MXEvent: editedEventFromReplacementEvent: Use decrypted replacing eve…

…nt data

It solves 2 things:
 - avoid synchronous decryption
 - decryption of the  MXRoomSummary.lastMessageEvent when it is edited (element-hq/element-ios/issues/4322)

Plus it saves a decryption.

CHANGES.rst

@@ -9,7 +9,7 @@ Changes to be released in next version
  * MXStore: New commit method accepting a completion block.
 
 🐛 Bugfix
- * 
+ * MXRoomSummary: Fix decryption of the last message when it is edited (vector-im/element-ios/issues/4322).
 
 ⚠️ API Changes
  * 

MatrixSDK/Aggregations/MXAggregatedEditsUpdater.m

@@ -243,13 +243,6 @@ - (void)handleReplace:(MXEvent *)replaceEvent
             if (editedEvent)
             {
                 [self.matrixStore replaceEvent:editedEvent inRoom:roomId];
-
-                if (editedEvent.isEncrypted && !editedEvent.clearEvent)
-                {
-                    [self.mxSession decryptEvent:editedEvent inTimeline:nil];
-                }
-
-
                 [self notifyEventEditsListenersOfRoom:roomId replaceEvent:replaceEvent];
             }
         }

MatrixSDK/JSONModels/MXEvent.m

@@ -582,6 +582,8 @@ - (MXEvent*)editedEventFromReplacementEvent:(MXEvent*)replaceEvent
     MXEvent *event = self;
     NSDictionary *newContentDict;
     MXJSONModelSetDictionary(newContentDict, replaceEvent.content[@"m.new_content"])
+
+    MXEventDecryptionResult *replaceEventDecryptionResult;
 
     NSMutableDictionary *editedEventDict;
     if (replaceEvent.isEncrypted)
@@ -591,6 +593,9 @@ - (MXEvent*)editedEventFromReplacementEvent:(MXEvent*)replaceEvent
         NSMutableDictionary *editedEventContentDict = [replaceEvent.wireContent mutableCopy];
         [editedEventContentDict removeObjectForKey:@"m.relates_to"];
         editedEventDict[@"content"] = editedEventContentDict;
+
+        // Reuse its decryption data
+        replaceEventDecryptionResult = [replaceEvent decryptionResult];
     }
     else if (event.content[@"body"] && newContentDict && [newContentDict[@"msgtype"] isEqualToString:event.content[@"msgtype"]])
     {
@@ -630,6 +635,11 @@ - (MXEvent*)editedEventFromReplacementEvent:(MXEvent*)replaceEvent
         }
 
         editedEvent = [MXEvent modelFromJSON:editedEventDict];
+
+        if (replaceEventDecryptionResult)
+        {
+            [editedEvent setClearData:replaceEventDecryptionResult];
+        }
     }
 
     return editedEvent;
@@ -1001,6 +1011,24 @@ - (MXEncryptedContentFile*)getEncryptedContentFile
     return encryptedContentFiles;
 }
 
+// Extract the decryption result that allowed to decrypt the event.
+- (MXEventDecryptionResult*)decryptionResult
+{
+    MXEventDecryptionResult *decryptionResult = [MXEventDecryptionResult new];
+
+    if (_clearEvent)
+    {
+        decryptionResult.clearEvent = _clearEvent.JSONDictionary;
+        decryptionResult.senderCurve25519Key = _clearEvent->senderCurve25519Key;
+        decryptionResult.claimedEd25519Key = _clearEvent->claimedEd25519Key;
+        decryptionResult.forwardingCurve25519KeyChain = _clearEvent->forwardingCurve25519KeyChain;
+    }
+
+    decryptionResult.error = _decryptionError;
+
+    return decryptionResult;
+}
+
 #pragma mark - private
 - (NSMutableDictionary*)filterInEventWithKeys:(NSArray*)keys
 {