[BOT-1264] fix(mobile): #channel tags not tappable (#1695)

Signed-off-by: npub1shglkdhngx3hrnhf4gf8vhpqdrmeludctechdvpwd3988zzs7ncq2cmtxu <85d1fb36f341a371cee9aa12765c2068f79ff1b85e7176b02e6c4a738850f4f0@sprout-oss.stage.blox.sqprod.co>
Co-authored-by: npub1shglkdhngx3hrnhf4gf8vhpqdrmeludctechdvpwd3988zzs7ncq2cmtxu <85d1fb36f341a371cee9aa12765c2068f79ff1b85e7176b02e6c4a738850f4f0@sprout-oss.stage.blox.sqprod.co>

mobile/lib/features/channels/channel_detail_page.dart

@@ -15,6 +15,7 @@ import '../profile/user_cache_provider.dart';
 import '../profile/user_profile.dart';
 import '../forum/forum_posts_view.dart';
 import 'channel.dart';
+import 'channel_link_navigation.dart';
 import 'agent_activity/working_bots_provider.dart';
 import 'channel_management_provider.dart';
 import 'channel_messages_provider.dart';

mobile/lib/features/channels/channel_detail_page/message_bubble.dart

@@ -115,24 +115,11 @@ class _MessageBubble extends ConsumerWidget {
                     channelNames: channelNames,
                     tags: message.tags,
                     onChannelTap: (channelId) {
-                      if (channelId == currentChannelId) return;
-                      final channelsAsync = ref.read(channelsProvider);
-                      final channels = channelsAsync.hasValue
-                          ? channelsAsync.value
-                          : null;
-                      Channel? targetChannel;
-                      for (final channel in channels ?? const <Channel>[]) {
-                        if (channel.id == channelId) {
-                          targetChannel = channel;
-                          break;
-                        }
-                      }
-                      if (targetChannel == null) return;
-                      Navigator.of(context).push(
-                        MaterialPageRoute<void>(
-                          builder: (_) =>
-                              ChannelDetailPage(channel: targetChannel!),
-                        ),
+                      openChannelLink(
+                        context: context,
+                        ref: ref,
+                        channelId: channelId,
+                        currentChannelId: currentChannelId,
                       );
                     },
                   ),

mobile/lib/features/channels/channel_link_navigation.dart

@@ -0,0 +1,38 @@
+import 'package:flutter/material.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+
+import 'channel.dart';
+import 'channel_detail_page.dart';
+import 'channels_provider.dart';
+
+void openChannelLink({
+  required BuildContext context,
+  required WidgetRef ref,
+  required String channelId,
+  required String currentChannelId,
+}) {
+  if (channelId == currentChannelId) return;
+
+  final channelsAsync = ref.read(channelsProvider);
+  final channels = channelsAsync.hasValue ? channelsAsync.value : null;
+  Channel? targetChannel;
+  for (final channel in channels ?? const <Channel>[]) {
+    if (channel.id == channelId) {
+      targetChannel = channel;
+      break;
+    }
+  }
+
+  if (targetChannel == null) {
+    ScaffoldMessenger.of(context).showSnackBar(
+      const SnackBar(content: Text('Channel could not be opened')),
+    );
+    return;
+  }
+
+  Navigator.of(context).push(
+    MaterialPageRoute<void>(
+      builder: (_) => ChannelDetailPage(channel: targetChannel!),
+    ),
+  );
+}

mobile/lib/features/channels/thread_detail_page.dart

@@ -8,6 +8,7 @@ import '../../shared/widgets/frosted_app_bar.dart';
 import '../../shared/widgets/frosted_scaffold.dart';
 import '../profile/user_cache_provider.dart';
 import '../profile/user_profile.dart';
+import 'channel_link_navigation.dart';
 import 'channel_typing_provider.dart';
 import 'thread_replies_provider.dart';
 import 'channels_provider.dart';
@@ -468,7 +469,14 @@ class _ThreadMessage extends ConsumerWidget {
                     mentionNames: mentionNames,
                     channelNames: channelNames,
                     tags: message.tags,
-                    onChannelTap: (_) {},
+                    onChannelTap: (targetChannelId) {
+                      openChannelLink(
+                        context: context,
+                        ref: ref,
+                        channelId: targetChannelId,
+                        currentChannelId: channelId,
+                      );
+                    },
                   ),
                   if (message.reactions.isNotEmpty)
                     ReactionRow(

mobile/test/features/channels/channel_detail_page_test.dart

@@ -10,6 +10,8 @@ import 'package:buzz/features/channels/channel_detail_page.dart';
 import 'package:buzz/features/channels/channel_management_provider.dart';
 import 'package:buzz/features/channels/channel_messages_provider.dart';
 import 'package:buzz/features/channels/channel_typing_provider.dart';
+import 'package:buzz/features/channels/thread_detail_page.dart';
+import 'package:buzz/features/channels/timeline_message.dart';
 import 'package:buzz/features/channels/channels_provider.dart';
 import 'package:buzz/features/channels/read_state/read_state_provider.dart';
 import 'package:buzz/features/profile/profile_provider.dart';
@@ -1099,17 +1101,7 @@ void main() {
 
   group('Channel links', () {
     testWidgets('tapping a channel link opens that channel', (tester) async {
-      final randomChannel = Channel(
-        id: 'random-channel',
-        name: 'random',
-        channelType: 'stream',
-        visibility: 'open',
-        description: 'Random discussion',
-        createdBy: 'abc123',
-        createdAt: DateTime(2025),
-        memberCount: 3,
-        isMember: true,
-      );
+      final randomChannel = _channel(id: 'random-channel', name: 'random');
       final observer = _TestNavigatorObserver();
 
       await tester.pumpWidget(
@@ -1137,9 +1129,107 @@ void main() {
 
       expect(observer.pushCount, initialPushCount + 1);
     });
+
+    testWidgets('missing channel link shows an error', (tester) async {
+      final randomChannel = _channel(id: 'random-channel', name: 'random');
+      final channelsNotifier = _FakeChannelsNotifier([
+        _testChannel,
+        randomChannel,
+      ]);
+
+      await tester.pumpWidget(
+        _buildTestable(
+          messages: [
+            _textMsg(
+              id: 'msg1',
+              pubkey: 'alice',
+              content: 'Take this to #random',
+              createdAt: 1000,
+            ),
+          ],
+          users: {
+            'alice': const UserProfile(pubkey: 'alice', displayName: 'Alice'),
+          },
+          channelsNotifier: channelsNotifier,
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      channelsNotifier.setChannels([_testChannel]);
+      await tester.tap(find.text('#random'));
+      await tester.pump();
+
+      expect(find.text('Channel could not be opened'), findsOneWidget);
+    });
+
+    testWidgets('tapping a channel link inside a thread opens that channel', (
+      tester,
+    ) async {
+      final randomChannel = _channel(id: 'random-channel', name: 'random');
+      final observer = _TestNavigatorObserver();
+
+      await tester.pumpWidget(
+        _buildTestable(
+          messages: [
+            _textMsg(
+              id: 'msg1',
+              pubkey: 'alice',
+              content: 'Thread root #random',
+              createdAt: 1000,
+            ),
+          ],
+          users: {
+            'alice': const UserProfile(pubkey: 'alice', displayName: 'Alice'),
+          },
+          channels: [_testChannel, randomChannel],
+          navigatorObservers: [observer],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      final threadMessages = formatTimeline([
+        _textMsg(
+          id: 'msg1',
+          pubkey: 'alice',
+          content: 'Thread root #random',
+          createdAt: 1000,
+        ),
+      ]);
+      Navigator.of(tester.element(find.byType(ChannelDetailPage))).push(
+        MaterialPageRoute<void>(
+          builder: (_) => ThreadDetailPage(
+            threadHead: threadMessages.single,
+            allMessages: threadMessages,
+            channelId: _channelId,
+            currentPubkey: 'self',
+            isMember: true,
+            isArchived: false,
+          ),
+        ),
+      );
+      await tester.pumpAndSettle();
+      final initialPushCount = observer.pushCount;
+
+      await tester.tap(find.text('#random').last);
+      await tester.pumpAndSettle();
+
+      expect(observer.pushCount, initialPushCount + 1);
+    });
   });
 }
 
+Channel _channel({required String id, required String name}) => Channel(
+  id: id,
+  name: name,
+  channelType: 'stream',
+  visibility: 'open',
+  description: '$name discussion',
+  createdBy: 'abc123',
+  createdAt: DateTime(2025),
+  memberCount: 3,
+  isMember: true,
+);
+
 class _FakeMessagesNotifier extends ChannelMessagesNotifier {
   List<NostrEvent> _messages;
   _FakeMessagesNotifier(this._messages) : super(_channelId);