firebase-messaging.html

<!--
@license
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file or at
https://github.com/firebase/polymerfire/blob/master/LICENSE
-->

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="firebase-common-behavior.html">
<link rel="import" href="firebase-messaging-script.html">

<!--
`firebase-messaging` is a wrapper around the Firebase Cloud Messaging API. It
allows you to receive Web Push messages in your application, including when
your site isn't in an open tab.

Example Usage:
```html
<firebase-messaging id="messaging"
  token="{{token}}"
  on-message="handleMessage">
</firebase-messaging>
```

Before you can start receiving push messages, you'll need to request permission
to use notifications:

```js
this.$.messaging.requestPermission().then(function() {
  // permission was granted
}, function(err) {
  // permission was denied
});
```

You'll also need to persist your token somewhere that a server can access it so
you can actually send push messsages:

```html
<firebase-messaging token="{{token}}"></firebase-messaging>
<firebase-document path="/users/[[user.uid]]/token" data="[[token]]"></firebase-document>
```

You'll also need a [Web App Manifest](https://developer.mozilla.org/en-US/docs/Web/Manifest)
for your site. It must contain the following:

```json
{
  "gcm_sender_id": "103953800507"
}
```

**Note:** You must use the **exact line specified above**. Do *not* change the sender
id to your project's individual sender id.

Finally, Firebase Cloud Messaging requires a service worker to handle push messages.
The easiest way is using a service worker called `firebase-messaging-sw.js` in your
app's root directory. See [the FCM docs](https://firebase.google.com/docs/cloud-messaging/js/receive#handle_messages_when_your_web_app_is_in_the_foreground)
for more information.

To use a different service worker than the default, you will need to add the
`custom-sw` attribute to your `<firebase-messaging>` element, and then explicitly
call `.activate()` on the element once you've
-->
<dom-module id="firebase-messaging">
  <script>
    (function() {
      var stateMap = {};

      /**
       *
       * @param {Object} app
       * @param {string} method
       * @param {...*} var_args
      */
      function applyAll(app, method, var_args) {
        var args = Array.prototype.slice.call(arguments, 2);
        stateMap[app.name].instances.forEach(function(el) {
          el[method].apply(el, args);
        });
      }

      function refreshToken(app) {
        var state = stateMap[app.name];

        app.messaging().getToken().then(function(token) {
          applyAll(app, '_setToken', token);
          applyAll(app, '_setStatusKnown', true);
          return token;
        }, function(err) {
          applyAll(app, '_setToken', null);
          applyAll(app, '_setStatusKnown', true);
          applyAll(app, 'fire', 'error', err);
          throw err;
        });
      }

      function activateMessaging(el, app) {
        var name = app.name;

        stateMap[name] = stateMap[name] || {messaging: app.messaging()};
        var state = stateMap[name];

        state.instances = state.instances || [];
        if (state.instances.indexOf(el) < 0) {
          state.instances.push(el);
        }

        if (!state.listener) {
          state.listener = app.messaging().onMessage(function(message) {
            state.instances.forEach(function(el) {
              el._setLastMessage(message);
              el.fire('message', {message: message});
            });
          });
        }

        if (!state.tokenListener) {
          state.tokenListener = app.messaging().onTokenRefresh(function() {
            refreshToken(app);
          });
        }

        return refreshToken(app);
      }

      Polymer({
        is: 'firebase-messaging',

        behaviors: [
          Polymer.FirebaseCommonBehavior,
        ],

        properties: {
          /**
           * The current registration token for this session. Save this
           * somewhere server-accessible so that you can target push messages
           * to this device.
           * @type {string|null}
           */
          token: {
            type: String,
            value: null,
            notify: true,
            readOnly: true,
          },
          /**
           * True when Firebase Cloud Messaging is successfully
           * registered and actively listening for messages.
           */
          active: {
            type: Boolean,
            notify: true,
            computed: '_computeActive(statusKnown, token)',
          },
          /**
           * True after an attempt has been made to fetch a push
           * registration token, regardless of whether one was available.
           */
          statusKnown: {
            type: Boolean,
            value: false,
            notify: true,
            readOnly: true,
          },
          /**
           * The most recent push message received. Generally in the format:
           *
           *     {
           *       "from": "<sender_id>",
           *       "category": "",
           *       "collapse_key": "do_not_collapse",
           *       "data": {
           *         "...": "..."
           *       },
           *       "notification": {
           *         "...": "..."
           *       }
           *     }
           */
          lastMessage: {
            type: Object,
            value: null,
            notify: true,
            readOnly: true,
          },
          /**
           * When true, Firebase Messaging will not initialize until `activate()`
           * is called explicitly. This allows for custom service worker registration.
           */
          customSw: {
            type: Boolean,
            value: false
          },
          /**
           * True if the Push API is supported in the user's browser.
           */
          pushSupported: {
            type: Boolean,
            value: function() {
              return ('serviceWorker' in navigator && 'PushManager' in window);
            },
            notify: true,
            readOnly: true
          }
        },

        observers: [
          '_bootstrapApp(app, customSw)'
        ],

        /**
         * Requests Notifications permission and returns a `Promise` that
         * resolves if it is granted. Resolves immediately if already granted.
         */
        requestPermission: function() {
          if (!this.messaging) {
            throw new Error('firebase-messaging: No app configured!');
          }

          return this.messaging.requestPermission().then(function() {
            return refreshToken(this.app);
          }.bind(this));
        },

        /**
         * When the `custom-sw` is added to `firebase-messaging`, this method
         * must be called after initialization to start listening for push
         * messages.
         *
         * @param {ServiceWorkerRegistration=}  swreg the custom service worker registration with which to activate
         */
        activate: function(swreg) {
          this.statusKnown = false;
          this.active = false;
          this.token = null;
          if (this.app) {
            this.messaging = this.app.messaging();
            if (swreg) {
              this.messaging.useServiceWorker(swreg);
            }
            activateMessaging(this, this.app);
          } else {
            this.messaging = null;
            this.statusKnown = false;
            this.active = false;
            this.token = null;
            return;
          }
        },

        _computeActive: function(statusKnown, token) {
          return !!(statusKnown && token);
        },

        _bootstrapApp: function(app, customSw) {
          if (app && !customSw) {
            this.activate();
          }
        },
      });
    })();

  </script>
</dom-module>