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// Copyright 2006 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//      http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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 * @fileoverview Implementation of DataNode for wrapping JSON data.
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 *
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 */
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goog.provide('goog.ds.JsonDataSource');
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goog.require('goog.Uri');
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goog.require('goog.dom');
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goog.require('goog.dom.TagName');
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goog.require('goog.ds.DataManager');
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goog.require('goog.ds.JsDataSource');
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goog.require('goog.ds.LoadState');
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goog.require('goog.ds.logger');
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goog.require('goog.log');
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/**
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 * Data source whose backing is a JSON-like service, in which
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 * retreiving the resource specified by URL with the additional parameter
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 * callback. The resource retreived is executable JavaScript that
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 * makes a call to the named function with a JavaScript object literal
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 * as the only parameter.
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 *
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 * Example URI could be:
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 * http://www.google.com/data/search?q=monkey&callback=mycb
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 * which might return the JS:
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 * mycb({searchresults:
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 *   [{uri: 'http://www.monkey.com', title: 'Site About Monkeys'}]});
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 *
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 * TODO(user): Evaluate using goog.net.Jsonp here.
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 *
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 * A URI of an empty string will mean that no request is made
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 * and the data source will be a data source with no child nodes
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 *
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 * @param {string|goog.Uri} uri URI for the request.
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 * @param {string} name Name of the datasource.
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 * @param {string=} opt_callbackParamName The parameter name that is used to
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 *     specify the callback. Defaults to 'callback'.
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 *
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 * @extends {goog.ds.JsDataSource}
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 * @constructor
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 * @final
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 */
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goog.ds.JsonDataSource = function(uri, name, opt_callbackParamName) {
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  goog.ds.JsDataSource.call(this, null, name, null);
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  if (uri) {
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    this.uri_ = new goog.Uri(uri);
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  } else {
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    this.uri_ = null;
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  }
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  /**
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   * This is the callback parameter name that is added to the uri.
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   * @type {string}
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   * @private
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   */
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  this.callbackParamName_ = opt_callbackParamName || 'callback';
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};
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goog.inherits(goog.ds.JsonDataSource, goog.ds.JsDataSource);
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/**
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 * Default load state is NOT_LOADED
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 * @private
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 */
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goog.ds.JsonDataSource.prototype.loadState_ = goog.ds.LoadState.NOT_LOADED;
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/**
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 * Map of all data sources, needed for callbacks
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 * Doesn't work unless dataSources is exported (not renamed)
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 */
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goog.ds.JsonDataSource['dataSources'] = {};
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/**
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 * Load or reload the backing data for this node.
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 * Fires the JsonDataSource
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 * @override
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 */
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goog.ds.JsonDataSource.prototype.load = function() {
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  if (this.uri_) {
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    // NOTE: "dataSources" is expose above by name so that it will not be
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    // renamed.  It should therefore be accessed via array notation here so
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    // that it also doesn't get renamed and stops the compiler from complaining
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    goog.ds.JsonDataSource['dataSources'][this.dataName_] = this;
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    goog.log.info(
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        goog.ds.logger, 'Sending JS request for DataSource ' +
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            this.getDataName() + ' to ' + this.uri_);
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    this.loadState_ = goog.ds.LoadState.LOADING;
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    var uriToCall = new goog.Uri(this.uri_);
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    uriToCall.setParameterValue(
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        this.callbackParamName_, 'JsonReceive.' + this.dataName_);
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    goog.global['JsonReceive'][this.dataName_] =
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        goog.bind(this.receiveData, this);
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    var scriptEl =
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        goog.dom.createDom(goog.dom.TagName.SCRIPT, {'src': uriToCall});
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    goog.dom.getElementsByTagNameAndClass(goog.dom.TagName.HEAD)[0].appendChild(
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        scriptEl);
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  } else {
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    this.root_ = {};
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    this.loadState_ = goog.ds.LoadState.NOT_LOADED;
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  }
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};
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/**
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 * Gets the state of the backing data for this node
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 * @return {goog.ds.LoadState} The state.
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 * @override
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 */
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goog.ds.JsonDataSource.prototype.getLoadState = function() {
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  return this.loadState_;
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};
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/**
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 * Receives data from a Json request
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 * @param {Object} obj The JSON data.
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 */
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goog.ds.JsonDataSource.prototype.receiveData = function(obj) {
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  this.setRoot(obj);
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  this.loadState_ = goog.ds.LoadState.LOADED;
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  goog.ds.DataManager.getInstance().fireDataChange(this.getDataName());
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};
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/**
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* Temp variable to hold callbacks
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* until BUILD supports multiple externs.js files
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*/
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goog.global['JsonReceive'] = {};
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