// **********************************  AJAX.JS  ********************************
// *
// * Author: Lars Povlsen
// *
// * --------------------------------------------------------------------------
// *
// * Description:  Client-side JavaScript functions.
// *
// * To include in HTML file use:
// *
// * <script language="javascript" type="text/javascript" src="lib/ajax.js"></script>
// *
// * --------------------------------------------------------------------------

function initXMLHTTP() {
    // branch for native XMLHttpRequest object
    var req = false;
    if(window.XMLHttpRequest) {
    	try {
            req = new XMLHttpRequest();
        } catch(e) {
            req = false;
        }
    // branch for IE/Windows ActiveX version
    } else if(window.ActiveXObject) {
       	try {
            req = new ActiveXObject("Msxml2.XMLHTTP");
      	} catch(e) {
            try {
                req = new ActiveXObject("Microsoft.XMLHTTP");
            } catch(e) {
                req = false;
            }
        }
    }
    return req;
}


function loadXMLDocEx(file,callback,ref,error)
{
    var req = initXMLHTTP();
    if(typeof(configURLRemap) == "function")
        file = configURLRemap(file);
    req.open("GET", file, true);
    req.onreadystatechange = function () {
        try {
            if (req.readyState == 4) {
                if (req.status && req.status == 200) {
                    callback(req, ref);
                    req = null; // MSIE leak avoidance
                } else {
                    var status;
                    try{
                        status = req.statusText;
                    }
                    catch(e){
                        status = "Unknown error";
                    }
                    if (error)
                     alert("There was a problem retrieving the dynamic data:\n" +
                            status);
                    callback(null, ref);
                    req = null; // MSIE leak avoidance
                }
            }
        }
        catch(e){
            // If a page is currently being requested and the user clicks another link on
            // the web page, FireFox (2.0 at least - haven't tested with 1.5) will throw
            // an exception causing this piece of code to be called, whereas Internet
            // Explorer (7.0 at least - haven't tested with 6.0) doesn't. If the Web
            // page that requested the error calls SpomHandleError() then the main
            // page will get recalled. The best thing is therefore not to call the
            // callback function unless there's real data associated; hence the
            // commenting out of the callback() call below.
            // alert("Request error (file = " + file + ". e = " + e + "req = " + req + ")");
            // callback(req, ref);
            req = null; // MSIE leak avoidance
        }
    };
    req.send("");
    return req;
}

function loadXMLDoc(file,callback,ref)
{
 loadXMLDocEx(file,callback,ref, true);
}

function redirectOnErrorExtract(req, def_url)
{
    var str = req.responseText;
    var url = false;
    if(req.responseText) {
        if(str.match(/^Error:\s+/)) {
            url = str.replace(/^Error:\s+/, "");
        }
    } else {
        // Use default error URL, if any!
        if(def_url)
            url = def_url;
    }
    return url;
}

function redirectOnError(req, def_url)
{
    var url = redirectOnErrorExtract(req, def_url);
    if(url) {
        if(typeof(top.setErrorReferrer) == "function")
            top.setErrorReferrer(window.location.pathname);
        window.location.pathname = url;
    }
    return url;
}