Simplify capability handling in ChatViewModel.messagesFlow

spreedCapabilities was only needed inside the terminal map step of
messagesFlow (to filter system messages for channels), but it was
being combined into the outer flatMapLatest trigger. Any capabilities
emission unrelated to the conversation forced the whole message
source subscription to cancel and restart.

Move the capabilities dependency to a dedicated isChannelFlow
(conversationAndUserFlow + spreedCapabilities -> Boolean, with
distinctUntilChanged), and combine only that into the innermost step.
handleSystemMessages() now takes a plain Boolean instead of
ConversationModel/SpreedCapability, making it simpler to reason about
and test.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

Author: mahibi

app/src/main/java/com/nextcloud/talk/chat/viewmodels/ChatViewModel.kt

@@ -496,6 +496,11 @@ class ChatViewModel @AssistedInject constructor(
                 replay = 1
             )
 
+    private val isChannelFlow: Flow<Boolean> =
+        combine(conversationAndUserFlow, spreedCapabilities) { (conversation, _), capabilities ->
+            ConversationUtils.isChannel(conversation, capabilities)
+        }.distinctUntilChanged()
+
     // ------------------------------
     // Messages
     // ------------------------------
@@ -511,10 +516,8 @@ class ChatViewModel @AssistedInject constructor(
 
     @OptIn(ExperimentalCoroutinesApi::class)
     private val messagesFlow: Flow<List<ChatMessage>> =
-        combine(conversationAndUserFlow, spreedCapabilities) { (conversation, user), capabilities ->
-            Triple(conversation, user, capabilities)
-        }
-            .flatMapLatest { (conversation, user, capabilities) ->
+        conversationAndUserFlow
+            .flatMapLatest { (conversation, user) ->
                 combine(chatMode, contextAnchorMessageId) { mode, anchorMessageId ->
                     mode to anchorMessageId
                 }
@@ -533,8 +536,8 @@ class ChatViewModel @AssistedInject constructor(
                             .distinctUntilChanged()
                             .mapToChatMessages(user.userId!!)
                     }
-                    .map { messages ->
-                        handleSystemMessages(messages, conversation, capabilities)
+                    .combine(isChannelFlow) { messages, isChannel ->
+                        handleSystemMessages(messages, isChannel)
                             .let(::handleThreadMessages)
                     }
             }
@@ -1369,12 +1372,8 @@ class ChatViewModel @AssistedInject constructor(
         }
         Log.d(TAG, "fetchNewMessagesWithRetry: no new messages after $POST_UPLOAD_FETCH_MAX_ATTEMPTS attempts")
     }
-    private fun handleSystemMessages(
-        chatMessageList: List<ChatMessage>,
-        conversation: ConversationModel?,
-        capabilities: SpreedCapability?
-    ): List<ChatMessage> {
-        if (ConversationUtils.isChannel(conversation, capabilities)) {
+    private fun handleSystemMessages(chatMessageList: List<ChatMessage>, isChannel: Boolean): List<ChatMessage> {
+        if (isChannel) {
             return chatMessageList.filter { !it.isSystemMessage }
         }