From 7780bd7e1198a3e3c4420267f33d0279c93c0dbc Mon Sep 17 00:00:00 2001
From: ganfra <francoisg@matrix.org>
Date: Wed, 2 Oct 2024 17:52:06 +0200
Subject: [PATCH] timeline : add synchronisation around timelineItemIndexer

---
 .../impl/timeline/TimelineItemIndexer.kt      | 28 ++++++++++++++-----
 .../impl/timeline/TimelineItemIndexerTest.kt  |  3 +-
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/TimelineItemIndexer.kt b/features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/TimelineItemIndexer.kt
index 877b4ea385..2db5003f4a 100644
--- a/features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/TimelineItemIndexer.kt
+++ b/features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/TimelineItemIndexer.kt
@@ -11,26 +11,39 @@ import io.element.android.features.messages.impl.timeline.model.TimelineItem
 import io.element.android.libraries.di.RoomScope
 import io.element.android.libraries.di.SingleIn
 import io.element.android.libraries.matrix.api.core.EventId
+import kotlinx.coroutines.CompletableDeferred
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
 import timber.log.Timber
 import javax.inject.Inject
 
 @SingleIn(RoomScope::class)
 class TimelineItemIndexer @Inject constructor() {
+    // This is a latch to wait for the first process call
+    private val firstProcessLatch = CompletableDeferred<Unit>()
     private val timelineEventsIndexes = mutableMapOf<EventId, Int>()
 
-    fun isKnown(eventId: EventId): Boolean {
-        return timelineEventsIndexes.containsKey(eventId).also {
-            Timber.d("$eventId isKnown = $it")
+    private val mutex = Mutex()
+
+    suspend fun isKnown(eventId: EventId): Boolean {
+        firstProcessLatch.await()
+        return mutex.withLock {
+            timelineEventsIndexes.containsKey(eventId).also {
+                Timber.d("$eventId isKnown = $it")
+            }
         }
     }
 
-    fun indexOf(eventId: EventId): Int {
-        return (timelineEventsIndexes[eventId] ?: -1).also {
-            Timber.d("indexOf $eventId= $it")
+    suspend fun indexOf(eventId: EventId): Int {
+        firstProcessLatch.await()
+        return mutex.withLock {
+            (timelineEventsIndexes[eventId] ?: -1).also {
+                Timber.d("indexOf $eventId= $it")
+            }
         }
     }
 
-    fun process(timelineItems: List<TimelineItem>) {
+    suspend fun process(timelineItems: List<TimelineItem>) = mutex.withLock {
         Timber.d("process ${timelineItems.size} items")
         timelineEventsIndexes.clear()
         timelineItems.forEachIndexed { index, timelineItem ->
@@ -46,6 +59,7 @@ class TimelineItemIndexer @Inject constructor() {
                 else -> Unit
             }
         }
+        firstProcessLatch.complete(Unit)
     }
 
     private fun processEvent(event: TimelineItem.Event, index: Int) {
diff --git a/features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/TimelineItemIndexerTest.kt b/features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/TimelineItemIndexerTest.kt
index 3e20250910..2e3687b74e 100644
--- a/features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/TimelineItemIndexerTest.kt
+++ b/features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/TimelineItemIndexerTest.kt
@@ -13,11 +13,12 @@ import io.element.android.features.messages.impl.timeline.model.virtual.Timeline
 import io.element.android.libraries.matrix.api.core.EventId
 import io.element.android.libraries.matrix.api.core.UniqueId
 import io.element.android.libraries.matrix.test.AN_EVENT_ID
+import kotlinx.coroutines.test.runTest
 import org.junit.Test
 
 class TimelineItemIndexerTest {
     @Test
-    fun `test TimelineItemIndexer`() {
+    fun `test TimelineItemIndexer`() = runTest {
         val eventIds = mutableListOf<EventId>()
         val data = listOf(
             aTimelineItemEvent().also { eventIds.add(it.eventId!!) },