/**
+ * Extends the IO base class to provide an alternate, Flash transport, for making
+ * cross-domain requests.
+ * @module io
+ * @submodule io-xdr
+ */
+
+ /**
+ * @event io:xdrReady
+ * @description This event is fired by YUI.io when the specified transport is
+ * ready for use.
+ * @type Event Custom
+ */
+ var E_XDR_READY = 'io:xdrReady',
+
+
+ /**
+ * @description Object that stores callback handlers for cross-domain requests
+ * when using Flash as the transport.
+ *
+ * @property _fn
+ * @private
+ * @static
+ * @type object
+ */
+ _fn = {},
+
+ /**
+ * @description Map of transaction state used when XDomainRequest is the
+ * XDR transport.
+ *
+ * @property _rS
+ * @private
+ * @static
+ * @type object
+ */
+ _rS = {};
+
+ /**
+ * @description Method that creates the Flash transport swf.
+ *
+ * @method _swf
+ * @private
+ * @static
+ * @param {string} uri - location of io.swf.
+ * @param {string} yid - YUI instance id.
+ * @return void
+ */
+ function _swf(uri, yid) {
+ var o = '<object id="yuiIoSwf" type="application/x-shockwave-flash" data="' +
+ uri + '" width="0" height="0">' +
+ '<param name="movie" value="' + uri + '">' +
+ '<param name="FlashVars" value="yid=' + yid + '">' +
+ '<param name="allowScriptAccess" value="always">' +
+ '</object>',
+ c = document.createElement('div');
+
+ document.body.appendChild(c);
+ c.innerHTML = o;
+ }
+
+ /**
+ * @description Sets event handlers for XDomainRequest transactions.
+ *
+ * @method _xdr
+ * @private
+ * @static
+ * @param {object} o - Transaction object generated by _create() in io-base.
+ * @param {object} c - configuration object for the transaction.
+ * @return void
+ */
+ function _xdr(o, c) {
+ o.c.onprogress = function() { _rS[o.id] = 3; }
+ o.c.onload = function() {
+ _rS[o.id] = 4;
+ Y.io.xdrResponse(o, c, 'success');
+ };
+ o.c.onerror = function() {
+ _rS[o.id] = 4;
+ Y.io.xdrResponse(o, c, 'failure');
+ };
+ if (c.timeout) {
+ o.c.ontimeout = function() {
+ _rS[o.id] = 4;
+ Y.io.xdrResponse(o, c, 'timeout');
+ };
+ o.c.timeout = c.timeout;
+ }
+ }
+
+ /**
+ * @description Creates a response object for XDR transactions, for success
+ * and failure cases.
+ *
+ * @method _data
+ * @private
+ * @static
+ * @param {object} o - Transaction object generated by _create() in io-base.
+ * @param {boolean} isFlash - True if Flash was used as the transport.
+ * @param {boolean} isXML - True if the response data are XML.
+ *
+ * @return object
+ */
+ function _data(o, isFlash, isXML) {
+ var text, xml;
+
+ if (!o.status) {
+ text = isFlash ? decodeURI(o.c.responseText) : o.c.responseText;
+ xml = isXML ? Y.DataType.XML.parse(text) : null;
+
+ return { id: o.id, c: { responseText: text, responseXML: xml } };
+ }
+ else {
+ return { id: o.id, status: o.status };
+ }
+
+ }
+
+ /**
+ * @description Method for intiating an XDR transaction abort.
+ *
+ * @method _abort
+ * @private
+ * @static
+ * @param {object} o - Transaction object generated by _create() in io-base.
+ * @param {object} c - configuration object for the transaction.
+ */
+ function _abort(o, c) {
+ return c.xdr.use === 'flash' ? o.c.abort(o.id, c) : o.c.abort();
+ }
+
+ /**
+ * @description Method for determining if an XDR transaction has completed
+ * and all data are received.
+ *
+ * @method _isInProgress.
+ * @private
+ * @static
+ * @param {object} o - Transaction object generated by _create() in io-base.
+ * @param {object} c - configuration object for the transaction.
+ */
+ function _isInProgress(o, t) {
+ return (t === 'flash' && o.c) ? o.c.isInProgress(o.id) : _rS[o.id] !== 4;
+ }
+
+ Y.mix(Y.io, {
+
+ /**
+ * @description Map of io transports.
+ *
+ * @property _transport
+ * @private
+ * @static
+ * @type object
+ */
+ _transport: {},
+
+ /**
+ * @description Method for accessing the transport's interface for making a
+ * cross-domain transaction.
+ *
+ * @method _xdr
+ * @private
+ * @static
+ * @param {string} uri - qualified path to transaction resource.
+ * @param {object} o - Transaction object generated by _create() in io-base.
+ * @param {object} c - configuration object for the transaction.
+ */
+ xdr: function(uri, o, c) {
+ if (c.on && c.xdr.use === 'flash') {
+ _fn[o.id] = {
+ on: c.on,
+ context: c.context,
+ arguments: c.arguments
+ };
+ // These nodes do not need to be serialized across Flash's
+ // ExternalInterface. Doing so will result in exceptions.
+ c.context = null;
+ c.form = null;
+
+ o.c.send(uri, c, o.id);
+ }
+ else if (window.XDomainRequest) {
+ _xdr(o, c);
+ o.c.open(c.method || 'GET', uri);
+ o.c.send(c.data);
+ }
+
+ return {
+ id: o.id,
+ abort: function() {
+ return o.c ? _abort(o, c) : false;
+ },
+ isInProgress: function() {
+ return o.c ? _isInProgress(o, c.xdr.use) : false;
+ }
+ }
+ },
+
+ /**
+ * @description Response controller for cross-domain requests when using the
+ * Flash transport or IE8's XDomainRequest object.
+ *
+ * @method xdrResponse
+ * @private
+ * @static
+ * @param {object} o - Transaction object generated by _create() in io-base.
+ * @param {object} c - configuration object for the transaction.
+ * @param {string} e - Event name
+ * @return object
+ */
+ xdrResponse: function(o, c, e) {
+ var m, fn,
+ isFlash = c.xdr.use === 'flash' ? true : false,
+ isXML = c.xdr.dataType === 'xml' ? true : false;
+ c.on = c.on || {};
+
+ if (isFlash) {
+ m = _fn || {};
+ fn = m[o.id] ? m[o.id] : null;
+ if (fn) {
+ c.on = fn.on;
+ c.context = fn.context;
+ c.arguments = fn.arguments;
+ }
+ }
+ if (e === ('abort' || 'timeout')) {
+ o.status = e;
+ }
+
+ switch (e) {
+ case 'start':
+ Y.io.start(o.id, c);
+ break;
+ case 'success':
+ Y.io.success(_data(o, isFlash, isXML), c);
+ isFlash ? delete m[o.id] : delete _rS[o.id];
+ break;
+ case 'timeout':
+ case 'abort':
+ case 'failure':
+ Y.io.failure(_data(o, isFlash, isXML), c);
+ isFlash ? delete m[o.id] : delete _rS[o.id];
+ break;
+ }
+ },
+
+ /**
+ * @description Fires event "io:xdrReady"
+ *
+ * @method xdrReady
+ * @private
+ * @static
+ * @param {number} id - transaction id
+ * @param {object} c - configuration object for the transaction.
+ *
+ * @return void
+ */
+ xdrReady: function(id) {
+ Y.fire(E_XDR_READY, id);
+ },
+
+ /**
+ * @description Method to initialize the desired transport.
+ *
+ * @method transport
+ * @public
+ * @static
+ * @param {object} o - object of transport configurations.
+ * @return void
+ */
+ transport: function(o) {
+ var id = o.yid ? o.yid : Y.id;
+
+ _swf(o.src, id);
+ this._transport.flash = Y.config.doc.getElementById('yuiIoSwf');
+ }
+ });
+