feat(app): 剧场列表增加语种筛选

test/discover/discover_logic_test.dart

@@ -8,7 +8,8 @@ import 'package:fruitshorts/pages/discover/discover_logic.dart';
 
 import '../support/fake_watch_history.dart';
 
-Drama _drama(String id, {List<int> numbers = const [1, 2, 3]}) => Drama(
+Drama _drama(String id, {List<int> numbers = const [1, 2, 3], String language = ''}) => Drama(
+  language: language,
   id: id,
   title: id,
   synopsis: 'synopsis',
@@ -64,6 +65,36 @@ void main() {
     logic.dispose();
   });
 
+  test('should_filter_visible_dramas_when_language_is_selected', () {
+    final logic = DiscoverLogic(history: FakeWatchHistory(), drama: _drama('s'));
+    final dramas = [
+      _drama('zh', language: 'zh-CN'),
+      _drama('id', language: 'id'),
+      _drama('unknown'),
+    ];
+
+    expect(logic.visibleDramas(dramas), hasLength(3));
+
+    logic.selectLanguage('id');
+    expect(logic.visibleDramas(dramas).map((item) => item.id), ['id']);
+
+    logic.selectLanguage(null);
+    expect(logic.visibleDramas(dramas), hasLength(3));
+    logic.dispose();
+  });
+
+  test('should_list_distinct_languages_when_feed_has_cards', () {
+    final logic = DiscoverLogic(history: FakeWatchHistory(), drama: _drama('s'));
+    final dramas = [
+      _drama('zh', language: 'zh-CN'),
+      _drama('id', language: 'id'),
+      _drama('id2', language: 'id'),
+      _drama('unknown'),
+    ];
+
+    expect(logic.languagesOf(dramas), ['zh-CN', 'id']);
+    logic.dispose();
+  });
   test('should_have_no_resume_position_when_server_has_no_record', () async {
     final history = FakeWatchHistory();
     final logic = DiscoverLogic(