refactor(db-repository): convert message download operations to suspend functions

- Add suspend modifier to Backend.downloadCompleteMessage and related chain
- Add suspend to BackendFolder.saveMessage and FetchListener.onFetchResponse
- Add suspend to ImapFolder.fetch and ImapSync download methods
- Wrap blocking Backend calls with runBlocking(ioDispatcher) in implementations
- Add downloadCompleteMessageBlocking wrapper for legacy MessagingController
- Add ioDispatcher parameter to DemoBackend and ImapBackend constructors
- Replace direct runBlocking calls in Pop3Sync with proper suspend propagation

GG-ID: c-e9f0142

Author: rafaeltonholo

backend/api/src/main/java/com/fsck/k9/backend/api/Backend.kt

@@ -31,7 +31,7 @@ interface Backend {
     fun downloadMessageStructure(folderServerId: String, messageServerId: String)
 
     @Throws(MessagingException::class)
-    fun downloadCompleteMessage(folderServerId: String, messageServerId: String)
+    suspend fun downloadCompleteMessage(folderServerId: String, messageServerId: String)
 
     @Throws(MessagingException::class)
     fun setFlag(folderServerId: String, messageServerIds: List<String>, flag: Flag, newState: Boolean)

backend/api/src/main/java/com/fsck/k9/backend/api/BackendFolder.kt

@@ -21,7 +21,7 @@ interface BackendFolder {
     fun isMessagePresent(messageServerId: String): Boolean
     fun getMessageFlags(messageServerId: String): Set<Flag>
     fun setMessageFlag(messageServerId: String, flag: Flag, value: Boolean)
-    fun saveMessage(message: Message, downloadState: MessageDownloadState)
+    suspend fun saveMessage(message: Message, downloadState: MessageDownloadState)
     fun getOldestMessageDate(): Date?
     fun getFolderExtraString(name: String): String?
     fun setFolderExtraString(name: String, value: String?)

backend/demo/src/main/kotlin/app/k9mail/backend/demo/CommandSendMessage.kt

@@ -13,7 +13,7 @@ internal class CommandSendMessage(
     private val demoStore: DemoStore,
 ) {
 
-    fun sendMessage(message: Message) {
+    suspend fun sendMessage(message: Message) {
         val inboxServerId = demoStore.getInboxFolderId()
         val backendFolder = backendStorage.getFolder(inboxServerId)
 

backend/demo/src/main/kotlin/app/k9mail/backend/demo/CommandSync.kt

@@ -10,7 +10,7 @@ internal class CommandSync(
     private val demoStore: DemoStore,
 ) {
 
-    fun sync(folderServerId: String, listener: SyncListener) {
+    suspend fun sync(folderServerId: String, listener: SyncListener) {
         listener.syncStarted(folderServerId)
 
         val folder = demoStore.getFolder(folderServerId)

backend/demo/src/main/kotlin/app/k9mail/backend/demo/DemoBackend.kt

@@ -10,11 +10,15 @@ import com.fsck.k9.backend.api.SyncListener
 import com.fsck.k9.mail.BodyFactory
 import com.fsck.k9.mail.Message
 import com.fsck.k9.mail.Part
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.runBlocking
 import net.thunderbird.core.common.mail.Flag
 import net.thunderbird.feature.mail.folder.api.FolderPathDelimiter
 
 class DemoBackend(
     private val backendStorage: BackendStorage,
+    private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO,
 ) : Backend {
     private val demoStore by lazy { DemoStore() }
 
@@ -36,9 +40,10 @@ class DemoBackend(
         return commandRefreshFolderList.refreshFolderList()
     }
 
-    override fun sync(folderServerId: String, syncConfig: SyncConfig, listener: SyncListener) {
-        commandSync.sync(folderServerId, listener)
-    }
+    override fun sync(folderServerId: String, syncConfig: SyncConfig, listener: SyncListener) =
+        runBlocking(ioDispatcher) {
+            commandSync.sync(folderServerId, listener)
+        }
 
     override fun downloadMessage(syncConfig: SyncConfig, folderServerId: String, messageServerId: String) {
         throw UnsupportedOperationException("not implemented")
@@ -48,7 +53,7 @@ class DemoBackend(
         throw UnsupportedOperationException("not implemented")
     }
 
-    override fun downloadCompleteMessage(folderServerId: String, messageServerId: String) {
+    override suspend fun downloadCompleteMessage(folderServerId: String, messageServerId: String) {
         throw UnsupportedOperationException("not implemented")
     }
 
@@ -113,7 +118,7 @@ class DemoBackend(
         return createNewServerId()
     }
 
-    override fun sendMessage(message: Message) {
+    override fun sendMessage(message: Message) = runBlocking(ioDispatcher) {
         commandSendMessage.sendMessage(message)
     }
 

backend/imap/src/main/java/com/fsck/k9/backend/imap/CommandDownloadMessage.kt

@@ -15,7 +15,7 @@ import com.fsck.k9.mail.store.imap.OpenMode
 
 internal class CommandDownloadMessage(private val backendStorage: BackendStorage, private val imapStore: ImapStore) {
 
-    fun downloadMessageStructure(folderServerId: String, messageServerId: String) {
+    suspend fun downloadMessageStructure(folderServerId: String, messageServerId: String) {
         val folder = imapStore.getFolder(folderServerId)
         try {
             folder.open(OpenMode.READ_ONLY)
@@ -33,7 +33,7 @@ internal class CommandDownloadMessage(private val backendStorage: BackendStorage
         }
     }
 
-    fun downloadCompleteMessage(folderServerId: String, messageServerId: String) {
+    suspend fun downloadCompleteMessage(folderServerId: String, messageServerId: String) {
         val folder = imapStore.getFolder(folderServerId)
         try {
             folder.open(OpenMode.READ_ONLY)
@@ -48,13 +48,13 @@ internal class CommandDownloadMessage(private val backendStorage: BackendStorage
         }
     }
 
-    private fun fetchMessage(remoteFolder: ImapFolder, message: ImapMessage, fetchProfile: FetchProfile) {
+    private suspend fun fetchMessage(remoteFolder: ImapFolder, message: ImapMessage, fetchProfile: FetchProfile) {
         val maxDownloadSize = 0
         remoteFolder.fetch(
             messages = listOf(element = message),
             fetchProfile = fetchProfile,
             listener = null,
-            maxDownloadSize = maxDownloadSize
+            maxDownloadSize = maxDownloadSize,
         )
     }
 }

backend/imap/src/main/java/com/fsck/k9/backend/imap/ImapBackend.kt

@@ -13,6 +13,10 @@ import com.fsck.k9.mail.power.PowerManager
 import com.fsck.k9.mail.store.imap.IdleRefreshManager
 import com.fsck.k9.mail.store.imap.ImapStore
 import com.fsck.k9.mail.transport.smtp.SmtpTransport
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.withContext
 import net.thunderbird.core.common.mail.Flag
 import net.thunderbird.feature.mail.folder.api.FolderPathDelimiter
 
@@ -24,6 +28,7 @@ class ImapBackend(
     private val idleRefreshManager: IdleRefreshManager,
     private val pushConfigProvider: ImapPushConfigProvider,
     private val smtpTransport: SmtpTransport,
+    private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO,
 ) : Backend {
     private val imapSync = ImapSync(accountName, backendStorage, imapStore)
     private val commandRefreshFolderList = CommandRefreshFolderList(backendStorage, imapStore)
@@ -53,21 +58,24 @@ class ImapBackend(
         return commandRefreshFolderList.refreshFolderList()
     }
 
-    override fun sync(folderServerId: String, syncConfig: SyncConfig, listener: SyncListener) {
-        imapSync.sync(folderServerId, syncConfig, listener)
-    }
+    override fun sync(folderServerId: String, syncConfig: SyncConfig, listener: SyncListener) =
+        runBlocking(ioDispatcher) {
+            imapSync.sync(folderServerId, syncConfig, listener)
+        }
 
-    override fun downloadMessage(syncConfig: SyncConfig, folderServerId: String, messageServerId: String) {
-        imapSync.downloadMessage(syncConfig, folderServerId, messageServerId)
-    }
+    override fun downloadMessage(syncConfig: SyncConfig, folderServerId: String, messageServerId: String) =
+        runBlocking(ioDispatcher) {
+            imapSync.downloadMessage(syncConfig, folderServerId, messageServerId)
+        }
 
-    override fun downloadMessageStructure(folderServerId: String, messageServerId: String) {
+    override fun downloadMessageStructure(folderServerId: String, messageServerId: String) = runBlocking(ioDispatcher) {
         commandDownloadMessage.downloadMessageStructure(folderServerId, messageServerId)
     }
 
-    override fun downloadCompleteMessage(folderServerId: String, messageServerId: String) {
-        commandDownloadMessage.downloadCompleteMessage(folderServerId, messageServerId)
-    }
+    override suspend fun downloadCompleteMessage(folderServerId: String, messageServerId: String) =
+        withContext(ioDispatcher) {
+            commandDownloadMessage.downloadCompleteMessage(folderServerId, messageServerId)
+        }
 
     override fun setFlag(folderServerId: String, messageServerIds: List<String>, flag: Flag, newState: Boolean) {
         commandSetFlag.setFlag(folderServerId, messageServerIds, flag, newState)

backend/imap/src/main/java/com/fsck/k9/backend/imap/ImapSync.kt

@@ -30,11 +30,12 @@ internal class ImapSync(
     private val backendStorage: BackendStorage,
     private val imapStore: ImapStore,
 ) {
-    fun sync(folder: String, syncConfig: SyncConfig, listener: SyncListener) {
+    suspend fun sync(folder: String, syncConfig: SyncConfig, listener: SyncListener) {
         synchronizeMailboxSynchronous(folder, syncConfig, listener)
     }
 
-    private fun synchronizeMailboxSynchronous(folder: String, syncConfig: SyncConfig, listener: SyncListener) {
+    @Suppress("CyclomaticComplexMethod", "LongMethod")
+    private suspend fun synchronizeMailboxSynchronous(folder: String, syncConfig: SyncConfig, listener: SyncListener) {
         Log.i("Synchronizing folder %s:%s", accountName, folder)
 
         var remoteFolder: ImapFolder? = null
@@ -267,7 +268,7 @@ internal class ImapSync(
         }
     }
 
-    fun downloadMessage(syncConfig: SyncConfig, folderServerId: String, messageServerId: String) {
+    suspend fun downloadMessage(syncConfig: SyncConfig, folderServerId: String, messageServerId: String) {
         val backendFolder = backendStorage.getFolder(folderServerId)
         val remoteFolder = imapStore.getFolder(folderServerId)
         try {
@@ -297,7 +298,8 @@ internal class ImapSync(
      * @param inputMessages
      * A list of messages objects that store the UIDs of which messages to download.
      */
-    private fun downloadMessages(
+    @Suppress("LongMethod")
+    private suspend fun downloadMessages(
         syncConfig: SyncConfig,
         remoteFolder: ImapFolder,
         backendFolder: BackendFolder,
@@ -463,7 +465,7 @@ internal class ImapSync(
         return false
     }
 
-    private fun fetchUnsyncedMessages(
+    private suspend fun fetchUnsyncedMessages(
         syncConfig: SyncConfig,
         remoteFolder: ImapFolder,
         unsyncedMessages: List<ImapMessage>,
@@ -483,7 +485,7 @@ internal class ImapSync(
             messages = unsyncedMessages,
             fetchProfile = fetchProfile,
             listener = object : FetchListener {
-                override fun onFetchResponse(message: ImapMessage, isFirstResponse: Boolean) {
+                override suspend fun onFetchResponse(message: ImapMessage, isFirstResponse: Boolean) {
                     try {
                         if (message.isSet(Flag.DELETED)) {
                             Log.v(
@@ -519,7 +521,7 @@ internal class ImapSync(
         )
     }
 
-    private fun downloadSmallMessages(
+    private suspend fun downloadSmallMessages(
         remoteFolder: ImapFolder,
         backendFolder: BackendFolder,
         smallMessages: List<ImapMessage>,
@@ -540,7 +542,7 @@ internal class ImapSync(
             messages = smallMessages,
             fetchProfile = fetchProfile,
             listener = object : FetchListener {
-                override fun onFetchResponse(message: ImapMessage, isFirstResponse: Boolean) {
+                override suspend fun onFetchResponse(message: ImapMessage, isFirstResponse: Boolean) {
                     try {
                         // Store the updated message locally
                         backendFolder.saveMessage(message, MessageDownloadState.FULL)
@@ -578,7 +580,7 @@ internal class ImapSync(
         Log.d("SYNC: Done fetching small messages for folder %s", folder)
     }
 
-    private fun downloadLargeMessages(
+    private suspend fun downloadLargeMessages(
         remoteFolder: ImapFolder,
         backendFolder: BackendFolder,
         largeMessages: List<ImapMessage>,
@@ -634,7 +636,7 @@ internal class ImapSync(
         Log.d("SYNC: Done fetching large messages for folder %s", folder)
     }
 
-    private fun refreshLocalMessageFlags(
+    private suspend fun refreshLocalMessageFlags(
         syncConfig: SyncConfig,
         remoteFolder: ImapFolder,
         backendFolder: BackendFolder,
@@ -673,7 +675,7 @@ internal class ImapSync(
         }
     }
 
-    private fun downloadSaneBody(
+    private suspend fun downloadSaneBody(
         remoteFolder: ImapFolder,
         backendFolder: BackendFolder,
         message: ImapMessage,
@@ -703,7 +705,7 @@ internal class ImapSync(
         backendFolder.saveMessage(message, MessageDownloadState.PARTIAL)
     }
 
-    private fun downloadPartial(
+    private suspend fun downloadPartial(
         remoteFolder: ImapFolder,
         backendFolder: BackendFolder,
         message: ImapMessage,