From d62a706a44d24b737282070aa71643b5f707ec2a Mon Sep 17 00:00:00 2001
From: Sam Wedgwood <sam@wedgwood.dev>
Date: Tue, 4 Jul 2023 16:44:55 +0100
Subject: [PATCH] Add federated route for room/space hierarchy

---
 federationapi/routing/query.go   | 47 ++++++++++++++++++++++++++++++++
 federationapi/routing/routing.go |  7 +++++
 2 files changed, 54 insertions(+)

diff --git a/federationapi/routing/query.go b/federationapi/routing/query.go
index 2e845f32c..c8e466431 100644
--- a/federationapi/routing/query.go
+++ b/federationapi/routing/query.go
@@ -20,6 +20,7 @@ import (
 
 	federationAPI "github.com/matrix-org/dendrite/federationapi/api"
 	roomserverAPI "github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/gomatrix"
 	"github.com/matrix-org/gomatrixserverlib"
@@ -116,3 +117,49 @@ func RoomAliasToID(
 		JSON: resp,
 	}
 }
+
+func QueryRoomHierarchy(httpReq *http.Request, request *fclient.FederationRequest, roomIDStr string, rsAPI roomserverAPI.FederationRoomserverAPI) util.JSONResponse {
+	parsedRoomID, err := spec.NewRoomID(roomIDStr)
+	if err != nil {
+		return util.JSONResponse{
+			Code: http.StatusNotFound,
+			JSON: spec.InvalidParam("room is unknown/forbidden"),
+		}
+	}
+	roomID := *parsedRoomID
+
+	suggestedOnly := false // Defaults to false (spec-defined)
+	switch httpReq.URL.Query().Get("suggested_only") {
+	case "true":
+		suggestedOnly = true
+	case "false":
+	case "": // Empty string is returned when query param is not set
+	default:
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: spec.InvalidParam("query parameter 'suggested_only', if set, must be 'true' or 'false'"),
+		}
+	}
+
+	walker := rsAPI.QueryRoomHierarchy(httpReq.Context(), types.NewServerNameNotDevice(request.Origin()), roomID, suggestedOnly, 1)
+
+	discoveredRooms, err := walker.NextPage(-1)
+
+	if err != nil {
+		// TODO
+	}
+
+	if len(discoveredRooms) == 0 {
+		return util.JSONResponse{
+			Code: 404,
+			JSON: spec.NotFound("room is unknown/forbidden"),
+		}
+	}
+	return util.JSONResponse{
+		Code: 200,
+		JSON: fclient.MSC2946SpacesResponse{
+			Room:     discoveredRooms[0],
+			Children: discoveredRooms[1:],
+		},
+	}
+}
diff --git a/federationapi/routing/routing.go b/federationapi/routing/routing.go
index 4f998821a..dc7a363e7 100644
--- a/federationapi/routing/routing.go
+++ b/federationapi/routing/routing.go
@@ -596,6 +596,13 @@ func Setup(
 			return GetOpenIDUserInfo(req, userAPI)
 		}),
 	).Methods(http.MethodGet)
+
+	v1fedmux.Handle("/hierarchy/{roomID}", MakeFedAPI(
+		"federation_room_hierarchy", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
+		func(httpReq *http.Request, request *fclient.FederationRequest, vars map[string]string) util.JSONResponse {
+			return QueryRoomHierarchy(httpReq, request, vars["roomID"], rsAPI)
+		},
+	)).Methods(http.MethodGet)
 }
 
 func ErrorIfLocalServerNotInRoom(