Timeline: move TimelineEncryptedHistoryPostProcessor off the main thread

libraries/matrix/impl/build.gradle.kts

@@ -45,4 +45,5 @@ dependencies {
     testImplementation(libs.test.junit)
     testImplementation(libs.test.truth)
     testImplementation(projects.libraries.matrix.test)
+    testImplementation(libs.coroutines.test)
 }

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/RustMatrixTimeline.kt

@@ -81,6 +81,7 @@ class RustMatrixTimeline(
         lastLoginTimestamp = lastLoginTimestamp,
         isRoomEncrypted = matrixRoom.isEncrypted,
         paginationStateFlow = _paginationState,
+        dispatcher = dispatcher,
     )
 
     private val timelineItemFactory = MatrixTimelineItemMapper(

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/postprocessor/TimelineEncryptedHistoryPostProcessor.kt

@@ -19,18 +19,23 @@ package io.element.android.libraries.matrix.impl.timeline.postprocessor
 import io.element.android.libraries.matrix.api.timeline.MatrixTimeline
 import io.element.android.libraries.matrix.api.timeline.MatrixTimelineItem
 import io.element.android.libraries.matrix.api.timeline.item.virtual.VirtualTimelineItem
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.getAndUpdate
+import kotlinx.coroutines.withContext
+import timber.log.Timber
 import java.util.Date
 
 class TimelineEncryptedHistoryPostProcessor(
+    private val dispatcher: CoroutineDispatcher,
     private val lastLoginTimestamp: Date?,
     private val isRoomEncrypted: Boolean,
     private val paginationStateFlow: MutableStateFlow<MatrixTimeline.PaginationState>,
 ) {
 
-    fun process(items: List<MatrixTimelineItem>): List<MatrixTimelineItem> {
+    suspend fun process(items: List<MatrixTimelineItem>): List<MatrixTimelineItem> = withContext(dispatcher) {
-        if (!isRoomEncrypted || lastLoginTimestamp == null) return items
+        Timber.d("Process on Thread=${Thread.currentThread()}")
+        if (!isRoomEncrypted || lastLoginTimestamp == null) return@withContext items
 
         val filteredItems = replaceWithEncryptionHistoryBannerIfNeeded(items)
         // Disable back pagination
@@ -43,7 +48,7 @@ class TimelineEncryptedHistoryPostProcessor(
                 )
             }
         }
-        return filteredItems
+        filteredItems
     }
 
     private fun replaceWithEncryptionHistoryBannerIfNeeded(list: List<MatrixTimelineItem>): List<MatrixTimelineItem> {

libraries/matrix/impl/src/test/kotlin/io/element/android/libraries/matrix/impl/timeline/postprocessor/TimelineEncryptedHistoryPostProcessorTest.kt

@@ -22,6 +22,9 @@ import io.element.android.libraries.matrix.api.timeline.MatrixTimelineItem
 import io.element.android.libraries.matrix.api.timeline.item.virtual.VirtualTimelineItem
 import io.element.android.libraries.matrix.test.room.anEventTimelineItem
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.test.StandardTestDispatcher
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.runTest
 import org.junit.Test
 import java.util.Date
 
@@ -30,7 +33,7 @@ class TimelineEncryptedHistoryPostProcessorTest {
     private val defaultLastLoginTimestamp = Date(1689061264L)
 
     @Test
-    fun `given an unencrypted room, nothing is done`() {
+    fun `given an unencrypted room, nothing is done`() = runTest {
         val processor = createPostProcessor(isRoomEncrypted = false)
         val items = listOf(
             MatrixTimelineItem.Event(0L, anEventTimelineItem())
@@ -39,7 +42,7 @@ class TimelineEncryptedHistoryPostProcessorTest {
     }
 
     @Test
-    fun `given a null lastLoginTimestamp, nothing is done`() {
+    fun `given a null lastLoginTimestamp, nothing is done`() = runTest {
         val processor = createPostProcessor(lastLoginTimestamp = null)
         val items = listOf(
             MatrixTimelineItem.Event(0L, anEventTimelineItem())
@@ -48,14 +51,14 @@ class TimelineEncryptedHistoryPostProcessorTest {
     }
 
     @Test
-    fun `given an empty list, nothing is done`() {
+    fun `given an empty list, nothing is done`() = runTest {
         val processor = createPostProcessor()
         val items = emptyList<MatrixTimelineItem>()
         assertThat(processor.process(items)).isSameInstanceAs(items)
     }
 
     @Test
-    fun `given a list with no items before lastLoginTimestamp, nothing is done`() {
+    fun `given a list with no items before lastLoginTimestamp, nothing is done`() = runTest {
         val processor = createPostProcessor()
         val items = listOf(
             MatrixTimelineItem.Event(0L, anEventTimelineItem(timestamp = defaultLastLoginTimestamp.time + 1))
@@ -64,7 +67,7 @@ class TimelineEncryptedHistoryPostProcessorTest {
     }
 
     @Test
-    fun `given a list with an item with equal timestamp as lastLoginTimestamp, it's replaced`() {
+    fun `given a list with an item with equal timestamp as lastLoginTimestamp, it's replaced`() = runTest {
         val processor = createPostProcessor()
         val items = listOf(
             MatrixTimelineItem.Event(0L, anEventTimelineItem(timestamp = defaultLastLoginTimestamp.time))
@@ -74,7 +77,7 @@ class TimelineEncryptedHistoryPostProcessorTest {
     }
 
     @Test
-    fun `given a list with an item with a lower timestamp than lastLoginTimestamp, it's replaced`() {
+    fun `given a list with an item with a lower timestamp than lastLoginTimestamp, it's replaced`() = runTest {
         val processor = createPostProcessor()
         val items = listOf(
             MatrixTimelineItem.Event(0L, anEventTimelineItem(timestamp = defaultLastLoginTimestamp.time - 1))
@@ -85,7 +88,7 @@ class TimelineEncryptedHistoryPostProcessorTest {
     }
 
     @Test
-    fun `given a list with several with lower or equal timestamps than lastLoginTimestamp, they're replaced and the user can't back paginate`() {
+    fun `given a list with several with lower or equal timestamps than lastLoginTimestamp, they're replaced and the user can't back paginate`() = runTest {
         val paginationStateFlow = MutableStateFlow(MatrixTimeline.PaginationState(hasMoreToLoadBackwards = true, isBackPaginating = false))
         val processor = createPostProcessor(paginationStateFlow = paginationStateFlow)
         val items = listOf(
@@ -102,7 +105,7 @@ class TimelineEncryptedHistoryPostProcessorTest {
         assertThat(paginationStateFlow.value).isEqualTo(MatrixTimeline.PaginationState(hasMoreToLoadBackwards = false, isBackPaginating = false))
     }
 
-    private fun createPostProcessor(
+    private fun TestScope.createPostProcessor(
         lastLoginTimestamp: Date? = defaultLastLoginTimestamp,
         isRoomEncrypted: Boolean = true,
         paginationStateFlow: MutableStateFlow<MatrixTimeline.PaginationState> =
@@ -111,5 +114,6 @@ class TimelineEncryptedHistoryPostProcessorTest {
         lastLoginTimestamp = lastLoginTimestamp,
         isRoomEncrypted = isRoomEncrypted,
         paginationStateFlow = paginationStateFlow,
+        dispatcher = StandardTestDispatcher(testScheduler)
     )
 }