minstrel/flutter_client/lib/cache/db.dart

// Drift database for Minstrel's offline cache (#357 plan B).
//
// Two cache layers in one database:
//   - Metadata cache (CachedArtists, CachedAlbums, CachedTracks,
//     CachedLikes, CachedPlaylists, CachedPlaylistTracks) — populated
//     by SyncController via /api/library/sync
//   - Audio cache index (AudioCacheIndex) — owned by AudioCacheManager
//
// Plus SyncMetadata holding the latest sync cursor.
//
// All entity ids are TEXT (server-side UUIDs serialized as strings).
// build_runner generates db.g.dart from this file; it's gitignored and
// regenerated in CI.

import 'package:drift/drift.dart';
import 'package:drift_flutter/drift_flutter.dart';

part 'db.g.dart';

class CachedArtists extends Table {
  TextColumn get id => text()();
  TextColumn get name => text()();
  TextColumn get sortName => text()();
  TextColumn get mbid => text().nullable()();
  TextColumn get artistThumbPath => text().nullable()();
  TextColumn get artistFanartPath => text().nullable()();
  DateTimeColumn get fetchedAt => dateTime().withDefault(currentDateAndTime)();
  @override
  Set<Column> get primaryKey => {id};
}

class CachedAlbums extends Table {
  TextColumn get id => text()();
  TextColumn get artistId => text()();
  TextColumn get title => text()();
  TextColumn get sortTitle => text()();
  TextColumn get releaseDate => text().nullable()();
  TextColumn get coverPath => text().nullable()();
  TextColumn get mbid => text().nullable()();
  DateTimeColumn get fetchedAt => dateTime().withDefault(currentDateAndTime)();
  @override
  Set<Column> get primaryKey => {id};
}

class CachedTracks extends Table {
  TextColumn get id => text()();
  TextColumn get albumId => text()();
  TextColumn get artistId => text()();
  TextColumn get title => text()();
  IntColumn get durationMs => integer().withDefault(const Constant(0))();
  IntColumn get trackNumber => integer().nullable()();
  IntColumn get discNumber => integer().nullable()();
  TextColumn get filePath => text().nullable()();
  TextColumn get fileFormat => text().nullable()();
  TextColumn get genre => text().nullable()();
  DateTimeColumn get fetchedAt => dateTime().withDefault(currentDateAndTime)();
  @override
  Set<Column> get primaryKey => {id};
}

class CachedLikes extends Table {
  TextColumn get userId => text()();
  TextColumn get entityType => text()(); // 'track' | 'album' | 'artist'
  TextColumn get entityId => text()();
  DateTimeColumn get likedAt => dateTime().withDefault(currentDateAndTime)();
  @override
  Set<Column> get primaryKey => {userId, entityType, entityId};
}

class CachedPlaylists extends Table {
  TextColumn get id => text()();
  TextColumn get userId => text()();
  TextColumn get name => text()();
  TextColumn get description => text().withDefault(const Constant(''))();
  BoolColumn get isPublic => boolean().withDefault(const Constant(false))();
  TextColumn get coverPath => text().nullable()();
  IntColumn get trackCount => integer().withDefault(const Constant(0))();
  IntColumn get durationSec => integer().withDefault(const Constant(0))();
  /// Server's system_variant: null for user playlists, "for_you" /
  /// "songs_like_artist" / "discover" for system-generated mixes.
  /// Added in schemaVersion 2 to let the add-to-playlist sheet filter
  /// out system playlists locally without a REST round-trip.
  TextColumn get systemVariant => text().nullable()();
  DateTimeColumn get fetchedAt => dateTime().withDefault(currentDateAndTime)();
  @override
  Set<Column> get primaryKey => {id};
}

class CachedPlaylistTracks extends Table {
  TextColumn get playlistId => text()();
  TextColumn get trackId => text()();
  IntColumn get position => integer().withDefault(const Constant(0))();
  @override
  Set<Column> get primaryKey => {playlistId, trackId};
}

/// One row per fully-downloaded audio file. `source` drives tiered LRU
/// eviction; `incidental` evicts first, `manual` last.
class AudioCacheIndex extends Table {
  TextColumn get trackId => text()();
  TextColumn get path => text()();
  IntColumn get sizeBytes => integer()();
  DateTimeColumn get cachedAt => dateTime().withDefault(currentDateAndTime)();
  TextColumn get source => textEnum<CacheSource>()();
  @override
  Set<Column> get primaryKey => {trackId};
}

/// Single-row table holding the latest sync cursor.
class SyncMetadata extends Table {
  IntColumn get id => integer().withDefault(const Constant(1))();
  IntColumn get cursor => integer().withDefault(const Constant(0))();
  DateTimeColumn get lastSyncAt => dateTime().nullable()();
  @override
  Set<Column> get primaryKey => {id};
}

/// Single-row cache of the /api/home response (#357 follow-up). The
/// home screen is the first thing the user sees on app open; storing
/// the last successful HomeData as JSON lets us yield it immediately
/// before the REST round-trip resolves, eliminating the cold-start
/// blank on slow / remote connections. Schema 3+.
class CachedHomeSnapshot extends Table {
  IntColumn get id => integer().withDefault(const Constant(1))();
  TextColumn get json => text()();
  DateTimeColumn get updatedAt => dateTime().withDefault(currentDateAndTime)();
  @override
  Set<Column> get primaryKey => {id};
}

/// Single-row cache of the /api/me/history response. Mirrors the
/// CachedHomeSnapshot pattern: opening the History tab in the Library
/// screen yields the last-known page immediately while a fresh REST
/// pull lands underneath via SWR. Also makes basic offline scrollback
/// possible — the last fetched page survives both app restart and
/// loss of connectivity. Schema 4+.
class CachedHistorySnapshot extends Table {
  IntColumn get id => integer().withDefault(const Constant(1))();
  TextColumn get json => text()();
  DateTimeColumn get updatedAt => dateTime().withDefault(currentDateAndTime)();
  @override
  Set<Column> get primaryKey => {id};
}

enum CacheSource { manual, autoLiked, autoPlaylist, autoPrefetch, incidental }

@DriftDatabase(tables: [
  CachedArtists,
  CachedAlbums,
  CachedTracks,
  CachedLikes,
  CachedPlaylists,
  CachedPlaylistTracks,
  AudioCacheIndex,
  SyncMetadata,
  CachedHomeSnapshot,
  CachedHistorySnapshot,
])
class AppDb extends _$AppDb {
  AppDb([QueryExecutor? e]) : super(e ?? driftDatabase(name: 'minstrel_cache'));

  @override
  int get schemaVersion => 4;

  @override
  MigrationStrategy get migration => MigrationStrategy(
        onCreate: (m) => m.createAll(),
        onUpgrade: (m, from, to) async {
          if (from < 2) {
            // Schema 2: add CachedPlaylists.systemVariant. Existing
            // rows get null and the next sync rebuilds them with the
            // server's system_variant value.
            await m.addColumn(cachedPlaylists, cachedPlaylists.systemVariant);
            // Reset cursor so the next /api/library/sync re-emits all
            // playlists; otherwise the new column would stay null on
            // pre-existing rows until they happen to change server-side.
            await customStatement('UPDATE sync_metadata SET cursor = 0');
          }
          if (from < 3) {
            // Schema 3: cached_home_snapshot for #357 drift-first
            // home page. No existing rows to migrate — table starts
            // empty; the first /api/home fetch populates it.
            await m.createTable(cachedHomeSnapshot);
          }
          if (from < 4) {
            // Schema 4: cached_history_snapshot for drift-first
            // History tab. Same pattern as cached_home_snapshot —
            // empty on upgrade; first /api/me/history fetch populates.
            await m.createTable(cachedHistorySnapshot);
          }
        },
      );
}