Initial implementation of Google Now Notifications integration

chrome/browser/resources/google_now/background.js

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+'use strict';
+
+/**
+ * @fileoverview The event page for Google Now for Chrome implementation.
+ * The Google Now event page gets Google Now cards from the server and shows
+ * them as Chrome notifications.
+ * The service performs periodic updating of Google Now cards.
+ * Each updating of the cards includes 3 steps:
+ * 1. Obtaining the location of the machine;
+ * 2. Making a server request based on that location;
+ * 3. Showing the received cards as notifications.
+ */
+
+// TODO(vadimt): Use background permission to show notifications even when all
+// browser windows are closed.
+// TODO(vadimt): Remove the C++ implementation.
+// TODO(vadimt): Decide what to do in incognito mode.
+// TODO(vadimt): Gather UMAs.
+// TODO(vadimt): Honor the flag the enables Google Now integration.
+// TODO(vadimt): Figure out the final values of the constants.
+// TODO(vadimt): Report errors to the user.
+
+// TODO(vadimt): Figure out the server name. Use it in the manifest and for
+// NOTIFICATION_CARDS_URL. Meanwhile, to use the feature, you need to manually
+// edit NOTIFICATION_CARDS_URL before building Chrome.
+/**
+ * URL to retrieve notification cards.
+ */
+var NOTIFICATION_CARDS_URL = '';
+
+/**
+ * Standard response code for successful HTTP requests. This is the only success
+ * code the server will send.
+ */
+var HTTP_OK = 200;
+
+/**
+ * Period for polling for Google Now Notifications cards to use when the period
+ * from the server is not available.
+ */
+var DEFAULT_POLLING_PERIOD_SECONDS = 300;  // 5 minutes
+
+/**
+ * Parse JSON response of the notifications server, show notifications and
+ * schedule next update.
+ * @param {string} response Server response.
+ */
+function parseAndShowNotificationCards(response) {
+  try {
+    var parsedResponse = JSON.parse(response);
+  } catch (error) {
+    // TODO(vadimt): Report errors to the user.
+    return;
+  }
+
+  var cards = parsedResponse.cards;
+
+  if (!(cards instanceof Array)) {
+    // TODO(vadimt): Report errors to the user.
+    return;
+  }
+
+  if (typeof parsedResponse.expiration_timestamp_seconds != 'number') {
+    // TODO(vadimt): Report errors to the user.
+    return;
+  }
+
+  for (var i = 0; i != cards.length; ++i) {
+    try {
+      chrome.experimental.notification.show(cards[i], function(showInfo) {});
+    } catch (error) {
+      // TODO(vadimt): Report errors to the user.
+      return;
+    }
+  }
+
+  scheduleNextUpdate(parsedResponse.expiration_timestamp_seconds);
+}
+
+/**
+ * Request notification cards from the server.
+ * @param {string} requestParameters Query string for the request.
+ */
+function requestNotificationCards(requestParameters) {
+  // TODO(vadimt): Figure out how to send user's identity to the server.
+  var request = new XMLHttpRequest();
+
+  request.responseType = 'text';
+  request.onload = function(event) {
+    if (request.status == HTTP_OK)
+      parseAndShowNotificationCards(request.response);
+  }
+
+  request.open('GET', NOTIFICATION_CARDS_URL + requestParameters, true);
+  request.send();
+}
+
+/**
+ * Request notification cards from the server when we have geolocation.
+ * @param {Geoposition} position Location of this computer.
+ */
+function requestNotificationCardsWithLocation(position) {
+  // TODO(vadimt): Should we use 'q' as the parameter name?
+  var requestParameters =
+      '?q=' + position.coords.latitude +
+      ',' + position.coords.longitude +
+      ',' + position.coords.accuracy;
+
+  requestNotificationCards(requestParameters);
+}
+
+/**
+ * Request notification cards from the server when we don't have geolocation.
+ * @param {PositionError} positionError Position error.
+ */
+function requestNotificationCardsWithoutLocation(positionError) {
+  requestNotificationCards('');
+}
+
+/**
+ * Obtain new location; request and show notification cards based on this
+ * location.
+ */
+function updateNotificationsCards() {
+  // Immediately schedule the update after the default period. If we
+  // successfully retrieve, parse and show the notifications cards, we'll
+  // schedule next update based on the expiration timestamp received from the
+  // server. At that point scheduled time will be overwritten by the new one
+  // based on the expiration timestamp.
+  // TODO(vadimt): Implement exponential backoff with randomized jitter.
+  scheduleNextUpdate(DEFAULT_POLLING_PERIOD_SECONDS);
+
+  // TODO(vadimt): Use chrome.* geolocation API once it's ready.
+  navigator.geolocation.getCurrentPosition(
+      requestNotificationCardsWithLocation,
+      requestNotificationCardsWithoutLocation);
+}
+
+/**
+ * Schedule next update for notification cards.
+ * @param {int} delaySeconds Length of time in seconds after which the alarm
+ *     event should fire.
+ */
+function scheduleNextUpdate(delaySeconds) {
+  chrome.alarms.create({delayInMinutes: delaySeconds / 60});
+}
+
+/**
+ * Initialize the event page on install or on browser startup.
+ */
+function initialize() {
+  updateNotificationsCards();
+}
+
+chrome.runtime.onInstalled.addListener(function(details) {
+  if (details.reason != 'chrome_update')
+    initialize();
+});
+
+chrome.runtime.onStartup.addListener(function() {
+  initialize();
+});
+
+chrome.alarms.onAlarm.addListener(function(alarm) {
+  updateNotificationsCards();
+});