blind stab at adding a peek section to /sync

syncapi/storage/shared/syncserver.go

@@ -606,6 +606,8 @@ func (d *Database) IncrementalSync(
 		}
 	}
 
+	// TODO: handle EDUs in peeked rooms
+
 	err = d.addEDUDeltaToResponse(
 		fromPos, toPos, joinedRoomIDs, res,
 	)
@@ -742,6 +744,8 @@ func (d *Database) CompleteSync(
 		return nil, fmt.Errorf("d.getResponseWithPDUsForCompleteSync: %w", err)
 	}
 
+	// TODO: handle EDUs in peeked rooms
+
 	// Use a zero value SyncPosition for fromPos so all EDU states are added.
 	err = d.addEDUDeltaToResponse(
 		types.NewStreamToken(0, 0, nil), toPos, joinedRoomIDs, res,
@@ -847,6 +851,14 @@ func (d *Database) addRoomDeltaToResponse(
 		jr.Timeline.Limited = limited
 		jr.State.Events = gomatrixserverlib.HeaderedToClientEvents(delta.stateEvents, gomatrixserverlib.FormatSync)
 		res.Rooms.Join[delta.roomID] = *jr
+	case gomatrixserverlib.Peek:
+		jr := types.NewJoinResponse()
+
+		jr.Timeline.PrevBatch = prevBatch.String()
+		jr.Timeline.Events = gomatrixserverlib.HeaderedToClientEvents(recentEvents, gomatrixserverlib.FormatSync)
+		jr.Timeline.Limited = limited
+		jr.State.Events = gomatrixserverlib.HeaderedToClientEvents(delta.stateEvents, gomatrixserverlib.FormatSync)
+		res.Rooms.Peek[delta.roomID] = *jr
 	case gomatrixserverlib.Leave:
 		fallthrough // transitions to leave are the same as ban
 	case gomatrixserverlib.Ban:
@@ -968,7 +980,7 @@ func (d *Database) getStateDeltas(
 	// - Get all CURRENTLY joined rooms, and add them to 'joined' block.
 	var deltas []stateDelta
 
-	// get all the state events ever between these two positions
+	// get all the state events ever (i.e. for all available rooms) between these two positions
 	stateNeeded, eventMap, err := d.OutputEvents.SelectStateInRange(ctx, txn, r, stateFilter)
 	if err != nil {
 		return nil, nil, err
@@ -978,6 +990,40 @@ func (d *Database) getStateDeltas(
 		return nil, nil, err
 	}
 
+	// find out which rooms this user is peeking, if any.
+	// We do this before joins so joins overwrite peeks
+	peeks, err := d.Peeks.SelectPeeks(ctx, txn, userID, device.DeviceID)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// add peek blocks
+	for _, peek := range peeks {
+		if peek.New {
+			// send full room state down instead of a delta
+			var s []types.StreamEvent
+			s, err = d.currentStateStreamEventsForRoom(ctx, txn, peek.RoomID, stateFilter)
+			if err != nil {
+				return nil, nil, err
+			}
+			state[roomID] = s
+		}
+
+		deltas = append(deltas, stateDelta{
+			membership:  gomatrixserverlib.Peek,
+			stateEvents: d.StreamEventsToEvents(device, state[peek.RoomID]),
+			roomID:      peek.RoomID,
+		})
+	}
+
+	if len(peeks) > 0 {
+		err := d.Peeks.MarkPeeksAsOld(ctx, txn, userID, device.DeviceID)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	// handle newly joined rooms and non-joined rooms
 	for roomID, stateStreamEvents := range state {
 		for _, ev := range stateStreamEvents {
 			// TODO: Currently this will incorrectly add rooms which were ALREADY joined but they sent another no-op join event.
@@ -1038,8 +1084,13 @@ func (d *Database) getStateDeltasForFullStateSync(
 		return nil, nil, err
 	}
 
+	peeks, err = d.Peeks.SelectPeeks(ctx, txn, userID, device,ID)
+	if err != nil {
+		return nil, nil, err
+	}
+
 	// Use a reasonable initial capacity
-	deltas := make([]stateDelta, 0, len(joinedRoomIDs))
+	deltas := make([]stateDelta, 0, len(joinedRoomIDs) + len(peeks))
 
 	// Add full states for all joined rooms
 	for _, joinedRoomID := range joinedRoomIDs {
@@ -1054,6 +1105,26 @@ func (d *Database) getStateDeltasForFullStateSync(
 		})
 	}
 
+	// Add full states for all peeking rooms
+	for _, peek := range peeks {
+		s, stateErr := d.currentStateStreamEventsForRoom(ctx, txn, peek.RoomID, stateFilter)
+		if stateErr != nil {
+			return nil, nil, stateErr
+		}
+		deltas = append(deltas, stateDelta{
+			membership:  gomatrixserverlib.Peek,
+			stateEvents: d.StreamEventsToEvents(device, s),
+			roomID:      peek.RoomID,
+		})
+	}
+
+	if len(peeks) > 0 {
+		err := d.Peeks.MarkPeeksAsOld(ctx, txn, userID, device.DeviceID)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+
 	// Get all the state events ever between these two positions
 	stateNeeded, eventMap, err := d.OutputEvents.SelectStateInRange(ctx, txn, r, stateFilter)
 	if err != nil {