narrow [nfc]: Make containsMessage support DisplayableMessage

For some narrows, this is in the way of the message handling hot path.
This refactor takes care to make sure that calling containsMessage
with StreamMessage or DmMessage remains about as efficient as before.

Author: PIG208

lib/model/narrow.dart

@@ -19,7 +19,7 @@ sealed class Narrow {
   /// This does not necessarily mean the message list would show this message
   /// when navigated to this narrow; in particular it does not address the
   /// question of whether the stream or topic, or the sending user, is muted.
-  bool containsMessage(Message message);
+  bool containsMessage(DisplayableMessage message);
 
   /// This narrow, expressed as an [ApiNarrow].
   ApiNarrow apiEncode();
@@ -47,7 +47,7 @@ class CombinedFeedNarrow extends Narrow {
   const CombinedFeedNarrow();
 
   @override
-  bool containsMessage(Message message) {
+  bool containsMessage(DisplayableMessage message) {
     return true;
   }
 
@@ -71,8 +71,12 @@ class ChannelNarrow extends Narrow {
   final int streamId;
 
   @override
-  bool containsMessage(Message message) {
-    return message is StreamMessage && message.streamId == streamId;
+  bool containsMessage(DisplayableMessage message) {
+    if (message is StreamMessage) {
+      return message.streamId == streamId;
+    }
+    return message is DisplayableMessage<StreamDestination>
+      && message.destination.streamId == streamId;
   }
 
   @override
@@ -105,9 +109,15 @@ class TopicNarrow extends Narrow implements SendableNarrow {
   TopicNarrow sansWith() => TopicNarrow(streamId, topic);
 
   @override
-  bool containsMessage(Message message) {
-    return (message is StreamMessage
-      && message.streamId == streamId && message.topic == topic);
+  bool containsMessage(DisplayableMessage message) {
+    if (message is StreamMessage) {
+      return message.streamId == streamId && message.topic == topic;
+    }
+    if (message case DisplayableMessage<StreamDestination>(:final destination)
+          when destination.streamId == streamId && destination.topic == topic) {
+      return true;
+    }
+    return false;
   }
 
   @override
@@ -260,11 +270,13 @@ class DmNarrow extends Narrow implements SendableNarrow {
   late final String _key = otherRecipientIds.join(',');
 
   @override
-  bool containsMessage(Message message) {
-    if (message is! DmMessage) return false;
-    if (message.allRecipientIds.length != allRecipientIds.length) return false;
+  bool containsMessage(DisplayableMessage message) {
+    if (message is! DisplayableMessage<DmDestination>) return false;
+    final messageUserIds = message is DmMessage
+      ? message.allRecipientIds : message.destination.userIds;
+    if (messageUserIds.length != allRecipientIds.length) return false;
     int i = 0;
-    for (final userId in message.allRecipientIds) {
+    for (final userId in messageUserIds) {
       if (userId != allRecipientIds[i]) return false;
       i++;
     }
@@ -304,7 +316,8 @@ class MentionsNarrow extends Narrow {
   const MentionsNarrow();
 
   @override
-  bool containsMessage(Message message) {
+  bool containsMessage(DisplayableMessage message) {
+    if (message is! Message) return false;
     return message.flags.any((flag) {
       switch (flag) {
         case MessageFlag.mentioned:
@@ -343,7 +356,8 @@ class StarredMessagesNarrow extends Narrow {
   ApiNarrow apiEncode() => [ApiNarrowIs(IsOperand.starred)];
 
   @override
-  bool containsMessage(Message message) {
+  bool containsMessage(DisplayableMessage message) {
+    if (message is! Message) return false;
     return message.flags.contains(MessageFlag.starred);
   }