Implement /sync `limited` and read timeline limit from stored filters (#1168)

* Move filter table to syncapi where it is used

* Implement /sync `limited` and read timeline limit from stored filters

We now fully handle `room.timeline.limit` filters (in-line + stored) and
return the right value for `limited` syncs.

* Update whitelist

* Default to the default timeline limit if it's unset, also strip the extra event correctly

* Update whitelist

3 files changed, 26 insertions, 11 deletions

diff --git a/syncapi/sync/notifier_test.go b/syncapi/sync/notifier_test.go
index ecc4fcbf..f2a368ec 100644
--- a/syncapi/sync/notifier_test.go
+++ b/syncapi/sync/notifier_test.go
@@ -363,7 +363,7 @@ func newTestSyncRequest(userID, deviceID string, since types.StreamingToken) syn
 		timeout:       1 * time.Minute,
 		since:         &since,
 		wantFullState: false,
-		limit:         defaultTimelineLimit,
+		limit:         DefaultTimelineLimit,
 		log:           util.GetLogger(context.TODO()),
 		ctx:           context.TODO(),
 	}
diff --git a/syncapi/sync/request.go b/syncapi/sync/request.go
index 5dd92c85..41b18aa1 100644
--- a/syncapi/sync/request.go
+++ b/syncapi/sync/request.go
@@ -21,14 +21,16 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/matrix-org/dendrite/syncapi/storage"
 	"github.com/matrix-org/dendrite/syncapi/types"
 	userapi "github.com/matrix-org/dendrite/userapi/api"
+	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
 	log "github.com/sirupsen/logrus"
 )
 
 const defaultSyncTimeout = time.Duration(0)
-const defaultTimelineLimit = 20
+const DefaultTimelineLimit = 20
 
 type filter struct {
 	Room struct {
@@ -49,7 +51,7 @@ type syncRequest struct {
 	log           *log.Entry
 }
 
-func newSyncRequest(req *http.Request, device userapi.Device) (*syncRequest, error) {
+func newSyncRequest(req *http.Request, device userapi.Device, syncDB storage.Database) (*syncRequest, error) {
 	timeout := getTimeout(req.URL.Query().Get("timeout"))
 	fullState := req.URL.Query().Get("full_state")
 	wantFullState := fullState != "" && fullState != "false"
@@ -66,15 +68,28 @@ func newSyncRequest(req *http.Request, device userapi.Device) (*syncRequest, err
 		tok := types.NewStreamToken(0, 0)
 		since = &tok
 	}
-	timelineLimit := defaultTimelineLimit
+	timelineLimit := DefaultTimelineLimit
 	// TODO: read from stored filters too
 	filterQuery := req.URL.Query().Get("filter")
-	if filterQuery != "" && filterQuery[0] == '{' {
-		// attempt to parse the timeline limit at least
-		var f filter
-		err := json.Unmarshal([]byte(filterQuery), &f)
-		if err == nil && f.Room.Timeline.Limit != nil {
-			timelineLimit = *f.Room.Timeline.Limit
+	if filterQuery != "" {
+		if filterQuery[0] == '{' {
+			// attempt to parse the timeline limit at least
+			var f filter
+			err := json.Unmarshal([]byte(filterQuery), &f)
+			if err == nil && f.Room.Timeline.Limit != nil {
+				timelineLimit = *f.Room.Timeline.Limit
+			}
+		} else {
+			// attempt to load the filter ID
+			localpart, _, err := gomatrixserverlib.SplitID('@', device.UserID)
+			if err != nil {
+				util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
+				return nil, err
+			}
+			f, err := syncDB.GetFilter(req.Context(), localpart, filterQuery)
+			if err == nil {
+				timelineLimit = f.Room.Timeline.Limit
+			}
 		}
 	}
 	// TODO: Additional query params: set_presence, filter
diff --git a/syncapi/sync/requestpool.go b/syncapi/sync/requestpool.go
index 743c63a6..196d446a 100644
--- a/syncapi/sync/requestpool.go
+++ b/syncapi/sync/requestpool.go
@@ -49,7 +49,7 @@ func (rp *RequestPool) OnIncomingSyncRequest(req *http.Request, device *userapi.
 	var syncData *types.Response
 
 	// Extract values from request
-	syncReq, err := newSyncRequest(req, *device)
+	syncReq, err := newSyncRequest(req, *device, rp.db)
 	if err != nil {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,