[ios][alohalytics] Built-in processing of basic app lifecycle events.

@TODO(AlexZ): Refactor stats engine to allow synchronous uploading on the app background.

3party/Alohalytics/examples/ios/SampleClient/AppDelegate.m

@@ -41,39 +41,13 @@
   UIDevice * device = [UIDevice currentDevice];
   [Alohalytics logEvent:@"deviceInfo" withKeyValueArray:@[@"deviceName", device.name, @"systemName", device.systemName, @"systemVersion", device.systemVersion]];
 
-  // Used for example purposes only to upload statistics in background.
+  // Used for example purposes only to upload statistics (unpredictable) in background, when system wakes app up.
   [application setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];
 
   return YES;
 }
 
-- (void)applicationWillResignActive:(UIApplication *)application {
-  // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
-  // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
-  [Alohalytics logEvent:@"$willResignActive"];
-}
-
-- (void)applicationDidEnterBackground:(UIApplication *)application {
-  // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
-  // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
-  [Alohalytics logEvent:@"$didEnterBackground"];
-}
-
-- (void)applicationWillEnterForeground:(UIApplication *)application {
-  // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
-  [Alohalytics logEvent:@"$willEnterForeground"];
-}
-
-- (void)applicationDidBecomeActive:(UIApplication *)application {
-  // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
-  [Alohalytics logEvent:@"$didBecomeActive"];
-}
-
-- (void)applicationWillTerminate:(UIApplication *)application {
-  // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
-  [Alohalytics logEvent:@"$willTerminate"];
-}
-
+// This is an additional/optional way to upload statistics on the server after a long offline usage.
 // You have to set "fetch" in UIBackgroundsModes in your plist so system will call this method.
 // See https://developer.apple.com/library/ios/documentation/General/Reference/InfoPlistKeyReference/Articles/iPhoneOSKeys.html for more details.
 -(void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler

3party/Alohalytics/src/apple/alohalytics_objc.mm

@@ -266,6 +266,13 @@ static alohalytics::TStringMap ParseLaunchOptions(NSDictionary * options) {
   }
   return parsed;
 }
+
+// ********* Objective-C implementation part. *********
+// We process all events on a non-main thread.
+static dispatch_queue_t sBackgroundThreadQueue = nil;
+// Need it to effectively upload data when app goes into the background.
+static UIBackgroundTaskIdentifier sBackgroundTaskId = UIBackgroundTaskInvalid;
+
 #endif  // TARGET_OS_IPHONE
 } // namespace
 
@@ -280,6 +287,18 @@ static alohalytics::TStringMap ParseLaunchOptions(NSDictionary * options) {
 }
 
 + (void)setup:(NSString *)serverUrl andFirstLaunch:(BOOL)isFirstLaunch withLaunchOptions:(NSDictionary *)options {
+
+#if (TARGET_OS_IPHONE > 0)
+  // Subscribe to basic app lifecycle events.
+  sBackgroundThreadQueue = ::dispatch_queue_create([serverUrl UTF8String], DISPATCH_QUEUE_SERIAL);
+  NSNotificationCenter * nc = [NSNotificationCenter defaultCenter];
+  Class cls = [Alohalytics class];
+  [nc addObserver:cls selector:@selector(applicationDidBecomeActive:) name:UIApplicationDidBecomeActiveNotification object:nil];
+  [nc addObserver:cls selector:@selector(applicationWillResignActive:) name:UIApplicationWillResignActiveNotification object:nil];
+  [nc addObserver:cls selector:@selector(applicationWillEnterForeground:) name:UIApplicationWillEnterForegroundNotification object:nil];
+  [nc addObserver:cls selector:@selector(applicationDidEnterBackground:) name:UIApplicationDidEnterBackgroundNotification object:nil];
+  [nc addObserver:cls selector:@selector(applicationWillTerminate:) name:UIApplicationWillTerminateNotification object:nil];
+#endif // TARGET_OS_IPHONE
   const auto installationId = InstallationId();
   Stats & instance = Stats::Instance();
   instance.SetClientId(installationId.first)
@@ -366,4 +385,49 @@ static alohalytics::TStringMap ParseLaunchOptions(NSDictionary * options) {
   Stats::Instance().LogEvent(ToStdString(event), ToStringMap(dictionary), ExtractLocation(location));
 }
 
+#pragma mark App lifecycle notifications used to calculate basic metrics.
+#if (TARGET_OS_IPHONE > 0)
++ (void)applicationDidBecomeActive:(NSNotification *)notification {
+  Stats::Instance().LogEvent("$applicationDidBecomeActive");
+}
+
++ (void)applicationWillResignActive:(NSNotification *)notification {
+  Stats::Instance().LogEvent("$applicationWillResignActive");
+}
+
++ (void)endBackgroundTask {
+  [[UIApplication sharedApplication] endBackgroundTask:sBackgroundTaskId];
+  sBackgroundTaskId = UIBackgroundTaskInvalid;
+}
+
++ (void)applicationWillEnterForeground:(NSNotificationCenter *)notification {
+  Stats::Instance().LogEvent("$applicationWillEnterForeground");
+
+  ::dispatch_async(sBackgroundThreadQueue, ^{
+    if (sBackgroundTaskId != UIBackgroundTaskInvalid) {
+      [Alohalytics endBackgroundTask];
+    }
+  });
+}
+
++ (void)applicationDidEnterBackground:(NSNotification *)notification {
+  Stats::Instance().LogEvent("$applicationDidEnterBackground");
+
+  sBackgroundTaskId = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
+    [Alohalytics endBackgroundTask];
+  }];
+
+  ::dispatch_async(sBackgroundThreadQueue, ^{
+    // TODO: Here upload should be refactored and called synchronously to work correctly.
+    //alohalytics::Stats::Instance().Upload();
+    if (sBackgroundTaskId != UIBackgroundTaskInvalid) {
+      [Alohalytics endBackgroundTask];
+    }
+  });
+}
+
++ (void)applicationWillTerminate:(NSNotification *)notification {
+  Stats::Instance().LogEvent("$applicationWillTerminate");
+}
+#endif // TARGET_OS_IPHONE
 @end

iphone/Maps/Classes/MapsAppDelegate.mm

@@ -223,16 +223,12 @@ void InitLocalizedStrings()
 
 - (void)applicationWillTerminate:(UIApplication *)application
 {
-  [Alohalytics logEvent:@"$applicationWillTerminate"];
-
-	[self.m_mapViewController onTerminate];
+  [self.m_mapViewController onTerminate];
 }
 
 - (void)applicationDidEnterBackground:(UIApplication *)application
 {
-  [Alohalytics logEvent:@"$applicationDidEnterBackground"];
-
-	[self.m_mapViewController onEnterBackground];
+  [self.m_mapViewController onEnterBackground];
   if (m_activeDownloadsCounter)
   {
     m_backgroundTask = [application beginBackgroundTaskWithExpirationHandler:^{
@@ -242,23 +238,14 @@ void InitLocalizedStrings()
   }
 }
 
-- (void)applicationWillResignActive:(UIApplication *)application
-{
-  [Alohalytics logEvent:@"$applicationWillResignActive"];
-}
-
 - (void)applicationWillEnterForeground:(UIApplication *)application
 {
-  [Alohalytics logEvent:@"$applicationWillEnterForeground"];
-
   [self.m_locationManager orientationChanged];
   [self.m_mapViewController onEnterForeground];
 }
 
 - (void)applicationDidBecomeActive:(UIApplication *)application
 {
-  [Alohalytics logEvent:@"$applicationDidBecomeActive"];
-
   Framework & f = GetFramework();
   if (m_geoURL)
   {