/**
 * getXMLHttpRequest()
 * Function for establishing the cross-browser XMLHttpRequest object.
 * @access public
 * @return mixed    false = browser does not suport AJAX | object if it does
 * @author Steven Mapes
 **/
function getXMLHttpRequest() {
    var request = false;

    try {
        request = new XMLHttpRequest();
    } catch (e) {
        try {
            request = new ActiveXObject("Msxml2.XMLHTTP");
        } catch(e) {
            try {
                request = new ActiveXObject("Microsoft.XMLHTTP");
           } catch(e) {
                // Browser really doesn't support AJAX
           }
        }
    }
    return request;
}

/**
 * ajaxRequest()
 * Common function to set and make the AJAX request.  Can be called from another
 * function of directly is enough information is given.
 * @param string url                The URL to connect to
 * @param string callbackHandler    The name of the function that will handle the response
 * @param string method             The method to use.  GET or POST
 * @param string getXML             FALSE = responseText | TRUE = responseXML
 * @param string postData           If the METHOD is POST then this is the data to send
 * @param string contentType        If the METHOD is POST then set the RequestHeader to this
 * @param boolean async             If true then asynchronous request
 * @access public
 * @return void
 * @author Steven Mapes
 * <example>
 *   // Make a call to update the Version Select list for SiteID 1
 *   ajaxRequest("ajax/nav.php?method=getVersions&siteId=1","displayVersionList");
 * </example>
 **/
function ajaxRequest(url,callbackHandler,method,getXML,postData,contentType,async){
    // Handle parameter defaults
    method = method || "GET";
    getXML = getXML || false;
    postData = postData || false;
    contentType = contentType || 'application/x-www-form-urlencoded';
    async = async || true;

    requestObj = getXMLHttpRequest();    // Need to put this here as IE7 breaks otherwise

    try {
        // Create the Callback Function to handle the various status
        requestObj.onreadystatechange = function() {
            // readyStates: 0 = Uninitialised | 1 = Loading | 2 = Loaded | 3 = Interactive | 4 = Completed

            if (requestObj.readyState == 4) {
                // The request has been completed
                hideSpinner();  // Hide the spinner

                if (requestObj.status == 200) {
                    // Good response sent. Gather the response based on value of getXML
                    var output = requestObj.responseText;   // Using Plain-Text
                    if (getXML == true) {
                        output = requestObj.responseXML;    // Using XML
                    }

                    // Pass the response into the specified callbackHandler
                    performCallback(callbackHandler,output);
                } else {
                    // Bad response sent from the server
                    alert("The server returned a status of "+requestObj.status+", aborting the request");
                }
            } else {
                // Display the in progress icon
                document.onmousemove = displaySpinner;
            }
        }

        // If we're using GET generate a random int to help expire the browser cache
        if (method == 'GET') {
            var rand = parseInt(Math.random()*99999999);
            url += "&random="+rand;
        }

        // Specify the METHOD, URL, asynch mode
        requestObj.open(method,url,async);

        if (method == 'POST') {
            // If we're using POST data then you may need to set the request header
            if (contentType) {
                requestObj.setRequestHeader('Content-Type',contentType);
            }
        } else {
            postData = null;
        }

        // Send the request with the POST data if required
        requestObj.send(postData);

    } catch (e) {
        handleException(e);
    }
}

/**
 * performCallback()
 * Common middle function that calls the ACTUAL callback handler.
 * Separate from ajaxRequest() incase we wish to do apply extra logic
 * @param string callbackHandler    The name of the callback function to handle the response
 * @param string output             The AJAX reponse
 * @access public
 * @return void
 * @author Steven Mapes
 **/
function performCallback(callbackHandler,output) {
    eval(callbackHandler+'(output)');
}

/**
 * displaySpinner()
 * Displays a spinner icon near to the mousepointer.
 * Used during the AJAX requests to show something is happening
 * @param object anEvent    The event in action, in this case mousemove
 * @access public
 * @author Steven Mapes
 **/
function displaySpinner(anEvent) {

	// Get the current mouse position on the page
	var xPos = 0;
	var yPos = 0;

	// Check for and handle non-DOM browser
	if (!anEvent) {
		var anEvent = window.event;
	}

	// Two ways of getting the mouse position depending on the browser
	if (anEvent.pageX || anEvent.pageY) {
		xPos = anEvent.pageX;
		yPos = anEvent.pageY;
	}
	else if (anEvent.clientX || eanEvent.clientY) 	{
		xPos = anEvent.clientX + document.body.scrollLeft + document.documentElement.scrollLeft;
		yPos = anEvent.clientY + document.body.scrollTop + document.documentElement.scrollTop;
	}

    // Move the loading spinnger underneath the mouse
    icon = document.getElementById('loadingSpinner');
    if (icon) {
        icon.style.left = xPos+10+"px";
        icon.style.top = yPos+10+"px";
        icon.style.visibility = "visible";  // Ensure its now visible
    }
}

/**
 * hideSpinner()
 * Hides the spinner icon by turning its visiblity state off and moving the position off screen
 * @access public
 * @return void
 * @author Steven Mapes
 **/
function hideSpinner() {
    document.onmousemove = null;    // Turn off the mousemove event listener

    icon = document.getElementById('loadingSpinner');
    if (icon) {
        icon.style.left = 0+"px";
        icon.style.top = 0+"px";
        icon.style.visibility = "hidden";
    }
}


/** INLINE JAVASCRIPT TO PREPARE CERTAIN THINGS **/
// Initialise the XMLHttpRequest object as the page loads so its available to everything
var requestObj = getXMLHttpRequest();
if (requestObj == false) {
    // Prompt if the users browser does not support AJAX
    alert("Your browser does not appear to support AJAX.  Therefore this page will not work");
}

// Handle placing the spinner DIV somewhere onto the page
var spinner=["/img/layout/spinner.gif", 16, 16];        // An array of details about the spinner icon
if (! document.getElementById('loadingSpinner')) {
    // Doesn't exist.  Add it now
    document.write('<span id="loadingSpinner" style="position:absolute;visibility:hidden;left:0;top:0;">'
        +'<img src="'+spinner[0]+'" width="'+spinner[1]+'" height="'+spinner[2]+'" alt="Loading"></span>');
}
/** INLINE JAVASCRIPT TO PREPARE CERTAIN THINGS **/