From da02b5fe2de8df94c864f4c5023fe9e56c05caa3 Mon Sep 17 00:00:00 2001
From: Bruno Windels <bruno@windels.cloud>
Date: Wed, 26 May 2021 13:10:19 +0200
Subject: [PATCH] transfer local echo state when replacing event entry

e.g. after decryption or remote echo of other relation comes in
---
 src/matrix/room/timeline/Timeline.js             |  4 +++-
 .../room/timeline/entries/BaseEventEntry.js      |  5 +++++
 src/observable/list/SortedArray.js               | 16 ++++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/matrix/room/timeline/Timeline.js b/src/matrix/room/timeline/Timeline.js
index 0b6fb5ec..36bcc110 100644
--- a/src/matrix/room/timeline/Timeline.js
+++ b/src/matrix/room/timeline/Timeline.js
@@ -122,7 +122,9 @@ export class Timeline {
         for (const entry of entries) {
             // this will use the comparator and thus
             // check for equality using the compare method in BaseEntry
-            this._remoteEntries.update(entry);
+            this._remoteEntries.findAndUpdate(entry, (previousEntry, entry) => {
+                entry.transferLocalEchoState(previousEntry);
+            });
         }
     }
 
diff --git a/src/matrix/room/timeline/entries/BaseEventEntry.js b/src/matrix/room/timeline/entries/BaseEventEntry.js
index 4706f5f2..a3748c8b 100644
--- a/src/matrix/room/timeline/entries/BaseEventEntry.js
+++ b/src/matrix/room/timeline/entries/BaseEventEntry.js
@@ -31,6 +31,11 @@ export class BaseEventEntry extends BaseEntry {
         return this.isRedacting;
     }
 
+    // when replacing an entry, local echo state can be transfered here
+    transferLocalEchoState(oldEntry) {
+        if (oldEntry._pendingRedactions) {
+            this._pendingRedactions = oldEntry._pendingRedactions;
+        }
     }
 
     /**
diff --git a/src/observable/list/SortedArray.js b/src/observable/list/SortedArray.js
index 24378658..d2663f37 100644
--- a/src/observable/list/SortedArray.js
+++ b/src/observable/list/SortedArray.js
@@ -41,6 +41,22 @@ export class SortedArray extends BaseObservableList {
         }
     }
 
+    findAndUpdate(newValue, updater) {
+        const index = this.indexOf(newValue);
+        if (index !== -1) {
+            const oldValue = this._items[index];
+            // allow bailing out of sending an emit if updater determined its not needed
+            const params = updater(oldValue, newValue);
+            if (params !== false) {
+                this._items[index] = newValue;
+                this.emitUpdate(index, newValue, params);
+            }
+            // found
+            return true;
+        }
+        return false;
+    }
+
     update(item, updateParams = null) {
         const idx = this.indexOf(item);
         if (idx !== -1) {