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

import 'dart:async';

import 'package:collection/collection.dart';
import 'package:hooks_riverpod/hooks_riverpod.dart';
import 'package:immich_mobile/extensions/album_extensions.dart';
import 'package:immich_mobile/modules/album/models/album.model.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/utils/async_mutex.dart';
import 'package:immich_mobile/extensions/collection_extensions.dart';
import 'package:immich_mobile/utils/diff.dart';
import 'package:isar/isar.dart';
import 'package:logging/logging.dart';
import 'package:openapi/api.dart';

final syncServiceProvider = Provider(
  (ref) => SyncService(ref.watch(dbProvider)),
);

class SyncService {
  final Isar _db;
  static final AsyncMutex lock = AsyncMutex();
  final Logger _log = Logger('SyncService');

  SyncService(this._db);

  // public methods:

  /// Syncs users from the server to the local database
  /// Returns `true`if there were any changes
  Future<bool> syncUsersFromServer(List<User> users) =>
      lock.run(() => _syncUsersFromServer(users));

  /// Syncs remote assets owned by the logged-in user to the DB
  /// Returns `true` if there were any changes
  Future<bool> syncRemoteAssetsToDb(
    User user,
    Future<(List<Asset>? toUpsert, List<String>? toDelete)> Function(
      User user,
      DateTime since,
    ) getChangedAssets,
    FutureOr<List<Asset>?> Function(User user) loadAssets,
  ) =>
      lock.run(
        () async =>
            await _syncRemoteAssetChanges(user, getChangedAssets) ??
            await _syncRemoteAssetsFull(user, loadAssets),
      );

  /// Syncs remote albums to the database
  /// returns `true` if there were any changes
  Future<bool> syncRemoteAlbumsToDb(
    List<AlbumResponseDto> remote, {
    required bool isShared,
    required FutureOr<AlbumResponseDto> Function(AlbumResponseDto) loadDetails,
  }) =>
      lock.run(() => _syncRemoteAlbumsToDb(remote, isShared, loadDetails));

  /// returns all Asset IDs that are not contained in the existing list
  List<int> sharedAssetsToRemove(
    List<Asset> deleteCandidates,
    List<Asset> existing,
  ) {
    if (deleteCandidates.isEmpty) {
      return [];
    }
    deleteCandidates.sort(Asset.compareById);
    existing.sort(Asset.compareById);
    return diffAssets(existing, deleteCandidates, compare: Asset.compareById)
        .$3
        .map((e) => e.id)
        .toList();
  }

  /// Syncs a new asset to the db. Returns `true` if successful
  Future<bool> syncNewAssetToDb(Asset newAsset) =>
      lock.run(() => _syncNewAssetToDb(newAsset));

  // private methods:

  /// Syncs users from the server to the local database
  /// Returns `true`if there were any changes
  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(
      users,
      dbUsers,
      compare: (User a, User b) => a.id.compareTo(b.id),
      both: (User a, User b) {
        if (!a.updatedAt.isAtSameMomentAs(b.updatedAt) ||
            a.isPartnerSharedBy != b.isPartnerSharedBy ||
            a.isPartnerSharedWith != b.isPartnerSharedWith) {
          toUpsert.add(a);
          return true;
        }
        return false;
      },
      onlyFirst: (User a) => toUpsert.add(a),
      onlySecond: (User b) => toDelete.add(b.isarId),
    );
    if (changes) {
      await _db.writeTxn(() async {
        await _db.users.deleteAll(toDelete);
        await _db.users.putAll(toUpsert);
      });
    }
    return changes;
  }

  /// Syncs a new asset to the db. Returns `true` if successful
  Future<bool> _syncNewAssetToDb(Asset a) async {
    final Asset? inDb =
        await _db.assets.getByOwnerIdChecksum(a.ownerId, a.checksum);
    if (inDb != null) {
      // unify local/remote assets by replacing the
      // local-only asset in the DB with a local&remote asset
      a = inDb.updatedCopy(a);
    }
    try {
      await _db.writeTxn(() => a.put(_db));
    } on IsarError catch (e) {
      _log.severe("Failed to put new asset into db", e);
      return false;
    }
    return true;
  }

  /// Efficiently syncs assets via changes. Returns `null` when a full sync is required.
  Future<bool?> _syncRemoteAssetChanges(
    User user,
    Future<(List<Asset>? toUpsert, List<String>? toDelete)> Function(
      User user,
      DateTime since,
    ) getChangedAssets,
  ) async {
    final DateTime? since = _db.eTags.getByIdSync(user.id)?.time?.toUtc();
    if (since == null) return null;
    final DateTime now = DateTime.now();
    final (toUpsert, toDelete) = await getChangedAssets(user, since);
    if (toUpsert == null || toDelete == null) return null;
    try {
      if (toDelete.isNotEmpty) {
        await handleRemoteAssetRemoval(toDelete);
      }
      if (toUpsert.isNotEmpty) {
        final (_, updated) = await _linkWithExistingFromDb(toUpsert);
        await upsertAssetsWithExif(updated);
      }
      if (toUpsert.isNotEmpty || toDelete.isNotEmpty) {
        await _updateUserAssetsETag(user, now);
        return true;
      }
      return false;
    } on IsarError catch (e) {
      _log.severe("Failed to sync remote assets to db", e);
    }
    return null;
  }

  /// Deletes remote-only assets, updates merged assets to be local-only
  Future<void> handleRemoteAssetRemoval(List<String> idsToDelete) {
    return _db.writeTxn(() async {
      final idsToRemove = await _db.assets
          .remote(idsToDelete)
          .filter()
          .localIdIsNull()
          .idProperty()
          .findAll();
      await _db.assets.deleteAll(idsToRemove);
      await _db.exifInfos.deleteAll(idsToRemove);
      final onlyLocal = await _db.assets.remote(idsToDelete).findAll();
      if (onlyLocal.isNotEmpty) {
        for (final Asset a in onlyLocal) {
          a.remoteId = null;
          a.isTrashed = false;
        }
        await _db.assets.putAll(onlyLocal);
      }
    });
  }

  /// Syncs assets by loading and comparing all assets from the server.
  Future<bool> _syncRemoteAssetsFull(
    User user,
    FutureOr<List<Asset>?> Function(User user) loadAssets,
  ) async {
    final DateTime now = DateTime.now().toUtc();
    final List<Asset>? remote = await loadAssets(user);
    if (remote == null) {
      return false;
    }
    final List<Asset> inDb = await _db.assets
        .where()
        .ownerIdEqualToAnyChecksum(user.isarId)
        .sortByChecksum()
        .findAll();
    assert(inDb.isSorted(Asset.compareByChecksum), "inDb not sorted!");

    remote.sort(Asset.compareByChecksum);

    // filter our duplicates that might be introduced by the chunked retrieval
    remote.uniqueConsecutive(compare: Asset.compareByChecksum);

    final (toAdd, toUpdate, toRemove) = diffAssets(remote, inDb, remote: true);
    if (toAdd.isEmpty && toUpdate.isEmpty && toRemove.isEmpty) {
      await _updateUserAssetsETag(user, now);
      return false;
    }
    final idsToDelete = toRemove.map((e) => e.id).toList();
    try {
      await _db.writeTxn(() => _db.assets.deleteAll(idsToDelete));
      await upsertAssetsWithExif(toAdd + toUpdate);
    } on IsarError catch (e) {
      _log.severe("Failed to sync remote assets to db", e);
    }
    await _updateUserAssetsETag(user, now);
    return true;
  }

  Future<void> _updateUserAssetsETag(User user, DateTime time) =>
      _db.writeTxn(() => _db.eTags.put(ETag(id: user.id, time: time)));

  /// Syncs remote albums to the database
  /// returns `true` if there were any changes
  Future<bool> _syncRemoteAlbumsToDb(
    List<AlbumResponseDto> remote,
    bool isShared,
    FutureOr<AlbumResponseDto> Function(AlbumResponseDto) loadDetails,
  ) async {
    remote.sortBy((e) => e.id);

    final baseQuery = _db.remoteAlbums.where().filter();
    final QueryBuilder<RemoteAlbum, RemoteAlbum, QAfterFilterCondition> query;
    if (isShared) {
      query = baseQuery.sharedEqualTo(true);
    } else {
      final User me = Store.get(StoreKey.currentUser);
      query = baseQuery.owner((q) => q.isarIdEqualTo(me.isarId));
    }
    final List<RemoteAlbum> dbAlbums = await query.sortById().findAll();
    assert(dbAlbums.isSortedBy((e) => e.id), "dbAlbums not sorted!");

    final List<Asset> toDelete = [];
    final List<Asset> existing = [];

    final bool changes = await diffSortedLists(
      remote,
      dbAlbums,
      compare: (AlbumResponseDto a, RemoteAlbum b) => a.id.compareTo(b.id),
      both: (AlbumResponseDto a, RemoteAlbum b) =>
          _syncRemoteAlbum(a, b, toDelete, existing, loadDetails),
      onlyFirst: (AlbumResponseDto a) =>
          _addAlbumFromServer(a, existing, loadDetails),
      onlySecond: (RemoteAlbum a) => _removeAlbumFromDb(a, toDelete),
    );

    if (isShared && toDelete.isNotEmpty) {
      final List<int> idsToRemove = sharedAssetsToRemove(toDelete, existing);
      if (idsToRemove.isNotEmpty) {
        await _db.writeTxn(() async {
          await _db.assets.deleteAll(idsToRemove);
          await _db.exifInfos.deleteAll(idsToRemove);
        });
      }
    } else {
      assert(toDelete.isEmpty);
    }
    return changes;
  }

  /// syncs albums from the server to the local database (does not support
  /// syncing changes from local back to server)
  /// accumulates
  Future<bool> _syncRemoteAlbum(
    AlbumResponseDto dto,
    RemoteAlbum album,
    List<Asset> deleteCandidates,
    List<Asset> existing,
    FutureOr<AlbumResponseDto> Function(AlbumResponseDto) loadDetails,
  ) async {
    if (!_hasAlbumResponseDtoChanged(dto, album)) {
      return false;
    }
    // loadDetails (/api/album/:id) will not include lastModifiedAssetTimestamp,
    // i.e. it will always be null. Save it here.
    final originalDto = dto;
    dto = await loadDetails(dto);
    if (dto.assetCount != dto.assets.length) {
      return false;
    }
    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.compareByOwnerChecksum);
    final (toAdd, toUpdate, toUnlink) = diffAssets(
      assetsOnRemote,
      assetsInDb,
      compare: Asset.compareByOwnerChecksum,
    );

    // update shared users
    final List<User> sharedUsers = album.sharedUsers.toList(growable: false);
    sharedUsers.sort((a, b) => a.id.compareTo(b.id));
    dto.sharedUsers.sort((a, b) => a.id.compareTo(b.id));
    final List<String> userIdsToAdd = [];
    final List<User> usersToUnlink = [];
    diffSortedListsSync(
      dto.sharedUsers,
      sharedUsers,
      compare: (UserResponseDto a, User b) => a.id.compareTo(b.id),
      both: (a, b) => false,
      onlyFirst: (UserResponseDto a) => userIdsToAdd.add(a.id),
      onlySecond: (User a) => usersToUnlink.add(a),
    );

    // for shared album: put missing album assets into local DB
    final (existingInDb, updated) = await _linkWithExistingFromDb(toAdd);
    await upsertAssetsWithExif(updated);
    final assetsToLink = existingInDb + updated;
    final usersToLink = (await _db.users.getAllById(userIdsToAdd)).cast<User>();

    album.name = dto.albumName;
    album.shared = dto.shared;
    album.modifiedAt = dto.updatedAt;
    album.lastModifiedAssetTimestamp = originalDto.lastModifiedAssetTimestamp;
    if (album.thumbnail?.remoteId != dto.albumThumbnailAssetId) {
      album.thumb.value = await _db.assets
          .where()
          .remoteIdEqualTo(dto.albumThumbnailAssetId)
          .findFirst();
    }

    // write & commit all changes to DB
    try {
      await _db.writeTxn(() async {
        await _db.assets.putAll(toUpdate);
        await album.thumb.save();
        await album.sharedUsers
            .update(link: usersToLink, unlink: usersToUnlink);
        await album.assets.update(link: assetsToLink, unlink: toUnlink.cast());
        await _db.remoteAlbums.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);
    }

    if (album.shared || dto.shared) {
      final userId = Store.get(StoreKey.currentUser).isarId;
      final foreign =
          await album.assets.filter().not().ownerIdEqualTo(userId).findAll();
      existing.addAll(foreign);

      // delete assets in DB unless they belong to this user or part of some other shared album
      deleteCandidates.addAll(toUnlink.where((a) => a.ownerId != userId));
    }

    return true;
  }

  /// Adds a remote album to the database while making sure to add any foreign
  /// (shared) assets to the database beforehand
  /// accumulates assets already existing in the database
  Future<void> _addAlbumFromServer(
    AlbumResponseDto dto,
    List<Asset> existing,
    FutureOr<AlbumResponseDto> Function(AlbumResponseDto) loadDetails,
  ) async {
    if (dto.assetCount != dto.assets.length) {
      dto = await loadDetails(dto);
    }
    if (dto.assetCount == dto.assets.length) {
      // in case an album contains assets not yet present in local DB:
      // put missing album assets into local DB
      final (existingInDb, updated) =
          await _linkWithExistingFromDb(dto.getAssets());
      existing.addAll(existingInDb);
      await upsertAssetsWithExif(updated);

      final RemoteAlbum a = await RemoteAlbum.fromDto(dto, _db);
      await _db.writeTxn(() => _db.remoteAlbums.store(a));
    } else {
      _log.warning(
          "Failed to add album from server: assetCount ${dto.assetCount} != "
          "asset array length ${dto.assets.length} for album ${dto.albumName}");
    }
  }

  /// Accumulates all suitable album assets to the `deleteCandidates` and
  /// removes the album from the database.
  Future<void> _removeAlbumFromDb(
    RemoteAlbum album,
    List<Asset> deleteCandidates,
  ) async {
    if (album.shared) {
      final User user = Store.get(StoreKey.currentUser);
      // delete assets in DB unless they belong to this user or are part of some other shared album or belong to a partner
      final userIds = await _db.users
          .filter()
          .isPartnerSharedWithEqualTo(true)
          .isarIdProperty()
          .findAll();
      userIds.add(user.isarId);
      final orphanedAssets = await album.assets
          .filter()
          .not()
          .anyOf(userIds, (q, int id) => q.ownerIdEqualTo(id))
          .findAll();
      deleteCandidates.addAll(orphanedAssets);
    }
    try {
      final bool ok =
          await _db.writeTxn(() => _db.remoteAlbums.delete(album.isarId));
      assert(ok);
      _log.info("Removed local album $album from DB");
    } catch (e) {
      _log.severe("Failed to remove local album $album from DB", e);
    }
  }

  /// Returns a tuple (existing, updated)
  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.getAllByOwnerIdChecksum(
      assets.map((a) => a.ownerId).toInt64List(),
      assets.map((a) => a.checksum).toList(growable: false),
    );
    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);
  }

  /// Inserts or updates the assets in the database with their ExifInfo (if any)
  Future<void> upsertAssetsWithExif(List<Asset> assets) async {
    if (assets.isEmpty) {
      return;
    }
    final exifInfos = assets.map((e) => e.exifInfo).whereNotNull().toList();
    try {
      await _db.writeTxn(() async {
        await _db.assets.putAll(assets);
        for (final Asset added in assets) {
          added.exifInfo?.id = added.id;
        }
        await _db.exifInfos.putAll(exifInfos);
      });
      _log.info("Upserted ${assets.length} assets into the DB");
    } on IsarError catch (e) {
      _log.severe("Failed to upsert ${assets.length} assets into the DB", e);
      // give details on the errors
      assets.sort(Asset.compareByOwnerChecksum);
      final inDb = await _db.assets.getAllByOwnerIdChecksum(
        assets.map((e) => e.ownerId).toInt64List(),
        assets.map((e) => e.checksum).toList(growable: false),
      );
      for (int i = 0; i < assets.length; i++) {
        final Asset a = assets[i];
        final Asset? b = inDb[i];
        if (b == null) {
          if (a.id != Isar.autoIncrement) {
            _log.warning(
              "Trying to update an asset that does not exist in DB:\n$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]}",
          );
        }
      }
    }
  }

  /// Returns a triple(toAdd, toUpdate, toRemove)
  (List<Asset> toAdd, List<Asset> toUpdate, List<Asset> toRemove) diffAssets(
    List<Asset> assets,
    List<Asset> inDb, {
    bool? remote,
    int Function(Asset, Asset) compare = Asset.compareByChecksum,
  }) {
    // fast paths for trivial cases: reduces memory usage during initial sync etc.
    if (assets.isEmpty && inDb.isEmpty) {
      return const ([], [], []);
    } else if (assets.isEmpty && remote == null) {
      // remove all from database
      return (const [], const [], inDb);
    } else if (inDb.isEmpty) {
      // add all assets
      return (assets, const [], const []);
    }

    final List<Asset> toAdd = [];
    final List<Asset> toUpdate = [];
    final List<Asset> toRemove = [];
    diffSortedListsSync(
      inDb,
      assets,
      compare: compare,
      both: (Asset a, Asset b) {
        if (a.canUpdate(b)) {
          toUpdate.add(a.updatedCopy(b));
          return true;
        }
        return false;
      },
      onlyFirst: (Asset a) {
        if (remote == true && a.isLocal) {
          if (a.remoteId != null) {
            a.remoteId = null;
            toUpdate.add(a);
          }
        } else if (remote == false && a.isRemote) {
          if (a.isLocal) {
            a.localId = null;
            toUpdate.add(a);
          }
        } else {
          toRemove.add(a);
        }
      },
      onlySecond: (Asset b) => toAdd.add(b),
    );
    return (toAdd, toUpdate, toRemove);
  }

  /// returns `true` if the albums differ on the surface
  bool _hasAlbumResponseDtoChanged(AlbumResponseDto dto, RemoteAlbum a) {
    return dto.assetCount != a.assetCount ||
        dto.albumName != a.name ||
        dto.albumThumbnailAssetId != a.thumbnail?.remoteId ||
        dto.shared != a.shared ||
        dto.sharedUsers.length != a.sharedUsers.length ||
        !dto.updatedAt.isAtSameMomentAs(a.modifiedAt) ||
        (dto.lastModifiedAssetTimestamp == null &&
            a.lastModifiedAssetTimestamp != null) ||
        (dto.lastModifiedAssetTimestamp != null &&
            a.lastModifiedAssetTimestamp == null) ||
        (dto.lastModifiedAssetTimestamp != null &&
            a.lastModifiedAssetTimestamp != null &&
            !dto.lastModifiedAssetTimestamp!
                .isAtSameMomentAs(a.lastModifiedAssetTimestamp!));
  }
}