android: add realtime foreground local notifications with active chat gating

android/app/src/main/java/ru/daemonlord/messenger/core/notifications/ActiveChatTracker.kt

@@ -0,0 +1,23 @@
+package ru.daemonlord.messenger.core.notifications
+
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class ActiveChatTracker @Inject constructor() {
+    private val _activeChatId = MutableStateFlow<Long?>(null)
+    val activeChatId: StateFlow<Long?> = _activeChatId.asStateFlow()
+
+    fun setActiveChat(chatId: Long) {
+        _activeChatId.value = chatId
+    }
+
+    fun clearActiveChat(chatId: Long) {
+        if (_activeChatId.value == chatId) {
+            _activeChatId.value = null
+        }
+    }
+}

android/app/src/main/java/ru/daemonlord/messenger/data/chat/local/dao/ChatDao.kt

@@ -81,6 +81,9 @@ interface ChatDao {
     )
     fun observeChatById(chatId: Long): Flow<ChatListLocalModel?>
 
+    @Query("SELECT display_title FROM chats WHERE id = :chatId LIMIT 1")
+    suspend fun getChatDisplayTitle(chatId: Long): String?
+
     @Insert(onConflict = OnConflictStrategy.REPLACE)
     suspend fun upsertChats(chats: List<ChatEntity>)
 

android/app/src/main/java/ru/daemonlord/messenger/domain/realtime/usecase/HandleRealtimeEventsUseCase.kt

@@ -7,6 +7,9 @@ import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.launch
 import ru.daemonlord.messenger.data.chat.local.dao.ChatDao
+import ru.daemonlord.messenger.core.notifications.ActiveChatTracker
+import ru.daemonlord.messenger.core.notifications.ChatNotificationPayload
+import ru.daemonlord.messenger.core.notifications.NotificationDispatcher
 import ru.daemonlord.messenger.data.message.local.dao.MessageDao
 import ru.daemonlord.messenger.data.message.local.entity.MessageEntity
 import ru.daemonlord.messenger.domain.chat.repository.ChatRepository
@@ -21,6 +24,8 @@ class HandleRealtimeEventsUseCase @Inject constructor(
     private val chatRepository: ChatRepository,
     private val chatDao: ChatDao,
     private val messageDao: MessageDao,
+    private val notificationDispatcher: NotificationDispatcher,
+    private val activeChatTracker: ActiveChatTracker,
 ) {
 
     private val scope = CoroutineScope(SupervisorJob() + Dispatchers.IO)
@@ -69,6 +74,27 @@ class HandleRealtimeEventsUseCase @Inject constructor(
                             updatedSortAt = event.createdAt,
                         )
                         chatDao.incrementUnread(chatId = event.chatId)
+                        val activeChatId = activeChatTracker.activeChatId.value
+                        if (activeChatId != event.chatId) {
+                            val title = chatDao.getChatDisplayTitle(event.chatId) ?: "New message"
+                            val body = event.text?.takeIf { it.isNotBlank() }
+                                ?: when (event.type?.lowercase()) {
+                                    "image" -> "Photo"
+                                    "video" -> "Video"
+                                    "audio" -> "Audio"
+                                    "voice" -> "Voice message"
+                                    "file" -> "File"
+                                    else -> "Open chat"
+                                }
+                            notificationDispatcher.showChatMessage(
+                                ChatNotificationPayload(
+                                    chatId = event.chatId,
+                                    messageId = event.messageId,
+                                    title = title,
+                                    body = body,
+                                )
+                            )
+                        }
                     }
 
                     is RealtimeEvent.MessageUpdated -> {

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

@@ -11,6 +11,7 @@ import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
+import ru.daemonlord.messenger.core.notifications.ActiveChatTracker
 import ru.daemonlord.messenger.domain.chat.usecase.ObserveChatUseCase
 import ru.daemonlord.messenger.domain.chat.usecase.ObserveChatsUseCase
 import ru.daemonlord.messenger.domain.common.AppError
@@ -53,6 +54,7 @@ class ChatViewModel @Inject constructor(
     private val observeChatUseCase: ObserveChatUseCase,
     private val observeChatsUseCase: ObserveChatsUseCase,
     private val handleRealtimeEventsUseCase: HandleRealtimeEventsUseCase,
+    private val activeChatTracker: ActiveChatTracker,
 ) : ViewModel() {
 
     private val chatId: Long = checkNotNull(savedStateHandle["chatId"])
@@ -62,6 +64,7 @@ class ChatViewModel @Inject constructor(
     private var lastReadMessageId: Long? = null
 
     init {
+        activeChatTracker.setActiveChat(chatId)
         handleRealtimeEventsUseCase.start()
         observeChatPermissions()
         observeMessages()
@@ -587,4 +590,10 @@ class ChatViewModel @Inject constructor(
             is AppError.Unknown -> "Unknown error."
         }
     }
+
+    override fun onCleared() {
+        activeChatTracker.clearActiveChat(chatId)
+        handleRealtimeEventsUseCase.stop()
+        super.onCleared()
+    }
 }