Move `/joined_members` back to the clientapi/roomserver (#3312)

Partly reverts #2827 by moving `/joined_members` back to the
clientAPI/roomserver

3 files changed, 276 insertions, 0 deletions

diff --git a/clientapi/clientapi_test.go b/clientapi/clientapi_test.go
index 2ff4b650..1b2f1358 100644
--- a/clientapi/clientapi_test.go
+++ b/clientapi/clientapi_test.go
@@ -2151,3 +2151,130 @@ func TestKeyBackup(t *testing.T) {
 		}
 	})
 }
+
+func TestGetMembership(t *testing.T) {
+	alice := test.NewUser(t)
+	bob := test.NewUser(t)
+
+	testCases := []struct {
+		name             string
+		roomID           string
+		user             *test.User
+		additionalEvents func(t *testing.T, room *test.Room)
+		request          func(t *testing.T, room *test.Room, accessToken string) *http.Request
+		wantOK           bool
+		wantMemberCount  int
+	}{
+
+		{
+			name: "/joined_members - Bob never joined",
+			user: bob,
+			request: func(t *testing.T, room *test.Room, accessToken string) *http.Request {
+				return test.NewRequest(t, "GET", fmt.Sprintf("/_matrix/client/v3/rooms/%s/joined_members", room.ID), test.WithQueryParams(map[string]string{
+					"access_token": accessToken,
+				}))
+			},
+			wantOK: false,
+		},
+		{
+			name: "/joined_members - Alice joined",
+			user: alice,
+			request: func(t *testing.T, room *test.Room, accessToken string) *http.Request {
+				return test.NewRequest(t, "GET", fmt.Sprintf("/_matrix/client/v3/rooms/%s/joined_members", room.ID), test.WithQueryParams(map[string]string{
+					"access_token": accessToken,
+				}))
+			},
+			wantOK:          true,
+			wantMemberCount: 1,
+		},
+		{
+			name: "/joined_members - Alice leaves, shouldn't be able to see members ",
+			user: alice,
+			request: func(t *testing.T, room *test.Room, accessToken string) *http.Request {
+				return test.NewRequest(t, "GET", fmt.Sprintf("/_matrix/client/v3/rooms/%s/joined_members", room.ID), test.WithQueryParams(map[string]string{
+					"access_token": accessToken,
+				}))
+			},
+			additionalEvents: func(t *testing.T, room *test.Room) {
+				room.CreateAndInsert(t, alice, spec.MRoomMember, map[string]interface{}{
+					"membership": "leave",
+				}, test.WithStateKey(alice.ID))
+			},
+			wantOK: false,
+		},
+		{
+			name: "/joined_members - Bob joins, Alice sees two members",
+			user: alice,
+			request: func(t *testing.T, room *test.Room, accessToken string) *http.Request {
+				return test.NewRequest(t, "GET", fmt.Sprintf("/_matrix/client/v3/rooms/%s/joined_members", room.ID), test.WithQueryParams(map[string]string{
+					"access_token": accessToken,
+				}))
+			},
+			additionalEvents: func(t *testing.T, room *test.Room) {
+				room.CreateAndInsert(t, bob, spec.MRoomMember, map[string]interface{}{
+					"membership": "join",
+				}, test.WithStateKey(bob.ID))
+			},
+			wantOK:          true,
+			wantMemberCount: 2,
+		},
+	}
+
+	test.WithAllDatabases(t, func(t *testing.T, dbType test.DBType) {
+
+		cfg, processCtx, close := testrig.CreateConfig(t, dbType)
+		routers := httputil.NewRouters()
+		cm := sqlutil.NewConnectionManager(processCtx, cfg.Global.DatabaseOptions)
+		caches := caching.NewRistrettoCache(128*1024*1024, time.Hour, caching.DisableMetrics)
+		defer close()
+		natsInstance := jetstream.NATSInstance{}
+		jsctx, _ := natsInstance.Prepare(processCtx, &cfg.Global.JetStream)
+		defer jetstream.DeleteAllStreams(jsctx, &cfg.Global.JetStream)
+
+		// Use an actual roomserver for this
+		rsAPI := roomserver.NewInternalAPI(processCtx, cfg, cm, &natsInstance, caches, caching.DisableMetrics)
+		rsAPI.SetFederationAPI(nil, nil)
+		userAPI := userapi.NewInternalAPI(processCtx, cfg, cm, &natsInstance, rsAPI, nil, caching.DisableMetrics, testIsBlacklistedOrBackingOff)
+
+		// We mostly need the rsAPI for this test, so nil for other APIs/caches etc.
+		AddPublicRoutes(processCtx, routers, cfg, &natsInstance, nil, rsAPI, nil, nil, nil, userAPI, nil, nil, caching.DisableMetrics)
+
+		accessTokens := map[*test.User]userDevice{
+			alice: {},
+			bob:   {},
+		}
+		createAccessTokens(t, accessTokens, userAPI, processCtx.Context(), routers)
+
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				room := test.NewRoom(t, alice)
+				t.Cleanup(func() {
+					t.Logf("running cleanup for %s", tc.name)
+				})
+				// inject additional events
+				if tc.additionalEvents != nil {
+					tc.additionalEvents(t, room)
+				}
+				if err := api.SendEvents(context.Background(), rsAPI, api.KindNew, room.Events(), "test", "test", "test", nil, false); err != nil {
+					t.Fatalf("failed to send events: %v", err)
+				}
+
+				w := httptest.NewRecorder()
+				routers.Client.ServeHTTP(w, tc.request(t, room, accessTokens[tc.user].accessToken))
+				if w.Code != 200 && tc.wantOK {
+					t.Logf("%s", w.Body.String())
+					t.Fatalf("got HTTP %d want %d", w.Code, 200)
+				}
+				t.Logf("[%s] Resp: %s", tc.name, w.Body.String())
+
+				// check we got the expected events
+				if tc.wantOK {
+					memberCount := len(gjson.GetBytes(w.Body.Bytes(), "joined").Map())
+					if memberCount != tc.wantMemberCount {
+						t.Fatalf("expected %d members, got %d", tc.wantMemberCount, memberCount)
+					}
+				}
+			})
+		}
+	})
+}
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,
+	}
+}
diff --git a/clientapi/routing/routing.go b/clientapi/routing/routing.go
index d4aa1d08..3e23ab40 100644
--- a/clientapi/routing/routing.go
+++ b/clientapi/routing/routing.go
@@ -1513,4 +1513,14 @@ func Setup(
 			return GetPresence(req, device, natsClient, cfg.Matrix.JetStream.Prefixed(jetstream.RequestPresence), vars["userId"])
 		}),
 	).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)
+			}
+			return GetJoinedMembers(req, device, vars["roomID"], rsAPI)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
 }