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.
+
+/**
+ * @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) {
+    return;
+  }
+
+  var cards = parsedResponse.cards;
+
+  if (!(cards instanceof Array))
+    return;
+
+  if (typeof parsedResponse.expiration_timestamp_seconds != 'number')

[rgustafson, 2013/01/22 21:10:28]

If the timestamp isn't present, it should still display the cards, but use the
default time. Move this below the cards loop, so this only prevents resetting
the alarm.

[vadimt, 2013/01/23 03:04:05]

The fact that the timestamp is not present most likely means that the whole
server response is malformed. Should we then show notifications that are part of
such response?

[rgustafson, 2013/01/23 23:18:56]

I'd prefer to give the user everything we have, and assume we would catch errors
in the actual cards when looping through. This whole scenario was imagined and
shouldn't actually be happening from the server side though, so it should be
fine how it is.
On 2013/01/23 03:04:05, vadimt wrote:

+    return;
+
+  for (var i = 0; i != cards.length; ++i) {
+    try {
+      chrome.experimental.notification.show(cards[i], function(showInfo) {});
+    } catch (error) {
+      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.onreadystatechange = function(event) {
+    if (request.readyState == request.DONE && 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({ when: Date.now() + delaySeconds * 1000 });
+}
+
+/**
+ * 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();
+});