[mob] Minor refactor

mobile/lib/services/entity_service.dart

@@ -100,15 +100,17 @@ class EntityService {
     }
   }
 
-  Future<void> syncEntity(EntityType type) async {
+  Future<int> syncEntity(EntityType type) async {
     try {
-      await _remoteToLocalSync(type);
+      return _remoteToLocalSync(type);
     } catch (e) {
       _logger.severe("Failed to sync entities", e);
+      return -1;
     }
   }
 
-  Future<void> _remoteToLocalSync(EntityType type) async {
+  Future<int> _remoteToLocalSync(EntityType type,
+      {int prevFetchCount = 0}) async {
     final int lastSyncTime =
         _prefs.getInt(_getEntityLastSyncTimePrefix(type)) ?? 0;
     final List<EntityData> result = await _gateway.getDiff(
@@ -117,7 +119,7 @@ class EntityService {
       limit: fetchLimit,
     );
     if (result.isEmpty) {
-      return;
+      return prevFetchCount;
     }
     final bool hasMoreItems = result.length == fetchLimit;
     _logger.info("${result.length} entries of type $type fetched");
@@ -161,6 +163,7 @@ class EntityService {
           );
         } catch (e, s) {
           _logger.severe("Failed to decrypted data for key $type", e, s);
+          rethrow;
         }
       }
       if (entities.isNotEmpty) {
@@ -170,8 +173,10 @@ class EntityService {
     await _prefs.setInt(_getEntityLastSyncTimePrefix(type), maxSyncTime);
     if (hasMoreItems) {
       _logger.info("Diff limit reached, pulling again");
-      await _remoteToLocalSync(type);
+      await _remoteToLocalSync(type,
+          prevFetchCount: prevFetchCount + result.length);
     }
+    return prevFetchCount + result.length;
   }
 
   Future<Uint8List> getOrCreateEntityKey(EntityType type) async {

mobile/lib/services/machine_learning/face_ml/person/person_service.dart

@@ -252,8 +252,13 @@ class PersonService {
   }
 
   Future<void> fetchRemoteClusterFeedback() async {
-    await entityService.syncEntities();
+    await entityService.syncEntity(EntityType.cgroup);
     final entities = await entityService.getEntities(EntityType.cgroup);
+    // todo: (neerajg) perf change, this can be expensive to do on every sync
+    // especially when we have a lot of people. We should only do this when the
+    // last sync time is updated for cgroup entity type. To avoid partial update,
+    // we need to maintain a lastSyncTime value whenever this data is processed
+    // and stored in the db.
     entities.sort((a, b) => a.updatedAt.compareTo(b.updatedAt));
     final Map<String, String> faceIdToClusterID = {};
     final Map<String, String> clusterToPersonID = {};
@@ -286,7 +291,6 @@ class PersonService {
         );
       }
     }
-
     logger.info("Storing feedback for ${faceIdToClusterID.length} faces");
     await faceMLDataDB.updateFaceIdToClusterId(faceIdToClusterID);
     await faceMLDataDB.bulkAssignClusterToPersonID(clusterToPersonID);