From 5d928f07a05da3f05a54bbec400b7db6775959be Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@matrix.org>
Date: Tue, 9 Jul 2019 15:06:07 +0200
Subject: [PATCH] don't accept any edit earlier than the server-side set edit.

---
 src/models/event.js     |  6 +++---
 src/models/relations.js | 10 ++++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/models/event.js b/src/models/event.js
index 01804e6d32f..3a418c60aa5 100644
--- a/src/models/event.js
+++ b/src/models/event.js
@@ -898,7 +898,7 @@ utils.extend(module.exports.MatrixEvent.prototype, {
         return this.status;
     },
 
-    _getServerAggregatedRelation(relType) {
+    getServerAggregatedRelation(relType) {
         const relations = this.getUnsigned()["m.relations"];
         if (relations) {
             return relations[relType];
@@ -911,7 +911,7 @@ utils.extend(module.exports.MatrixEvent.prototype, {
      * @return {string?}
      */
     replacingEventId() {
-        const replaceRelation = this._getServerAggregatedRelation("m.replace");
+        const replaceRelation = this.getServerAggregatedRelation("m.replace");
         if (replaceRelation) {
             return replaceRelation.event_id;
         } else if (this._replacingEvent) {
@@ -936,7 +936,7 @@ utils.extend(module.exports.MatrixEvent.prototype, {
      * @return {Date?}
      */
     replacingEventDate() {
-        const replaceRelation = this._getServerAggregatedRelation("m.replace");
+        const replaceRelation = this.getServerAggregatedRelation("m.replace");
         if (replaceRelation) {
             const ts = replaceRelation.origin_server_ts;
             if (Number.isFinite(ts)) {
diff --git a/src/models/relations.js b/src/models/relations.js
index 22ed41669f5..5b2045a4533 100644
--- a/src/models/relations.js
+++ b/src/models/relations.js
@@ -301,10 +301,20 @@ export default class Relations extends EventEmitter {
             // event is known anyway.
             return null;
         }
+
+        // the all-knowning server tells us that the event at some point had
+        // this timestamp for its replacement, so any following replacement should definitely not be less
+        const replaceRelation =
+            this._targetEvent.getServerAggregatedRelation("m.replace");
+        const minTs = replaceRelation && replaceRelation.origin_server_ts;
+
         return this.getRelations().reduce((last, event) => {
             if (event.getSender() !== this._targetEvent.getSender()) {
                 return last;
             }
+            if (minTs && minTs > event.getTs()) {
+                return last;
+            }
             if (last && last.getTs() > event.getTs()) {
                 return last;
             }