Add handling for tombstoned room

commet/lib/client/matrix/matrix_room.dart

@@ -33,6 +33,7 @@ import 'package:commet/client/matrix/timeline_events/matrix_timeline_event_membe
 import 'package:commet/client/matrix/timeline_events/matrix_timeline_event_message.dart';
 import 'package:commet/client/matrix/timeline_events/matrix_timeline_event_pinned_messages.dart';
 import 'package:commet/client/matrix/timeline_events/matrix_timeline_event_redaction.dart';
+import 'package:commet/client/matrix/timeline_events/matrix_timeline_event_room_tombstone.dart';
 import 'package:commet/client/matrix/timeline_events/matrix_timeline_event_sticker.dart';
 import 'package:commet/client/matrix/timeline_events/matrix_timeline_event_unknown.dart';
 import 'package:commet/client/member.dart';
@@ -94,6 +95,20 @@ class MatrixRoom extends Room {
   @override
   bool get isE2EE => _matrixRoom.encrypted;
 
+  @override
+  bool get isTombstoned =>
+      matrixRoom.getState(matrix.EventTypes.RoomTombstone) != null;
+
+  @override
+  String? get tombstoneReplacementRoomId => matrixRoom
+      .getState(matrix.EventTypes.RoomTombstone)
+      ?.content["replacement_room"] as String?;
+
+  @override
+  String? get tombstoneBody =>
+      matrixRoom.getState(matrix.EventTypes.RoomTombstone)?.content["body"]
+          as String?;
+
   @override
   int get highlightedNotificationCount => _matrixRoom.highlightCount;
 
@@ -531,6 +546,8 @@ class MatrixRoom extends Room {
           MatrixTimelineEventCall(event, client: c),
         matrix.EventTypes.RoomPinnedEvents =>
           MatrixTimelineEventPinnedMessages(event, client: c),
+        matrix.EventTypes.RoomTombstone =>
+          MatrixTimelineEventRoomTombstone(event, client: c),
         "chat.commet.calendar_events" =>
           MatrixTimelineEventEditCalendar(event, client: c),
         _ => null
@@ -718,7 +735,8 @@ class MatrixRoom extends Room {
     _displayName = _matrixRoom.getLocalizedDisplayname();
     if (event.state.type == "m.room.name" ||
         event.state.type == "m.room.avatar" ||
-        event.state.type == "m.room.topic") {
+        event.state.type == "m.room.topic" ||
+        event.state.type == matrix.EventTypes.RoomTombstone) {
       _onUpdate.add(null);
     }
   }

commet/lib/client/matrix/timeline_events/matrix_timeline_event_room_tombstone.dart

@@ -0,0 +1,49 @@
+import 'package:commet/client/matrix/timeline_events/matrix_timeline_event.dart';
+import 'package:commet/client/timeline.dart';
+import 'package:commet/client/timeline_events/timeline_event_generic.dart';
+import 'package:commet/client/timeline_events/timeline_event_room_tombstone.dart';
+import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
+
+class MatrixTimelineEventRoomTombstone extends MatrixTimelineEvent
+    implements TimelineEventRoomTombstone, TimelineEventGeneric {
+  MatrixTimelineEventRoomTombstone(super.event, {required super.client});
+
+  String messageRoomUpgraded(String sender) => Intl.message(
+        "$sender upgraded this room",
+        name: "messageRoomUpgraded",
+        args: [sender],
+        desc: "Shown when a room was replaced by another room",
+      );
+
+  String get fallbackMessage => Intl.message(
+        "This room has been upgraded or replaced",
+        name: "messageRoomReplaced",
+        desc: "Fallback tombstone text when no sender/body available",
+      );
+
+  @override
+  String? get replacementRoomId => event.content["replacement_room"] as String?;
+
+  @override
+  String getBody({Timeline? timeline}) {
+    final body = event.content["body"] as String?;
+    if (body != null && body.trim().isNotEmpty) return body;
+
+    final sender = timeline != null
+        ? timeline.room.getMemberOrFallback(event.senderId).displayName
+        : event.senderId.split(":").first.replaceFirst("@", "");
+
+    if (sender != null && sender.isNotEmpty) {
+      return messageRoomUpgraded(sender);
+    }
+
+    return fallbackMessage;
+  }
+
+  @override
+  IconData? get icon => Icons.upgrade_rounded;
+
+  @override
+  bool get showSenderAvatar => false;
+}

commet/lib/client/matrix_background/matrix_background_room.dart

@@ -215,6 +215,20 @@ class MatrixBackgroundRoom implements Room {
   bool get isE2EE =>
       _stateEvents.any((e) => e.type == matrix.EventTypes.Encryption);
 
+  @override
+  bool get isTombstoned => _stateEvents
+      .any((event) => event.type == matrix.EventTypes.RoomTombstone);
+
+  matrix.BasicEvent? get _tombstoneState => _stateEvents.firstWhereOrNull(
+      (event) => event.type == matrix.EventTypes.RoomTombstone);
+
+  @override
+  String? get tombstoneReplacementRoomId =>
+      _tombstoneState?.content["replacement_room"] as String?;
+
+  @override
+  String? get tombstoneBody => _tombstoneState?.content["body"] as String?;
+
   @override
   bool get isMembersListComplete => throw UnimplementedError();
 

commet/lib/client/room.dart

@@ -91,6 +91,15 @@ abstract class Room {
   /// Returns true if the room is secured by end to end encryption
   bool get isE2EE;
 
+  /// Returns true if the room has a tombstone state
+  bool get isTombstoned;
+
+  /// Returns the replacement room ID when tombstoned
+  String? get tombstoneReplacementRoomId;
+
+  /// Returns the tombstone body message when available
+  String? get tombstoneBody;
+
   bool get isSpecialRoomType;
 
   IconData get icon {

commet/lib/client/timeline_events/timeline_event_room_tombstone.dart

@@ -0,0 +1,5 @@
+import 'package:commet/client/timeline_events/timeline_event.dart';
+
+abstract class TimelineEventRoomTombstone extends TimelineEvent {
+  String? get replacementRoomId;
+}

commet/lib/ui/molecules/timeline_events/timeline_view_entry.dart

@@ -6,6 +6,7 @@ import 'package:commet/client/timeline_events/timeline_event_emote.dart';
 import 'package:commet/client/timeline_events/timeline_event_encrypted.dart';
 import 'package:commet/client/timeline_events/timeline_event_generic.dart';
 import 'package:commet/client/timeline_events/timeline_event_message.dart';
+import 'package:commet/client/timeline_events/timeline_event_room_tombstone.dart';
 import 'package:commet/client/timeline_events/timeline_event_sticker.dart';
 import 'package:commet/config/layout_config.dart';
 import 'package:commet/debug/log.dart';
@@ -134,6 +135,8 @@ class TimelineViewEntryState extends State<TimelineViewEntry>
         event is TimelineEventSticker ||
         event is TimelineEventEncrypted) {
       return TimelineEventWidgetDisplayType.message;
+    } else if (event is TimelineEventRoomTombstone) {
+      return TimelineEventWidgetDisplayType.generic;
     } else if (event is TimelineEventGeneric) {
       return TimelineEventWidgetDisplayType.generic;
     } else if (event.status == TimelineEventStatus.error) {

commet/lib/ui/organisms/chat/chat_view.dart

@@ -32,6 +32,33 @@ class ChatView extends StatelessWidget {
       name: "cantSentMessagePrompt",
       desc: "Text that explains the user cannot send a message in this room");
 
+  String get tombstoneRoomReplacedMessage =>
+      Intl.message("This room has been replaced",
+          name: "tombstoneRoomReplacedMessage",
+          desc: "Text that explains a room was replaced by another room");
+
+  String get tombstoneEnterNewRoom => Intl.message("Enter new room",
+      name: "tombstoneEnterNewRoom",
+      desc: "Button label for navigating to the replacement room");
+
+  Future<void> openReplacementRoomAndLeave(String replacementRoomId) async {
+    final client = state.room.client;
+    Room? targetRoom = client.getRoom(replacementRoomId);
+
+    targetRoom ??= client.getRoomByAlias(replacementRoomId);
+
+    if (targetRoom == null) {
+      try {
+        targetRoom = await client.joinRoom(replacementRoomId);
+      } catch (_) {
+        return;
+      }
+    }
+
+    EventBus.openRoom.add((targetRoom.identifier, client.identifier));
+    await client.leaveRoom(state.room);
+  }
+
   String? get relatedEventSenderName => state.interactingEvent == null
       ? null
       : state.room
@@ -50,7 +77,7 @@ class ChatView extends StatelessWidget {
         fit: StackFit.expand,
         children: [timeline(), const ParticlePlayer()],
       )),
-      input(),
+      input(context),
     ]);
   }
 
@@ -89,7 +116,7 @@ class ChatView extends StatelessWidget {
     NotificationManager.clearNotifications(room);
   }
 
-  Widget input() {
+  Widget input(BuildContext context) {
     String? interactingEventBody = state.interactingEvent?.plainTextBody;
 
     if (state.interactingEvent case TimelineEventMessage m) {
@@ -98,6 +125,42 @@ class ChatView extends StatelessWidget {
       }
     }
 
+    if (state.room.isTombstoned) {
+      final replacementRoomId = state.room.tombstoneReplacementRoomId;
+      final body = state.room.tombstoneBody?.trim();
+      final displayMessage =
+          body != null && body.isNotEmpty ? body : tombstoneRoomReplacedMessage;
+
+      return ClipRRect(
+        child: Container(
+          width: double.infinity,
+          padding: const EdgeInsets.fromLTRB(16, 10, 16, 10),
+          color: Theme.of(context).colorScheme.surface,
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Text(
+                displayMessage,
+                style: Theme.of(context).textTheme.bodySmall,
+              ),
+              if (replacementRoomId != null && replacementRoomId.isNotEmpty)
+                Padding(
+                  padding: const EdgeInsets.only(top: 8),
+                  child: TextButton.icon(
+                    onPressed: () async {
+                      await openReplacementRoomAndLeave(replacementRoomId);
+                    },
+                    icon: const Icon(Icons.arrow_forward),
+                    label: Text(tombstoneEnterNewRoom),
+                  ),
+                ),
+            ],
+          ),
+        ),
+      );
+    }
+
     return ClipRRect(
       child: MessageInput(
         client: state.room.client,