jQuery.extend({
    getInternetExplorerVersion: function() {
        var rv = -1; // Return value assumes failure.
        if (navigator.appName == 'Microsoft Internet Explorer') {
            var ua = navigator.userAgent;
            var re = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");
            if (re.exec(ua) != null)
                rv = parseFloat(RegExp.$1);
        }
        return rv;
    },
    createUploadIframe: function(id, uri) {
        //create frame
        var frameId = 'jUploadFrame' + id;
        var ieVer = jQuery.getInternetExplorerVersion();

        if (window.ActiveXObject) {
            if (ieVer < 9) {
                // Fails in IE 9
                var io = document.createElement('<iframe id="' + frameId + '" name="' + frameId + '" />');
            }
            else {
                var io = document.createElement('iframe');
                io.id = frameId;
                io.name = frameId;
            }

            if (typeof uri == 'boolean') {
                io.src = 'javascript:false';
            }
            else if (typeof uri == 'string') {
                io.src = uri;
            }
        }
        else {
            var io = document.createElement('iframe');
            io.id = frameId;
            io.name = frameId;
        }

        io.style.position = 'absolute';
        io.style.top = '-1000px';
        io.style.left = '-1000px';

        document.body.appendChild(io);

        return io;
    },
    createUploadForm: function(id, fileElementId) {
        //create form	
        var formId = 'jUploadForm' + id;
        var fileId = 'jUploadFile' + id;
        var form = $('<form  action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>');
        var oldElement = $('#' + fileElementId);
        var newElement = $(oldElement).clone();
        $(oldElement).attr('id', fileId);
        $(oldElement).before(newElement);
        $(oldElement).appendTo(form);

        //set attributes
        $(form).css('position', 'absolute');
        $(form).css('top', '-1200px');
        $(form).css('left', '-1200px');
        $(form).appendTo('body');

        return form;
    },
    ajaxFileUpload: function(s) {
        // TODO introduce global settings, allowing the client to modify them for all requests, not only timeout		
        s = jQuery.extend({}, jQuery.ajaxSettings, s);
        var id = new Date().getTime()
        var form = jQuery.createUploadForm(id, s.fileElementId);
        var io = jQuery.createUploadIframe(id, s.secureuri);
        var frameId = 'jUploadFrame' + id;
        var formId = 'jUploadForm' + id;

        // Watch for a new set of requests
        if (s.global && !jQuery.active++) {
            jQuery.event.trigger("ajaxStart");
        }

        var requestDone = false;

        // Create the request object
        var xml = {}
        if (s.global)
            jQuery.event.trigger("ajaxSend", [xml, s]);

        // Wait for a response to come back
        var uploadCallback = function(isTimeout) {
            var frm = document.getElementById(frameId);
            try {
                if (frm.contentWindow) {
                    xml.responseText = frm.contentWindow.document.body ? frm.contentWindow.document.body.innerHTML : null;
                    xml.responseXML = frm.contentWindow.document.XMLDocument ? frm.contentWindow.document.XMLDocument : frm.contentWindow.document;
                }
                else if (frm.contentDocument) {
                    xml.responseText = frm.contentDocument.document.body ? frm.contentDocument.document.body.innerHTML : null;
                    xml.responseXML = frm.contentDocument.document.XMLDocument ? frm.contentDocument.document.XMLDocument : frm.contentDocument.document;
                }
            }
            catch (e) {
                jQuery.handleError(s, xml, null, e);
            }

            if (xml || isTimeout == "timeout") {
                requestDone = true;
                var status;
                try {
                    status = isTimeout != "timeout" ? "success" : "error";

                    // Make sure that the request was successful or notmodified
                    if (status != "error") {
                        // process the data (runs the xml through httpData regardless of callback)
                        var data = jQuery.uploadHttpData(xml, s.dataType);

                        // If a local callback was specified, fire it and pass it the data
                        if (s.success)
                            s.success(data, status);

                        // Fire the global callback
                        if (s.global)
                            jQuery.event.trigger("ajaxSuccess", [xml, s]);
                    }
                    else
                        jQuery.handleError(s, xml, status);
                }
                catch (e) {
                    status = "error";
                    jQuery.handleError(s, xml, status, e);
                }

                // The request was completed
                if (s.global)
                    jQuery.event.trigger("ajaxComplete", [xml, s]);

                // Handle the global AJAX counter
                if (s.global && ! --jQuery.active)
                    jQuery.event.trigger("ajaxStop");

                // Process result
                if (s.complete)
                    s.complete(xml, status);

                jQuery(io).unbind();

                setTimeout(function() {
                    try {
                        $(io).remove();
                        $(form).remove();

                    }
                    catch (e) {
                        jQuery.handleError(s, xml, null, e);
                    }
                }, 100);

                xml = null;
            }
        }

        // Timeout checker
        if (s.timeout > 0) {
            setTimeout(function() {
                // Check to see if the request is still happening
                if (!requestDone)
                    uploadCallback("timeout");
            }, s.timeout);
        }

        try {
            // var io = $('#' + frameId);
            var form = $('#' + formId);
            $(form).attr('action', s.url);
            $(form).attr('method', 'POST');
            $(form).attr('target', frameId);
            if (form.encoding) {
                form.encoding = 'multipart/form-data';
            }
            else {
                form.enctype = 'multipart/form-data';
            }

            $(form).submit();
        }
        catch (e) {
            jQuery.handleError(s, xml, null, e);
        }

        if (window.attachEvent) {
            document.getElementById(frameId).attachEvent('onload', uploadCallback);
        }
        else {
            document.getElementById(frameId).addEventListener('load', uploadCallback, false);
        }

        return { abort: function() { } };
    },
    uploadHttpData: function(r, type) {
        var xml = (type == "xml");
        var ct = !type;
        var data = (xml || ct ? r.responseXML : r.responseText.replace("<PRE>", "").replace("</PRE>", ""));

        if (xml && data.documentElement.tagName == "parsererror")
            throw "parsererror";

        // If the type is "script", eval it in global context
        if (type == "script")
            jQuery.globalEval(data);

        // Get the JavaScript object, if JSON is used.
        if (type == "json") {
            data = eval("(" + data.replace("<pre>", "").replace("</pre>", "") + ")");
        }

        // evaluate scripts within html
        if (type == "html")
            jQuery("<div>").html(data).evalScripts();

        return data;
    }
})