SGH / COMPONENTS

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-->
<link rel="import" href="../polymer/polymer.html">

<script>
(function() {
  "use strict";
  /**
    `Polymer.IronJsonpLibraryBehavior` loads a jsonp library.
    Multiple components can request same library, only one copy will load.

    Some libraries require a specific global function be defined.
    If this is the case, specify the `callbackName` property.

    You should use an HTML Import to load library dependencies
    when possible instead of using this element.

    @hero hero.svg
    @demo demo/index.html
    @polymerBehavior
   */
  Polymer.IronJsonpLibraryBehavior = {

    properties: {
      /**
       * True if library has been successfully loaded
       */
      libraryLoaded: {
        type: Boolean,
        value: false,
        notify: true,
        readOnly: true
      },
      /**
       * Not null if library has failed to load
       */
      libraryErrorMessage: {
        type: String,
        value: null,
        notify: true,
        readOnly: true
      }
      // Following properties are to be set by behavior users
      /**
       * Library url. Must contain string `%%callback_name%%`.
       *
       * `%%callback_name%%` is a placeholder for jsonp wrapper function name
       *
       * Ex: https://maps.googleapis.com/maps/api/js?callback=%%callback%%
       * @property libraryUrl
       */
      /**
       * Set if library requires specific callback name.
       * Name will be automatically generated if not set.
       * @property callbackName
       */
      /**
       * name of event to be emitted when library loads. Standard is `api-load`
       * @property notifyEvent
       */
      /**
       * event with name specified in `notifyEvent` attribute
       * will fire upon successful load2
       * @event `notifyEvent`
       */
    },

    observers: [
      '_libraryUrlChanged(libraryUrl)'
    ],

    _libraryUrlChanged: function(libraryUrl) {
      // can't load before ready because notifyEvent might not be set
      if (this._isReady && this.libraryUrl)
        this._loadLibrary();
    },

    _libraryLoadCallback: function(err, result) {
      if (err) {
        console.warn("Library load failed:", err.message);
        this._setLibraryErrorMessage(err.message);
      }
      else {
        this._setLibraryErrorMessage(null);
        this._setLibraryLoaded(true);
        if (this.notifyEvent)
          this.fire(this.notifyEvent, result);
      }
    },

    /** loads the library, and fires this.notifyEvent upon completion */
    _loadLibrary: function() {
      LoaderMap.require(
        this.libraryUrl,
        this._libraryLoadCallback.bind(this),
        this.callbackName
      );
    },

    ready: function() {
      this._isReady = true;
      if (this.libraryUrl)
        this._loadLibrary();
    }
  };

  /**
   * LoaderMap keeps track of all Loaders
   */
  var LoaderMap = {
    apiMap: {}, // { hash -> Loader }

    /**
     * @param {Function} notifyCallback loaded callback fn(result)
     * @param {string} jsonpCallbackName name of jsonpcallback. If API does not provide it, leave empty. Optional.
     */
    require: function(url, notifyCallback, jsonpCallbackName) {

      // make hashable string form url
      var name = this.nameFromUrl(url);

      // create a loader as needed
      if (!this.apiMap[name])
        this.apiMap[name] = new Loader(name, url, jsonpCallbackName);

      // ask for notification
      this.apiMap[name].requestNotify(notifyCallback);
    },

    nameFromUrl: function(url) {
      return url.replace(/[\:\/\%\?\&\.\=\-\,]/g, '_') + '_api';
    }
  };

  /** @constructor */
  var Loader = function(name, url, callbackName) {
    this.notifiers = [];  // array of notifyFn [ notifyFn* ]

    // callback is specified either as callback name
    // or computed dynamically if url has callbackMacro in it
    if (!callbackName) {
      if (url.indexOf(this.callbackMacro) >= 0) {
        callbackName = name + '_loaded';
        url = url.replace(this.callbackMacro, callbackName);
      } else {
        this.error = new Error('IronJsonpLibraryBehavior a %%callback_name%% parameter is required in libraryUrl');
        // TODO(sjmiles): we should probably fallback to listening to script.load
        return;
      }
    }
    this.callbackName = callbackName;
    window[this.callbackName] = this.success.bind(this);
    this.addScript(url);
  };

  Loader.prototype = {

    callbackMacro: '%%callback%%',
    loaded: false,

    addScript: function(src) {
      var script = document.createElement('script');
      script.src = src;
      script.onerror = this.handleError.bind(this);
      var s = document.querySelector('script') || document.body;
      s.parentNode.insertBefore(script, s);
      this.script = script;
    },

    removeScript: function() {
      if (this.script.parentNode) {
        this.script.parentNode.removeChild(this.script);
      }
      this.script = null;
    },

    handleError: function(ev) {
      this.error = new Error("Library failed to load");
      this.notifyAll();
      this.cleanup();
    },

    success: function() {
      this.loaded = true;
      this.result = Array.prototype.slice.call(arguments);
      this.notifyAll();
      this.cleanup();
    },

    cleanup: function() {
      delete window[this.callbackName];
    },

    notifyAll: function() {
      this.notifiers.forEach( function(notifyCallback) {
        notifyCallback(this.error, this.result);
      }.bind(this));
      this.notifiers = [];
    },

    requestNotify: function(notifyCallback) {
      if (this.loaded || this.error) {
        notifyCallback( this.error, this.result);
      } else {
        this.notifiers.push(notifyCallback);
      }
    }
  };
})();
</script>

<!--
  Loads specified jsonp library.

  Example:

    <iron-jsonp-library
      library-url="https://apis.google.com/js/plusone.js?onload=%%callback%%"
      notify-event="api-load"
      library-loaded="{{loaded}}"></iron-jsonp-library>

  Will emit 'api-load' event when loaded, and set 'loaded' to true

  Implemented by  Polymer.IronJsonpLibraryBehavior. Use it
  to create specific library loader elements.

  @demo
-->
<script>
  Polymer({

    is: 'iron-jsonp-library',

    behaviors: [ Polymer.IronJsonpLibraryBehavior ],

    properties: {
      /**
       * Library url. Must contain string `%%callback_name%%`.
       *
       * `%%callback_name%%` is a placeholder for jsonp wrapper function name
       *
       * Ex: https://maps.googleapis.com/maps/api/js?callback=%%callback%%
       */
      libraryUrl: String,
      /**
       * Set if library requires specific callback name.
       * Name will be automatically generated if not set.
       */
      callbackName: String,
      /**
       * event with name specified in 'notifyEvent' attribute
       * will fire upon successful load
       */
      notifyEvent: String
      /**
       * event with name specified in 'notifyEvent' attribute
       * will fire upon successful load
       * @event `notifyEvent`
       */

    }
  });

</script>