feat(jellyfin): songs and their lyrics, read as subtitles are

A music library's artists and albums open as shows and seasons do, and
can be tied to a studyset. A song plays as sound alone (`/Audio/{id}/
stream`, as stored) with its lyrics as Jellyfin keeps them (`/Audio/{id}/
Lyrics`: an LRC file beside it, or its tags), cut into the dictionary's
words as a video's subtitles are, with no translation. Timed lyrics
follow the song: the line sung large and bright among the others faded,
scrolled to as it comes, a line tapped played from its start; untimed
ones show whole. A song without lyrics shows greyed and doesn't open
(`HasLyrics`), as there is nothing in it to read. Its cover stands where
the picture would, glowing as a video does, and its words are tagged
with the artist, shown, and "artist · title", hidden.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/test/feature/jellyfin/jellyfin_data_test.dart

@@ -2,6 +2,7 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_learn_flutter/src/core/video/subtitles.dart';
 import 'package:halkyon_learn_flutter/src/feature/jellyfin/bloc/watch_cubit.dart';
 import 'package:halkyon_learn_flutter/src/feature/jellyfin/data/jellyfin_gateway.dart';
 import 'package:halkyon_learn_flutter/src/feature/jellyfin/data/jellyfin_repository.dart';
@@ -56,10 +57,35 @@ MockClient jellyfin12(List<http.Request> requests) => MockClient((
           'CollectionType': 'tvshows',
           'ImageTags': <String, String>{},
         },
-        {'Name': 'Music', 'Id': 'lib-2', 'Type': 'MusicAlbum'},
+        {
+          'Name': 'Music',
+          'Id': 'lib-2',
+          'Type': 'CollectionFolder',
+          'CollectionType': 'music',
+        },
+        {'Name': 'A book', 'Id': 'book-1', 'Type': 'Book'},
       ],
       'TotalRecordCount': 2,
     }),
+    ('GET', '/Items/song-1') => json({
+      'Name': '幽霊船戦',
+      'Id': 'song-1',
+      'Type': 'Audio',
+      'AlbumArtist': '宝鐘マリン',
+      'Album': 'Ahoy!!',
+      'HasLyrics': true,
+      'IndexNumber': 3,
+      'ParentIndexNumber': 1,
+      'RunTimeTicks': 2000000000,
+      'ImageTags': {'Primary': 'a1'},
+    }),
+    ('GET', '/Audio/song-1/Lyrics') => json({
+      'Metadata': <String, Object?>{},
+      'Lyrics': [
+        {'Text': '海賊なら Yo-Ho!', 'Start': 68200000, 'Cues': <Object?>[]},
+        {'Text': 'さぁ今旗のもとへ', 'Start': 95800000, 'Cues': <Object?>[]},
+      ],
+    }),
     ('GET', '/Items/ep-1') => json({
       'Name': 'Sample Journey S01E01',
       'Id': 'ep-1',
@@ -204,7 +230,8 @@ void main() {
       },
     );
 
-    test('lists libraries, leaving out what is no video', () async {
+    test('lists libraries of videos and of music, leaving out what is '
+        'neither', () async {
       final account = await signIn();
 
       final libraries = await gateway.libraries(account);
@@ -215,6 +242,11 @@ void main() {
           name: 'Anime',
           kind: JellyfinItemKind.library,
         ),
+        const JellyfinItem(
+          id: 'lib-2',
+          name: 'Music',
+          kind: JellyfinItemKind.library,
+        ),
       ]);
       expect(requests.last.headers['Authorization'], contains('Token="t-1"'));
       expect(requests.last.url.queryParameters['userId'], 'u-1');
@@ -286,6 +318,38 @@ void main() {
       );
     });
 
+    test('a song is one, with its artist and whether it has lyrics, its '
+        'lyrics timed line by line, none for a song without; a song streams '
+        'as sound', () async {
+      final account = await signIn();
+
+      final song = await gateway.item(account, 'song-1');
+      expect(song.kind, JellyfinItemKind.audio);
+      expect(song.artist, '宝鐘マリン');
+      expect(song.hasLyrics, isTrue);
+      expect(song.seasonNumber, isNull);
+      expect(await gateway.lyrics(account, 'song-1'), [
+        (text: '海賊なら Yo-Ho!', start: const Duration(milliseconds: 6820)),
+        (text: 'さぁ今旗のもとへ', start: const Duration(milliseconds: 9580)),
+      ]);
+      expect(await gateway.lyrics(account, 'song-2'), isEmpty);
+      expect(
+        gateway
+            .streamOf(
+              account,
+              const JellyfinPlayback(
+                itemId: 'song-1',
+                mediaSourceId: 'song-1',
+                playSessionId: 'ps-2',
+                subtitles: [],
+                audioOnly: true,
+              ),
+            )
+            .path,
+        '/Audio/song-1/stream',
+      );
+    });
+
     test('a token the server no longer takes is signed out; nothing '
         'answering is unreachable', () async {
       final server = await gateway.server(
@@ -342,6 +406,44 @@ void main() {
   });
 
   group('JellyfinRepository', () {
+    test("a song's lyrics are lines, each until the next, the last until "
+        'the song ends; empty ones left out; untimed lyrics are text '
+        'alone', () async {
+      JellyfinRepository with_(List<({String text, Duration? start})> lines) =>
+          JellyfinRepository(
+            (_) => FakeJellyfinGateway(lyricsOf: {'song-1': lines}),
+            signedInJellyfin(),
+            deviceName: 'Test',
+            appVersion: '1',
+          );
+
+      final timed = await with_(const [
+        (text: '一', start: Duration(seconds: 1)),
+        (text: ' ', start: Duration(seconds: 4)),
+        (text: '二', start: Duration(seconds: 6)),
+      ]).lyrics('song-1', runTime: const Duration(minutes: 3));
+      expect(timed.synced, isTrue);
+      expect(timed.lines, const [
+        SubtitleCue(
+          start: Duration(seconds: 1),
+          end: Duration(seconds: 6),
+          text: '一',
+        ),
+        SubtitleCue(
+          start: Duration(seconds: 6),
+          end: Duration(minutes: 3),
+          text: '二',
+        ),
+      ]);
+
+      final untimed = await with_(const [
+        (text: '一', start: null),
+        (text: '二', start: null),
+      ]).lyrics('song-1');
+      expect(untimed.synced, isFalse);
+      expect([for (final line in untimed.lines) line.text], ['一', '二']);
+    });
+
     test('an address is reached over HTTPS only, plain HTTP refused '
         'before anything is sent', () async {
       final asked = <Uri>[];