Refactor room hierarchy walker

clientapi/routing/room_hierarchy.go

@@ -30,24 +30,28 @@ import (
 )
 
 type RoomHierarchyPaginationCache struct {
-	cache map[string]roomserverAPI.CachedRoomHierarchyWalker
+	cache map[string]roomserverAPI.RoomHierarchyWalker
 	mu    sync.Mutex
 }
 
 func NewRoomHierarchyPaginationCache() RoomHierarchyPaginationCache {
 	return RoomHierarchyPaginationCache{
-		cache: map[string]roomserverAPI.CachedRoomHierarchyWalker{},
+		cache: map[string]roomserverAPI.RoomHierarchyWalker{},
 	}
 }
 
-func (c *RoomHierarchyPaginationCache) Get(token string) roomserverAPI.CachedRoomHierarchyWalker {
+func (c *RoomHierarchyPaginationCache) Get(token string) *roomserverAPI.RoomHierarchyWalker {
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	line := c.cache[token]
-	return line
+	line, ok := c.cache[token]
+	if ok {
+		return &line
+	} else {
+		return nil
+	}
 }
 
-func (c *RoomHierarchyPaginationCache) AddLine(line roomserverAPI.CachedRoomHierarchyWalker) string {
+func (c *RoomHierarchyPaginationCache) AddLine(line roomserverAPI.RoomHierarchyWalker) string {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	token := uuid.NewString()
@@ -114,21 +118,21 @@ func QueryRoomHierarchy(req *http.Request, device *userapi.Device, roomIDStr str
 
 	var walker roomserverAPI.RoomHierarchyWalker
 	if from == "" { // No pagination token provided, so start new hierarchy walker
-		walker = rsAPI.QueryRoomHierarchy(req.Context(), types.NewDeviceNotServerName(*device), roomID, suggestedOnly, maxDepth)
+		walker = roomserverAPI.NewRoomHierarchyWalker(types.NewDeviceNotServerName(*device), roomID, suggestedOnly, maxDepth)
 	} else { // Attempt to resume cached walker
 		cachedWalker := paginationCache.Get(from)
 
-		if cachedWalker == nil || !cachedWalker.ValidateParams(suggestedOnly, maxDepth) {
+		if cachedWalker == nil || cachedWalker.SuggestedOnly != suggestedOnly || cachedWalker.MaxDepth != maxDepth {
 			return util.JSONResponse{
 				Code: http.StatusBadRequest,
 				JSON: spec.InvalidParam("pagination not found for provided token ('from') with given 'max_depth', 'suggested_only' and room ID"),
 			}
 		}
 
-		walker = cachedWalker.GetWalker()
+		walker = *cachedWalker
 	}
 
-	discoveredRooms, err := walker.NextPage(limit)
+	discoveredRooms, nextWalker, err := rsAPI.QueryNextRoomHierarchyPage(req.Context(), walker, limit)
 
 	if err != nil {
 		switch err.(type) {
@@ -147,9 +151,9 @@ func QueryRoomHierarchy(req *http.Request, device *userapi.Device, roomIDStr str
 	}
 
 	nextBatch := ""
-	if !walker.Done() {
-		cacheLine := walker.GetCached()
-		nextBatch = paginationCache.AddLine(cacheLine)
+	// nextWalker will be nil if there's no more rooms left to walk
+	if nextWalker != nil {
+		nextBatch = paginationCache.AddLine(*nextWalker)
 	}
 
 	return util.JSONResponse{

federationapi/routing/query.go

@@ -145,9 +145,8 @@ func QueryRoomHierarchy(httpReq *http.Request, request *fclient.FederationReques
 		}
 	}
 
-	walker := rsAPI.QueryRoomHierarchy(httpReq.Context(), types.NewServerNameNotDevice(request.Origin()), roomID, suggestedOnly, 1)
-
-	discoveredRooms, err := walker.NextPage(-1)
+	walker := roomserverAPI.NewRoomHierarchyWalker(types.NewServerNameNotDevice(request.Origin()), roomID, suggestedOnly, 1)
+	discoveredRooms, _, err := rsAPI.QueryNextRoomHierarchyPage(httpReq.Context(), walker, -1)
 
 	if err != nil {
 		switch err.(type) {

roomserver/api/api.go

@@ -125,7 +125,7 @@ type QueryEventsAPI interface {
 }
 
 type QueryRoomHierarchyAPI interface {
-	QueryRoomHierarchy(ctx context.Context, caller types.DeviceOrServerName, roomID spec.RoomID, suggestedOnly bool, maxDepth int) RoomHierarchyWalker
+	QueryNextRoomHierarchyPage(ctx context.Context, walker RoomHierarchyWalker, limit int) ([]fclient.MSC2946Room, *RoomHierarchyWalker, error)
 }
 
 // API functions required by the syncapi

roomserver/api/query.go

@@ -23,7 +23,6 @@ import (
 	"strings"
 
 	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/matrix-org/gomatrixserverlib/fclient"
 	"github.com/matrix-org/gomatrixserverlib/spec"
 	"github.com/matrix-org/util"
 
@@ -512,24 +511,63 @@ type QueryRoomHierarchyRequest struct {
 	From          int  `json:"json"`
 }
 
-// An iterator-like interface for walking a room/space hierarchy, returning each rooms information.
+// A struct storing the intermediate state of a room hierarchy query for pagination purposes.
 //
 // Used for implementing space summaries / room hierarchies
-type RoomHierarchyWalker interface {
-	// Walk the room hierarchy to retrieve room information until either
-	// no room left, or provided limit reached. If limit provided is -1, then this is
-	// treated as no limit.
-	NextPage(limit int) ([]fclient.MSC2946Room, error)
-	// Returns true if there are no more rooms left to walk
-	Done() bool
-	// Returns a stripped down version of the hiearchy walker suitable for pagination caching
-	GetCached() CachedRoomHierarchyWalker
+//
+// Use NewRoomHierarchyWalker on the roomserver API to construct this.
+type RoomHierarchyWalker struct {
+	RootRoomID    spec.RoomID
+	Caller        types.DeviceOrServerName
+	SuggestedOnly bool
+	MaxDepth      int
+	Processed     RoomSet
+	Unvisited     []RoomHierarchyWalkerQueuedRoom
 }
 
-// Stripped down version of RoomHierarchyWalker suitable for caching (for pagination)
-type CachedRoomHierarchyWalker interface {
-	// Converts this cached walker back into an actual walker, to resume walking from.
-	GetWalker() RoomHierarchyWalker
-	// Validates that the given parameters match those stored in the cache
-	ValidateParams(suggestedOnly bool, maxDepth int) bool
+type RoomHierarchyWalkerQueuedRoom struct {
+	RoomID       spec.RoomID
+	ParentRoomID *spec.RoomID
+	Depth        int
+	Vias         []string // vias to query this room by
+}
+
+func NewRoomHierarchyWalker(caller types.DeviceOrServerName, roomID spec.RoomID, suggestedOnly bool, maxDepth int) RoomHierarchyWalker {
+	walker := RoomHierarchyWalker{
+		RootRoomID:    roomID,
+		Caller:        caller,
+		SuggestedOnly: suggestedOnly,
+		MaxDepth:      maxDepth,
+		Unvisited: []RoomHierarchyWalkerQueuedRoom{{
+			RoomID:       roomID,
+			ParentRoomID: nil,
+			Depth:        0,
+		}},
+		Processed: NewRoomSet(),
+	}
+
+	return walker
+}
+
+type RoomSet map[spec.RoomID]struct{}
+
+func NewRoomSet() RoomSet {
+	return RoomSet{}
+}
+
+func (s RoomSet) Contains(val spec.RoomID) bool {
+	_, ok := s[val]
+	return ok
+}
+
+func (s RoomSet) Add(val spec.RoomID) {
+	s[val] = struct{}{}
+}
+
+func (s RoomSet) Copy() RoomSet {
+	copied := make(RoomSet, len(s))
+	for k, _ := range s {
+		copied.Add(k)
+	}
+	return copied
 }

roomserver/internal/query/query_room_hierarchy.go

@@ -22,7 +22,6 @@ import (
 	"strings"
 
 	fs "github.com/matrix-org/dendrite/federationapi/api"
-	"github.com/matrix-org/dendrite/internal/caching"
 	roomserver "github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/types"
 	userapi "github.com/matrix-org/dendrite/userapi/api"
@@ -33,59 +32,6 @@ import (
 	"github.com/tidwall/gjson"
 )
 
-// Query the hierarchy of a room (A.K.A 'space summary')
-//
-// This function returns a iterator-like struct over the hierarchy of a room.
-func (r *Queryer) QueryRoomHierarchy(ctx context.Context, caller types.DeviceOrServerName, roomID spec.RoomID, suggestedOnly bool, maxDepth int) roomserver.RoomHierarchyWalker {
-	walker := RoomHierarchyWalker{
-		rootRoomID:         roomID.String(),
-		caller:             caller,
-		thisServer:         r.Cfg.Global.ServerName,
-		rsAPI:              r,
-		fsAPI:              r.FSAPI,
-		ctx:                ctx,
-		roomHierarchyCache: r.Cache,
-		suggestedOnly:      suggestedOnly,
-		maxDepth:           maxDepth,
-		unvisited: []roomVisit{{
-			roomID:       roomID.String(),
-			parentRoomID: "",
-			depth:        0,
-		}},
-		processed: stringSet{},
-	}
-
-	return &walker
-}
-
-type stringSet map[string]struct{}
-
-func (s stringSet) contains(val string) bool {
-	_, ok := s[val]
-	return ok
-}
-
-func (s stringSet) add(val string) {
-	s[val] = struct{}{}
-}
-
-type RoomHierarchyWalker struct {
-	rootRoomID         string // TODO change to spec.RoomID
-	caller             types.DeviceOrServerName
-	thisServer         spec.ServerName
-	rsAPI              *Queryer
-	fsAPI              fs.RoomserverFederationAPI
-	ctx                context.Context
-	roomHierarchyCache caching.RoomHierarchyCache
-	suggestedOnly      bool
-	maxDepth           int
-
-	processed stringSet
-	unvisited []roomVisit
-
-	done bool
-}
-
 const (
 	ConstCreateEventContentKey        = "type"
 	ConstCreateEventContentValueSpace = "m.space"
@@ -96,34 +42,39 @@ const (
 // Walk the room hierarchy to retrieve room information until either
 // no room left, or provided limit reached. If limit provided is -1, then this is
 // treated as no limit.
-func (w *RoomHierarchyWalker) NextPage(limit int) ([]fclient.MSC2946Room, error) {
-	if authorised, _ := w.authorised(w.rootRoomID, ""); !authorised {
-		return nil, roomserver.ErrRoomUnknownOrNotAllowed{Err: fmt.Errorf("room is unknown/forbidden")}
+func (querier *Queryer) QueryNextRoomHierarchyPage(ctx context.Context, walker roomserver.RoomHierarchyWalker, limit int) ([]fclient.MSC2946Room, *roomserver.RoomHierarchyWalker, error) {
+	if authorised, _ := authorised(ctx, querier, walker.Caller, walker.RootRoomID, nil); !authorised {
+		return nil, nil, roomserver.ErrRoomUnknownOrNotAllowed{Err: fmt.Errorf("room is unknown/forbidden")}
 	}
 
 	var discoveredRooms []fclient.MSC2946Room
 
+	// Copy unvisited and processed to avoid modifying walker
+	unvisited := []roomserver.RoomHierarchyWalkerQueuedRoom{}
+	copy(unvisited, walker.Unvisited)
+	processed := walker.Processed.Copy()
+
 	// Depth first -> stack data structure
-	for len(w.unvisited) > 0 {
+	for len(unvisited) > 0 {
 		if len(discoveredRooms) >= limit {
 			break
 		}
 
 		// pop the stack
-		rv := w.unvisited[len(w.unvisited)-1]
-		w.unvisited = w.unvisited[:len(w.unvisited)-1]
+		queuedRoom := unvisited[len(unvisited)-1]
+		unvisited = unvisited[:len(unvisited)-1]
 		// If this room has already been processed, skip.
 		// If this room exceeds the specified depth, skip.
-		if w.processed.contains(rv.roomID) || rv.roomID == "" || (w.maxDepth > 0 && rv.depth > w.maxDepth) {
+		if processed.Contains(queuedRoom.RoomID) || (walker.MaxDepth > 0 && queuedRoom.Depth > walker.MaxDepth) {
 			continue
 		}
 
 		// Mark this room as processed.
-		w.processed.add(rv.roomID)
+		processed.Add(queuedRoom.RoomID)
 
 		// if this room is not a space room, skip.
 		var roomType string
-		create := w.stateEvent(rv.roomID, spec.MRoomCreate, "")
+		create := stateEvent(ctx, querier, queuedRoom.RoomID, spec.MRoomCreate, "")
 		if create != nil {
 			// escape the `.`s so gjson doesn't think it's nested
 			roomType = gjson.GetBytes(create.Content(), strings.ReplaceAll(ConstCreateEventContentKey, ".", `\.`)).Str
@@ -134,11 +85,11 @@ func (w *RoomHierarchyWalker) NextPage(limit int) ([]fclient.MSC2946Room, error)
 
 		// If we know about this room and the caller is authorised (joined/world_readable) then pull
 		// events locally
-		roomExists := w.roomExists(rv.roomID)
+		roomExists := roomExists(ctx, querier, queuedRoom.RoomID)
 		if !roomExists {
 			// attempt to query this room over federation, as either we've never heard of it before
 			// or we've left it and hence are not authorised (but info may be exposed regardless)
-			fedRes := w.federatedRoomInfo(rv.roomID, rv.vias)
+			fedRes := federatedRoomInfo(ctx, querier, walker.Caller, walker.SuggestedOnly, queuedRoom.RoomID, queuedRoom.Vias)
 			if fedRes != nil {
 				discoveredChildEvents = fedRes.Room.ChildrenState
 				discoveredRooms = append(discoveredRooms, fedRes.Room)
@@ -150,16 +101,16 @@ func (w *RoomHierarchyWalker) NextPage(limit int) ([]fclient.MSC2946Room, error)
 				// as these children may be rooms we do know about.
 				roomType = ConstCreateEventContentValueSpace
 			}
-		} else if authorised, isJoinedOrInvited := w.authorised(rv.roomID, rv.parentRoomID); authorised {
+		} else if authorised, isJoinedOrInvited := authorised(ctx, querier, walker.Caller, queuedRoom.RoomID, queuedRoom.ParentRoomID); authorised {
 			// Get all `m.space.child` state events for this room
-			events, err := w.childReferences(rv.roomID)
+			events, err := childReferences(querier, walker.SuggestedOnly, queuedRoom.RoomID)
 			if err != nil {
-				util.GetLogger(w.ctx).WithError(err).WithField("room_id", rv.roomID).Error("failed to extract references for room")
+				util.GetLogger(ctx).WithError(err).WithField("room_id", queuedRoom.RoomID).Error("failed to extract references for room")
 				continue
 			}
 			discoveredChildEvents = events
 
-			pubRoom := w.publicRoomsChunk(rv.roomID)
+			pubRoom := publicRoomsChunk(ctx, querier, queuedRoom.RoomID)
 
 			discoveredRooms = append(discoveredRooms, fclient.MSC2946Room{
 				PublicRoom:    *pubRoom,
@@ -192,51 +143,213 @@ func (w *RoomHierarchyWalker) NextPage(limit int) ([]fclient.MSC2946Room, error)
 			}{}
 			ev := discoveredChildEvents[i]
 			_ = json.Unmarshal(ev.Content, &spaceContent)
-			w.unvisited = append(w.unvisited, roomVisit{
-				roomID:       ev.StateKey,
-				parentRoomID: rv.roomID,
-				depth:        rv.depth + 1,
-				vias:         spaceContent.Via,
+
+			childRoomID, err := spec.NewRoomID(ev.StateKey)
+
+			if err != nil {
+				util.GetLogger(ctx).WithError(err).WithField("invalid_room_id", ev.StateKey).WithField("parent_room_id", queuedRoom.RoomID).Warn("Invalid room ID in m.space.child state event")
+			} else {
+				unvisited = append(unvisited, roomserver.RoomHierarchyWalkerQueuedRoom{
+					RoomID:       *childRoomID,
+					ParentRoomID: &queuedRoom.RoomID,
+					Depth:        queuedRoom.Depth + 1,
+					Vias:         spaceContent.Via,
 				})
 			}
 		}
-
-	if len(w.unvisited) == 0 {
-		w.done = true
 	}
 
-	return discoveredRooms, nil
+	if len(unvisited) == 0 {
+		// If no more rooms to walk, then don't return a walker for future pages
+		return discoveredRooms, nil, nil
+	} else {
+		// If there are more rooms to walk, then return a new walker to resume walking from (for querying more pages)
+		newWalker := roomserver.RoomHierarchyWalker{
+			RootRoomID:    walker.RootRoomID,
+			Caller:        walker.Caller,
+			SuggestedOnly: walker.SuggestedOnly,
+			MaxDepth:      walker.MaxDepth,
+			Unvisited:     unvisited,
+			Processed:     processed,
+		}
+
+		return discoveredRooms, &newWalker, nil
+	}
+
 }
 
-func (w *RoomHierarchyWalker) Done() bool {
-	return w.done
-}
-
-func (w *RoomHierarchyWalker) GetCached() roomserver.CachedRoomHierarchyWalker {
-	return CachedRoomHierarchyWalker{
-		rootRoomID:    w.rootRoomID,
-		caller:        w.caller,
-		thisServer:    w.thisServer,
-		rsAPI:         w.rsAPI,
-		fsAPI:         w.fsAPI,
-		ctx:           w.ctx,
-		cache:         w.roomHierarchyCache,
-		suggestedOnly: w.suggestedOnly,
-		maxDepth:      w.maxDepth,
-		processed:     w.processed,
-		unvisited:     w.unvisited,
-		done:          w.done,
+// authorised returns true iff the user is joined this room or the room is world_readable
+func authorised(ctx context.Context, querier *Queryer, caller types.DeviceOrServerName, roomID spec.RoomID, parentRoomID *spec.RoomID) (authed, isJoinedOrInvited bool) {
+	if clientCaller := caller.Device(); clientCaller != nil {
+		return authorisedUser(ctx, querier, clientCaller, roomID, parentRoomID)
+	} else {
+		return authorisedServer(ctx, querier, roomID, *caller.ServerName()), false
 	}
 }
 
-func (w *RoomHierarchyWalker) stateEvent(roomID, evType, stateKey string) *types.HeaderedEvent {
+// authorisedServer returns true iff the server is joined this room or the room is world_readable, public, or knockable
+func authorisedServer(ctx context.Context, querier *Queryer, roomID spec.RoomID, callerServerName spec.ServerName) bool {
+	// Check history visibility / join rules first
+	hisVisTuple := gomatrixserverlib.StateKeyTuple{
+		EventType: spec.MRoomHistoryVisibility,
+		StateKey:  "",
+	}
+	joinRuleTuple := gomatrixserverlib.StateKeyTuple{
+		EventType: spec.MRoomJoinRules,
+		StateKey:  "",
+	}
+	var queryRoomRes roomserver.QueryCurrentStateResponse
+	err := querier.QueryCurrentState(ctx, &roomserver.QueryCurrentStateRequest{
+		RoomID: roomID.String(),
+		StateTuples: []gomatrixserverlib.StateKeyTuple{
+			hisVisTuple, joinRuleTuple,
+		},
+	}, &queryRoomRes)
+	if err != nil {
+		util.GetLogger(ctx).WithError(err).Error("failed to QueryCurrentState")
+		return false
+	}
+	hisVisEv := queryRoomRes.StateEvents[hisVisTuple]
+	if hisVisEv != nil {
+		hisVis, _ := hisVisEv.HistoryVisibility()
+		if hisVis == "world_readable" {
+			return true
+		}
+	}
+
+	// check if this room is a restricted room and if so, we need to check if the server is joined to an allowed room ID
+	// in addition to the actual room ID (but always do the actual one first as it's quicker in the common case)
+	allowJoinedToRoomIDs := []spec.RoomID{roomID}
+	joinRuleEv := queryRoomRes.StateEvents[joinRuleTuple]
+
+	if joinRuleEv != nil {
+		rule, ruleErr := joinRuleEv.JoinRule()
+		if ruleErr != nil {
+			util.GetLogger(ctx).WithError(ruleErr).WithField("parent_room_id", roomID).Warn("failed to get join rule")
+			return false
+		}
+
+		if rule == spec.Public || rule == spec.Knock {
+			return true
+		}
+
+		if rule == spec.Restricted {
+			allowJoinedToRoomIDs = append(allowJoinedToRoomIDs, restrictedJoinRuleAllowedRooms(ctx, joinRuleEv, "m.room_membership")...)
+		}
+	}
+
+	// check if server is joined to any allowed room
+	for _, allowedRoomID := range allowJoinedToRoomIDs {
+		var queryRes fs.QueryJoinedHostServerNamesInRoomResponse
+		err = querier.FSAPI.QueryJoinedHostServerNamesInRoom(ctx, &fs.QueryJoinedHostServerNamesInRoomRequest{
+			RoomID: allowedRoomID.String(),
+		}, &queryRes)
+		if err != nil {
+			util.GetLogger(ctx).WithError(err).Error("failed to QueryJoinedHostServerNamesInRoom")
+			continue
+		}
+		for _, srv := range queryRes.ServerNames {
+			if srv == callerServerName {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// authorisedUser returns true iff the user is invited/joined this room or the room is world_readable
+// or if the room has a public or knock join rule.
+// Failing that, if the room has a restricted join rule and belongs to the space parent listed, it will return true.
+func authorisedUser(ctx context.Context, querier *Queryer, clientCaller *userapi.Device, roomID spec.RoomID, parentRoomID *spec.RoomID) (authed bool, isJoinedOrInvited bool) {
+	hisVisTuple := gomatrixserverlib.StateKeyTuple{
+		EventType: spec.MRoomHistoryVisibility,
+		StateKey:  "",
+	}
+	joinRuleTuple := gomatrixserverlib.StateKeyTuple{
+		EventType: spec.MRoomJoinRules,
+		StateKey:  "",
+	}
+	roomMemberTuple := gomatrixserverlib.StateKeyTuple{
+		EventType: spec.MRoomMember,
+		StateKey:  clientCaller.UserID,
+	}
+	var queryRes roomserver.QueryCurrentStateResponse
+	err := querier.QueryCurrentState(ctx, &roomserver.QueryCurrentStateRequest{
+		RoomID: roomID.String(),
+		StateTuples: []gomatrixserverlib.StateKeyTuple{
+			hisVisTuple, joinRuleTuple, roomMemberTuple,
+		},
+	}, &queryRes)
+	if err != nil {
+		util.GetLogger(ctx).WithError(err).Error("failed to QueryCurrentState")
+		return false, false
+	}
+	memberEv := queryRes.StateEvents[roomMemberTuple]
+	if memberEv != nil {
+		membership, _ := memberEv.Membership()
+		if membership == spec.Join || membership == spec.Invite {
+			return true, true
+		}
+	}
+	hisVisEv := queryRes.StateEvents[hisVisTuple]
+	if hisVisEv != nil {
+		hisVis, _ := hisVisEv.HistoryVisibility()
+		if hisVis == "world_readable" {
+			return true, false
+		}
+	}
+	joinRuleEv := queryRes.StateEvents[joinRuleTuple]
+	if parentRoomID != nil && joinRuleEv != nil {
+		var allowed bool
+		rule, ruleErr := joinRuleEv.JoinRule()
+		if ruleErr != nil {
+			util.GetLogger(ctx).WithError(ruleErr).WithField("parent_room_id", parentRoomID).Warn("failed to get join rule")
+		} else if rule == spec.Public || rule == spec.Knock {
+			allowed = true
+		} else if rule == spec.Restricted {
+			allowedRoomIDs := restrictedJoinRuleAllowedRooms(ctx, joinRuleEv, "m.room_membership")
+			// check parent is in the allowed set
+			for _, a := range allowedRoomIDs {
+				if *parentRoomID == a {
+					allowed = true
+					break
+				}
+			}
+		}
+		if allowed {
+			// ensure caller is joined to the parent room
+			var queryRes2 roomserver.QueryCurrentStateResponse
+			err = querier.QueryCurrentState(ctx, &roomserver.QueryCurrentStateRequest{
+				RoomID: parentRoomID.String(),
+				StateTuples: []gomatrixserverlib.StateKeyTuple{
+					roomMemberTuple,
+				},
+			}, &queryRes2)
+			if err != nil {
+				util.GetLogger(ctx).WithError(err).WithField("parent_room_id", parentRoomID).Warn("failed to check user is joined to parent room")
+			} else {
+				memberEv = queryRes2.StateEvents[roomMemberTuple]
+				if memberEv != nil {
+					membership, _ := memberEv.Membership()
+					if membership == spec.Join {
+						return true, false
+					}
+				}
+			}
+		}
+	}
+	return false, false
+}
+
+func stateEvent(ctx context.Context, querier *Queryer, roomID spec.RoomID, evType, stateKey string) *types.HeaderedEvent {
 	var queryRes roomserver.QueryCurrentStateResponse
 	tuple := gomatrixserverlib.StateKeyTuple{
 		EventType: evType,
 		StateKey:  stateKey,
 	}
-	err := w.rsAPI.QueryCurrentState(w.ctx, &roomserver.QueryCurrentStateRequest{
-		RoomID:      roomID,
+	err := querier.QueryCurrentState(ctx, &roomserver.QueryCurrentStateRequest{
+		RoomID:      roomID.String(),
 		StateTuples: []gomatrixserverlib.StateKeyTuple{tuple},
 	}, &queryRes)
 	if err != nil {
@@ -245,14 +358,14 @@ func (w *RoomHierarchyWalker) stateEvent(roomID, evType, stateKey string) *types
 	return queryRes.StateEvents[tuple]
 }
 
-func (w *RoomHierarchyWalker) roomExists(roomID string) bool {
+func roomExists(ctx context.Context, querier *Queryer, roomID spec.RoomID) bool {
 	var queryRes roomserver.QueryServerJoinedToRoomResponse
-	err := w.rsAPI.QueryServerJoinedToRoom(w.ctx, &roomserver.QueryServerJoinedToRoomRequest{
-		RoomID:     roomID,
-		ServerName: w.thisServer,
+	err := querier.QueryServerJoinedToRoom(ctx, &roomserver.QueryServerJoinedToRoomRequest{
+		RoomID:     roomID.String(),
+		ServerName: querier.Cfg.Global.ServerName,
 	}, &queryRes)
 	if err != nil {
-		util.GetLogger(w.ctx).WithError(err).Error("failed to QueryServerJoinedToRoom")
+		util.GetLogger(ctx).WithError(err).Error("failed to QueryServerJoinedToRoom")
 		return false
 	}
 	// if the room exists but we aren't in the room then we might have stale data so we want to fetch
@@ -262,26 +375,26 @@ func (w *RoomHierarchyWalker) roomExists(roomID string) bool {
 
 // federatedRoomInfo returns more of the spaces graph from another server. Returns nil if this was
 // unsuccessful.
-func (w *RoomHierarchyWalker) federatedRoomInfo(roomID string, vias []string) *fclient.MSC2946SpacesResponse {
+func federatedRoomInfo(ctx context.Context, querier *Queryer, caller types.DeviceOrServerName, suggestedOnly bool, roomID spec.RoomID, vias []string) *fclient.MSC2946SpacesResponse {
 	// only do federated requests for client requests
-	if w.caller.Device() == nil {
+	if caller.Device() == nil {
 		return nil
 	}
-	resp, ok := w.roomHierarchyCache.GetRoomHierarchy(roomID)
+	resp, ok := querier.Cache.GetRoomHierarchy(roomID.String())
 	if ok {
-		util.GetLogger(w.ctx).Debugf("Returning cached response for %s", roomID)
+		util.GetLogger(ctx).Debugf("Returning cached response for %s", roomID)
 		return &resp
 	}
-	util.GetLogger(w.ctx).Debugf("Querying %s via %+v", roomID, vias)
-	ctx := context.Background()
+	util.GetLogger(ctx).Debugf("Querying %s via %+v", roomID, vias)
+	innerCtx := context.Background()
 	// query more of the spaces graph using these servers
 	for _, serverName := range vias {
-		if serverName == string(w.thisServer) {
+		if serverName == string(querier.Cfg.Global.ServerName) {
 			continue
 		}
-		res, err := w.fsAPI.RoomHierarchies(ctx, w.thisServer, spec.ServerName(serverName), roomID, w.suggestedOnly)
+		res, err := querier.FSAPI.RoomHierarchies(innerCtx, querier.Cfg.Global.ServerName, spec.ServerName(serverName), roomID.String(), suggestedOnly)
 		if err != nil {
-			util.GetLogger(w.ctx).WithError(err).Warnf("failed to call RoomHierarchies on server %s", serverName)
+			util.GetLogger(ctx).WithError(err).Warnf("failed to call RoomHierarchies on server %s", serverName)
 			continue
 		}
 		// ensure nil slices are empty as we send this to the client sometimes
@@ -295,7 +408,7 @@ func (w *RoomHierarchyWalker) federatedRoomInfo(roomID string, vias []string) *f
 			}
 			res.Children[i] = child
 		}
-		w.roomHierarchyCache.StoreRoomHierarchy(roomID, res)
+		querier.Cache.StoreRoomHierarchy(roomID.String(), res)
 
 		return &res
 	}
@@ -303,14 +416,14 @@ func (w *RoomHierarchyWalker) federatedRoomInfo(roomID string, vias []string) *f
 }
 
 // references returns all child references pointing to or from this room.
-func (w *RoomHierarchyWalker) childReferences(roomID string) ([]fclient.MSC2946StrippedEvent, error) {
+func childReferences(querier *Queryer, suggestedOnly bool, roomID spec.RoomID) ([]fclient.MSC2946StrippedEvent, error) {
 	createTuple := gomatrixserverlib.StateKeyTuple{
 		EventType: spec.MRoomCreate,
 		StateKey:  "",
 	}
 	var res roomserver.QueryCurrentStateResponse
-	err := w.rsAPI.QueryCurrentState(context.Background(), &roomserver.QueryCurrentStateRequest{
-		RoomID:         roomID,
+	err := querier.QueryCurrentState(context.Background(), &roomserver.QueryCurrentStateRequest{
+		RoomID:         roomID.String(),
 		AllowWildcards: true,
 		StateTuples: []gomatrixserverlib.StateKeyTuple{
 			createTuple, {
@@ -346,7 +459,7 @@ func (w *RoomHierarchyWalker) childReferences(roomID string) ([]fclient.MSC2946S
 			}
 			// if suggested only and this child isn't suggested, skip it.
 			// if suggested only = false we include everything so don't need to check the content.
-			if w.suggestedOnly && !content.Get("suggested").Bool() {
+			if suggestedOnly && !content.Get("suggested").Bool() {
 				continue
 			}
 			el = append(el, *strip)
@@ -360,174 +473,10 @@ func (w *RoomHierarchyWalker) childReferences(roomID string) ([]fclient.MSC2946S
 	return el, nil
 }
 
-// authorised returns true iff the user is joined this room or the room is world_readable
-func (w *RoomHierarchyWalker) authorised(roomID, parentRoomID string) (authed, isJoinedOrInvited bool) {
-	if clientCaller := w.caller.Device(); clientCaller != nil {
-		return w.authorisedUser(roomID, clientCaller, parentRoomID)
-	} else {
-		return w.authorisedServer(roomID, *w.caller.ServerName()), false
-	}
-}
-
-// authorisedServer returns true iff the server is joined this room or the room is world_readable, public, or knockable
-func (w *RoomHierarchyWalker) authorisedServer(roomID string, callerServerName spec.ServerName) bool {
-	// Check history visibility / join rules first
-	hisVisTuple := gomatrixserverlib.StateKeyTuple{
-		EventType: spec.MRoomHistoryVisibility,
-		StateKey:  "",
-	}
-	joinRuleTuple := gomatrixserverlib.StateKeyTuple{
-		EventType: spec.MRoomJoinRules,
-		StateKey:  "",
-	}
-	var queryRoomRes roomserver.QueryCurrentStateResponse
-	err := w.rsAPI.QueryCurrentState(w.ctx, &roomserver.QueryCurrentStateRequest{
-		RoomID: roomID,
-		StateTuples: []gomatrixserverlib.StateKeyTuple{
-			hisVisTuple, joinRuleTuple,
-		},
-	}, &queryRoomRes)
+func publicRoomsChunk(ctx context.Context, querier *Queryer, roomID spec.RoomID) *fclient.PublicRoom {
+	pubRooms, err := roomserver.PopulatePublicRooms(ctx, []string{roomID.String()}, querier)
 	if err != nil {
-		util.GetLogger(w.ctx).WithError(err).Error("failed to QueryCurrentState")
-		return false
-	}
-	hisVisEv := queryRoomRes.StateEvents[hisVisTuple]
-	if hisVisEv != nil {
-		hisVis, _ := hisVisEv.HistoryVisibility()
-		if hisVis == "world_readable" {
-			return true
-		}
-	}
-
-	// check if this room is a restricted room and if so, we need to check if the server is joined to an allowed room ID
-	// in addition to the actual room ID (but always do the actual one first as it's quicker in the common case)
-	allowJoinedToRoomIDs := []string{roomID}
-	joinRuleEv := queryRoomRes.StateEvents[joinRuleTuple]
-
-	if joinRuleEv != nil {
-		rule, ruleErr := joinRuleEv.JoinRule()
-		if ruleErr != nil {
-			util.GetLogger(w.ctx).WithError(ruleErr).WithField("parent_room_id", roomID).Warn("failed to get join rule")
-			return false
-		}
-
-		if rule == spec.Public || rule == spec.Knock {
-			return true
-		}
-
-		if rule == spec.Restricted {
-			allowJoinedToRoomIDs = append(allowJoinedToRoomIDs, w.restrictedJoinRuleAllowedRooms(joinRuleEv, "m.room_membership")...)
-		}
-	}
-
-	// check if server is joined to any allowed room
-	for _, allowedRoomID := range allowJoinedToRoomIDs {
-		var queryRes fs.QueryJoinedHostServerNamesInRoomResponse
-		err = w.fsAPI.QueryJoinedHostServerNamesInRoom(w.ctx, &fs.QueryJoinedHostServerNamesInRoomRequest{
-			RoomID: allowedRoomID,
-		}, &queryRes)
-		if err != nil {
-			util.GetLogger(w.ctx).WithError(err).Error("failed to QueryJoinedHostServerNamesInRoom")
-			continue
-		}
-		for _, srv := range queryRes.ServerNames {
-			if srv == callerServerName {
-				return true
-			}
-		}
-	}
-
-	return false
-}
-
-// authorisedUser returns true iff the user is invited/joined this room or the room is world_readable
-// or if the room has a public or knock join rule.
-// Failing that, if the room has a restricted join rule and belongs to the space parent listed, it will return true.
-func (w *RoomHierarchyWalker) authorisedUser(roomID string, clientCaller *userapi.Device, parentRoomID string) (authed bool, isJoinedOrInvited bool) {
-	hisVisTuple := gomatrixserverlib.StateKeyTuple{
-		EventType: spec.MRoomHistoryVisibility,
-		StateKey:  "",
-	}
-	joinRuleTuple := gomatrixserverlib.StateKeyTuple{
-		EventType: spec.MRoomJoinRules,
-		StateKey:  "",
-	}
-	roomMemberTuple := gomatrixserverlib.StateKeyTuple{
-		EventType: spec.MRoomMember,
-		StateKey:  clientCaller.UserID,
-	}
-	var queryRes roomserver.QueryCurrentStateResponse
-	err := w.rsAPI.QueryCurrentState(w.ctx, &roomserver.QueryCurrentStateRequest{
-		RoomID: roomID,
-		StateTuples: []gomatrixserverlib.StateKeyTuple{
-			hisVisTuple, joinRuleTuple, roomMemberTuple,
-		},
-	}, &queryRes)
-	if err != nil {
-		util.GetLogger(w.ctx).WithError(err).Error("failed to QueryCurrentState")
-		return false, false
-	}
-	memberEv := queryRes.StateEvents[roomMemberTuple]
-	if memberEv != nil {
-		membership, _ := memberEv.Membership()
-		if membership == spec.Join || membership == spec.Invite {
-			return true, true
-		}
-	}
-	hisVisEv := queryRes.StateEvents[hisVisTuple]
-	if hisVisEv != nil {
-		hisVis, _ := hisVisEv.HistoryVisibility()
-		if hisVis == "world_readable" {
-			return true, false
-		}
-	}
-	joinRuleEv := queryRes.StateEvents[joinRuleTuple]
-	if parentRoomID != "" && joinRuleEv != nil {
-		var allowed bool
-		rule, ruleErr := joinRuleEv.JoinRule()
-		if ruleErr != nil {
-			util.GetLogger(w.ctx).WithError(ruleErr).WithField("parent_room_id", parentRoomID).Warn("failed to get join rule")
-		} else if rule == spec.Public || rule == spec.Knock {
-			allowed = true
-		} else if rule == spec.Restricted {
-			allowedRoomIDs := w.restrictedJoinRuleAllowedRooms(joinRuleEv, "m.room_membership")
-			// check parent is in the allowed set
-			for _, a := range allowedRoomIDs {
-				if parentRoomID == a {
-					allowed = true
-					break
-				}
-			}
-		}
-		if allowed {
-			// ensure caller is joined to the parent room
-			var queryRes2 roomserver.QueryCurrentStateResponse
-			err = w.rsAPI.QueryCurrentState(w.ctx, &roomserver.QueryCurrentStateRequest{
-				RoomID: parentRoomID,
-				StateTuples: []gomatrixserverlib.StateKeyTuple{
-					roomMemberTuple,
-				},
-			}, &queryRes2)
-			if err != nil {
-				util.GetLogger(w.ctx).WithError(err).WithField("parent_room_id", parentRoomID).Warn("failed to check user is joined to parent room")
-			} else {
-				memberEv = queryRes2.StateEvents[roomMemberTuple]
-				if memberEv != nil {
-					membership, _ := memberEv.Membership()
-					if membership == spec.Join {
-						return true, false
-					}
-				}
-			}
-		}
-	}
-	return false, false
-}
-
-func (w *RoomHierarchyWalker) publicRoomsChunk(roomID string) *fclient.PublicRoom {
-	pubRooms, err := roomserver.PopulatePublicRooms(w.ctx, []string{roomID}, w.rsAPI)
-	if err != nil {
-		util.GetLogger(w.ctx).WithError(err).Error("failed to PopulatePublicRooms")
+		util.GetLogger(ctx).WithError(err).Error("failed to PopulatePublicRooms")
 		return nil
 	}
 	if len(pubRooms) == 0 {
@@ -536,13 +485,6 @@ func (w *RoomHierarchyWalker) publicRoomsChunk(roomID string) *fclient.PublicRoo
 	return &pubRooms[0]
 }
 
-type roomVisit struct {
-	roomID       string
-	parentRoomID string
-	depth        int
-	vias         []string // vias to query this room by
-}
-
 func stripped(ev gomatrixserverlib.PDU) *fclient.MSC2946StrippedEvent {
 	if ev.StateKey() == nil {
 		return nil
@@ -556,61 +498,25 @@ func stripped(ev gomatrixserverlib.PDU) *fclient.MSC2946StrippedEvent {
 	}
 }
 
-func (w *RoomHierarchyWalker) restrictedJoinRuleAllowedRooms(joinRuleEv *types.HeaderedEvent, allowType string) (allows []string) {
+func restrictedJoinRuleAllowedRooms(ctx context.Context, joinRuleEv *types.HeaderedEvent, allowType string) (allows []spec.RoomID) {
 	rule, _ := joinRuleEv.JoinRule()
 	if rule != spec.Restricted {
 		return nil
 	}
 	var jrContent gomatrixserverlib.JoinRuleContent
 	if err := json.Unmarshal(joinRuleEv.Content(), &jrContent); err != nil {
-		util.GetLogger(w.ctx).Warnf("failed to check join_rule on room %s: %s", joinRuleEv.RoomID(), err)
+		util.GetLogger(ctx).Warnf("failed to check join_rule on room %s: %s", joinRuleEv.RoomID(), err)
 		return nil
 	}
 	for _, allow := range jrContent.Allow {
 		if allow.Type == allowType {
-			allows = append(allows, allow.RoomID)
+			allowedRoomID, err := spec.NewRoomID(allow.RoomID)
+			if err != nil {
+				util.GetLogger(ctx).Warnf("invalid room ID '%s' found in join_rule on room %s: %s", allow.RoomID, joinRuleEv.RoomID(), err)
+			} else {
+				allows = append(allows, *allowedRoomID)
+			}
 		}
 	}
 	return
 }
-
-// Stripped down version of RoomHierarchyWalker suitable for caching (For pagination purposes)
-//
-// TODO remove more stuff
-type CachedRoomHierarchyWalker struct {
-	rootRoomID    string
-	caller        types.DeviceOrServerName
-	thisServer    spec.ServerName
-	rsAPI         *Queryer
-	fsAPI         fs.RoomserverFederationAPI
-	ctx           context.Context
-	cache         caching.RoomHierarchyCache
-	suggestedOnly bool
-	maxDepth      int
-
-	processed stringSet
-	unvisited []roomVisit
-
-	done bool
-}
-
-func (c CachedRoomHierarchyWalker) GetWalker() roomserver.RoomHierarchyWalker {
-	return &RoomHierarchyWalker{
-		rootRoomID:         c.rootRoomID,
-		caller:             c.caller,
-		thisServer:         c.thisServer,
-		rsAPI:              c.rsAPI,
-		fsAPI:              c.fsAPI,
-		ctx:                c.ctx,
-		roomHierarchyCache: c.cache,
-		suggestedOnly:      c.suggestedOnly,
-		maxDepth:           c.maxDepth,
-		processed:          c.processed,
-		unvisited:          c.unvisited,
-		done:               c.done,
-	}
-}
-
-func (c CachedRoomHierarchyWalker) ValidateParams(suggestedOnly bool, maxDepth int) bool {
-	return c.suggestedOnly == suggestedOnly && c.maxDepth == maxDepth
-}