jQuery.extend({
	
	createUploadIframe: function(id, uri) {
		//create frame
		var frameId = 'jUploadFrame' + id;
		
		if (window.ActiveXObject) {
			var 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 {
			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 io = document.getElementById(frameId);
			try {				
				if (io.contentWindow) {
					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;
				} else if(io.contentDocument) {
					xml.responseText = io.contentDocument.document.body? io.contentDocument.document.body.innerHTML : null;
					xml.responseXML = io.contentDocument.document.XMLDocument? io.contentDocument.document.XMLDocument : io.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 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 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();
		}
		//alert($('param', data).each(function(){alert($(this).attr('value'));}));
		return data;
	}

});