import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart' as p;
import '../models/song.dart';
import '../models/tag.dart';

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

  Database? _db;

  Future<Database> get db async {
    if (_db != null) return _db!;
    _db = await _init();
    return _db!;
  }

  Future<Database> _init() async {
    final pfad = await getDatabasesPath();
    return openDatabase(
      p.join(pfad, 'melo.db'),
      version: 1,
      onCreate: (db, version) async {
        await db.execute('''
          CREATE TABLE songs (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            titel TEXT NOT NULL,
            kuenstler TEXT NOT NULL,
            album TEXT DEFAULT '',
            dauer_sekunden INTEGER NOT NULL,
            datei_pfad TEXT NOT NULL UNIQUE,
            cover_pfad TEXT,
            groesse_bytes INTEGER DEFAULT 0,
            ist_heruntergeladen INTEGER DEFAULT 0,
            hinzugefuegt_am TEXT NOT NULL,
            download_quelle TEXT DEFAULT 'local',
            zuletzt_position INTEGER
          )
        ''');
        await db.execute('''
          CREATE TABLE tags (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            name TEXT NOT NULL UNIQUE,
            icon TEXT,
            farbe_hex TEXT
          )
        ''');
        await db.execute('''
          CREATE TABLE song_tags (
            song_id INTEGER NOT NULL,
            tag_id INTEGER NOT NULL,
            PRIMARY KEY (song_id, tag_id),
            FOREIGN KEY (song_id) REFERENCES songs(id) ON DELETE CASCADE,
            FOREIGN KEY (tag_id) REFERENCES tags(id) ON DELETE CASCADE
          )
        ''');
        await db.execute('''
          CREATE TABLE playlists (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            name TEXT NOT NULL,
            erstellt_am TEXT NOT NULL
          )
        ''');
        await db.execute('''
          CREATE TABLE playlist_songs (
            playlist_id INTEGER NOT NULL,
            song_id INTEGER NOT NULL,
            position INTEGER NOT NULL,
            PRIMARY KEY (playlist_id, song_id),
            FOREIGN KEY (playlist_id) REFERENCES playlists(id) ON DELETE CASCADE,
            FOREIGN KEY (song_id) REFERENCES songs(id) ON DELETE CASCADE
          )
        ''');
        await db.execute('''
          CREATE TABLE wiedergabe_verlauf (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            song_id INTEGER NOT NULL,
            position INTEGER DEFAULT 0,
            zuletzt_abgespielt TEXT NOT NULL,
            FOREIGN KEY (song_id) REFERENCES songs(id) ON DELETE CASCADE
          )
        ''');
      },
    );
  }

  // ─── Songs ──────────────────────────────────────

  Future<int> songEinfuegen(Song song) async {
    final d = await db;
    return d.insert('songs', song.toMap(),
      conflictAlgorithm: ConflictAlgorithm.ignore);
  }

  Future<void> songsEinfuegen(List<Song> songs) async {
    final d = await db;
    final batch = d.batch();
    for (final song in songs) {
      batch.insert('songs', song.toMap(),
        conflictAlgorithm: ConflictAlgorithm.ignore);
    }
    await batch.commit(noResult: true);
  }

  Future<List<Song>> alleSongs() async {
    final d = await db;
    final rows = await d.query('songs', orderBy: 'hinzugefuegt_am DESC');
    return rows.map((r) => Song.fromMap(r)).toList();
  }

  Future<Song?> songNachId(int id) async {
    final d = await db;
    final rows = await d.query('songs', where: 'id = ?', whereArgs: [id]);
    if (rows.isEmpty) return null;
    return Song.fromMap(rows.first);
  }

  Future<Song?> songNachPfad(String pfad) async {
    final d = await db;
    final rows = await d.query('songs', where: 'datei_pfad = ?', whereArgs: [pfad]);
    if (rows.isEmpty) return null;
    return Song.fromMap(rows.first);
  }

  Future<void> positionAktualisieren(int songId, int position) async {
    final d = await db;
    await d.update('songs', {'zuletzt_position': position},
      where: 'id = ?', whereArgs: [songId]);
    final rows = await d.update('wiedergabe_verlauf',
      {'position': position, 'zuletzt_abgespielt': DateTime.now().toIso8601String()},
      where: 'song_id = ?', whereArgs: [songId]);
    if (rows == 0) {
      await d.insert('wiedergabe_verlauf', {
        'song_id': songId,
        'position': position,
        'zuletzt_abgespielt': DateTime.now().toIso8601String(),
      });
    }
  }

  // ─── Tags ────────────────────────────────────────

  Future<int> tagErstellen(String name, {String? icon, String? farbe}) async {
    final d = await db;
    return d.insert('tags', {
      'name': name, 'icon': icon, 'farbe_hex': farbe,
    }, conflictAlgorithm: ConflictAlgorithm.ignore);
  }

  Future<List<Tag>> alleTags() async {
    final d = await db;
    final rows = await d.query('tags', orderBy: 'name');
    return rows.map((r) => Tag.fromMap(r)).toList();
  }

  Future<void> songTagHinzufuegen(int songId, int tagId) async {
    final d = await db;
    await d.insert('song_tags', {'song_id': songId, 'tag_id': tagId},
      conflictAlgorithm: ConflictAlgorithm.ignore);
  }

  Future<List<Tag>> tagsFuerSong(int songId) async {
    final d = await db;
    final rows = await d.rawQuery('''
      SELECT t.* FROM tags t
      JOIN song_tags st ON t.id = st.tag_id
      WHERE st.song_id = ?
    ''', [songId]);
    return rows.map((r) => Tag.fromMap(r)).toList();
  }

  // ─── Playlists ───────────────────────────────────

  Future<int> playlistErstellen(String name) async {
    final d = await db;
    return d.insert('playlists', {
      'name': name,
      'erstellt_am': DateTime.now().toIso8601String(),
    });
  }

  Future<void> songZurPlaylist(int playlistId, int songId, int position) async {
    final d = await db;
    await d.insert('playlist_songs', {
      'playlist_id': playlistId,
      'song_id': songId,
      'position': position,
    });
  }

  Future<List<Map<String, dynamic>>> allePlaylists() async {
    final d = await db;
    return d.query('playlists', orderBy: 'erstellt_am DESC');
  }

  Future<void> songAusPlaylistEntfernen(int playlistId, int songId) async {
    final d = await db;
    await d.delete('playlist_songs',
      where: 'playlist_id = ? AND song_id = ?',
      whereArgs: [playlistId, songId]);
  }

  Future<void> metadatenAktualisieren(int songId, {String? titel, String? kuenstler, String? album}) async {
    final d = await db;
    final update = <String, dynamic>{};
    if (titel != null) update['titel'] = titel;
    if (kuenstler != null) update['kuenstler'] = kuenstler;
    if (album != null) update['album'] = album;
    if (update.isNotEmpty) {
      await d.update('songs', update, where: 'id = ?', whereArgs: [songId]);
    }
  }

  Future<List<Song>> songsDerPlaylist(int playlistId) async {
    final d = await db;
    final rows = await d.rawQuery('''
      SELECT s.* FROM songs s
      JOIN playlist_songs ps ON s.id = ps.song_id
      WHERE ps.playlist_id = ?
      ORDER BY ps.position
    ''', [playlistId]);
    return rows.map((r) => Song.fromMap(r)).toList();
  }

  Future<void> loeschen() async {
    final d = await db;
    await d.transaction((txn) async {
      await txn.delete('wiedergabe_verlauf');
      await txn.delete('song_tags');
      await txn.delete('playlist_songs');
      await txn.delete('playlists');
      await txn.delete('tags');
      await txn.delete('songs');
    });
  }
}