import 'package:flutter/foundation.dart';
import '../database/db_helper.dart';
import '../models/song.dart';
import 'melo_logger.dart';

class FavoritenService {
  static final FavoritenService _instanz = FavoritenService._();
  factory FavoritenService() => _instanz;
  FavoritenService._();

  final DbHelper _db = DbHelper();
  int? _favoritenPlaylistId;

  int? get favoritenId => _favoritenPlaylistId;

  Future<void> init() async {
    final playlists = await _db.allePlaylists();
    final vorhanden = playlists.where((p) => p['name'] == '⭐ Favoriten').toList();
    if (vorhanden.isNotEmpty) {
      _favoritenPlaylistId = vorhanden.first['id'] as int;
    } else {
      _favoritenPlaylistId = await _db.playlistErstellen('⭐ Favoriten');
    }
  }

  Future<bool> istFavorit(int songId) async {
    if (_favoritenPlaylistId == null) return false;
    final songs = await _db.songsDerPlaylist(_favoritenPlaylistId!);
    return songs.any((s) => s.id == songId);
  }

  /// Schaltet den Favoriten-Status um und gibt den NEUEN Status zurück
  /// (true = jetzt Favorit). Bei Fehlern (z. B. DB-Race) wird der Zustand
  /// aus der DB neu geladen statt blind geflippt — kein unhandled Throw.
  Future<bool> umschalten(int songId) async {
    if (_favoritenPlaylistId == null) return false;
    try {
      if (await istFavorit(songId)) {
        await _db.songAusPlaylistEntfernen(_favoritenPlaylistId!, songId);
        return false;
      } else {
        final songs = await _db.songsDerPlaylist(_favoritenPlaylistId!);
        // INSERT OR IGNORE in songZurPlaylist fängt Doppel-Tap-Races ab
        await _db.songZurPlaylist(_favoritenPlaylistId!, songId, songs.length);
        return true;
      }
    } catch (e) {
      debugPrint('Favoriten-Toggle fehlgeschlagen: $e');
      MeloLogger().fehler('favoriten_toggle', e);
      // Zustand nach Fehler aus der DB synchronisieren (Quelle der Wahrheit)
      return istFavorit(songId);
    }
  }

  Future<List<Song>> alleFavoriten() async {
    if (_favoritenPlaylistId == null) return [];
    return _db.songsDerPlaylist(_favoritenPlaylistId!);
  }

  Future<int> anzahlFavoriten() async {
    if (_favoritenPlaylistId == null) await init();
    if (_favoritenPlaylistId == null) return 0;
    final songs = await _db.songsDerPlaylist(_favoritenPlaylistId!);
    return songs.length;
  }

  Future<Set<int>> favoritenIds() async {
    if (_favoritenPlaylistId == null) return {};
    final d = await _db.db;
    final rows = await d.rawQuery(
      'SELECT song_id FROM playlist_songs WHERE playlist_id = ?',
      [_favoritenPlaylistId],
    );
    return rows.map((r) => r['song_id'] as int).toSet();
  }
}