1 files changed, 139 insertions, 0 deletions
diff --git a/clientapi/routing/memberships.go b/clientapi/routing/memberships.go
new file mode 100644
index 00000000..84be498d
--- /dev/null
+++ b/clientapi/routing/memberships.go
@@ -0,0 +1,139 @@
+// Copyright 2024 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 (
+	"encoding/json"
+	"net/http"
+
+	"github.com/matrix-org/dendrite/roomserver/api"
+	userapi "github.com/matrix-org/dendrite/userapi/api"
+	"github.com/matrix-org/gomatrixserverlib/spec"
+	"github.com/matrix-org/util"
+)
+
+// 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"`
+}
+
+// GetJoinedMembers implements
+//
+//	GET /rooms/{roomId}/joined_members
+func GetJoinedMembers(
+	req *http.Request, device *userapi.Device, roomID string,
+	rsAPI api.ClientRoomserverAPI,
+) util.JSONResponse {
+	// Validate the userID
+	userID, err := spec.NewUserID(device.UserID, true)
+	if err != nil {
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: spec.InvalidParam("Device UserID is invalid"),
+		}
+	}
+
+	// Validate the roomID
+	validRoomID, err := spec.NewRoomID(roomID)
+	if err != nil {
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: spec.InvalidParam("RoomID is invalid"),
+		}
+	}
+
+	// Get the current memberships for the requesting user to determine
+	// if they are allowed to query this endpoint.
+	queryReq := api.QueryMembershipForUserRequest{
+		RoomID: validRoomID.String(),
+		UserID: *userID,
+	}
+
+	var queryRes api.QueryMembershipForUserResponse
+	if queryErr := rsAPI.QueryMembershipForUser(req.Context(), &queryReq, &queryRes); queryErr != nil {
+		util.GetLogger(req.Context()).WithError(queryErr).Error("rsAPI.QueryMembershipsForRoom failed")
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
+	}
+
+	if !queryRes.HasBeenInRoom {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: spec.Forbidden("You aren't a member of the room and weren't previously a member of the room."),
+		}
+	}
+
+	if !queryRes.IsInRoom {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: spec.Forbidden("You aren't a member of the room and weren't previously a member of the room."),
+		}
+	}
+
+	// Get the current membership events
+	var membershipsForRoomResp api.QueryMembershipsForRoomResponse
+	if err = rsAPI.QueryMembershipsForRoom(req.Context(), &api.QueryMembershipsForRoomRequest{
+		JoinedOnly: true,
+		RoomID:     validRoomID.String(),
+	}, &membershipsForRoomResp); err != nil {
+		util.GetLogger(req.Context()).WithError(err).Error("rsAPI.QueryEventsByID failed")
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
+	}
+
+	var res getJoinedMembersResponse
+	res.Joined = make(map[string]joinedMember)
+	for _, ev := range membershipsForRoomResp.JoinEvents {
+		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 util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
+		}
+
+		userID, err := rsAPI.QueryUserIDForSender(req.Context(), *validRoomID, spec.SenderID(ev.Sender))
+		if err != nil || userID == nil {
+			util.GetLogger(req.Context()).WithError(err).Error("rsAPI.QueryUserIDForSender failed")
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
+		}
+
+		res.Joined[userID.String()] = joinedMember(content)
+	}
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: res,
+	}
+}