Membership viewing API when user left the room (#194)

* Implement case where user left the room

* Filter by membership event

* Move the logic from the storage to the query API

* Fix check on state entries iteration

* Remove aliases methods from query API

* Use structure for response to match with the spec

* Remove filtering on /members and implement /joined_members

src/github.com/matrix-org/dendrite/clientapi/readers/memberships.go

@@ -23,18 +23,24 @@ import (
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/dendrite/common/config"
 	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
 )
 
+type response struct {
+	Chunk []gomatrixserverlib.ClientEvent `json:"chunk"`
+}
+
 // GetMemberships implements GET /rooms/{roomId}/members
 func GetMemberships(
-	req *http.Request, device *authtypes.Device, roomID string,
+	req *http.Request, device *authtypes.Device, roomID string, joinedOnly bool,
 	accountDB *accounts.Database, cfg config.Dendrite,
 	queryAPI api.RoomserverQueryAPI,
 ) util.JSONResponse {
 	queryReq := api.QueryMembershipsForRoomRequest{
-		RoomID: roomID,
-		Sender: device.UserID,
+		JoinedOnly: joinedOnly,
+		RoomID:     roomID,
+		Sender:     device.UserID,
 	}
 	var queryRes api.QueryMembershipsForRoomResponse
 	if err := queryAPI.QueryMembershipsForRoom(&queryReq, &queryRes); err != nil {
@@ -50,6 +56,6 @@ func GetMemberships(
 
 	return util.JSONResponse{
 		Code: 200,
-		JSON: queryRes.JoinEvents,
+		JSON: response{queryRes.JoinEvents},
 	}
 }

src/github.com/matrix-org/dendrite/clientapi/routing/routing.go

@@ -302,7 +302,14 @@ func Setup(
 	r0mux.Handle("/rooms/{roomID}/members",
 		common.MakeAuthAPI("rooms_members", deviceDB, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
 			vars := mux.Vars(req)
-			return readers.GetMemberships(req, device, vars["roomID"], accountDB, cfg, queryAPI)
+			return readers.GetMemberships(req, device, vars["roomID"], false, accountDB, cfg, queryAPI)
+		}),
+	)
+
+	r0mux.Handle("/rooms/{roomID}/joined_members",
+		common.MakeAuthAPI("rooms_members", deviceDB, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
+			vars := mux.Vars(req)
+			return readers.GetMemberships(req, device, vars["roomID"], true, accountDB, cfg, queryAPI)
 		}),
 	)
 

src/github.com/matrix-org/dendrite/roomserver/api/query.go

@@ -102,6 +102,8 @@ type QueryEventsByIDResponse struct {
 
 // QueryMembershipsForRoomRequest is a request to QueryMembershipsForRoom
 type QueryMembershipsForRoomRequest struct {
+	// If true, only returns the membership events of "join" membership
+	JoinedOnly bool `json:"joined_only"`
 	// ID of the room to fetch memberships from
 	RoomID string `json:"room_id"`
 	// ID of the user sending the request

src/github.com/matrix-org/dendrite/roomserver/query/query.go

@@ -40,13 +40,20 @@ type RoomserverQueryAPIDatabase interface {
 	// Look up the numeric IDs for a list of events.
 	// Returns an error if there was a problem talking to the database.
 	EventNIDs(eventIDs []string) (map[string]types.EventNID, error)
-	// Look up the join events for all members in a room as requested by a given
-	// user. If the user is currently in the room, returns the room's current
-	// members, if not returns an empty array (TODO: Fix it)
-	// If the user requesting the list of members has never been in the room,
-	// returns nil.
-	// If there was an issue retrieving the events, returns an error.
-	GetMembershipEvents(roomNID types.RoomNID, requestSenderUserID string) (events []types.Event, err error)
+	// Lookup the event IDs for a batch of event numeric IDs.
+	// Returns an error if the retrieval went wrong.
+	EventIDs(eventNIDs []types.EventNID) (map[types.EventNID]string, error)
+	// Lookup the membership of a given user in a given room.
+	// Returns the numeric ID of the latest membership event sent from this user
+	// in this room, along a boolean set to true if the user is still in this room,
+	// false if not.
+	// Returns an error if there was a problem talking to the database.
+	GetMembership(roomNID types.RoomNID, requestSenderUserID string) (membershipEventNID types.EventNID, stillInRoom bool, err error)
+	// Lookup the membership event numeric IDs for all user that are or have
+	// been members of a given room. Only lookup events of "join" membership if
+	// joinOnly is set to true.
+	// Returns an error if there was a problem talking to the database.
+	GetMembershipEventNIDsForRoom(roomNID types.RoomNID, joinOnly bool) ([]types.EventNID, error)
 	// Look up the active invites targeting a user in a room and return the
 	// numeric state key IDs for the user IDs who sent them.
 	// Returns an error if there was a problem talking to the database.
@@ -194,12 +201,12 @@ func (r *RoomserverQueryAPI) QueryMembershipsForRoom(
 		return err
 	}
 
-	events, err := r.DB.GetMembershipEvents(roomNID, request.Sender)
+	membershipEventNID, stillInRoom, err := r.DB.GetMembership(roomNID, request.Sender)
 	if err != nil {
 		return nil
 	}
 
-	if events == nil {
+	if membershipEventNID == 0 {
 		response.HasBeenInRoom = false
 		response.JoinEvents = nil
 		return nil
@@ -207,6 +214,24 @@ func (r *RoomserverQueryAPI) QueryMembershipsForRoom(
 
 	response.HasBeenInRoom = true
 	response.JoinEvents = []gomatrixserverlib.ClientEvent{}
+
+	var events []types.Event
+	if stillInRoom {
+		var eventNIDs []types.EventNID
+		eventNIDs, err = r.DB.GetMembershipEventNIDsForRoom(roomNID, request.JoinedOnly)
+		if err != nil {
+			return err
+		}
+
+		events, err = r.DB.Events(eventNIDs)
+	} else {
+		events, err = r.getMembershipsBeforeEventNID(membershipEventNID, request.JoinedOnly)
+	}
+
+	if err != nil {
+		return err
+	}
+
 	for _, event := range events {
 		clientEvent := gomatrixserverlib.ToClientEvent(event.Event, gomatrixserverlib.FormatAll)
 		response.JoinEvents = append(response.JoinEvents, clientEvent)
@@ -215,6 +240,63 @@ func (r *RoomserverQueryAPI) QueryMembershipsForRoom(
 	return nil
 }
 
+// getMembershipsBeforeEventNID takes the numeric ID of an event and fetches the state
+// of the event's room as it was when this event was fired, then filters the state events to
+// only keep the "m.room.member" events with a "join" membership. These events are returned.
+// Returns an error if there was an issue fetching the events.
+func (r *RoomserverQueryAPI) getMembershipsBeforeEventNID(eventNID types.EventNID, joinedOnly bool) ([]types.Event, error) {
+	events := []types.Event{}
+	// Lookup the event NID
+	eIDs, err := r.DB.EventIDs([]types.EventNID{eventNID})
+	if err != nil {
+		return nil, err
+	}
+	eventIDs := []string{eIDs[eventNID]}
+
+	prevState, err := r.DB.StateAtEventIDs(eventIDs)
+	if err != nil {
+		return nil, err
+	}
+
+	// Fetch the state as it was when this event was fired
+	stateEntries, err := state.LoadCombinedStateAfterEvents(r.DB, prevState)
+	if err != nil {
+		return nil, err
+	}
+
+	var eventNIDs []types.EventNID
+	for _, entry := range stateEntries {
+		// Filter the events to retrieve to only keep the membership events
+		if entry.EventTypeNID == types.MRoomMemberNID {
+			eventNIDs = append(eventNIDs, entry.EventNID)
+		}
+	}
+
+	// Get all of the events in this state
+	stateEvents, err := r.DB.Events(eventNIDs)
+	if err != nil {
+		return nil, err
+	}
+
+	if !joinedOnly {
+		return stateEvents, nil
+	}
+
+	// Filter the events to only keep the "join" membership events
+	for _, event := range stateEvents {
+		membership, err := event.Membership()
+		if err != nil {
+			return nil, err
+		}
+
+		if membership == "join" {
+			events = append(events, event)
+		}
+	}
+
+	return events, nil
+}
+
 // QueryInvitesForUser implements api.RoomserverQueryAPI
 func (r *RoomserverQueryAPI) QueryInvitesForUser(
 	request *api.QueryInvitesForUserRequest,

src/github.com/matrix-org/dendrite/roomserver/storage/membership_table.go

@@ -77,7 +77,7 @@ const selectMembershipsFromRoomAndMembershipSQL = "" +
 	" WHERE room_nid = $1 AND membership_nid = $2"
 
 const selectMembershipsFromRoomSQL = "" +
-	"SELECT membership_nid, event_nid FROM roomserver_membership" +
+	"SELECT event_nid FROM roomserver_membership" +
 	" WHERE room_nid = $1"
 
 const selectMembershipForUpdateSQL = "" +
@@ -140,20 +140,18 @@ func (s *membershipStatements) selectMembershipFromRoomAndTarget(
 
 func (s *membershipStatements) selectMembershipsFromRoom(
 	roomNID types.RoomNID,
-) (eventNIDs map[types.EventNID]membershipState, err error) {
+) (eventNIDs []types.EventNID, err error) {
 	rows, err := s.selectMembershipsFromRoomStmt.Query(roomNID)
 	if err != nil {
 		return
 	}
 
-	eventNIDs = make(map[types.EventNID]membershipState)
 	for rows.Next() {
 		var eNID types.EventNID
-		var membership membershipState
-		if err = rows.Scan(&membership, &eNID); err != nil {
+		if err = rows.Scan(&eNID); err != nil {
 			return
 		}
-		eventNIDs[eNID] = membership
+		eventNIDs = append(eventNIDs, eNID)
 	}
 	return
 }

src/github.com/matrix-org/dendrite/roomserver/storage/storage.go

@@ -552,8 +552,8 @@ func (u *membershipUpdater) SetToLeave(senderUserID string, eventID string) ([]s
 	return inviteEventIDs, nil
 }
 
-// GetMembershipEvents implements query.RoomserverQueryAPIDB
-func (d *Database) GetMembershipEvents(roomNID types.RoomNID, requestSenderUserID string) (events []types.Event, err error) {
+// GetMembership implements query.RoomserverQueryAPIDB
+func (d *Database) GetMembership(roomNID types.RoomNID, requestSenderUserID string) (membershipEventNID types.EventNID, stillInRoom bool, err error) {
 	txn, err := d.db.Begin()
 	if err != nil {
 		return
@@ -565,36 +565,24 @@ func (d *Database) GetMembershipEvents(roomNID types.RoomNID, requestSenderUserI
 		return
 	}
 
-	_, senderMembership, err := d.statements.selectMembershipFromRoomAndTarget(roomNID, requestSenderUserNID)
+	senderMembershipEventNID, senderMembership, err := d.statements.selectMembershipFromRoomAndTarget(roomNID, requestSenderUserNID)
 	if err == sql.ErrNoRows {
 		// The user has never been a member of that room
-		return nil, nil
+		return 0, false, nil
 	} else if err != nil {
 		return
 	}
 
-	if senderMembership == membershipStateJoin {
-		// The user is still in the room: Send the current list of joined members
-		var joinEventNIDs []types.EventNID
-		joinEventNIDs, err = d.statements.selectMembershipsFromRoomAndMembership(roomNID, membershipStateJoin)
-		if err != nil {
-			return nil, err
-		}
+	return senderMembershipEventNID, senderMembership == membershipStateJoin, nil
+}
 
-		events, err = d.Events(joinEventNIDs)
-	} else {
-		// The user isn't in the room anymore
-		// TODO: Send the list of joined member as it was when the user left
-		//       We cannot do this using only the memberships database, as it
-		//       only stores the latest join event NID for a given target user.
-		//       The solution would be to build the state of a room after before
-		//       the leave event and extract a members list from it.
-		//       For now, we return an empty slice so we know the user has been
-		//       in the room before.
-		events = []types.Event{}
+// GetMembershipEventNIDsForRoom implements query.RoomserverQueryAPIDB
+func (d *Database) GetMembershipEventNIDsForRoom(roomNID types.RoomNID, joinOnly bool) ([]types.EventNID, error) {
+	if joinOnly {
+		return d.statements.selectMembershipsFromRoomAndMembership(roomNID, membershipStateJoin)
 	}
 
-	return
+	return d.statements.selectMembershipsFromRoom(roomNID)
 }
 
 type transaction struct {