From fe707a163e8973d91d2450fbec11099dfb56f003 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Wed, 22 Jan 2020 18:16:42 +0000
Subject: [PATCH] Thwarted by gocyclo again

---
 syncapi/storage/postgres/syncserver.go | 35 +++++++++++++++++---------
 1 file changed, 23 insertions(+), 12 deletions(-)

diff --git a/syncapi/storage/postgres/syncserver.go b/syncapi/storage/postgres/syncserver.go
index c103089f4..aabb9474b 100644
--- a/syncapi/storage/postgres/syncserver.go
+++ b/syncapi/storage/postgres/syncserver.go
@@ -777,6 +777,26 @@ func (d *SyncServerDatasource) addInvitesToResponse(
 	return nil
 }
 
+// Retrieve the backward topology position, i.e. the position of the
+// oldest event in the room's topology.
+func (d *SyncServerDatasource) getBackwardTopologyPos(
+	ctx context.Context,
+	events []types.StreamEvent,
+) (pos types.StreamPosition, err error) {
+	if len(events) > 0 {
+		pos, err = d.topology.selectPositionInTopology(ctx, events[0].EventID())
+		if err != nil {
+			return
+		}
+	}
+	if pos-1 <= 0 {
+		pos = types.StreamPosition(1)
+	} else {
+		pos = pos - 1
+	}
+	return
+}
+
 // addRoomDeltaToResponse adds a room state delta to a sync response
 func (d *SyncServerDatasource) addRoomDeltaToResponse(
 	ctx context.Context,
@@ -826,19 +846,10 @@ func (d *SyncServerDatasource) addRoomDeltaToResponse(
 		prevPDUPos = 1
 	}
 
-	// Retrieve the backward topology position, i.e. the position of the
-	// oldest event in the room's topology.
 	var backwardTopologyPos types.StreamPosition
-	if len(recentStreamEvents) > 0 {
-		backwardTopologyPos, err = d.topology.selectPositionInTopology(ctx, recentStreamEvents[0].EventID())
-		if err != nil {
-			return err
-		}
-	}
-	if backwardTopologyPos-1 <= 0 {
-		backwardTopologyPos = types.StreamPosition(1)
-	} else {
-		backwardTopologyPos = backwardTopologyPos - 1
+	backwardTopologyPos, err = d.getBackwardTopologyPos(ctx, recentStreamEvents)
+	if err != nil {
+		return err
 	}
 
 	switch delta.membership {