Use foreground services to process notification when appropriate.

Right now, the only condition is once every 3 minutes on Android 12.

This is ok because Android 12 will allow us (once every 2 minutes or
so) to start a foreground service, and it won't show it for the first 10
seconds. So we can kind of do it without any visual penalty.

app/src/main/java/org/thoughtcrime/securesms/gcm/FcmFetchService.java

@@ -1,5 +1,6 @@
 package org.thoughtcrime.securesms.gcm;
 
+import android.app.PendingIntent;
 import android.app.Service;
 import android.content.Context;
 import android.content.Intent;
@@ -8,15 +9,21 @@ import android.os.IBinder;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.core.app.NotificationCompat;
 
 import com.google.firebase.messaging.RemoteMessage;
 
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
+import org.thoughtcrime.securesms.MainActivity;
+import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.dependencies.ApplicationDependencies;
 import org.thoughtcrime.securesms.jobs.PushNotificationReceiveJob;
 import org.thoughtcrime.securesms.messages.BackgroundMessageRetriever;
 import org.thoughtcrime.securesms.messages.RestStrategy;
+import org.thoughtcrime.securesms.notifications.NotificationChannels;
+import org.thoughtcrime.securesms.notifications.NotificationIds;
 import org.thoughtcrime.securesms.util.concurrent.SerialMonoLifoExecutor;
 
 import java.util.concurrent.atomic.AtomicInteger;
@@ -43,10 +50,18 @@ public class FcmFetchService extends Service {
 
   private static final String TAG = Log.tag(FcmFetchService.class);
 
+  static final String KEY_FOREGROUND = "is_foreground";
+
   private static final SerialMonoLifoExecutor EXECUTOR = new SerialMonoLifoExecutor(SignalExecutors.UNBOUNDED);
 
   private final AtomicInteger activeCount = new AtomicInteger(0);
 
+  public static @NonNull Intent buildIntent(@NonNull Context context, boolean foreground) {
+    Intent intent = new Intent(context, FcmFetchService.class);
+    intent.putExtra(KEY_FOREGROUND, foreground);
+    return intent;
+  }
+
   @Override
   public int onStartCommand(Intent intent, int flags, int startId) {
     boolean performedReplace = EXECUTOR.enqueue(this::fetch);
@@ -58,6 +73,18 @@ public class FcmFetchService extends Service {
       Log.i(TAG, "Incrementing active count to " + count);
     }
 
+    if (intent.getBooleanExtra(KEY_FOREGROUND, false)) {
+      Log.i(TAG, "Launching in the foreground.");
+      startForeground(NotificationIds.FCM_FETCH, new NotificationCompat.Builder(this, NotificationChannels.OTHER)
+          .setSmallIcon(R.drawable.ic_notification)
+          .setContentTitle(getString(R.string.BackgroundMessageRetriever_checking_for_messages))
+          .setCategory(NotificationCompat.CATEGORY_SERVICE)
+          .setProgress(0, 0, true)
+          .setContentIntent(PendingIntent.getActivity(this, 0, MainActivity.clearTop(this), 0))
+          .setVibrate(new long[] { 0 })
+          .build());
+    }
+
     return START_NOT_STICKY;
   }
 

app/src/main/java/org/thoughtcrime/securesms/gcm/FcmReceiveService.java

@@ -2,8 +2,11 @@ package org.thoughtcrime.securesms.gcm;
 
 import android.content.Context;
 import android.content.Intent;
+import android.os.Build;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.core.content.ContextCompat;
 
 import com.google.firebase.messaging.FirebaseMessagingService;
 import com.google.firebase.messaging.RemoteMessage;
@@ -16,11 +19,13 @@ import org.thoughtcrime.securesms.keyvalue.SignalStore;
 import org.thoughtcrime.securesms.registration.PushChallengeRequest;
 
 import java.util.Locale;
+import java.util.concurrent.TimeUnit;
 
 public class FcmReceiveService extends FirebaseMessagingService {
 
   private static final String TAG = Log.tag(FcmReceiveService.class);
 
+  private static final long FCM_FOREGROUND_INTERVAL = TimeUnit.MINUTES.toMillis(3);
 
   @Override
   public void onMessageReceived(RemoteMessage remoteMessage) {
@@ -38,15 +43,15 @@ public class FcmReceiveService extends FirebaseMessagingService {
       handleRegistrationPushChallenge(registrationChallenge);
     } else if (rateLimitChallenge != null) {
       handleRateLimitPushChallenge(rateLimitChallenge);
-    }else {
-      handleReceivedNotification(ApplicationDependencies.getApplication());
+    } else {
+      handleReceivedNotification(ApplicationDependencies.getApplication(), remoteMessage);
     }
   }
 
   @Override
   public void onDeletedMessages() {
     Log.w(TAG, "onDeleteMessages() -- Messages may have been dropped. Doing a normal message fetch.");
-    handleReceivedNotification(ApplicationDependencies.getApplication());
+    handleReceivedNotification(ApplicationDependencies.getApplication(), null);
   }
 
   @Override
@@ -71,11 +76,17 @@ public class FcmReceiveService extends FirebaseMessagingService {
     Log.w(TAG, "onSendError()", e);
   }
 
-  private static void handleReceivedNotification(Context context) {
+  private static void handleReceivedNotification(Context context, @Nullable RemoteMessage remoteMessage) {
     try {
-      context.startService(new Intent(context, FcmFetchService.class));
+      long timeSinceLastRefresh = System.currentTimeMillis() - SignalStore.misc().getLastFcmForegroundServiceTime();
+      if (Build.VERSION.SDK_INT >= 31 && remoteMessage != null && remoteMessage.getPriority() == RemoteMessage.PRIORITY_HIGH && timeSinceLastRefresh > FCM_FOREGROUND_INTERVAL) {
+        ContextCompat.startForegroundService(context, FcmFetchService.buildIntent(context, true));
+        SignalStore.misc().setLastFcmForegroundServiceTime(System.currentTimeMillis());
+      } else {
+        context.startService(FcmFetchService.buildIntent(context, false));
+      }
     } catch (Exception e) {
-      Log.w(TAG, "Failed to start service. Falling back to legacy approach.");
+      Log.w(TAG, "Failed to start service. Falling back to legacy approach.", e);
       FcmFetchService.retrieveMessages(context);
     }
   }

app/src/main/java/org/thoughtcrime/securesms/keyvalue/MiscellaneousValues.java

@@ -21,6 +21,7 @@ public final class MiscellaneousValues extends SignalStoreValues {
   private static final String CENSORSHIP_SERVICE_REACHABLE    = "misc.censorship.service_reachable";
   private static final String LAST_GV2_PROFILE_CHECK_TIME     = "misc.last_gv2_profile_check_time";
   private static final String CDS_TOKEN                       = "misc.cds_token";
+  private static final String LAST_FCM_FOREGROUND_TIME        = "misc.last_fcm_foreground_time";
 
   MiscellaneousValues(@NonNull KeyValueStore store) {
     super(store);
@@ -149,4 +150,12 @@ public final class MiscellaneousValues extends SignalStoreValues {
               .putBlob(CDS_TOKEN, token)
               .commit();
   }
+
+  public long getLastFcmForegroundServiceTime() {
+    return getLong(LAST_FCM_FOREGROUND_TIME, 0);
+  }
+
+  public void setLastFcmForegroundServiceTime(long time) {
+    putLong(LAST_FCM_FOREGROUND_TIME, time);
+  }
 }

app/src/main/java/org/thoughtcrime/securesms/notifications/NotificationIds.java

@@ -14,6 +14,7 @@ public final class NotificationIds {
   public static final int USER_NOTIFICATION_MIGRATION = 525600;
   public static final int DEVICE_TRANSFER             = 625420;
   public static final int DONOR_BADGE_FAILURE         = 630001;
+  public static final int FCM_FETCH                   = 630002;
 
   private NotificationIds() { }