Refactor out calculateAndSetState to decrease cyclomatic complexity

src/github.com/matrix-org/dendrite/roomserver/input/events.go

@@ -105,24 +105,7 @@ func processRoomEvent(
 	if stateAtEvent.BeforeStateSnapshotNID == 0 {
 		// We haven't calculated a state for this event yet.
 		// Lets calculate one.
-		if input.HasState {
+		err = calculateAndSetState(ctx, db, input, roomNID, &stateAtEvent, event)
-			// We've been told what the state at the event is so we don't need to calculate it.
-			// Check that those state events are in the database and store the state.
-			var entries []types.StateEntry
-			if entries, err = db.StateEntriesForEventIDs(ctx, input.StateEventIDs); err != nil {
-				return err
-			}
-
-			if stateAtEvent.BeforeStateSnapshotNID, err = db.AddState(ctx, roomNID, nil, entries); err != nil {
-				return err
-			}
-		} else {
-			// We haven't been told what the state at the event is so we need to calculate it from the prev_events
-			if stateAtEvent.BeforeStateSnapshotNID, err = state.CalculateAndStoreStateBeforeEvent(ctx, db, event, roomNID); err != nil {
-				return err
-			}
-		}
-		err = db.SetState(ctx, stateAtEvent.EventNID, stateAtEvent.BeforeStateSnapshotNID)
 		if err != nil {
 			return err
 		}
@@ -137,6 +120,35 @@ func processRoomEvent(
 	return updateLatestEvents(ctx, db, ow, roomNID, stateAtEvent, event, input.SendAsServer, input.TransactionID)
 }
 
+func calculateAndSetState(
+	ctx context.Context,
+	db RoomEventDatabase,
+	input api.InputRoomEvent,
+	roomNID types.RoomNID,
+	stateAtEvent *types.StateAtEvent,
+	event gomatrixserverlib.Event,
+) error {
+	var err error
+	if input.HasState {
+		// We've been told what the state at the event is so we don't need to calculate it.
+		// Check that those state events are in the database and store the state.
+		var entries []types.StateEntry
+		if entries, err = db.StateEntriesForEventIDs(ctx, input.StateEventIDs); err != nil {
+			return err
+		}
+
+		if stateAtEvent.BeforeStateSnapshotNID, err = db.AddState(ctx, roomNID, nil, entries); err != nil {
+			return err
+		}
+	} else {
+		// We haven't been told what the state at the event is so we need to calculate it from the prev_events
+		if stateAtEvent.BeforeStateSnapshotNID, err = state.CalculateAndStoreStateBeforeEvent(ctx, db, event, roomNID); err != nil {
+			return err
+		}
+	}
+	return db.SetState(ctx, stateAtEvent.EventNID, stateAtEvent.BeforeStateSnapshotNID)
+}
+
 func processInviteEvent(
 	ctx context.Context,
 	db RoomEventDatabase,