Melo/lib/library/category_list.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import '../settings/app_settings.dart';
import '../shared/cover.dart';
import 'categories.dart';
import 'category_service.dart';
import 'database.dart';
import 'song_list.dart';

/// Bibliotheks-Reiter „Kategorie": alle Kategorien der Bibliothek.
///
/// Ersetzt den früheren Alben-Reiter — der Album-Titel eines Liedes **ist**
/// in Melo seine Kategorie (siehe [kategorienAusTags]). Wer seine Sammlung
/// über das Album-Feld sortiert hat, findet sie hier unverändert wieder.
class CategoryListScreen extends StatelessWidget {
  const CategoryListScreen({super.key});

  @override
  Widget build(BuildContext context) {
    final db = context.read<MeloDb>();
    final categories = context.watch<CategoryService>();
    final settings = context.watch<AppSettings>();

    return StreamBuilder<List<Song>>(
      stream: db.watchSongs(),
      builder: (context, snapshot) {
        final songs = snapshot.data ?? const <Song>[];
        if (songs.isEmpty) {
          return const Center(
            child: Text('Keine Kategorien',
                style: TextStyle(color: Colors.white54)),
          );
        }
        final grouped = groupByCategory(
          songs,
          {for (final s in songs) s.id: categories.of(s.id)},
        );
        final namen = grouped.keys.toList();
        return ListView.builder(
          itemCount: namen.length,
          itemBuilder: (context, i) {
            final name = namen[i];
            final lieder = grouped[name]!;
            final cover = categories.coverFor(lieder.first,
                groupByCategory: settings.groupCoversByCategory);
            return ListTile(
              leading: CoverImage(
                artUri: cover != null ? Uri.file(cover) : null,
                size: 48,
                radius: 6,
              ),
              title: Text(name, maxLines: 1, overflow: TextOverflow.ellipsis),
              subtitle: Text('${lieder.length} Lieder'),
              onTap: () => Navigator.push(
                context,
                MaterialPageRoute(
                  builder: (_) =>
                      _KategorieLiederScreen(name: name, songs: lieder),
                ),
              ),
            );
          },
        );
      },
    );
  }
}

/// Zeigt alle Lieder einer Kategorie.
class _KategorieLiederScreen extends StatelessWidget {
  const _KategorieLiederScreen({required this.name, required this.songs});
  final String name;
  final List<Song> songs;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(name)),
      body: SongList(songs),
    );
  }
}