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/**
 * Provides a DataSource implementation which can be used to retrieve data via the Get Utility.
 *
 * @module datasource
 * @submodule datasource-get
 */
/**
 * Get Utility subclass for the DataSource Utility.
 * @class DataSource.Get
 * @extends DataSource.Local
 * @constructor
 */
var DSGet = function() {
 DSGet.superclass.constructor.apply(this, arguments);
};
Y.DataSource.Get = Y.extend(DSGet, Y.DataSource.Local, {
 /**
 * Passes query string to Get Utility. Fires <code>response</code> event when
 * response is received asynchronously.
 *
 * @method _defRequestFn
 * @param e {EventFacade} Event Facade with the following properties:
 * <dl>
 * <dt>tId (Number)</dt> <dd>Unique transaction ID.</dd>
 * <dt>request (Object)</dt> <dd>The request.</dd>
 * <dt>callback (Object)</dt> <dd>The callback object with the following properties:
 * <dl>
 * <dt>success (Function)</dt> <dd>Success handler.</dd>
 * <dt>failure (Function)</dt> <dd>Failure handler.</dd>
 * </dl>
 * </dd>
 * <dt>cfg (Object)</dt> <dd>Configuration object.</dd>
 * </dl>
 * @protected
 */
 _defRequestFn: function(e) {
 var uri = this.get("source"),
 get = this.get("get"),
 guid = Y.guid().replace(/\-/g, '_'),
 generateRequest = this.get( "generateRequestCallback" ),
 payload = e.details[0],
 self = this;
 /**
 * Stores the most recent request id for validation against stale
 * response handling.
 *
 * @property _last
 * @type {String}
 * @protected
 */
 this._last = guid;
 // Dynamically add handler function with a closure to the callback stack
 // for access to guid
 YUI.Env.DataSource.callbacks[guid] = function(response) {
 delete YUI.Env.DataSource.callbacks[guid];
 delete Y.DataSource.Local.transactions[e.tId];
 var process = self.get('asyncMode') !== "ignoreStaleResponses" ||
 self._last === guid;
 if (process) {
 payload.data = response;
 self.fire("data", payload);
 } else {
 Y.log("DataSource ignored stale response for id " + e.tId + "(" + e.request + ")", "info", "datasource-get");
 }
 };
 // Add the callback param to the request url
 uri += e.request + generateRequest.call( this, guid );
 Y.log("DataSource is querying URL " + uri, "info", "datasource-get");
 Y.DataSource.Local.transactions[e.tId] = get.script(uri, {
 autopurge: true,
 // Works in Firefox only....
 onFailure: function (o) {
 delete YUI.Env.DataSource.callbacks[guid];
 delete Y.DataSource.Local.transactions[e.tId];
 payload.error = new Error(o.msg || "Script node data failure");
 Y.log("Script node data failure", "error", "datasource-get");
 self.fire("data", payload);
 },
 onTimeout: function(o) {
 delete YUI.Env.DataSource.callbacks[guid];
 delete Y.DataSource.Local.transactions[e.tId];
 payload.error = new Error(o.msg || "Script node data timeout");
 Y.log("Script node data timeout", "error", "datasource-get");
 self.fire("data", payload);
 }
 });
 return e.tId;
 },
 /**
 * Default method for adding callback param to url. See
 * generateRequestCallback attribute.
 *
 * @method _generateRequest
 * @param guid {String} unique identifier for callback function wrapper
 * @protected
 */
 _generateRequest: function (guid) {
 return "&" + this.get("scriptCallbackParam") +
 "=YUI.Env.DataSource.callbacks." + guid;
 }
}, {
 /**
 * Class name.
 *
 * @property NAME
 * @type String
 * @static
 * @final
 * @value "dataSourceGet"
 */
 NAME: "dataSourceGet",
 ////////////////////////////////////////////////////////////////////////////
 //
 // DataSource.Get Attributes
 //
 ////////////////////////////////////////////////////////////////////////////
 ATTRS: {
 /**
 * Pointer to Get Utility.
 *
 * @attribute get
 * @type Y.Get
 * @default Y.Get
 */
 get: {
 value: Y.Get,
 cloneDefaultValue: false
 },
 /**
 * Defines request/response management in the following manner:
 * <dl>
 * <!--<dt>queueRequests</dt>
 * <dd>If a request is already in progress, wait until response is
 * returned before sending the next request.</dd>
 * <dt>cancelStaleRequests</dt>
 * <dd>If a request is already in progress, cancel it before
 * sending the next request.</dd>-->
 * <dt>ignoreStaleResponses</dt>
 * <dd>Send all requests, but handle only the response for the most
 * recently sent request.</dd>
 * <dt>allowAll</dt>
 * <dd>Send all requests and handle all responses.</dd>
 * </dl>
 *
 * @attribute asyncMode
 * @type String
 * @default "allowAll"
 */
 asyncMode: {
 value: "allowAll"
 },
 /**
 * Callback string parameter name sent to the remote script. By default,
 * requests are sent to
 * &#60;URI&#62;?&#60;scriptCallbackParam&#62;=callbackFunction
 *
 * @attribute scriptCallbackParam
 * @type String
 * @default "callback"
 */
 scriptCallbackParam : {
 value: "callback"
 },
 /**
 * Accepts the DataSource instance and a callback ID, and returns a callback
 * param/value string that gets appended to the script URI. Implementers
 * can customize this string to match their server's query syntax.
 *
 * @attribute generateRequestCallback
 * @type Function
 */
 generateRequestCallback : {
 value: function () {
 return this._generateRequest.apply(this, arguments);
 }
 }
 }
});
YUI.namespace("Env.DataSource.callbacks");