Add logic for determining when device lists have changed due to membership changes (#1220)

* Flesh out structure for handling device list updates for room membership changes

* First cut untested algorithm

* Add tests for determining changed/left device lists

* Linting

* Unbreak tests

* Sigh.. linting

syncapi/consumers/keychange.go

@@ -17,13 +17,14 @@ package consumers
 import (
 	"context"
 	"encoding/json"
+	"sync"
 
 	"github.com/Shopify/sarama"
 	currentstateAPI "github.com/matrix-org/dendrite/currentstateserver/api"
 	"github.com/matrix-org/dendrite/internal"
-	"github.com/matrix-org/dendrite/internal/config"
 	"github.com/matrix-org/dendrite/keyserver/api"
 	"github.com/matrix-org/dendrite/syncapi/storage"
+	"github.com/matrix-org/dendrite/syncapi/types"
 	"github.com/matrix-org/gomatrixserverlib"
 	log "github.com/sirupsen/logrus"
 )
@@ -35,28 +36,33 @@ type OutputKeyChangeEventConsumer struct {
 	serverName        gomatrixserverlib.ServerName // our server name
 	currentStateAPI   currentstateAPI.CurrentStateInternalAPI
 	// keyAPI            api.KeyInternalAPI
+	partitionToOffset   map[int32]int64
+	partitionToOffsetMu sync.Mutex
 }
 
 // NewOutputKeyChangeEventConsumer creates a new OutputKeyChangeEventConsumer.
 // Call Start() to begin consuming from the key server.
 func NewOutputKeyChangeEventConsumer(
-	cfg *config.Dendrite,
+	serverName gomatrixserverlib.ServerName,
+	topic string,
 	kafkaConsumer sarama.Consumer,
 	currentStateAPI currentstateAPI.CurrentStateInternalAPI,
 	store storage.Database,
 ) *OutputKeyChangeEventConsumer {
 
 	consumer := internal.ContinualConsumer{
-		Topic:          string(cfg.Kafka.Topics.OutputKeyChangeEvent),
+		Topic:          topic,
 		Consumer:       kafkaConsumer,
 		PartitionStore: store,
 	}
 
 	s := &OutputKeyChangeEventConsumer{
-		keyChangeConsumer: &consumer,
-		db:                store,
-		serverName:        cfg.Matrix.ServerName,
-		currentStateAPI:   currentStateAPI,
+		keyChangeConsumer:   &consumer,
+		db:                  store,
+		serverName:          serverName,
+		currentStateAPI:     currentStateAPI,
+		partitionToOffset:   make(map[int32]int64),
+		partitionToOffsetMu: sync.Mutex{},
 	}
 
 	consumer.ProcessMessage = s.onMessage
@@ -66,10 +72,25 @@ func NewOutputKeyChangeEventConsumer(
 
 // Start consuming from the key server
 func (s *OutputKeyChangeEventConsumer) Start() error {
-	return s.keyChangeConsumer.Start()
+	offsets, err := s.keyChangeConsumer.StartOffsets()
+	s.partitionToOffsetMu.Lock()
+	for _, o := range offsets {
+		s.partitionToOffset[o.Partition] = o.Offset
+	}
+	s.partitionToOffsetMu.Unlock()
+	return err
+}
+
+func (s *OutputKeyChangeEventConsumer) updateOffset(msg *sarama.ConsumerMessage) {
+	s.partitionToOffsetMu.Lock()
+	defer s.partitionToOffsetMu.Unlock()
+	s.partitionToOffset[msg.Partition] = msg.Offset
 }
 
 func (s *OutputKeyChangeEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
+	defer func() {
+		s.updateOffset(msg)
+	}()
 	var output api.DeviceKeys
 	if err := json.Unmarshal(msg.Value, &output); err != nil {
 		// If the message was invalid, log it and move on to the next message in the stream
@@ -78,18 +99,190 @@ func (s *OutputKeyChangeEventConsumer) onMessage(msg *sarama.ConsumerMessage) er
 	}
 	// work out who we need to notify about the new key
 	var queryRes currentstateAPI.QuerySharedUsersResponse
-	err := s.currentStateAPI.QuerySharedUsers(context.Background(), &currentstateAPI.QuerySharedUsersRequest{}, &queryRes)
+	err := s.currentStateAPI.QuerySharedUsers(context.Background(), &currentstateAPI.QuerySharedUsersRequest{
+		UserID: output.UserID,
+	}, &queryRes)
 	if err != nil {
 		log.WithError(err).Error("syncapi: failed to QuerySharedUsers for key change event from key server")
 		return err
 	}
-	// TODO: notify users by waking up streams
+	// TODO: f.e queryRes.UserIDsToCount : notify users by waking up streams
 	return nil
 }
 
-// Catchup returns a list of user IDs of users who have changed their device keys between the partition|offset given and now.
-// Returns the new offset for this partition.
-func (s *OutputKeyChangeEventConsumer) Catchup(parition int32, offset int64) (userIDs []string, newOffset int, err error) {
-	//return s.keyAPI.QueryKeyChangeCatchup(ctx, partition, offset)
+// Catchup fills in the given response for the given user ID to bring it up-to-date with device lists. hasNew=true if the response
+// was filled in, else false if there are no new device list changes because there is nothing to catch up on. The response MUST
+// be already filled in with join/leave information.
+func (s *OutputKeyChangeEventConsumer) Catchup(
+	ctx context.Context, userID string, res *types.Response, tok types.StreamingToken,
+) (hasNew bool, err error) {
+	// Track users who we didn't track before but now do by virtue of sharing a room with them, or not.
+	newlyJoinedRooms := joinedRooms(res, userID)
+	newlyLeftRooms := leftRooms(res)
+	if len(newlyJoinedRooms) > 0 || len(newlyLeftRooms) > 0 {
+		changed, left, err := s.trackChangedUsers(ctx, userID, newlyJoinedRooms, newlyLeftRooms)
+		if err != nil {
+			return false, err
+		}
+		res.DeviceLists.Changed = changed
+		res.DeviceLists.Left = left
+		hasNew = len(changed) > 0 || len(left) > 0
+	}
+
+	// TODO: now also track users who we already share rooms with but who have updated their devices between the two tokens
 	return
 }
+
+func (s *OutputKeyChangeEventConsumer) OnJoinEvent(ev *gomatrixserverlib.HeaderedEvent) {
+	// work out who we are now sharing rooms with which we previously were not and notify them about the joining
+	// users keys:
+	changed, _, err := s.trackChangedUsers(context.Background(), *ev.StateKey(), []string{ev.RoomID()}, nil)
+	if err != nil {
+		log.WithError(err).Error("OnJoinEvent: failed to work out changed users")
+		return
+	}
+	// TODO: f.e changed, wake up stream
+	for _, userID := range changed {
+		log.Infof("OnJoinEvent:Notify %s that %s should have device lists tracked", userID, *ev.StateKey())
+	}
+}
+
+func (s *OutputKeyChangeEventConsumer) OnLeaveEvent(ev *gomatrixserverlib.HeaderedEvent) {
+	// work out who we are no longer sharing any rooms with and notify them about the leaving user
+	_, left, err := s.trackChangedUsers(context.Background(), *ev.StateKey(), nil, []string{ev.RoomID()})
+	if err != nil {
+		log.WithError(err).Error("OnLeaveEvent: failed to work out left users")
+		return
+	}
+	// TODO: f.e left, wake up stream
+	for _, userID := range left {
+		log.Infof("OnLeaveEvent:Notify %s that %s should no longer track device lists", userID, *ev.StateKey())
+	}
+
+}
+
+// nolint:gocyclo
+func (s *OutputKeyChangeEventConsumer) trackChangedUsers(
+	ctx context.Context, userID string, newlyJoinedRooms, newlyLeftRooms []string,
+) (changed, left []string, err error) {
+	// process leaves first, then joins afterwards so if we join/leave/join/leave we err on the side of including users.
+
+	// Leave algorithm:
+	// - Get set of users and number of times they appear in rooms prior to leave. - QuerySharedUsersRequest with 'IncludeRoomID'.
+	// - Get users in newly left room. - QueryCurrentState
+	// - Loop set of users and decrement by 1 for each user in newly left room.
+	// - If count=0 then they share no more rooms so inform BOTH parties of this via 'left'=[...] in /sync.
+	var queryRes currentstateAPI.QuerySharedUsersResponse
+	err = s.currentStateAPI.QuerySharedUsers(ctx, &currentstateAPI.QuerySharedUsersRequest{
+		UserID:         userID,
+		IncludeRoomIDs: newlyLeftRooms,
+	}, &queryRes)
+	if err != nil {
+		return nil, nil, err
+	}
+	var stateRes currentstateAPI.QueryBulkStateContentResponse
+	err = s.currentStateAPI.QueryBulkStateContent(ctx, &currentstateAPI.QueryBulkStateContentRequest{
+		RoomIDs: newlyLeftRooms,
+		StateTuples: []gomatrixserverlib.StateKeyTuple{
+			{
+				EventType: gomatrixserverlib.MRoomMember,
+				StateKey:  "*",
+			},
+		},
+		AllowWildcards: true,
+	}, &stateRes)
+	if err != nil {
+		return nil, nil, err
+	}
+	for _, state := range stateRes.Rooms {
+		for tuple, membership := range state {
+			if membership != gomatrixserverlib.Join {
+				continue
+			}
+			queryRes.UserIDsToCount[tuple.StateKey]--
+		}
+	}
+	for userID, count := range queryRes.UserIDsToCount {
+		if count <= 0 {
+			left = append(left, userID) // left is returned
+		}
+	}
+
+	// Join algorithm:
+	// - Get the set of all joined users prior to joining room - QuerySharedUsersRequest with 'ExcludeRoomID'.
+	// - Get users in newly joined room - QueryCurrentState
+	// - Loop set of users in newly joined room, do they appear in the set of users prior to joining?
+	// - If yes: then they already shared a room in common, do nothing.
+	// - If no: then they are a brand new user so inform BOTH parties of this via 'changed=[...]'
+	err = s.currentStateAPI.QuerySharedUsers(ctx, &currentstateAPI.QuerySharedUsersRequest{
+		UserID:         userID,
+		ExcludeRoomIDs: newlyJoinedRooms,
+	}, &queryRes)
+	if err != nil {
+		return nil, left, err
+	}
+	err = s.currentStateAPI.QueryBulkStateContent(ctx, &currentstateAPI.QueryBulkStateContentRequest{
+		RoomIDs: newlyJoinedRooms,
+		StateTuples: []gomatrixserverlib.StateKeyTuple{
+			{
+				EventType: gomatrixserverlib.MRoomMember,
+				StateKey:  "*",
+			},
+		},
+		AllowWildcards: true,
+	}, &stateRes)
+	if err != nil {
+		return nil, left, err
+	}
+	for _, state := range stateRes.Rooms {
+		for tuple, membership := range state {
+			if membership != gomatrixserverlib.Join {
+				continue
+			}
+			// new user who we weren't previously sharing rooms with
+			if _, ok := queryRes.UserIDsToCount[tuple.StateKey]; !ok {
+				changed = append(changed, tuple.StateKey) // changed is returned
+			}
+		}
+	}
+	return changed, left, nil
+}
+
+func joinedRooms(res *types.Response, userID string) []string {
+	var roomIDs []string
+	for roomID, join := range res.Rooms.Join {
+		// we would expect to see our join event somewhere if we newly joined the room.
+		// Normal events get put in the join section so it's not enough to know the room ID is present in 'join'.
+		newlyJoined := membershipEventPresent(join.State.Events, userID)
+		if newlyJoined {
+			roomIDs = append(roomIDs, roomID)
+			continue
+		}
+		newlyJoined = membershipEventPresent(join.Timeline.Events, userID)
+		if newlyJoined {
+			roomIDs = append(roomIDs, roomID)
+		}
+	}
+	return roomIDs
+}
+
+func leftRooms(res *types.Response) []string {
+	roomIDs := make([]string, len(res.Rooms.Leave))
+	i := 0
+	for roomID := range res.Rooms.Leave {
+		roomIDs[i] = roomID
+		i++
+	}
+	return roomIDs
+}
+
+func membershipEventPresent(events []gomatrixserverlib.ClientEvent, userID string) bool {
+	for _, ev := range events {
+		// it's enough to know that we have our member event here, don't need to check membership content
+		// as it's implied by being in the respective section of the sync response.
+		if ev.Type == gomatrixserverlib.MRoomMember && ev.StateKey != nil && *ev.StateKey == userID {
+			return true
+		}
+	}
+	return false
+}