fix(chat): do not retry a long poll while the chat is paused

app/src/main/java/com/nextcloud/talk/chat/data/network/ChatMessageSyncer.kt

@@ -714,9 +714,15 @@ class ChatMessageSyncer @Inject constructor(
      * [MAX_PULL_ATTEMPTS] times with a linearly growing delay in between. The requested limit is
      * kept across retries: a background catch-up that succeeds on a later attempt must still
      * create a full chat block, and backing off in time rather than in payload size also keeps a
-     * struggling or rate-limiting server from being hammered.
+     * struggling or rate-limiting server from being hammered. A failed request is not retried
+     * once [canRetry] returns false, e.g. a long poll must not restart while the chat is in the
+     * background.
      */
-    fun pullMessagesFlow(target: SyncTarget, fieldMap: HashMap<String, Int>): Flow<ChatPullResult> =
+    fun pullMessagesFlow(
+        target: SyncTarget,
+        fieldMap: HashMap<String, Int>,
+        canRetry: () -> Boolean = { true }
+    ): Flow<ChatPullResult> =
         flow {
             var attempts = 1
 
@@ -741,8 +747,17 @@ class ChatMessageSyncer @Inject constructor(
                     onFailure = { e ->
                         Log.e(TAG, "Attempt $attempts failed", e)
                         attempts++
+                        if (!canRetry()) {
+                            emit(ChatPullResult.Error(IllegalStateException("Retry cancelled")))
+                            return@flow
+                        }
                         if (attempts < MAX_PULL_ATTEMPTS) {
                             delay(PULL_RETRY_DELAY_MILLIS * (attempts - 1))
+                            // the chat may have been paused while backing off
+                            if (!canRetry()) {
+                                emit(ChatPullResult.Error(IllegalStateException("Retry cancelled")))
+                                return@flow
+                            }
                         }
                     }
                 )
@@ -758,7 +773,8 @@ class ChatMessageSyncer @Inject constructor(
     suspend fun pullAndPersistMessages(
         target: SyncTarget,
         fieldMap: HashMap<String, Int>,
-        events: Events = NO_EVENTS
+        events: Events = NO_EVENTS,
+        canRetry: () -> Boolean = { true }
     ): SyncOutcome {
         val isLongPoll = (fieldMap["timeout"] ?: 0) > 0
         if (!isLongPoll) events.onLoadingChanged(true)
@@ -770,7 +786,7 @@ class ChatMessageSyncer @Inject constructor(
             val queriedMessageId = fieldMap["lastKnownMessageId"]
             val lookIntoFuture = fieldMap["lookIntoFuture"] == 1
 
-            return when (val result = pullMessagesFlow(target, fieldMap).first()) {
+            return when (val result = pullMessagesFlow(target, fieldMap, canRetry).first()) {
                 is ChatPullResult.Success ->
                     handleSuccessfulPull(target, result, queriedMessageId, lookIntoFuture, events)
 

app/src/main/java/com/nextcloud/talk/chat/data/network/OfflineFirstChatRepository.kt

@@ -318,7 +318,7 @@ class OfflineFirstChatRepository @Inject constructor(
                 // sync database with server
                 // (This is a long blocking call because long polling (lookIntoFuture and timeout) is set)
                 Log.d(TAG, "Starting online request for long polling")
-                val outcome = syncer.pullAndPersistMessages(syncTarget, fieldMap, syncEvents)
+                val outcome = syncer.pullAndPersistMessages(syncTarget, fieldMap, syncEvents) { !itIsPaused }
 
                 // A failed request returns right away, e.g. with rejected credentials, which the server counts as a
                 // failed login. Without waiting, the next requests would follow at once until the server throttles.

app/src/test/java/com/nextcloud/talk/chat/data/network/ChatMessageSyncerTest.kt

@@ -9,6 +9,7 @@ package com.nextcloud.talk.chat.data.network
 
 import android.database.sqlite.SQLiteConstraintException
 import com.nextcloud.talk.chat.data.model.ChatMessage
+import com.nextcloud.talk.chat.domain.ChatPullResult
 import com.nextcloud.talk.conversationlist.data.network.ConversationListUpdater
 import com.nextcloud.talk.data.database.dao.ChatBlocksDao
 import com.nextcloud.talk.data.database.dao.ChatMessagesDao
@@ -25,6 +26,7 @@ import com.nextcloud.talk.utils.CapabilitiesUtil
 import java.io.IOException
 import kotlinx.coroutines.CompletableDeferred
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.test.runTest
@@ -235,6 +237,32 @@ class ChatMessageSyncerTest {
             assertEquals(REQUESTED_LIMIT, fieldMapCaptor.lastValue["limit"])
         }
 
+    @Test
+    fun `pullMessagesFlow does not retry a failed request once retrying is not allowed`() =
+        runTest {
+            wheneverBlocking { network.pullChatMessages(any(), any(), any()) }
+                .doSuspendableAnswer { throw IOException("connection reset") }
+
+            val result = syncer.pullMessagesFlow(target(), HashMap(), canRetry = { false }).first()
+
+            assertTrue(result is ChatPullResult.Error)
+            verifyBlocking(network, times(1)) { pullChatMessages(any(), any(), any()) }
+        }
+
+    @Test
+    fun `pullMessagesFlow does not send the retry when the chat is paused during the backoff`() =
+        runTest {
+            wheneverBlocking { network.pullChatMessages(any(), any(), any()) }
+                .doSuspendableAnswer { throw IOException("connection reset") }
+            // allowed right after the failure, paused by the time the backoff delay has elapsed
+            val answers = mutableListOf(true, false)
+
+            val result = syncer.pullMessagesFlow(target(), HashMap(), canRetry = { answers.removeFirst() }).first()
+
+            assertTrue(result is ChatPullResult.Error)
+            verifyBlocking(network, times(1)) { pullChatMessages(any(), any(), any()) }
+        }
+
     @Test
     fun `catchUpRoom marks the sync as failed when the server request errors`() =
         runTest {