From b91adf937623c6b12da1661e0aa92f3aa330d25c Mon Sep 17 00:00:00 2001
From: ganfra <francoisg@element.io>
Date: Mon, 17 Jan 2022 19:16:32 +0100
Subject: [PATCH] Timeline : fix 4959

---
 changelog.d/4959.bugfix                          |  1 +
 .../detail/timeline/TimelineEventController.kt   | 16 ++++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 changelog.d/4959.bugfix

diff --git a/changelog.d/4959.bugfix b/changelog.d/4959.bugfix
new file mode 100644
index 00000000000..6ffa3937f93
--- /dev/null
+++ b/changelog.d/4959.bugfix
@@ -0,0 +1 @@
+Prevent crash in Timeline and add more logs.
\ No newline at end of file
diff --git a/vector/src/main/java/im/vector/app/features/home/room/detail/timeline/TimelineEventController.kt b/vector/src/main/java/im/vector/app/features/home/room/detail/timeline/TimelineEventController.kt
index 241ccb7428d..bf0c5ee062c 100644
--- a/vector/src/main/java/im/vector/app/features/home/room/detail/timeline/TimelineEventController.kt
+++ b/vector/src/main/java/im/vector/app/features/home/room/detail/timeline/TimelineEventController.kt
@@ -72,6 +72,7 @@ import org.matrix.android.sdk.api.session.room.timeline.Timeline
 import org.matrix.android.sdk.api.session.room.timeline.TimelineEvent
 import timber.log.Timber
 import javax.inject.Inject
+import kotlin.math.min
 import kotlin.system.measureTimeMillis
 
 class TimelineEventController @Inject constructor(private val dateFormatter: VectorDateFormatter,
@@ -185,6 +186,8 @@ class TimelineEventController @Inject constructor(private val dateFormatter: Vec
         override fun onChanged(position: Int, count: Int, payload: Any?) {
             synchronized(modelCache) {
                 assertUpdateCallbacksAllowed()
+                Timber.v("listUpdateCallback.onChanged(position: $position, count: $count). " +
+                        "\ncurrentSnapshot has size of ${currentSnapshot.size} items")
                 (position until position + count).forEach {
                     // Invalidate cache
                     modelCache[it] = null
@@ -192,10 +195,12 @@ class TimelineEventController @Inject constructor(private val dateFormatter: Vec
                 // Also invalidate the first previous displayable event if
                 // it's sent by the same user so we are sure we have up to date information.
                 val invalidatedSenderId: String? = currentSnapshot.getOrNull(position)?.senderInfo?.userId
-                val prevDisplayableEventIndex = currentSnapshot.subList(0, position).indexOfLast {
+                // In some cases onChanged will be called before onRemoved and onInserted so position will be smaller than currentSnapshot.size.
+                val prevList = currentSnapshot.subList(0, min(position, currentSnapshot.size))
+                val prevDisplayableEventIndex = prevList.indexOfLast {
                     timelineEventVisibilityHelper.shouldShowEvent(it, partialState.highlightedEventId)
                 }
-                if (prevDisplayableEventIndex != -1 && currentSnapshot[prevDisplayableEventIndex].senderInfo.userId == invalidatedSenderId) {
+                if (prevDisplayableEventIndex != -1 && currentSnapshot.getOrNull(prevDisplayableEventIndex)?.senderInfo?.userId == invalidatedSenderId) {
                     modelCache[prevDisplayableEventIndex] = null
                 }
                 requestModelBuild()
@@ -205,6 +210,8 @@ class TimelineEventController @Inject constructor(private val dateFormatter: Vec
         override fun onMoved(fromPosition: Int, toPosition: Int) {
             synchronized(modelCache) {
                 assertUpdateCallbacksAllowed()
+                Timber.v("listUpdateCallback.onMoved(fromPosition: $fromPosition, toPosition: $toPosition). " +
+                        "\ncurrentSnapshot has size of ${currentSnapshot.size} items")
                 val model = modelCache.removeAt(fromPosition)
                 modelCache.add(toPosition, model)
                 requestModelBuild()
@@ -214,6 +221,8 @@ class TimelineEventController @Inject constructor(private val dateFormatter: Vec
         override fun onInserted(position: Int, count: Int) {
             synchronized(modelCache) {
                 assertUpdateCallbacksAllowed()
+                Timber.v("listUpdateCallback.onInserted(position: $position, count: $count). " +
+                        "\ncurrentSnapshot has size of ${currentSnapshot.size} items")
                 repeat(count) {
                     modelCache.add(position, null)
                 }
@@ -224,6 +233,8 @@ class TimelineEventController @Inject constructor(private val dateFormatter: Vec
         override fun onRemoved(position: Int, count: Int) {
             synchronized(modelCache) {
                 assertUpdateCallbacksAllowed()
+                Timber.v("listUpdateCallback.onRemoved(position: $position, count: $count). " +
+                        "\ncurrentSnapshot has size of ${currentSnapshot.size} items")
                 repeat(count) {
                     modelCache.removeAt(position)
                 }
@@ -306,6 +317,7 @@ class TimelineEventController @Inject constructor(private val dateFormatter: Vec
             inSubmitList = true
             val diffCallback = TimelineEventDiffUtilCallback(currentSnapshot, newSnapshot)
             currentSnapshot = newSnapshot
+            Timber.v("Submit a new snapshot of ${currentSnapshot.size} items.")
             val diffResult = DiffUtil.calculateDiff(diffCallback)
             diffResult.dispatchUpdatesTo(listUpdateCallback)
             requestDelayedModelBuild(0)