[mob][photos] Cache results for Magic section (only visible to internal users) (#2282)

## Description

- Use cached results for magic section so that it does't anymore have to
wait for ML framework to be initialised and doesn't have to re-compute
results every time, which means faster loading of the search tab.
- For internal users, all results in
[here](https://discover.ente.io/v1.json) will show up.
- For non-internal users, once available, results will be limited to 4.
- 4 random prompts are selected from
[here](https://discover.ente.io/v1.json) with non-empty results and are
cached.
- The cache updates when the data updates
[here](https://discover.ente.io/v1.json) (checks size to compare) or in
3 days since the last update.

mobile/lib/main.dart

@@ -37,6 +37,7 @@ import "package:photos/services/machine_learning/face_ml/person/person_service.d
 import 'package:photos/services/machine_learning/file_ml/remote_fileml_service.dart';
 import "package:photos/services/machine_learning/machine_learning_controller.dart";
 import 'package:photos/services/machine_learning/semantic_search/semantic_search_service.dart';
+import "package:photos/services/magic_cache_service.dart";
 import 'package:photos/services/memories_service.dart';
 import 'package:photos/services/push_service.dart';
 import 'package:photos/services/remote_sync_service.dart';
@@ -303,6 +304,8 @@ Future<void> _init(bool isBackground, {String via = ''}) async {
       preferences,
     );
 
+    MagicCacheService.instance.init(preferences);
+
     initComplete = true;
     _logger.info("Initialization done");
   } catch (e, s) {

mobile/lib/models/search/search_types.dart

@@ -13,7 +13,6 @@ import "package:photos/models/collection/collection_items.dart";
 import "package:photos/models/search/search_result.dart";
 import "package:photos/models/typedefs.dart";
 import "package:photos/services/collections_service.dart";
-import "package:photos/services/machine_learning/semantic_search/frameworks/ml_framework.dart";
 import "package:photos/services/search_service.dart";
 import "package:photos/ui/viewer/gallery/collection_page.dart";
 import "package:photos/ui/viewer/location/add_location_sheet.dart";
@@ -292,8 +291,6 @@ extension SectionTypeExtensions on SectionType {
     switch (this) {
       case SectionType.location:
         return [Bus.instance.on<LocationTagUpdatedEvent>()];
-      case SectionType.magic:
-        return [Bus.instance.on<MLFrameworkInitializationUpdateEvent>()];
       default:
         return [];
     }

mobile/lib/services/machine_learning/semantic_search/semantic_search_service.dart

@@ -267,6 +267,49 @@ class SemanticSearchService {
     return results;
   }
 
+  Future<List<int>> getMatchingFileIDs(String query, double minScore) async {
+    final textEmbedding = await _getTextEmbedding(query);
+
+    final queryResults =
+        await _getScores(textEmbedding, scoreThreshold: minScore);
+
+    final queryResultIds = <int>[];
+    for (QueryResult result in queryResults) {
+      queryResultIds.add(result.id);
+    }
+
+    final filesMap = await FilesDB.instance.getFilesFromIDs(
+      queryResultIds,
+    );
+    final results = <EnteFile>[];
+
+    final ignoredCollections =
+        CollectionsService.instance.getHiddenCollectionIds();
+    final deletedEntries = <int>[];
+    for (final result in queryResults) {
+      final file = filesMap[result.id];
+      if (file != null && !ignoredCollections.contains(file.collectionID)) {
+        results.add(file);
+      }
+      if (file == null) {
+        deletedEntries.add(result.id);
+      }
+    }
+
+    _logger.info(results.length.toString() + " results");
+
+    if (deletedEntries.isNotEmpty) {
+      unawaited(EmbeddingsDB.instance.deleteEmbeddings(deletedEntries));
+    }
+
+    final matchingFileIDs = <int>[];
+    for (EnteFile file in results) {
+      matchingFileIDs.add(file.uploadedFileID!);
+    }
+
+    return matchingFileIDs;
+  }
+
   void _addToQueue(EnteFile file) {
     if (!LocalSettings.instance.hasEnabledMagicSearch()) {
       return;

mobile/lib/services/magic_cache_service.dart

@@ -0,0 +1,225 @@
+import "dart:async";
+import "dart:convert";
+import "dart:io";
+
+import "package:logging/logging.dart";
+import "package:path_provider/path_provider.dart";
+import "package:photos/models/file/file.dart";
+import "package:photos/models/search/generic_search_result.dart";
+import "package:photos/models/search/search_types.dart";
+import "package:photos/service_locator.dart";
+import "package:photos/services/machine_learning/semantic_search/semantic_search_service.dart";
+import "package:photos/services/remote_assets_service.dart";
+import "package:photos/services/search_service.dart";
+import "package:shared_preferences/shared_preferences.dart";
+
+class MagicCache {
+  final String title;
+  final List<int> fileUploadedIDs;
+  MagicCache(this.title, this.fileUploadedIDs);
+
+  factory MagicCache.fromJson(Map<String, dynamic> json) {
+    return MagicCache(
+      json['title'],
+      List<int>.from(json['fileUploadedIDs']),
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'title': title,
+      'fileUploadedIDs': fileUploadedIDs,
+    };
+  }
+
+  static String encodeListToJson(List<MagicCache> magicCaches) {
+    final jsonList = magicCaches.map((cache) => cache.toJson()).toList();
+    return jsonEncode(jsonList);
+  }
+
+  static List<MagicCache> decodeJsonToList(String jsonString) {
+    final jsonList = jsonDecode(jsonString) as List;
+    return jsonList.map((json) => MagicCache.fromJson(json)).toList();
+  }
+}
+
+extension MagicCacheServiceExtension on MagicCache {
+  Future<GenericSearchResult> toGenericSearchResult() async {
+    final allEnteFiles = await SearchService.instance.getAllFiles();
+    final enteFilesInMagicCache = <EnteFile>[];
+    for (EnteFile file in allEnteFiles) {
+      if (file.uploadedFileID != null &&
+          fileUploadedIDs.contains(file.uploadedFileID as int)) {
+        enteFilesInMagicCache.add(file);
+      }
+    }
+    return GenericSearchResult(
+      ResultType.magic,
+      title,
+      enteFilesInMagicCache,
+    );
+  }
+}
+
+class MagicCacheService {
+  static const _lastMagicCacheUpdateTime = "last_magic_cache_update_time";
+  static const _kMagicPromptsDataUrl = "https://discover.ente.io/v1.json";
+
+  /// Delay is for cache update to be done not during app init, during which a
+  /// lot of other things are happening.
+  static const _kCacheUpdateDelay = Duration(seconds: 10);
+
+  late SharedPreferences _prefs;
+  final Logger _logger = Logger((MagicCacheService).toString());
+  MagicCacheService._privateConstructor();
+
+  static final MagicCacheService instance =
+      MagicCacheService._privateConstructor();
+
+  void init(SharedPreferences preferences) {
+    _prefs = preferences;
+    _updateCacheIfTheTimeHasCome();
+  }
+
+  Future<void> resetLastMagicCacheUpdateTime() async {
+    await _prefs.setInt(
+      _lastMagicCacheUpdateTime,
+      DateTime.now().millisecondsSinceEpoch,
+    );
+  }
+
+  int get lastMagicCacheUpdateTime {
+    return _prefs.getInt(_lastMagicCacheUpdateTime) ?? 0;
+  }
+
+  Future<void> _updateCacheIfTheTimeHasCome() async {
+    final jsonFile = await RemoteAssetsService.instance
+        .getAssetIfUpdated(_kMagicPromptsDataUrl);
+    if (jsonFile != null) {
+      Future.delayed(_kCacheUpdateDelay, () {
+        unawaited(_updateCache());
+      });
+      return;
+    }
+    if (lastMagicCacheUpdateTime <
+        DateTime.now()
+            .subtract(const Duration(days: 3))
+            .millisecondsSinceEpoch) {
+      Future.delayed(_kCacheUpdateDelay, () {
+        unawaited(_updateCache());
+      });
+    }
+  }
+
+  Future<String> _getCachePath() async {
+    return (await getApplicationSupportDirectory()).path + "/cache/magic_cache";
+  }
+
+  Future<List<int>> _getMatchingFileIDsForPromptData(
+    Map<String, dynamic> promptData,
+  ) async {
+    final result = await SemanticSearchService.instance.getMatchingFileIDs(
+      promptData["prompt"] as String,
+      promptData["minimumScore"] as double,
+    );
+
+    return result;
+  }
+
+  Future<void> _updateCache() async {
+    try {
+      _logger.info("updating magic cache");
+      final magicPromptsData = await _loadMagicPrompts();
+      final magicCaches = await nonEmptyMagicResults(magicPromptsData);
+      final file = File(await _getCachePath());
+      if (!file.existsSync()) {
+        file.createSync(recursive: true);
+      }
+      file.writeAsBytesSync(MagicCache.encodeListToJson(magicCaches).codeUnits);
+      unawaited(
+        resetLastMagicCacheUpdateTime().onError((error, stackTrace) {
+          _logger.warning(
+            "Error resetting last magic cache update time",
+            error,
+          );
+        }),
+      );
+    } catch (e) {
+      _logger.info("Error updating magic cache", e);
+    }
+  }
+
+  Future<List<MagicCache>?> _getMagicCache() async {
+    final file = File(await _getCachePath());
+    if (!file.existsSync()) {
+      _logger.info("No magic cache found");
+      return null;
+    }
+    final jsonString = file.readAsStringSync();
+    return MagicCache.decodeJsonToList(jsonString);
+  }
+
+  Future<void> clearMagicCache() async {
+    File(await _getCachePath()).deleteSync();
+  }
+
+  Future<List<GenericSearchResult>> getMagicGenericSearchResult() async {
+    try {
+      final magicCaches = await _getMagicCache();
+      if (magicCaches == null) {
+        _logger.info("No magic cache found");
+        return [];
+      }
+
+      final List<GenericSearchResult> genericSearchResults = [];
+      for (MagicCache magicCache in magicCaches) {
+        final genericSearchResult = await magicCache.toGenericSearchResult();
+        genericSearchResults.add(genericSearchResult);
+      }
+      return genericSearchResults;
+    } catch (e) {
+      _logger.info("Error getting magic generic search result", e);
+      return [];
+    }
+  }
+
+  Future<List<dynamic>> _loadMagicPrompts() async {
+    final file =
+        await RemoteAssetsService.instance.getAsset(_kMagicPromptsDataUrl);
+
+    final json = jsonDecode(await file.readAsString());
+    return json["prompts"];
+  }
+
+  ///Returns random non-empty magic results from magicPromptsData
+  ///Length is capped at [limit], can be less than [limit] if there are not enough
+  ///non-empty results
+  Future<List<MagicCache>> nonEmptyMagicResults(
+    List<dynamic> magicPromptsData,
+  ) async {
+    //Show all magic prompts to internal users for feedback on results
+    final limit = flagService.internalUser ? magicPromptsData.length : 4;
+    final results = <MagicCache>[];
+    final randomIndexes = List.generate(
+      magicPromptsData.length,
+      (index) => index,
+      growable: false,
+    )..shuffle();
+    for (final index in randomIndexes) {
+      final files =
+          await _getMatchingFileIDsForPromptData(magicPromptsData[index]);
+      if (files.isNotEmpty) {
+        results.add(
+          MagicCache(
+            magicPromptsData[index]["title"] as String,
+            files,
+          ),
+        );
+      }
+      if (results.length >= limit) {
+        break;
+      }
+    }
+    return results;
+  }
+}

mobile/lib/services/remote_assets_service.dart

@@ -21,17 +21,46 @@ class RemoteAssetsService {
   Future<File> getAsset(String remotePath, {bool refetch = false}) async {
     final path = await _getLocalPath(remotePath);
     final file = File(path);
-    if (await file.exists() && !refetch) {
+    if (file.existsSync() && !refetch) {
       _logger.info("Returning cached file for $remotePath");
       return file;
     } else {
       final tempFile = File(path + ".temp");
       await _downloadFile(remotePath, tempFile.path);
-      await tempFile.rename(path);
+      tempFile.renameSync(path);
       return File(path);
     }
   }
 
+  ///Returns asset if the remote asset is new compared to the local copy of it
+  Future<File?> getAssetIfUpdated(String remotePath) async {
+    try {
+      final path = await _getLocalPath(remotePath);
+      final file = File(path);
+      if (!file.existsSync()) {
+        final tempFile = File(path + ".temp");
+        await _downloadFile(remotePath, tempFile.path);
+        tempFile.renameSync(path);
+        return File(path);
+      } else {
+        final existingFileSize = File(path).lengthSync();
+        final tempFile = File(path + ".temp");
+        await _downloadFile(remotePath, tempFile.path);
+        final newFileSize = tempFile.lengthSync();
+        if (existingFileSize != newFileSize) {
+          tempFile.renameSync(path);
+          return File(path);
+        } else {
+          tempFile.deleteSync();
+          return null;
+        }
+      }
+    } catch (e) {
+      _logger.warning("Error getting asset if updated", e);
+      return null;
+    }
+  }
+
   Future<bool> hasAsset(String remotePath) async {
     final path = await _getLocalPath(remotePath);
     return File(path).exists();
@@ -60,8 +89,8 @@ class RemoteAssetsService {
   Future<void> _downloadFile(String url, String savePath) async {
     _logger.info("Downloading " + url);
     final existingFile = File(savePath);
-    if (await existingFile.exists()) {
-      await existingFile.delete();
+    if (existingFile.existsSync()) {
+      existingFile.deleteSync();
     }
 
     await NetworkClient.instance.getDio().download(

mobile/lib/services/search_service.dart

@@ -1,4 +1,3 @@
-import "dart:convert";
 import "dart:math";
 
 import "package:flutter/cupertino.dart";
@@ -33,13 +32,14 @@ import "package:photos/services/location_service.dart";
 import "package:photos/services/machine_learning/face_ml/face_filtering/face_filtering_constants.dart";
 import "package:photos/services/machine_learning/face_ml/person/person_service.dart";
 import 'package:photos/services/machine_learning/semantic_search/semantic_search_service.dart';
-import "package:photos/services/remote_assets_service.dart";
+import "package:photos/services/magic_cache_service.dart";
 import "package:photos/states/location_screen_state.dart";
 import "package:photos/ui/viewer/location/add_location_sheet.dart";
 import "package:photos/ui/viewer/location/location_screen.dart";
 import "package:photos/ui/viewer/people/cluster_page.dart";
 import "package:photos/ui/viewer/people/people_page.dart";
 import 'package:photos/utils/date_time_util.dart';
+import "package:photos/utils/local_settings.dart";
 import "package:photos/utils/navigation_util.dart";
 import 'package:tuple/tuple.dart';
 
@@ -49,9 +49,6 @@ class SearchService {
   final _logger = Logger((SearchService).toString());
   final _collectionService = CollectionsService.instance;
   static const _maximumResultsLimit = 20;
-  static const _kMagicPromptsDataUrl = "https://discover.ente.io/v1.json";
-
-  var magicPromptsData = [];
 
   SearchService._privateConstructor();
 
@@ -63,17 +60,6 @@ class SearchService {
       _cachedFilesFuture = null;
       _cachedHiddenFilesFuture = null;
     });
-    if (flagService.internalUser) {
-      _loadMagicPrompts();
-    }
-  }
-
-  Future<dynamic> _loadMagicPrompts() async {
-    final file = await RemoteAssetsService.instance
-        .getAsset(_kMagicPromptsDataUrl, refetch: true);
-
-    final json = jsonDecode(await file.readAsString());
-    magicPromptsData = json["prompts"];
   }
 
   Set<int> ignoreCollections() {
@@ -192,26 +178,12 @@ class SearchService {
   }
 
   Future<List<GenericSearchResult>> getMagicSectionResutls() async {
-    if (!SemanticSearchService.instance.isMagicSearchEnabledAndReady()) {
+    if (LocalSettings.instance.hasEnabledMagicSearch() &&
+        flagService.internalUser) {
+      return MagicCacheService.instance.getMagicGenericSearchResult();
+    } else {
       return <GenericSearchResult>[];
     }
-    final searchResuts = <GenericSearchResult>[];
-    for (Map<String, dynamic> magicPrompt in magicPromptsData) {
-      final files = await SemanticSearchService.instance.getMatchingFiles(
-        magicPrompt["prompt"],
-        scoreThreshold: magicPrompt["minimumScore"],
-      );
-      if (files.isNotEmpty) {
-        searchResuts.add(
-          GenericSearchResult(
-            ResultType.magic,
-            magicPrompt["title"],
-            files,
-          ),
-        );
-      }
-    }
-    return searchResuts;
   }
 
   Future<List<GenericSearchResult>> getRandomMomentsSearchResults(

mobile/lib/ui/viewer/search_tab/magic_section.dart

@@ -33,28 +33,6 @@ class _MagicSectionState extends State<MagicSection> {
     super.initState();
     _magicSearchResults = widget.magicSearchResults;
 
-    //At times, ml framework is not initialized when the search results are
-    //requested (widget.momentsSearchResults is empty) and is initialized
-    //(which fires MLFrameworkInitializationUpdateEvent with
-    //InitializationState.initialized) before initState of this widget is
-    //called. We do listen to MLFrameworkInitializationUpdateEvent and reload
-    //this widget but the event with InitializationState.initialized would have
-    //already been fired in the above case.
-    if (_magicSearchResults.isEmpty) {
-      SectionType.magic
-          .getData(
-        context,
-        limit: kSearchSectionLimit,
-      )
-          .then((value) {
-        if (mounted) {
-          setState(() {
-            _magicSearchResults = value as List<GenericSearchResult>;
-          });
-        }
-      });
-    }
-
     final streamsToListenTo = SectionType.magic.sectionUpdateEvents();
     for (Stream<Event> stream in streamsToListenTo) {
       streamSubscriptions.add(
@@ -84,7 +62,6 @@ class _MagicSectionState extends State<MagicSection> {
   @override
   void didUpdateWidget(covariant MagicSection oldWidget) {
     super.didUpdateWidget(oldWidget);
-    //widget.magicSearch is empty when doing a hot reload
     if (widget.magicSearchResults.isNotEmpty) {
       _magicSearchResults = widget.magicSearchResults;
     }
@@ -262,7 +239,7 @@ class MagicRecommendation extends StatelessWidget {
                       ),
                       ConstrainedBox(
                         constraints: const BoxConstraints(
-                          maxWidth: 76,
+                          maxWidth: 88,
                         ),
                         child: Padding(
                           padding: const EdgeInsets.only(