From 84aa0c6f4fa0134a5f45c5d9b1843a8c16079f2e Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Thu, 10 Aug 2023 11:35:20 +0300
Subject: [PATCH] Check existing messages when forward backfilling

---
 backfill.go | 22 ++++++++--------------
 portal.go   | 30 ++++++++++++++++++++----------
 2 files changed, 28 insertions(+), 24 deletions(-)

diff --git a/backfill.go b/backfill.go
index b4b9127..01bd3b2 100644
--- a/backfill.go
+++ b/backfill.go
@@ -141,20 +141,17 @@ func (portal *Portal) forwardBackfill(ctx context.Context, user *User, after tim
 	maxTS := portal.lastMessageTS
 	for i := len(resp.Messages) - 1; i >= 0; i-- {
 		evt := resp.Messages[i]
-		// TODO this should check the database too
-		if dbMsg := portal.isOutgoingMessage(evt); dbMsg != nil {
-			log.Debug().Str("event_id", dbMsg.MXID.String()).Msg("Got echo for outgoing message in backfill batch")
-			portal.handleExistingMessageUpdate(ctx, user, dbMsg, evt)
-			continue
-		} else if !time.UnixMicro(evt.Timestamp).After(after) {
+		isTooOld := !time.UnixMicro(evt.Timestamp).After(after)
+		if portal.handleExistingMessage(ctx, user, evt, isTooOld) || isTooOld {
 			continue
 		}
 		c := portal.convertGoogleMessage(ctx, user, evt, batchSending)
-		if c != nil {
-			converted = append(converted, c)
-			if c.Timestamp.After(maxTS) {
-				maxTS = c.Timestamp
-			}
+		if c == nil {
+			continue
+		}
+		converted = append(converted, c)
+		if c.Timestamp.After(maxTS) {
+			maxTS = c.Timestamp
 		}
 	}
 	if len(converted) == 0 {
@@ -261,9 +258,6 @@ func (portal *Portal) backfillSendLegacy(ctx context.Context, converted []*Conve
 	var lastEventID id.EventID
 	eventIDs := make(map[string]id.EventID)
 	for _, msg := range converted {
-		if len(msg.Parts) == 0 {
-			continue
-		}
 		msgEventIDs := portal.sendMessageParts(ctx, msg, eventIDs)
 		if len(msgEventIDs) > 0 {
 			eventIDs[msg.ID] = msgEventIDs[0]
diff --git a/portal.go b/portal.go
index a54ebc5..f312943 100644
--- a/portal.go
+++ b/portal.go
@@ -490,6 +490,25 @@ func (portal *Portal) handleExistingMessageUpdate(ctx context.Context, source *U
 	}
 }
 
+func (portal *Portal) handleExistingMessage(ctx context.Context, source *User, evt *gmproto.Message, outgoingOnly bool) bool {
+	log := zerolog.Ctx(ctx)
+	if existingMsg := portal.isOutgoingMessage(evt); existingMsg != nil {
+		log.Debug().Str("event_id", existingMsg.MXID.String()).Msg("Got echo for outgoing message")
+		portal.handleExistingMessageUpdate(ctx, source, existingMsg, evt)
+		return true
+	} else if outgoingOnly {
+		return false
+	}
+	existingMsg, err := portal.bridge.DB.Message.GetByID(ctx, portal.Key, evt.MessageID)
+	if err != nil {
+		log.Err(err).Msg("Failed to check if message is duplicate")
+	} else if existingMsg != nil {
+		portal.handleExistingMessageUpdate(ctx, source, existingMsg, evt)
+		return true
+	}
+	return false
+}
+
 func (portal *Portal) handleMessage(source *User, evt *gmproto.Message) {
 	if len(portal.MXID) == 0 {
 		portal.zlog.Warn().Msg("handleMessage called even though portal.MXID is empty")
@@ -506,16 +525,7 @@ func (portal *Portal) handleMessage(source *User, evt *gmproto.Message) {
 		Str("action", "handle google message").
 		Logger()
 	ctx := log.WithContext(context.TODO())
-	if existingMsg := portal.isOutgoingMessage(evt); existingMsg != nil {
-		log.Debug().Str("event_id", existingMsg.MXID.String()).Msg("Got echo for outgoing message")
-		portal.handleExistingMessageUpdate(ctx, source, existingMsg, evt)
-		return
-	}
-	existingMsg, err := portal.bridge.DB.Message.GetByID(ctx, portal.Key, evt.MessageID)
-	if err != nil {
-		log.Err(err).Msg("Failed to check if message is duplicate")
-	} else if existingMsg != nil {
-		portal.handleExistingMessageUpdate(ctx, source, existingMsg, evt)
+	if portal.handleExistingMessage(ctx, source, evt, false) {
 		return
 	}
 	if evt.GetMessageStatus().GetStatus() == gmproto.MessageStatusType_MESSAGE_DELETED {