fix(android): preload message reactions on chat open

android/app/src/main/java/ru/daemonlord/messenger/ui/chat/ChatViewModel.kt

@@ -68,6 +68,7 @@ class ChatViewModel @Inject constructor(
     private val visibleMessagesLimit = MutableStateFlow(MESSAGES_PAGE_SIZE)
     private var lastDeliveredMessageId: Long? = null
     private var lastReadMessageId: Long? = null
+    private val reactionsRequestedMessageIds = mutableSetOf<Long>()
 
     init {
         activeChatTracker.setActiveChat(chatId)
@@ -562,13 +563,14 @@ class ChatViewModel @Inject constructor(
             visibleMessagesLimit
                 .flatMapLatest { limit -> observeMessagesUseCase(chatId = chatId, limit = limit) }
                 .collectLatest { messages ->
+                val sortedMessages = messages.sortedBy { msg -> msg.id }
                 _uiState.update {
                     val pinnedId = it.pinnedMessageId
                     val normalized = it.inlineSearchQuery.trim().lowercase()
                     val inlineMatches = if (normalized.isBlank()) {
                         emptyList()
                     } else {
-                        messages
+                        sortedMessages
                             .filter { msg -> (msg.text ?: "").lowercase().contains(normalized) }
                             .map { msg -> msg.id }
                     }
@@ -579,13 +581,14 @@ class ChatViewModel @Inject constructor(
                     }
                     it.copy(
                         isLoading = false,
-                        messages = messages.sortedBy { msg -> msg.id },
-                        pinnedMessage = pinnedId?.let { id -> messages.firstOrNull { msg -> msg.id == id } },
+                        messages = sortedMessages,
+                        pinnedMessage = pinnedId?.let { id -> sortedMessages.firstOrNull { msg -> msg.id == id } },
                         inlineSearchMatches = inlineMatches,
                         highlightedMessageId = highlighted,
                     )
                 }
-                acknowledgeLatestMessages(messages)
+                preloadReactions(sortedMessages)
+                acknowledgeLatestMessages(sortedMessages)
             }
         }
     }
@@ -659,6 +662,28 @@ class ChatViewModel @Inject constructor(
         }
     }
 
+    private fun preloadReactions(messages: List<MessageItem>) {
+        val toRequest = messages
+            .asReversed()
+            .map { it.id }
+            .filter { reactionsRequestedMessageIds.add(it) }
+
+        if (toRequest.isEmpty()) return
+
+        toRequest.forEach { messageId ->
+            viewModelScope.launch {
+                when (val result = listMessageReactionsUseCase(messageId = messageId)) {
+                    is AppResult.Success -> {
+                        _uiState.update {
+                            it.copy(reactionByMessageId = it.reactionByMessageId + (messageId to result.data))
+                        }
+                    }
+                    is AppResult.Error -> Unit
+                }
+            }
+        }
+    }
+
     private fun acknowledgeLatestMessages(messages: List<MessageItem>) {
         val latestIncoming = messages.asReversed().firstOrNull { !it.isOutgoing }