From 8c66924be9686e186162e8c3c7e51bfc5a461e19 Mon Sep 17 00:00:00 2001
From: ganfra <francoisg@element.io>
Date: Mon, 26 Jun 2023 18:18:48 +0200
Subject: [PATCH] Timeline: refactor a bit

---
 .../matrix/impl/room/RustMatrixRoom.kt        | 17 ++++----
 .../timeline/MatrixTimelineDiffProcessor.kt   | 41 +++++++++++--------
 .../impl/timeline/RustMatrixTimeline.kt       |  8 ++--
 3 files changed, 35 insertions(+), 31 deletions(-)

diff --git a/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/room/RustMatrixRoom.kt b/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/room/RustMatrixRoom.kt
index 66c30be0da..39d829c6a8 100644
--- a/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/room/RustMatrixRoom.kt
+++ b/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/room/RustMatrixRoom.kt
@@ -108,13 +108,13 @@ class RustMatrixRoom(
             timelineLimit = null
         )
         roomListItem.subscribe(settings)
-        innerRoom.timelineDiffFlow { initialList ->
-            timeline.postItems(initialList)
-        }.onEach {
-            syncUpdateFlow.value = systemClock.epochMillis()
-            timeline.postDiff(it)
-        }.launchIn(roomCoroutineScope)
-        roomCoroutineScope.launch {
+        roomCoroutineScope.launch(coroutineDispatchers.computation) {
+            innerRoom.timelineDiffFlow { initialList ->
+                timeline.postItems(initialList)
+            }.onEach {
+                syncUpdateFlow.value = systemClock.epochMillis()
+                timeline.postDiff(it)
+            }.launchIn(this)
             fetchMembers()
         }
         isInit.value = true
@@ -122,7 +122,7 @@ class RustMatrixRoom(
     }
 
     override fun close() {
-        if(isInit.value) {
+        if (isInit.value) {
             isInit.value = false
             roomCoroutineScope.cancel()
             roomListItem.unsubscribe()
@@ -360,7 +360,6 @@ class RustMatrixRoom(
             }
         }
 
-
     private suspend fun fetchMembers() = withContext(coroutineDispatchers.io) {
         runCatching {
             innerRoom.fetchMembers()
diff --git a/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/MatrixTimelineDiffProcessor.kt b/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/MatrixTimelineDiffProcessor.kt
index bd30d826f2..02b34757da 100644
--- a/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/MatrixTimelineDiffProcessor.kt
+++ b/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/MatrixTimelineDiffProcessor.kt
@@ -19,11 +19,9 @@ package io.element.android.libraries.matrix.impl.timeline
 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.CoroutineScope
 import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.launch
-import kotlinx.coroutines.withContext
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
 import org.matrix.rustcomponents.sdk.TimelineChange
 import org.matrix.rustcomponents.sdk.TimelineDiff
 import org.matrix.rustcomponents.sdk.TimelineItem
@@ -31,20 +29,23 @@ import org.matrix.rustcomponents.sdk.TimelineItem
 internal class MatrixTimelineDiffProcessor(
     private val paginationState: MutableStateFlow<MatrixTimeline.PaginationState>,
     private val timelineItems: MutableStateFlow<List<MatrixTimelineItem>>,
-    private val coroutineScope: CoroutineScope,
-    private val diffDispatcher: CoroutineDispatcher,
     private val timelineItemFactory: MatrixTimelineItemMapper,
 ) {
 
-    fun postDiff(diff: TimelineDiff) {
-        coroutineScope.launch {
-            updateTimelineItems {
-                applyDiff(diff)
-            }
-            when (val firstItem = timelineItems.value.firstOrNull()) {
-                is MatrixTimelineItem.Virtual -> updateBackPaginationState(firstItem.virtual)
-                else -> updateBackPaginationState(null)
-            }
+    private val mutex = Mutex()
+
+    suspend fun postItems(items: List<TimelineItem>) {
+        updateTimelineItems {
+            val mappedItems = items.map { it.asMatrixTimelineItem() }
+            addAll(mappedItems)
+            updateBackPaginationState()
+        }
+    }
+
+    suspend fun postDiff(diff: TimelineDiff) {
+        updateTimelineItems {
+            applyDiff(diff)
+            updateBackPaginationState()
         }
     }
 
@@ -68,7 +69,7 @@ internal class MatrixTimelineDiffProcessor(
     }
 
     private suspend fun updateTimelineItems(block: MutableList<MatrixTimelineItem>.() -> Unit) =
-        withContext(diffDispatcher) {
+        mutex.withLock {
             val mutableTimelineItems = timelineItems.value.toMutableList()
             block(mutableTimelineItems)
             timelineItems.value = mutableTimelineItems
@@ -119,8 +120,14 @@ internal class MatrixTimelineDiffProcessor(
         }
     }
 
+    private fun List<MatrixTimelineItem>.updateBackPaginationState() {
+        when (val firstItem = firstOrNull()) {
+            is MatrixTimelineItem.Virtual -> updateBackPaginationState(firstItem.virtual)
+            else -> updateBackPaginationState(null)
+        }
+    }
+
     private fun TimelineItem.asMatrixTimelineItem(): MatrixTimelineItem {
         return timelineItemFactory.map(this)
     }
-
 }
diff --git a/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/RustMatrixTimeline.kt b/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/RustMatrixTimeline.kt
index 906ffa0967..1893c452bb 100644
--- a/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/RustMatrixTimeline.kt
+++ b/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/RustMatrixTimeline.kt
@@ -66,8 +66,6 @@ class RustMatrixTimeline(
     private val timelineDiffProcessor = MatrixTimelineDiffProcessor(
         paginationState = paginationState,
         timelineItems = timelineItems,
-        coroutineScope = roomCoroutineScope,
-        diffDispatcher = coroutineDispatchers.diffUpdateDispatcher,
         timelineItemFactory = timelineItemFactory,
     )
 
@@ -80,11 +78,11 @@ class RustMatrixTimeline(
         return timelineItems.sample(50)
     }
 
-    internal fun postItems(items: List<TimelineItem>)  {
-        timelineItems.value = items.map(timelineItemFactory::map)
+    internal suspend fun postItems(items: List<TimelineItem>) {
+        timelineDiffProcessor.postItems(items)
     }
 
-    internal fun postDiff(timelineDiff: TimelineDiff) {
+    internal suspend fun postDiff(timelineDiff: TimelineDiff) {
         timelineDiffProcessor.postDiff(timelineDiff)
     }