Event relations (#2790)

This adds support for tracking `m.relates_to`, as well as adding support
for the various `/room/{roomID}/relations/...` endpoints to the CS API.

syncapi/routing/relations.go

@@ -0,0 +1,124 @@
+// Copyright 2022 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package routing
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+	"github.com/sirupsen/logrus"
+
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/syncapi/internal"
+	"github.com/matrix-org/dendrite/syncapi/storage"
+	"github.com/matrix-org/dendrite/syncapi/types"
+	userapi "github.com/matrix-org/dendrite/userapi/api"
+)
+
+type RelationsResponse struct {
+	Chunk     []gomatrixserverlib.ClientEvent `json:"chunk"`
+	NextBatch string                          `json:"next_batch,omitempty"`
+	PrevBatch string                          `json:"prev_batch,omitempty"`
+}
+
+// nolint:gocyclo
+func Relations(
+	req *http.Request, device *userapi.Device,
+	syncDB storage.Database,
+	rsAPI api.SyncRoomserverAPI,
+	roomID, eventID, relType, eventType string,
+) util.JSONResponse {
+	var err error
+	var from, to types.StreamPosition
+	var limit int
+	dir := req.URL.Query().Get("dir")
+	if f := req.URL.Query().Get("from"); f != "" {
+		if from, err = types.NewStreamPositionFromString(f); err != nil {
+			return util.ErrorResponse(err)
+		}
+	}
+	if t := req.URL.Query().Get("to"); t != "" {
+		if to, err = types.NewStreamPositionFromString(t); err != nil {
+			return util.ErrorResponse(err)
+		}
+	}
+	if l := req.URL.Query().Get("limit"); l != "" {
+		if limit, err = strconv.Atoi(l); err != nil {
+			return util.ErrorResponse(err)
+		}
+	}
+	if limit == 0 || limit > 50 {
+		limit = 50
+	}
+	if dir == "" {
+		dir = "b"
+	}
+	if dir != "b" && dir != "f" {
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.MissingArgument("Bad or missing dir query parameter (should be either 'b' or 'f')"),
+		}
+	}
+
+	snapshot, err := syncDB.NewDatabaseSnapshot(req.Context())
+	if err != nil {
+		logrus.WithError(err).Error("Failed to get snapshot for relations")
+		return jsonerror.InternalServerError()
+	}
+	var succeeded bool
+	defer sqlutil.EndTransactionWithCheck(snapshot, &succeeded, &err)
+
+	res := &RelationsResponse{
+		Chunk: []gomatrixserverlib.ClientEvent{},
+	}
+	var events []types.StreamEvent
+	events, res.PrevBatch, res.NextBatch, err = snapshot.RelationsFor(
+		req.Context(), roomID, eventID, relType, eventType, from, to, dir == "b", limit,
+	)
+	if err != nil {
+		return util.ErrorResponse(err)
+	}
+
+	headeredEvents := make([]*gomatrixserverlib.HeaderedEvent, 0, len(events))
+	for _, event := range events {
+		headeredEvents = append(headeredEvents, event.HeaderedEvent)
+	}
+
+	// Apply history visibility to the result events.
+	filteredEvents, err := internal.ApplyHistoryVisibilityFilter(req.Context(), snapshot, rsAPI, headeredEvents, nil, device.UserID, "relations")
+	if err != nil {
+		return util.ErrorResponse(err)
+	}
+
+	// Convert the events into client events, and optionally filter based on the event
+	// type if it was specified.
+	res.Chunk = make([]gomatrixserverlib.ClientEvent, 0, len(filteredEvents))
+	for _, event := range filteredEvents {
+		res.Chunk = append(
+			res.Chunk,
+			gomatrixserverlib.ToClientEvent(event.Event, gomatrixserverlib.FormatAll),
+		)
+	}
+
+	succeeded = true
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: res,
+	}
+}

syncapi/routing/routing.go

@@ -45,6 +45,7 @@ func Setup(
 	lazyLoadCache caching.LazyLoadCache,
 	fts *fulltext.Search,
 ) {
+	v1unstablemux := csMux.PathPrefix("/{apiversion:(?:v1|unstable)}/").Subrouter()
 	v3mux := csMux.PathPrefix("/{apiversion:(?:r0|v3)}/").Subrouter()
 
 	// TODO: Add AS support for all handlers below.
@@ -110,6 +111,48 @@ func Setup(
 		}),
 	).Methods(http.MethodGet, http.MethodOptions)
 
+	v1unstablemux.Handle("/rooms/{roomId}/relations/{eventId}",
+		httputil.MakeAuthAPI(gomatrixserverlib.Join, userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
+			vars, err := httputil.URLDecodeMapValues(mux.Vars(req))
+			if err != nil {
+				return util.ErrorResponse(err)
+			}
+
+			return Relations(
+				req, device, syncDB, rsAPI,
+				vars["roomId"], vars["eventId"], "", "",
+			)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
+
+	v1unstablemux.Handle("/rooms/{roomId}/relations/{eventId}/{relType}",
+		httputil.MakeAuthAPI(gomatrixserverlib.Join, userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
+			vars, err := httputil.URLDecodeMapValues(mux.Vars(req))
+			if err != nil {
+				return util.ErrorResponse(err)
+			}
+
+			return Relations(
+				req, device, syncDB, rsAPI,
+				vars["roomId"], vars["eventId"], vars["relType"], "",
+			)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
+
+	v1unstablemux.Handle("/rooms/{roomId}/relations/{eventId}/{relType}/{eventType}",
+		httputil.MakeAuthAPI(gomatrixserverlib.Join, userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
+			vars, err := httputil.URLDecodeMapValues(mux.Vars(req))
+			if err != nil {
+				return util.ErrorResponse(err)
+			}
+
+			return Relations(
+				req, device, syncDB, rsAPI,
+				vars["roomId"], vars["eventId"], vars["relType"], vars["eventType"],
+			)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
+
 	v3mux.Handle("/search",
 		httputil.MakeAuthAPI("search", userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
 			if !cfg.Fulltext.Enabled {