From 9d480d58c95ad4626ec443ac916a86ff7f863ad3 Mon Sep 17 00:00:00 2001
From: Till Faelligen <tfaelligen@gmail.com>
Date: Fri, 16 Oct 2020 19:10:07 +0200
Subject: [PATCH] Better creation/usage of JoinResponse

---
 syncapi/storage/shared/syncserver.go | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/syncapi/storage/shared/syncserver.go b/syncapi/storage/shared/syncserver.go
index f2133dc89..e994b0d4e 100644
--- a/syncapi/storage/shared/syncserver.go
+++ b/syncapi/storage/shared/syncserver.go
@@ -540,10 +540,10 @@ func (d *Database) addTypingDeltaToResponse(
 	joinedRoomIDs []string,
 	res *types.Response,
 ) error {
-	var jr types.JoinResponse
 	var ok bool
 	var err error
 	for _, roomID := range joinedRoomIDs {
+		var jr types.JoinResponse
 		if typingUsers, updated := d.EDUCache.GetTypingUsersIfUpdatedAfter(
 			roomID, int64(since.EDUPosition()),
 		); updated {
@@ -574,9 +574,16 @@ func (d *Database) addReceiptDeltaToResponse(
 	joinedRoomIDs []string,
 	res *types.Response,
 ) error {
-	var jr types.JoinResponse
+	// TODO: pass joinedRoomIDs to SelectRoomReceiptsAfter instead of iterating over every room
 	// check all joinedRooms for receipts
 	for _, roomID := range joinedRoomIDs {
+		var jr types.JoinResponse
+		var ok bool
+		// Check if there's already a JoinResponse for this room,
+		// otherwise use a new one
+		if jr, ok = res.Rooms.Join[roomID]; !ok {
+			jr = types.JoinResponse{}
+		}
 		receipts, err := d.Receipts.SelectRoomReceiptsAfter(context.TODO(), roomID, since.EDUPosition())
 		if err != nil {
 			return err
@@ -605,6 +612,11 @@ func (d *Database) addReceiptDeltaToResponse(
 			jr.Ephemeral.Events = append(jr.Ephemeral.Events, ev)
 			res.Rooms.Join[roomID] = jr
 		}
+		// Only add new events if we didn't find the room in the map.
+		// If we found the room, they should already be added
+		if !ok {
+			res.Rooms.Join[roomID] = jr
+		}
 	}
 
 	return nil