feature(mobile): hash assets & sync via checksum (#2592)

* compare different sha1 implementations

* remove openssl sha1

* sync via checksum

* hash assets in batches

* hash in background, show spinner in tab

* undo tmp changes

* migrate by clearing assets

* ignore duplicate assets

* error handling

* trigger sync/merge after download and update view

* review feedback improvements

* hash in background isolate on iOS

* rework linking assets with existing from DB

* fine-grained errors on unique index violation

* hash lenth validation

* revert compute in background on iOS

* ignore duplicate assets on device

* fix bug with batching based on accumulated size

---------

Co-authored-by: Fynn Petersen-Frey <zoodyy@users.noreply.github.com>

mobile/lib/shared/services/hash.service.dart

@@ -0,0 +1,175 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:crypto/crypto.dart';
+import 'package:flutter/foundation.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:immich_mobile/modules/backup/background_service/background.service.dart';
+import 'package:immich_mobile/shared/models/android_device_asset.dart';
+import 'package:immich_mobile/shared/models/asset.dart';
+import 'package:immich_mobile/shared/models/device_asset.dart';
+import 'package:immich_mobile/shared/models/ios_device_asset.dart';
+import 'package:immich_mobile/shared/providers/db.provider.dart';
+import 'package:immich_mobile/utils/builtin_extensions.dart';
+import 'package:isar/isar.dart';
+import 'package:logging/logging.dart';
+import 'package:photo_manager/photo_manager.dart';
+
+class HashService {
+  HashService(this._db, this._backgroundService);
+  final Isar _db;
+  final BackgroundService _backgroundService;
+  final _log = Logger('HashService');
+
+  /// Returns all assets that were successfully hashed
+  Future<List<Asset>> getHashedAssets(
+    AssetPathEntity album, {
+    int start = 0,
+    int end = 0x7fffffffffffffff,
+    Set<String>? excludedAssets,
+  }) async {
+    final entities = await album.getAssetListRange(start: start, end: end);
+    final filtered = excludedAssets == null
+        ? entities
+        : entities.where((e) => !excludedAssets.contains(e.id)).toList();
+    return _hashAssets(filtered);
+  }
+
+  /// Converts a list of [AssetEntity]s to [Asset]s including only those
+  /// that were successfully hashed. Hashes are looked up in a DB table
+  /// [AndroidDeviceAsset] / [IOSDeviceAsset] by local id. Only missing
+  /// entries are newly hashed and added to the DB table.
+  Future<List<Asset>> _hashAssets(List<AssetEntity> assetEntities) async {
+    const int batchFileCount = 128;
+    const int batchDataSize = 1024 * 1024 * 1024; // 1GB
+
+    final ids = assetEntities
+        .map(Platform.isAndroid ? (a) => a.id.toInt() : (a) => a.id)
+        .toList();
+    final List<DeviceAsset?> hashes = await _lookupHashes(ids);
+    final List<DeviceAsset> toAdd = [];
+    final List<String> toHash = [];
+
+    int bytes = 0;
+
+    for (int i = 0; i < assetEntities.length; i++) {
+      if (hashes[i] != null) {
+        continue;
+      }
+      final file = await assetEntities[i].originFile;
+      if (file == null) {
+        _log.warning(
+          "Failed to get file for asset ${assetEntities[i].id}, skipping",
+        );
+        continue;
+      }
+      bytes += await file.length();
+      toHash.add(file.path);
+      final deviceAsset = Platform.isAndroid
+          ? AndroidDeviceAsset(id: ids[i] as int, hash: const [])
+          : IOSDeviceAsset(id: ids[i] as String, hash: const []);
+      toAdd.add(deviceAsset);
+      hashes[i] = deviceAsset;
+      if (toHash.length == batchFileCount || bytes >= batchDataSize) {
+        await _processBatch(toHash, toAdd);
+        toAdd.clear();
+        toHash.clear();
+        bytes = 0;
+      }
+    }
+    if (toHash.isNotEmpty) {
+      await _processBatch(toHash, toAdd);
+    }
+    return _mapAllHashedAssets(assetEntities, hashes);
+  }
+
+  /// Lookup hashes of assets by their local ID
+  Future<List<DeviceAsset?>> _lookupHashes(List<Object> ids) =>
+      Platform.isAndroid
+          ? _db.androidDeviceAssets.getAll(ids.cast())
+          : _db.iOSDeviceAssets.getAllById(ids.cast());
+
+  /// Processes a batch of files and saves any successfully hashed
+  /// values to the DB table.
+  Future<void> _processBatch(
+    final List<String> toHash,
+    final List<DeviceAsset> toAdd,
+  ) async {
+    final hashes = await _hashFiles(toHash);
+    bool anyNull = false;
+    for (int j = 0; j < hashes.length; j++) {
+      if (hashes[j]?.length == 20) {
+        toAdd[j].hash = hashes[j]!;
+      } else {
+        _log.warning("Failed to hash file ${toHash[j]}, skipping");
+        anyNull = true;
+      }
+    }
+    final validHashes = anyNull
+        ? toAdd.where((e) => e.hash.length == 20).toList(growable: false)
+        : toAdd;
+    await _db.writeTxn(
+      () => Platform.isAndroid
+          ? _db.androidDeviceAssets.putAll(validHashes.cast())
+          : _db.iOSDeviceAssets.putAll(validHashes.cast()),
+    );
+    _log.fine("Hashed ${validHashes.length}/${toHash.length} assets");
+  }
+
+  /// Hashes the given files and returns a list of the same length
+  /// files that could not be hashed have a `null` value
+  Future<List<Uint8List?>> _hashFiles(List<String> paths) async {
+    if (Platform.isAndroid) {
+      final List<Uint8List?>? hashes =
+          await _backgroundService.digestFiles(paths);
+      if (hashes == null) {
+        throw Exception("Hashing ${paths.length} files failed");
+      }
+      return hashes;
+    } else if (Platform.isIOS) {
+      final List<Uint8List?> result = List.filled(paths.length, null);
+      for (int i = 0; i < paths.length; i++) {
+        result[i] = await _hashAssetDart(File(paths[i]));
+      }
+      return result;
+    } else {
+      throw Exception("_hashFiles implementation missing");
+    }
+  }
+
+  /// Hashes a single file using Dart's crypto package
+  Future<Uint8List?> _hashAssetDart(File f) async {
+    late Digest output;
+    final sink = sha1.startChunkedConversion(
+      ChunkedConversionSink<Digest>.withCallback((accumulated) {
+        output = accumulated.first;
+      }),
+    );
+    await for (final chunk in f.openRead()) {
+      sink.add(chunk);
+    }
+    sink.close();
+    return Uint8List.fromList(output.bytes);
+  }
+
+  /// Converts [AssetEntity]s that were successfully hashed to [Asset]s
+  List<Asset> _mapAllHashedAssets(
+    List<AssetEntity> assets,
+    List<DeviceAsset?> hashes,
+  ) {
+    final List<Asset> result = [];
+    for (int i = 0; i < assets.length; i++) {
+      if (hashes[i] != null && hashes[i]!.hash.isNotEmpty) {
+        result.add(Asset.local(assets[i], hashes[i]!.hash));
+      }
+    }
+    return result;
+  }
+}
+
+final hashServiceProvider = Provider(
+  (ref) => HashService(
+    ref.watch(dbProvider),
+    ref.watch(backgroundServiceProvider),
+  ),
+);

mobile/lib/shared/services/sync.service.dart

@@ -4,10 +4,12 @@ import 'package:collection/collection.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:immich_mobile/shared/models/album.dart';
 import 'package:immich_mobile/shared/models/asset.dart';
+import 'package:immich_mobile/shared/models/etag.dart';
 import 'package:immich_mobile/shared/models/exif_info.dart';
 import 'package:immich_mobile/shared/models/store.dart';
 import 'package:immich_mobile/shared/models/user.dart';
 import 'package:immich_mobile/shared/providers/db.provider.dart';
+import 'package:immich_mobile/shared/services/hash.service.dart';
 import 'package:immich_mobile/utils/async_mutex.dart';
 import 'package:immich_mobile/utils/builtin_extensions.dart';
 import 'package:immich_mobile/utils/diff.dart';
@@ -16,15 +18,17 @@ import 'package:logging/logging.dart';
 import 'package:openapi/api.dart';
 import 'package:photo_manager/photo_manager.dart';
 
-final syncServiceProvider =
-    Provider((ref) => SyncService(ref.watch(dbProvider)));
+final syncServiceProvider = Provider(
+  (ref) => SyncService(ref.watch(dbProvider), ref.watch(hashServiceProvider)),
+);
 
 class SyncService {
   final Isar _db;
+  final HashService _hashService;
   final AsyncMutex _lock = AsyncMutex();
   final Logger _log = Logger('SyncService');
 
-  SyncService(this._db);
+  SyncService(this._db, this._hashService);
 
   // public methods:
 
@@ -33,6 +37,7 @@ class SyncService {
   Future<bool> syncUsersFromServer(List<User> users) async {
     users.sortBy((u) => u.id);
     final dbUsers = await _db.users.where().sortById().findAll();
+    assert(dbUsers.isSortedBy((u) => u.id), "dbUsers not sorted!");
     final List<int> toDelete = [];
     final List<User> toUpsert = [];
     final changes = diffSortedListsSync(
@@ -108,40 +113,16 @@ class SyncService {
   // private methods:
 
   /// Syncs a new asset to the db. Returns `true` if successful
-  Future<bool> _syncNewAssetToDb(Asset newAsset) async {
-    final List<Asset> inDb = await _db.assets
-        .where()
-        .localIdDeviceIdEqualTo(newAsset.localId, newAsset.deviceId)
-        .findAll();
-    Asset? match;
-    if (inDb.length == 1) {
-      // exactly one match: trivial case
-      match = inDb.first;
-    } else if (inDb.length > 1) {
-      // TODO instead of this heuristics: match by checksum once available
-      for (Asset a in inDb) {
-        if (a.ownerId == newAsset.ownerId &&
-            a.fileModifiedAt.isAtSameMomentAs(newAsset.fileModifiedAt)) {
-          assert(match == null);
-          match = a;
-        }
-      }
-      if (match == null) {
-        for (Asset a in inDb) {
-          if (a.ownerId == newAsset.ownerId) {
-            assert(match == null);
-            match = a;
-          }
-        }
-      }
-    }
-    if (match != null) {
+  Future<bool> _syncNewAssetToDb(Asset a) async {
+    final Asset? inDb =
+        await _db.assets.getByChecksumOwnerId(a.checksum, a.ownerId);
+    if (inDb != null) {
       // unify local/remote assets by replacing the
       // local-only asset in the DB with a local&remote asset
-      newAsset = match.updatedCopy(newAsset);
+      a = inDb.updatedCopy(a);
     }
     try {
-      await _db.writeTxn(() => newAsset.put(_db));
+      await _db.writeTxn(() => a.put(_db));
     } on IsarError catch (e) {
       _log.severe("Failed to put new asset into db: $e");
       return false;
@@ -162,11 +143,11 @@ class SyncService {
     final List<Asset> inDb = await _db.assets
         .filter()
         .ownerIdEqualTo(user.isarId)
-        .sortByDeviceId()
-        .thenByLocalId()
-        .thenByFileModifiedAt()
+        .sortByChecksum()
         .findAll();
-    remote.sort(Asset.compareByOwnerDeviceLocalIdModified);
+    assert(inDb.isSorted(Asset.compareByChecksum), "inDb not sorted!");
+
+    remote.sort(Asset.compareByChecksum);
     final (toAdd, toUpdate, toRemove) = _diffAssets(remote, inDb, remote: true);
     if (toAdd.isEmpty && toUpdate.isEmpty && toRemove.isEmpty) {
       return false;
@@ -199,6 +180,7 @@ class SyncService {
       query = baseQuery.owner((q) => q.isarIdEqualTo(me.isarId));
     }
     final List<Album> dbAlbums = await query.sortByRemoteId().findAll();
+    assert(dbAlbums.isSortedBy((e) => e.remoteId!), "dbAlbums not sorted!");
 
     final List<Asset> toDelete = [];
     final List<Asset> existing = [];
@@ -245,16 +227,16 @@ class SyncService {
     if (dto.assetCount != dto.assets.length) {
       return false;
     }
-    final assetsInDb = await album.assets
-        .filter()
-        .sortByOwnerId()
-        .thenByDeviceId()
-        .thenByLocalId()
-        .thenByFileModifiedAt()
-        .findAll();
+    final assetsInDb =
+        await album.assets.filter().sortByOwnerId().thenByChecksum().findAll();
+    assert(assetsInDb.isSorted(Asset.compareByOwnerChecksum), "inDb unsorted!");
     final List<Asset> assetsOnRemote = dto.getAssets();
-    assetsOnRemote.sort(Asset.compareByOwnerDeviceLocalIdModified);
-    final (toAdd, toUpdate, toUnlink) = _diffAssets(assetsOnRemote, assetsInDb);
+    assetsOnRemote.sort(Asset.compareByOwnerChecksum);
+    final (toAdd, toUpdate, toUnlink) = _diffAssets(
+      assetsOnRemote,
+      assetsInDb,
+      compare: Asset.compareByOwnerChecksum,
+    );
 
     // update shared users
     final List<User> sharedUsers = album.sharedUsers.toList(growable: false);
@@ -297,6 +279,7 @@ class SyncService {
         await album.assets.update(link: assetsToLink, unlink: toUnlink.cast());
         await _db.albums.put(album);
       });
+      _log.info("Synced changes of remote album ${album.name} to DB");
     } on IsarError catch (e) {
       _log.severe("Failed to sync remote album to database $e");
     }
@@ -382,10 +365,11 @@ class SyncService {
     Set<String>? excludedAssets,
   ]) async {
     onDevice.sort((a, b) => a.id.compareTo(b.id));
-    final List<Album> inDb =
+    final inDb =
         await _db.albums.where().localIdIsNotNull().sortByLocalId().findAll();
     final List<Asset> deleteCandidates = [];
     final List<Asset> existing = [];
+    assert(inDb.isSorted((a, b) => a.localId!.compareTo(b.localId!)), "sort!");
     final bool anyChanges = await diffSortedLists(
       onDevice,
       inDb,
@@ -447,14 +431,15 @@ class SyncService {
     final inDb = await album.assets
         .filter()
         .ownerIdEqualTo(Store.get(StoreKey.currentUser).isarId)
-        .deviceIdEqualTo(Store.get(StoreKey.deviceIdHash))
-        .sortByLocalId()
+        .sortByChecksum()
         .findAll();
+    assert(inDb.isSorted(Asset.compareByChecksum), "inDb not sorted!");
+    final int assetCountOnDevice = await ape.assetCountAsync;
     final List<Asset> onDevice =
-        await ape.getAssets(excludedAssets: excludedAssets);
-    onDevice.sort(Asset.compareByLocalId);
-    final (toAdd, toUpdate, toDelete) =
-        _diffAssets(onDevice, inDb, compare: Asset.compareByLocalId);
+        await _hashService.getHashedAssets(ape, excludedAssets: excludedAssets);
+    _removeDuplicates(onDevice);
+    // _removeDuplicates sorts `onDevice` by checksum
+    final (toAdd, toUpdate, toDelete) = _diffAssets(onDevice, inDb);
     if (toAdd.isEmpty &&
         toUpdate.isEmpty &&
         toDelete.isEmpty &&
@@ -491,6 +476,9 @@ class SyncService {
         await _db.albums.put(album);
         album.thumbnail.value ??= await album.assets.filter().findFirst();
         await album.thumbnail.save();
+        await _db.eTags.put(
+          ETag(id: ape.eTagKeyAssetCount, value: assetCountOnDevice.toString()),
+        );
       });
       _log.info("Synced changes of local album ${ape.name} to DB");
     } on IsarError catch (e) {
@@ -503,8 +491,13 @@ class SyncService {
   /// fast path for common case: only new assets were added to device album
   /// returns `true` if successfull, else `false`
   Future<bool> _syncDeviceAlbumFast(AssetPathEntity ape, Album album) async {
+    if (!(ape.lastModified ?? DateTime.now()).isAfter(album.modifiedAt)) {
+      return false;
+    }
     final int totalOnDevice = await ape.assetCountAsync;
-    final AssetPathEntity? modified = totalOnDevice > album.assetCount
+    final int lastKnownTotal =
+        (await _db.eTags.getById(ape.eTagKeyAssetCount))?.value?.toInt() ?? 0;
+    final AssetPathEntity? modified = totalOnDevice > lastKnownTotal
         ? await ape.fetchPathProperties(
             filterOptionGroup: FilterOptionGroup(
               updateTimeCond: DateTimeCond(
@@ -517,17 +510,22 @@ class SyncService {
     if (modified == null) {
       return false;
     }
-    final List<Asset> newAssets = await modified.getAssets();
-    if (totalOnDevice != album.assets.length + newAssets.length) {
+    final List<Asset> newAssets = await _hashService.getHashedAssets(modified);
+
+    if (totalOnDevice != lastKnownTotal + newAssets.length) {
       return false;
     }
     album.modifiedAt = ape.lastModified ?? DateTime.now();
+    _removeDuplicates(newAssets);
     final (existingInDb, updated) = await _linkWithExistingFromDb(newAssets);
     try {
       await _db.writeTxn(() async {
         await _db.assets.putAll(updated);
         await album.assets.update(link: existingInDb + updated);
         await _db.albums.put(album);
+        await _db.eTags.put(
+          ETag(id: ape.eTagKeyAssetCount, value: totalOnDevice.toString()),
+        );
       });
       _log.info("Fast synced local album ${ape.name} to DB");
     } on IsarError catch (e) {
@@ -547,7 +545,9 @@ class SyncService {
   ]) async {
     _log.info("Syncing a new local album to DB: ${ape.name}");
     final Album a = Album.local(ape);
-    final assets = await ape.getAssets(excludedAssets: excludedAssets);
+    final assets =
+        await _hashService.getHashedAssets(ape, excludedAssets: excludedAssets);
+    _removeDuplicates(assets);
     final (existingInDb, updated) = await _linkWithExistingFromDb(assets);
     _log.info(
       "${existingInDb.length} assets already existed in DB, to upsert ${updated.length}",
@@ -570,44 +570,29 @@ class SyncService {
   Future<(List<Asset> existing, List<Asset> updated)> _linkWithExistingFromDb(
     List<Asset> assets,
   ) async {
-    if (assets.isEmpty) {
-      return ([].cast<Asset>(), [].cast<Asset>());
-    }
-    final List<Asset> inDb = await _db.assets
-        .where()
-        .anyOf(
-          assets,
-          (q, Asset e) => q.localIdDeviceIdEqualTo(e.localId, e.deviceId),
-        )
-        .sortByOwnerId()
-        .thenByDeviceId()
-        .thenByLocalId()
-        .thenByFileModifiedAt()
-        .findAll();
-    assets.sort(Asset.compareByOwnerDeviceLocalIdModified);
-    final List<Asset> existing = [], toUpsert = [];
-    diffSortedListsSync(
-      inDb,
-      assets,
-      // do not compare by modified date because for some assets dates differ on
-      // client and server, thus never reaching "both" case below
-      compare: Asset.compareByOwnerDeviceLocalId,
-      both: (Asset a, Asset b) {
-        if (a.canUpdate(b)) {
-          toUpsert.add(a.updatedCopy(b));
-          return true;
-        } else {
-          existing.add(a);
-          return false;
-        }
-      },
-      onlyFirst: (Asset a) => _log.finer(
-        "_linkWithExistingFromDb encountered asset only in DB: $a",
-        null,
-        StackTrace.current,
-      ),
-      onlySecond: (Asset b) => toUpsert.add(b),
+    if (assets.isEmpty) return ([].cast<Asset>(), [].cast<Asset>());
+
+    final List<Asset?> inDb = await _db.assets.getAllByChecksumOwnerId(
+      assets.map((a) => a.checksum).toList(growable: false),
+      assets.map((a) => a.ownerId).toInt64List(),
     );
+    assert(inDb.length == assets.length);
+    final List<Asset> existing = [], toUpsert = [];
+    for (int i = 0; i < assets.length; i++) {
+      final Asset? b = inDb[i];
+      if (b == null) {
+        toUpsert.add(assets[i]);
+        continue;
+      }
+      if (b.canUpdate(assets[i])) {
+        final updated = b.updatedCopy(assets[i]);
+        assert(updated.id != Isar.autoIncrement);
+        toUpsert.add(updated);
+      } else {
+        existing.add(b);
+      }
+    }
+    assert(existing.length + toUpsert.length == assets.length);
     return (existing, toUpsert);
   }
 
@@ -627,11 +612,63 @@ class SyncService {
       });
       _log.info("Upserted ${assets.length} assets into the DB");
     } on IsarError catch (e) {
-      _log.warning(
+      _log.severe(
         "Failed to upsert ${assets.length} assets into the DB: ${e.toString()}",
       );
+      // give details on the errors
+      assets.sort(Asset.compareByOwnerChecksum);
+      final inDb = await _db.assets.getAllByChecksumOwnerId(
+        assets.map((e) => e.checksum).toList(growable: false),
+        assets.map((e) => e.ownerId).toInt64List(),
+      );
+      for (int i = 0; i < assets.length; i++) {
+        final Asset a = assets[i];
+        final Asset? b = inDb[i];
+        if (b == null) {
+          if (a.id != Isar.autoIncrement) {
+            _log.warning(
+              "Trying to update an asset that does not exist in DB:\n$a",
+            );
+          }
+        } else if (a.id != b.id) {
+          _log.warning(
+            "Trying to insert another asset with the same checksum+owner. In DB:\n$b\nTo insert:\n$a",
+          );
+        }
+      }
+      for (int i = 1; i < assets.length; i++) {
+        if (Asset.compareByOwnerChecksum(assets[i - 1], assets[i]) == 0) {
+          _log.warning(
+            "Trying to insert duplicate assets:\n${assets[i - 1]}\n${assets[i]}",
+          );
+        }
+      }
     }
   }
+
+  List<Asset> _removeDuplicates(List<Asset> assets) {
+    final int before = assets.length;
+    assets.sort(Asset.compareByOwnerChecksumCreatedModified);
+    assets.uniqueConsecutive(
+      compare: Asset.compareByOwnerChecksum,
+      onDuplicate: (a, b) =>
+          _log.info("Ignoring duplicate assets on device:\n$a\n$b"),
+    );
+    final int duplicates = before - assets.length;
+    if (duplicates > 0) {
+      _log.warning("Ignored $duplicates duplicate assets on device");
+    }
+    return assets;
+  }
+
+  /// returns `true` if the albums differ on the surface
+  Future<bool> _hasAssetPathEntityChanged(AssetPathEntity a, Album b) async {
+    return a.name != b.name ||
+        a.lastModified == null ||
+        !a.lastModified!.isAtSameMomentAs(b.modifiedAt) ||
+        await a.assetCountAsync !=
+            (await _db.eTags.getById(a.eTagKeyAssetCount))?.value?.toInt();
+  }
 }
 
 /// Returns a triple(toAdd, toUpdate, toRemove)
@@ -639,7 +676,7 @@ class SyncService {
   List<Asset> assets,
   List<Asset> inDb, {
   bool? remote,
-  int Function(Asset, Asset) compare = Asset.compareByOwnerDeviceLocalId,
+  int Function(Asset, Asset) compare = Asset.compareByChecksum,
 }) {
   final List<Asset> toAdd = [];
   final List<Asset> toUpdate = [];
@@ -663,7 +700,7 @@ class SyncService {
         }
       } else if (remote == false && a.isRemote) {
         if (a.isLocal) {
-          a.isLocal = false;
+          a.localId = null;
           toUpdate.add(a);
         }
       } else {
@@ -685,9 +722,9 @@ class SyncService {
     return const ([], []);
   }
   deleteCandidates.sort(Asset.compareById);
-  deleteCandidates.uniqueConsecutive((a) => a.id);
+  deleteCandidates.uniqueConsecutive(compare: Asset.compareById);
   existing.sort(Asset.compareById);
-  existing.uniqueConsecutive((a) => a.id);
+  existing.uniqueConsecutive(compare: Asset.compareById);
   final (tooAdd, toUpdate, toRemove) = _diffAssets(
     existing,
     deleteCandidates,
@@ -698,14 +735,6 @@ class SyncService {
   return (toRemove.map((e) => e.id).toList(), toUpdate);
 }
 
-/// returns `true` if the albums differ on the surface
-Future<bool> _hasAssetPathEntityChanged(AssetPathEntity a, Album b) async {
-  return a.name != b.name ||
-      a.lastModified == null ||
-      !a.lastModified!.isAtSameMomentAs(b.modifiedAt) ||
-      await a.assetCountAsync != b.assetCount;
-}
-
 /// returns `true` if the albums differ on the surface
 bool _hasAlbumResponseDtoChanged(AlbumResponseDto dto, Album a) {
   return dto.assetCount != a.assetCount ||