MSC2836: Threading - part one (#1589)

* Add mscs/hooks package, begin work for msc2836

* Flesh out hooks and add SQL schema

* Begin implementing core msc2836 logic

* Add test harness

* Linting

* Implement visibility checks; stub out APIs for tests

* Flesh out testing

* Flesh out walkThread a bit

* Persist the origin_server_ts as well

* Edges table instead of relationships

* Add nodes table for event metadata

* LEFT JOIN to extract origin_server_ts for children

* Add graph walking structs

* Implement walking algorithm

* Add more graph walking tests

* Add auto_join for local rooms

* Fix create table syntax on postgres

* Add relationship_room_id|servers to the unsigned section of events

* Persist the parent room_id/servers in edge metadata

Other events cannot assert the true room_id/servers for the
parent event, only make claims to them, hence why this is
edge metadata.

* guts to pass through room_id/servers

* Refactor msc2836 to allow handling from federation

* Add JoinedVia to PerformJoin responses

* Fix tests; review comments

3 files changed, 5 insertions, 9 deletions

diff --git a/federationsender/api/api.go b/federationsender/api/api.go
index b0522516..a4d15f1f 100644
--- a/federationsender/api/api.go
+++ b/federationsender/api/api.go
@@ -48,6 +48,7 @@ type FederationSenderInternalAPI interface {
 	// Query the server names of the joined hosts in a room.
 	// Unlike QueryJoinedHostsInRoom, this function returns a de-duplicated slice
 	// containing only the server names (without information for membership events).
+	// The response will include this server if they are joined to the room.
 	QueryJoinedHostServerNamesInRoom(
 		ctx context.Context,
 		request *QueryJoinedHostServerNamesInRoomRequest,
@@ -104,6 +105,7 @@ type PerformJoinRequest struct {
 }
 
 type PerformJoinResponse struct {
+	JoinedVia gomatrixserverlib.ServerName
 	LastError *gomatrix.HTTPError
 }
 
diff --git a/federationsender/internal/perform.go b/federationsender/internal/perform.go
index a7484476..45f33ff7 100644
--- a/federationsender/internal/perform.go
+++ b/federationsender/internal/perform.go
@@ -105,6 +105,7 @@ func (r *FederationSenderInternalAPI) PerformJoin(
 		}
 
 		// We're all good.
+		response.JoinedVia = serverName
 		return
 	}
 
diff --git a/federationsender/internal/query.go b/federationsender/internal/query.go
index 253400a2..8ba228d1 100644
--- a/federationsender/internal/query.go
+++ b/federationsender/internal/query.go
@@ -4,7 +4,6 @@ import (
 	"context"
 
 	"github.com/matrix-org/dendrite/federationsender/api"
-	"github.com/matrix-org/gomatrixserverlib"
 )
 
 // QueryJoinedHostServerNamesInRoom implements api.FederationSenderInternalAPI
@@ -13,17 +12,11 @@ func (f *FederationSenderInternalAPI) QueryJoinedHostServerNamesInRoom(
 	request *api.QueryJoinedHostServerNamesInRoomRequest,
 	response *api.QueryJoinedHostServerNamesInRoomResponse,
 ) (err error) {
-	joinedHosts, err := f.db.GetJoinedHosts(ctx, request.RoomID)
+	joinedHosts, err := f.db.GetJoinedHostsForRooms(ctx, []string{request.RoomID})
 	if err != nil {
 		return
 	}
-
-	response.ServerNames = make([]gomatrixserverlib.ServerName, 0, len(joinedHosts))
-	for _, host := range joinedHosts {
-		response.ServerNames = append(response.ServerNames, host.ServerName)
-	}
-
-	// TODO: remove duplicates?
+	response.ServerNames = joinedHosts
 
 	return
 }