feat(android): persist chat history in local Room database

android-client/app/build.gradle.kts

@@ -2,6 +2,7 @@ plugins {
     id("com.android.application")
     id("org.jetbrains.kotlin.android")
     id("org.jetbrains.kotlin.plugin.serialization")
+    id("com.google.devtools.ksp")
 }
 
 android {
@@ -71,6 +72,9 @@ dependencies {
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.8.1")
     implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.6.3")
     implementation("androidx.datastore:datastore-preferences:1.1.1")
+    implementation("androidx.room:room-runtime:2.6.1")
+    implementation("androidx.room:room-ktx:2.6.1")
+    ksp("androidx.room:room-compiler:2.6.1")
     implementation("com.squareup.okhttp3:okhttp:4.12.0")
 
     debugImplementation("androidx.compose.ui:ui-tooling")

android-client/app/src/main/java/com/onlinemsg/client/data/local/ChatDatabase.kt

@@ -0,0 +1,34 @@
+package com.onlinemsg.client.data.local
+
+import android.content.Context
+import androidx.room.Database
+import androidx.room.Room
+import androidx.room.RoomDatabase
+
+@Database(
+    entities = [ChatMessageEntity::class],
+    version = 1,
+    exportSchema = false
+)
+abstract class ChatDatabase : RoomDatabase() {
+    abstract fun chatMessageDao(): ChatMessageDao
+
+    companion object {
+        private const val DB_NAME = "onlinemsg_chat.db"
+
+        @Volatile
+        private var instance: ChatDatabase? = null
+
+        fun getInstance(context: Context): ChatDatabase {
+            return instance ?: synchronized(this) {
+                instance ?: Room.databaseBuilder(
+                    context.applicationContext,
+                    ChatDatabase::class.java,
+                    DB_NAME
+                ).build().also { db ->
+                    instance = db
+                }
+            }
+        }
+    }
+}

android-client/app/src/main/java/com/onlinemsg/client/data/local/ChatHistoryRepository.kt

@@ -0,0 +1,50 @@
+package com.onlinemsg.client.data.local
+
+import com.onlinemsg.client.ui.MessageChannel
+import com.onlinemsg.client.ui.MessageRole
+import com.onlinemsg.client.ui.UiMessage
+
+class ChatHistoryRepository(private val messageDao: ChatMessageDao) {
+    suspend fun loadMessages(limit: Int): List<UiMessage> {
+        return messageDao.listAll()
+            .asSequence()
+            .mapNotNull { entity -> entity.toUiMessageOrNull() }
+            .toList()
+            .takeLast(limit)
+    }
+
+    suspend fun appendMessage(message: UiMessage, limit: Int) {
+        messageDao.upsert(message.toEntity())
+        messageDao.trimToLatest(limit)
+    }
+
+    suspend fun clearAll() {
+        messageDao.clearAll()
+    }
+}
+
+private fun UiMessage.toEntity(): ChatMessageEntity {
+    return ChatMessageEntity(
+        id = id,
+        role = role.name,
+        sender = sender,
+        subtitle = subtitle,
+        content = content,
+        channel = channel.name,
+        timestampMillis = timestampMillis
+    )
+}
+
+private fun ChatMessageEntity.toUiMessageOrNull(): UiMessage? {
+    val parsedRole = runCatching { MessageRole.valueOf(role) }.getOrNull() ?: return null
+    val parsedChannel = runCatching { MessageChannel.valueOf(channel) }.getOrNull() ?: return null
+    return UiMessage(
+        id = id,
+        role = parsedRole,
+        sender = sender,
+        subtitle = subtitle,
+        content = content,
+        channel = parsedChannel,
+        timestampMillis = timestampMillis
+    )
+}

android-client/app/src/main/java/com/onlinemsg/client/data/local/ChatMessageDao.kt

@@ -0,0 +1,31 @@
+package com.onlinemsg.client.data.local
+
+import androidx.room.Dao
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.Query
+
+@Dao
+interface ChatMessageDao {
+    @Query("SELECT * FROM chat_messages ORDER BY timestampMillis ASC")
+    suspend fun listAll(): List<ChatMessageEntity>
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun upsert(message: ChatMessageEntity)
+
+    @Query(
+        """
+        DELETE FROM chat_messages
+        WHERE id NOT IN (
+            SELECT id
+            FROM chat_messages
+            ORDER BY timestampMillis DESC
+            LIMIT :limit
+        )
+        """
+    )
+    suspend fun trimToLatest(limit: Int)
+
+    @Query("DELETE FROM chat_messages")
+    suspend fun clearAll()
+}

android-client/app/src/main/java/com/onlinemsg/client/data/local/ChatMessageEntity.kt

@@ -0,0 +1,15 @@
+package com.onlinemsg.client.data.local
+
+import androidx.room.Entity
+import androidx.room.PrimaryKey
+
+@Entity(tableName = "chat_messages")
+data class ChatMessageEntity(
+    @PrimaryKey val id: String,
+    val role: String,
+    val sender: String,
+    val subtitle: String,
+    val content: String,
+    val channel: String,
+    val timestampMillis: Long
+)

android-client/app/src/main/java/com/onlinemsg/client/ui/ChatSessionManager.kt

@@ -15,6 +15,8 @@ import androidx.core.content.ContextCompat
 import com.onlinemsg.client.MainActivity
 import com.onlinemsg.client.R
 import com.onlinemsg.client.data.crypto.RsaCryptoManager
+import com.onlinemsg.client.data.local.ChatDatabase
+import com.onlinemsg.client.data.local.ChatHistoryRepository
 import com.onlinemsg.client.data.network.OnlineMsgSocketClient
 import com.onlinemsg.client.data.preferences.ServerUrlFormatter
 import com.onlinemsg.client.data.preferences.UserPreferencesRepository
@@ -60,6 +62,7 @@ object ChatSessionManager {
     private lateinit var app: Application
     private lateinit var preferencesRepository: UserPreferencesRepository
     private lateinit var cryptoManager: RsaCryptoManager
+    private lateinit var historyRepository: ChatHistoryRepository
     private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate)
     private val socketClient = OnlineMsgSocketClient()
     private var initialized = false
@@ -171,10 +174,14 @@ object ChatSessionManager {
         app = application
         preferencesRepository = UserPreferencesRepository(application, json)
         cryptoManager = RsaCryptoManager(application)
+        historyRepository = ChatHistoryRepository(ChatDatabase.getInstance(application).chatMessageDao())
         ensureMessageNotificationChannel()
 
         scope.launch {
             val pref = preferencesRepository.preferencesFlow.first()
+            val historyMessages = withContext(Dispatchers.IO) {
+                historyRepository.loadMessages(MAX_MESSAGES)
+            }
             keepAliveRequested = pref.shouldAutoReconnect
             _uiState.update { current ->
                 current.copy(
@@ -185,7 +192,8 @@ object ChatSessionManager {
                     showSystemMessages = pref.showSystemMessages,
                     themeId = pref.themeId,
                     useDynamicColor = pref.useDynamicColor,
-                    language = pref.language
+                    language = pref.language,
+                    messages = historyMessages
                 )
             }
             // 如果上次会话启用了自动重连，则自动恢复连接
@@ -294,6 +302,11 @@ object ChatSessionManager {
     fun clearMessages() {
         cancelSystemMessageExpiryJobs()
         _uiState.update { it.copy(messages = emptyList()) }
+        scope.launch(Dispatchers.IO) {
+            runCatching {
+                historyRepository.clearAll()
+            }
+        }
     }
 
     /**
@@ -894,6 +907,12 @@ object ChatSessionManager {
             }
             current.copy(messages = next)
         }
+        if (message.role == MessageRole.SYSTEM) return
+        scope.launch(Dispatchers.IO) {
+            runCatching {
+                historyRepository.appendMessage(message, MAX_MESSAGES)
+            }
+        }
     }
 
     /**
@@ -1155,4 +1174,4 @@ object ChatSessionManager {
     private const val MAX_RECONNECT_DELAY_SECONDS = 30
     private const val SYSTEM_MESSAGE_TTL_MS = 1_000L
     private const val MESSAGE_CHANNEL_ID = "onlinemsg_messages"
-}
+}

android-client/build.gradle.kts

@@ -2,4 +2,5 @@ plugins {
     id("com.android.application") version "8.5.2" apply false
     id("org.jetbrains.kotlin.android") version "1.9.24" apply false
     id("org.jetbrains.kotlin.plugin.serialization") version "1.9.24" apply false
+    id("com.google.devtools.ksp") version "1.9.24-1.0.20" apply false
 }