feat(channels): label All-feed posts with a topic chip

lib/channels/topic_chat_view.dart

@@ -42,6 +42,7 @@ import '../theme/theme_controller.dart';
 import 'forum_topic_fields.dart';
 import 'topic_list_actions.dart';
 import 'topic_list_host.dart';
+import 'topic_list_row.dart';
 import 'topic_navigation.dart';
 import 'topic_post_content.dart';
 
@@ -2003,6 +2004,8 @@ class _TopicChatViewState extends State<TopicChatView> {
               chatId: widget.chat.id,
               post: post,
               sender: _senderCache[post.message.senderId],
+              showTopicChip: _selectedThreadId == null,
+              onOpenTopic: () => _selectTopic(post.topic.id),
               onLike: () => _addReaction(post, '❤️'),
               onPickReaction: () => _showReactionPicker(post),
               onComments: () => _openComments(post),
@@ -2080,6 +2083,8 @@ class _TopicPostRow extends StatelessWidget {
     required this.onPickReaction,
     required this.onComments,
     required this.onShare,
+    this.showTopicChip = false,
+    this.onOpenTopic,
     this.sender,
   });
 
@@ -2091,6 +2096,12 @@ class _TopicPostRow extends StatelessWidget {
   final VoidCallback onComments;
   final VoidCallback onShare;
 
+  /// The aggregated "All" feed labels every post with its topic; a single
+  /// topic's feed already names itself in the header, so the chip is
+  /// redundant there.
+  final bool showTopicChip;
+  final VoidCallback? onOpenTopic;
+
   @override
   Widget build(BuildContext context) {
     final c = context.colors;
@@ -2105,6 +2116,10 @@ class _TopicPostRow extends StatelessWidget {
       child: Column(
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
+          if (showTopicChip) ...[
+            _TopicChip(topic: post.topic, onOpen: onOpenTopic),
+            const SizedBox(height: 10),
+          ],
           Row(
             children: [
               PhotoAvatar(title: name, photo: sender?.photo, size: 48),
@@ -2171,6 +2186,59 @@ class _TopicPostRow extends StatelessWidget {
       post.message.buttonRows.isNotEmpty;
 }
 
+/// Topic label above a post in the aggregated feed: a 20px `TopicIconSurface`
+/// (custom emoji or tinted hashtag tile), 6px gap, single-line 14px w600 topic
+/// name tinted with `topic.iconColor ?? AppTheme.avatarColor(topic.name)`, and
+/// an optional 12px `HeroAppIcons.lock` (`c.textTertiary`, 4px gap) for closed
+/// topics. Tapping it routes through `_selectTopic(post.topic.id)`.
+class _TopicChip extends StatelessWidget {
+  const _TopicChip({required this.topic, this.onOpen});
+
+  final _ForumTopic topic;
+  final VoidCallback? onOpen;
+
+  @override
+  Widget build(BuildContext context) {
+    final c = context.colors;
+    final tint = topic.iconColor ?? AppTheme.avatarColor(topic.name);
+    return GestureDetector(
+      key: ValueKey('topic-post-chip-${topic.id}'),
+      behavior: HitTestBehavior.opaque,
+      onTap: onOpen,
+      child: Padding(
+        padding: const EdgeInsets.symmetric(vertical: 2),
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            TopicIconSurface(
+              size: 20,
+              iconCustomEmojiId: topic.iconCustomEmojiId,
+              tint: tint,
+            ),
+            const SizedBox(width: 6),
+            Flexible(
+              child: Text(
+                topic.name,
+                maxLines: 1,
+                overflow: TextOverflow.ellipsis,
+                style: TextStyle(
+                  fontSize: 14,
+                  fontWeight: FontWeight.w600,
+                  color: tint,
+                ),
+              ),
+            ),
+            if (topic.isClosed) ...[
+              const SizedBox(width: 4),
+              AppIcon(HeroAppIcons.lock, size: 12, color: c.textTertiary),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}
+
 class _PostActions extends StatelessWidget {
   const _PostActions({
     required this.message,

test/topic_post_topic_chip_test.dart

@@ -0,0 +1,202 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mithka/channels/topic_chat_view.dart';
+import 'package:mithka/l10n/app_localizations.dart';
+import 'package:mithka/tdlib/td_models.dart';
+import 'package:mithka/theme/theme_controller.dart';
+import 'package:provider/provider.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  testWidgets('the aggregated feed labels every post with its topic chip', (
+    tester,
+  ) async {
+    tester.view.physicalSize = const Size(400, 2400);
+    tester.view.devicePixelRatio = 1.0;
+    addTearDown(tester.view.reset);
+    SharedPreferences.setMockInitialValues({});
+    final preferences = await SharedPreferences.getInstance();
+    final theme = ThemeController(preferences);
+    addTearDown(theme.dispose);
+    final requests = <Map<String, dynamic>>[];
+    final chat = ChatSummary(
+      id: -10042,
+      title: 'Forum',
+      lastMessage: 'Latest',
+      lastMessageId: 90,
+      date: 90,
+      unreadCount: 0,
+      order: 1,
+      isMuted: false,
+      isForum: true,
+    );
+
+    await tester.pumpWidget(
+      ChangeNotifierProvider<ThemeController>.value(
+        value: theme,
+        child: MaterialApp(
+          locale: const Locale('en'),
+          localizationsDelegates: const [AppLocalizations.delegate],
+          supportedLocales: AppLocalizations.supportedLocales,
+          home: TopicChatView(
+            chat: chat,
+            showBackButton: false,
+            query: (request) async {
+              requests.add(Map<String, dynamic>.from(request));
+              return switch (request['@type']) {
+                'getForumTopics' => _forumTopicsResponse(),
+                'getForumTopicHistory' => _historyResponse(
+                  int.parse((request['forum_topic_id'] as num).toString()),
+                ),
+                _ => {
+                  '@type': 'messages',
+                  'messages': const <Map<String, dynamic>>[],
+                },
+              };
+            },
+          ),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    // Both posts carry their topic's name in a chip in the "All" feed.
+    // Each topic's stubbed history holds two messages, so each chip
+    // renders twice.
+    expect(find.byKey(const ValueKey('topic-post-chip-1')), findsNWidgets(2));
+    expect(find.byKey(const ValueKey('topic-post-chip-2')), findsNWidgets(2));
+    expect(
+      find.text('Post in General 101', findRichText: true),
+      findsOneWidget,
+    );
+    expect(find.text('Post in Design 201', findRichText: true), findsOneWidget);
+
+    // Tapping a post's chip opens that topic: the chip disappears because
+    // the feed becomes topic-scoped.
+    await tester.tap(find.byKey(const ValueKey('topic-post-chip-2')).first);
+    await tester.pumpAndSettle();
+    expect(find.byKey(const ValueKey('topic-post-chip-1')), findsNothing);
+    expect(find.byKey(const ValueKey('topic-post-chip-2')), findsNothing);
+    expect(find.text('Post in Design 201', findRichText: true), findsOneWidget);
+    // Topic 2's messages were already cached by the All-feed preview, so
+    // the only topic-2 history request is that initial limit-6 probe; the
+    // scoping itself is asserted by the chips disappearing above.
+    expect(
+      requests.where((request) => request['@type'] == 'getForumTopicHistory'),
+      contains(
+        equals({
+          '@type': 'getForumTopicHistory',
+          'chat_id': -10042,
+          'forum_topic_id': 2,
+          'from_message_id': 0,
+          'offset': 0,
+          'limit': 6,
+        }),
+      ),
+    );
+    expect(tester.takeException(), isNull);
+  });
+
+  testWidgets('a topic-scoped feed does not label its posts', (tester) async {
+    SharedPreferences.setMockInitialValues({});
+    final preferences = await SharedPreferences.getInstance();
+    final theme = ThemeController(preferences);
+    addTearDown(theme.dispose);
+    final chat = ChatSummary(
+      id: -10042,
+      title: 'Forum',
+      lastMessage: 'Latest',
+      lastMessageId: 90,
+      date: 90,
+      unreadCount: 0,
+      order: 1,
+      isMuted: false,
+      isForum: true,
+    );
+
+    await tester.pumpWidget(
+      ChangeNotifierProvider<ThemeController>.value(
+        value: theme,
+        child: MaterialApp(
+          locale: const Locale('en'),
+          localizationsDelegates: const [AppLocalizations.delegate],
+          supportedLocales: AppLocalizations.supportedLocales,
+          home: TopicChatView(
+            chat: chat,
+            initialThreadId: 2,
+            showBackButton: false,
+            query: (request) async {
+              return switch (request['@type']) {
+                'getForumTopics' => _forumTopicsResponse(),
+                'getForumTopicHistory' => _historyResponse(2),
+                _ => {
+                  '@type': 'messages',
+                  'messages': const <Map<String, dynamic>>[],
+                },
+              };
+            },
+          ),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    expect(find.byKey(const ValueKey('topic-post-chip-2')), findsNothing);
+    expect(find.text('Design'), findsWidgets);
+    expect(tester.takeException(), isNull);
+  });
+}
+
+Map<String, dynamic> _forumTopicsResponse() => {
+  '@type': 'forumTopics',
+  'topics': [
+    _topic(1, 'General', 20, color: 1),
+    _topic(2, 'Design', 40, color: 2),
+  ],
+};
+
+Map<String, dynamic> _topic(
+  int id,
+  String name,
+  int lastMessageDate, {
+  int? color,
+}) => {
+  '@type': 'forumTopic',
+  'info': {
+    '@type': 'forumTopicInfo',
+    'forum_topic_id': id,
+    'name': name,
+    if (color != null) 'icon': {'@type': 'chatTheme', 'color': color},
+  },
+  'unread_count': 0,
+  'order': -lastMessageDate,
+  'last_message': _message(id * 100, lastMessageDate, topic: name),
+};
+
+Map<String, dynamic> _historyResponse(int topicId) => {
+  '@type': 'messages',
+  'messages': [
+    _message(
+      topicId * 100 + 1,
+      topicId * 10 + 1,
+      topic: topicId == 1 ? 'General' : 'Design',
+    ),
+    _message(
+      topicId * 100 + 2,
+      topicId * 10 + 2,
+      topic: topicId == 1 ? 'General' : 'Design',
+    ),
+  ],
+};
+
+Map<String, dynamic> _message(int id, int date, {required String topic}) => {
+  '@type': 'message',
+  'id': id,
+  'chat_id': -10042,
+  'date': date,
+  'is_outgoing': false,
+  'content': {
+    '@type': 'messageText',
+    'text': {'@type': 'formattedText', 'text': 'Post in $topic $id'},
+  },
+};