Failed to create required ActiveXObject

            try {
                // Try version supported by older versions
                // of Internet Explorer

                xmlreq = new ActiveXObject("Microsoft.XMLHTTP");

            } catch (e2) {

                // Unable to create an XMLHttpRequest with ActiveX
            }
        }
    }

    return xmlreq;
}

/*
* Returns a function that waits for the specified XMLHttpRequest
* to complete, then passes its XML response
* to the given handler function.
* req - The XMLHttpRequest whose state is changing
* responseXmlHandler - Function to pass the XML response to
*/
function getReadyStateHandler(req, responseXmlHandler) {
    // Return an anonymous function that listens to the 
    // XMLHttpRequest instance
    return function () {
        // If the request's status is "complete"
        if (req.readyState == 4) {

            // Check that a successful server response was received
            if (req.status == 200 || req.status == 0 || req.status == 404) {

                // Pass the XML payload of the response to the 
                // handler function
                responseXmlHandler(req.responseXML);
            } else {

                // An HTTP problem has occurred
                alert("HTTP error: " + req.status);
            }
        }
    }
}

/*
* Adds an item, identified by its product code, 
* to the shopping cart
* itemCode - product code of the item to add.
* addRemove - true = add / false = remove.
*/
function addToServiceCart(addRemove, itemCode) {
    // Obtain an XMLHttpRequest instance
    var req = newXMLHttpRequest();

    // Set the handler function to receive callback notifications
    // from the request object
    var handlerFunction = getReadyStateHandler(req, updateCart);
    req.onreadystatechange = handlerFunction;

    // Open an HTTP POST connection to the shopping cart servlet.
    // Third parameter specifies request is asynchronous.
    req.open("POST", "../Xml/ServiceCart/ServiceCartXML.aspx", true);

    // Specify that the body of the request contains form data
    req.setRequestHeader("Content-Type",
                       "application/x-www-form-urlencoded");

    // Send form encoded data stating that I want to add the 
    // specified item to the cart.
    if (addRemove)
        action = "add";
    else
        action = "remove";

    req.send("action=" + action + "&item=" + itemCode);
}

function addToTypeCart(addRemove, itemCode) {
    // Obtain an XMLHttpRequest instance
    var req = newXMLHttpRequest();

    // Set the handler function to receive callback notifications
    // from the request object
    var handlerFunction = getReadyStateHandler(req, updateCart);
    req.onreadystatechange = handlerFunction;

    // Open an HTTP POST connection to the shopping cart servlet.
    // Third parameter specifies request is asynchronous.
    req.open("POST", "../Xml/TypeCart/TypeCartXML.aspx", true);

    // Specify that the body of the request contains form data
    req.setRequestHeader("Content-Type",
                       "application/x-www-form-urlencoded");

    // Send form encoded data stating that I want to add the 
    // specified item to the cart.
    if (addRemove)
        action = "add";
    else
        action = "remove";

    req.send("action=" + action + "&item=" + itemCode);
}

// recive the xml and modify the html
function updateCart(xml) {
}