polymer-shared-lib.html

<!--
Copyright 2013 The Polymer Authors. All rights reserved.
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file.
-->
<link rel="import" href="../polymer/polymer.html">

<polymer-element name="polymer-shared-lib" attributes="url notifyEvent">
  <script>
    (function() {
      Polymer('polymer-shared-lib', {
        notifyEvent: 'polymer-shared-lib-loaded',
        ready: function() {
        },
        urlChanged: function() {
          requireApi(this);
        },
        provide: function() {
          this.async('notify');
        },
        notify: function() {
          this.fire(this.notifyEvent, arguments);
        }
      });

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

      var apiMap = {};
      function requireApi(instance) {
        instance._api_name = nameFromInstance(instance);
        var loader = apiMap[instance._api_name];
        if (!loader) {
          loader = new Loader(instance);
          apiMap[name] = loader;
        }
        loader.requireApi(instance);
      }
      
      Loader = function(instance) {
        this.instances = [];
        this.load(instance);
      };
      Loader.prototype = {
        loaded: false,
        requireApi: function(instance) {
          if (this.loaded) {
            this.provide(instance);
          } else {
            this.instances.push(instance);
          }
        },
        load: function(instance) {
          this.callbackName = instance._api_name + '_loaded';
          window[this.callbackName] = this.success.bind(this);
          var url = instance.url.replace('%%callback%%', this.callbackName);
          this.addScript(url);
        },
        addScript: function(src) {
          var script = document.createElement('script');
          script.src = src;
          script.onerror = this.error.bind(this);
          var s = document.querySelector('script');
          s.parentNode.insertBefore(script, s);
          this.script = script;
        },
        removeScript: function() {
          if (this.script.parentNode) {
            this.script.parentNode.removeChild(this.script);
          }
          this.script = null;
        },
        error: function() {
          this.cleanup();
        },
        success: function() {
          this.cleanup();
          this.result = Array.prototype.slice.call(arguments);
          this.instances.forEach(this.provide, this);
        },
        cleanup: function() {
          delete window[this.callbackName];
        },
        provide: function(instance) {
          instance.notify.apply(instance, this.result);
        }
      };
    })();
  </script>
</polymer-element>