jQuery.extend({

    createUploadIframe:function(id, uri){

            var frameId='jQuery'+id;
            var io;
            if(window.ActiveXObject){
                io=document.createElement('<iframe id="'+frameId+'" name="'+frameId+'" />');

                if(typeof(uri)=='boolean') io.src='javascript:false';
                else if(typeof(uri)=='string') io.src=uri;
            }
            else {
                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;

    },

    ajaxUpload: 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 io=jQuery.createUploadIframe(id, s.secureuri);

        // 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){
            try{
                xml.responseText=io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:null;
                xml.responseXML=io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;
            }
            catch(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);
                        if(s.error) s.error(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(){document.body.removeChild(io)},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 frameId='jQuery'+id;
            var io=document.getElementById(frameId);
            // Initialize the HTML form properties in case they are
            // not defined in the HTML form.
            s.uploadform.action=s.url;
            s.uploadform.method='POST';
            s.uploadform.target=frameId;

            if(s.uploadform.encoding){
                // IE does not respect property enctype for HTML forms.
                // Instead use property encoding.
                s.uploadform.encoding='multipart/form-data';
            }
            else{
                s.uploadform.enctype='multipart/form-data';
            }
            if(s.beforeSend) s.beforeSend();

            s.uploadform.submit();

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

        if(window.attachEvent) io.attachEvent('onload', uploadCallback);
        else io.addEventListener('load', uploadCallback, false);
        
        return {abort: function(){}};

    },

    uploadHttpData:function(r,type){
        var data=!type;
        data=type=="xml"||data?r.responseXML:r.responseText;

        // 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") eval("data="+data);

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

        return data;
    }
});