Filter `/members`, return members at given point (#2827)

Makes the tests
```
Can get rooms/{roomId}/members at a given point
Can filter rooms/{roomId}/members
```
pass, by moving `/members` and `/joined_members` to the SyncAPI.

2 files changed, 164 insertions, 0 deletions

diff --git a/syncapi/routing/memberships.go b/syncapi/routing/memberships.go
new file mode 100644
index 00000000..b4e34225
--- /dev/null
+++ b/syncapi/routing/memberships.go
@@ -0,0 +1,131 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// 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 (
+	"encoding/json"
+	"net/http"
+
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/syncapi/storage"
+	"github.com/matrix-org/dendrite/syncapi/types"
+	userapi "github.com/matrix-org/dendrite/userapi/api"
+)
+
+type getMembershipResponse struct {
+	Chunk []gomatrixserverlib.ClientEvent `json:"chunk"`
+}
+
+// https://matrix.org/docs/spec/client_server/r0.6.0#get-matrix-client-r0-rooms-roomid-joined-members
+type getJoinedMembersResponse struct {
+	Joined map[string]joinedMember `json:"joined"`
+}
+
+type joinedMember struct {
+	DisplayName string `json:"display_name"`
+	AvatarURL   string `json:"avatar_url"`
+}
+
+// The database stores 'displayname' without an underscore.
+// Deserialize into this and then change to the actual API response
+type databaseJoinedMember struct {
+	DisplayName string `json:"displayname"`
+	AvatarURL   string `json:"avatar_url"`
+}
+
+// GetMemberships implements
+//
+//	GET /rooms/{roomId}/members
+//	GET /rooms/{roomId}/joined_members
+func GetMemberships(
+	req *http.Request, device *userapi.Device, roomID string,
+	syncDB storage.Database, rsAPI api.SyncRoomserverAPI,
+	joinedOnly bool, membership, notMembership *string, at string,
+) util.JSONResponse {
+	queryReq := api.QueryMembershipForUserRequest{
+		RoomID: roomID,
+		UserID: device.UserID,
+	}
+
+	var queryRes api.QueryMembershipForUserResponse
+	if err := rsAPI.QueryMembershipForUser(req.Context(), &queryReq, &queryRes); err != nil {
+		util.GetLogger(req.Context()).WithError(err).Error("rsAPI.QueryMembershipsForRoom failed")
+		return jsonerror.InternalServerError()
+	}
+
+	if !queryRes.HasBeenInRoom {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden("You aren't a member of the room and weren't previously a member of the room."),
+		}
+	}
+
+	db, err := syncDB.NewDatabaseSnapshot(req.Context())
+	if err != nil {
+		return jsonerror.InternalServerError()
+	}
+
+	atToken, err := types.NewTopologyTokenFromString(at)
+	if err != nil {
+		if queryRes.HasBeenInRoom && !queryRes.IsInRoom {
+			// If you have left the room then this will be the members of the room when you left.
+			atToken, err = db.EventPositionInTopology(req.Context(), queryRes.EventID)
+		} else {
+			// If you are joined to the room then this will be the current members of the room.
+			atToken, err = db.MaxTopologicalPosition(req.Context(), roomID)
+		}
+		if err != nil {
+			util.GetLogger(req.Context()).WithError(err).Error("unable to get 'atToken'")
+			return jsonerror.InternalServerError()
+		}
+	}
+
+	eventIDs, err := db.SelectMemberships(req.Context(), roomID, atToken, membership, notMembership)
+	if err != nil {
+		util.GetLogger(req.Context()).WithError(err).Error("db.SelectMemberships failed")
+		return jsonerror.InternalServerError()
+	}
+
+	result, err := db.Events(req.Context(), eventIDs)
+	if err != nil {
+		util.GetLogger(req.Context()).WithError(err).Error("db.Events failed")
+		return jsonerror.InternalServerError()
+	}
+
+	if joinedOnly {
+		var res getJoinedMembersResponse
+		res.Joined = make(map[string]joinedMember)
+		for _, ev := range result {
+			var content databaseJoinedMember
+			if err := json.Unmarshal(ev.Content(), &content); err != nil {
+				util.GetLogger(req.Context()).WithError(err).Error("failed to unmarshal event content")
+				return jsonerror.InternalServerError()
+			}
+			res.Joined[ev.Sender()] = joinedMember(content)
+		}
+		return util.JSONResponse{
+			Code: http.StatusOK,
+			JSON: res,
+		}
+	}
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: getMembershipResponse{gomatrixserverlib.HeaderedToClientEvents(result, gomatrixserverlib.FormatSync)},
+	}
+}
diff --git a/syncapi/routing/routing.go b/syncapi/routing/routing.go
index 71fa93c1..bc3ad238 100644
--- a/syncapi/routing/routing.go
+++ b/syncapi/routing/routing.go
@@ -172,4 +172,37 @@ func Setup(
 			return Search(req, device, syncDB, fts, nextBatch)
 		}),
 	).Methods(http.MethodPost, http.MethodOptions)
+
+	v3mux.Handle("/rooms/{roomID}/members",
+		httputil.MakeAuthAPI("rooms_members", userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
+			vars, err := httputil.URLDecodeMapValues(mux.Vars(req))
+			if err != nil {
+				return util.ErrorResponse(err)
+			}
+			var membership, notMembership *string
+			if req.URL.Query().Has("membership") {
+				m := req.URL.Query().Get("membership")
+				membership = &m
+			}
+			if req.URL.Query().Has("not_membership") {
+				m := req.URL.Query().Get("not_membership")
+				notMembership = &m
+			}
+
+			at := req.URL.Query().Get("at")
+			return GetMemberships(req, device, vars["roomID"], syncDB, rsAPI, false, membership, notMembership, at)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
+
+	v3mux.Handle("/rooms/{roomID}/joined_members",
+		httputil.MakeAuthAPI("rooms_members", userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
+			vars, err := httputil.URLDecodeMapValues(mux.Vars(req))
+			if err != nil {
+				return util.ErrorResponse(err)
+			}
+			at := req.URL.Query().Get("at")
+			membership := gomatrixserverlib.Join
+			return GetMemberships(req, device, vars["roomID"], syncDB, rsAPI, true, &membership, nil, at)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
 }