From a6d47d2fa97745718b9d3a99c39d3516b9aa06f0 Mon Sep 17 00:00:00 2001
From: Remi Reuvekamp <git@remireuvekamp.nl>
Date: Wed, 15 Nov 2017 21:57:13 +0100
Subject: [PATCH] Implement new ReserveRoomID in CreateRoom

---
 .../dendrite/clientapi/routing/createroom.go  | 22 +++++++++++++++----
 .../dendrite/clientapi/routing/routing.go     |  2 +-
 .../dendrite/roomserver/api/query.go          |  7 ++++++
 3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/createroom.go b/src/github.com/matrix-org/dendrite/clientapi/routing/createroom.go
index 078a7319b..17941d202 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/createroom.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/createroom.go
@@ -23,7 +23,6 @@ import (
 
 	"github.com/matrix-org/dendrite/roomserver/api"
 
-	log "github.com/sirupsen/logrus"
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
 	"github.com/matrix-org/dendrite/clientapi/auth/storage/accounts"
 	"github.com/matrix-org/dendrite/clientapi/httputil"
@@ -33,6 +32,7 @@ import (
 	"github.com/matrix-org/dendrite/common/config"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
+	log "github.com/sirupsen/logrus"
 )
 
 // https://matrix.org/docs/spec/client_server/r0.2.0.html#post-matrix-client-r0-createroom
@@ -90,10 +90,24 @@ type fledglingEvent struct {
 func CreateRoom(req *http.Request, device *authtypes.Device,
 	cfg config.Dendrite, producer *producers.RoomserverProducer,
 	accountDB *accounts.Database, aliasAPI api.RoomserverAliasAPI,
+	queryAPI api.RoomserverQueryAPI,
 ) util.JSONResponse {
-	// TODO (#267): Check room ID doesn't clash with an existing one, and we
-	//              probably shouldn't be using pseudo-random strings, maybe GUIDs?
-	roomID := fmt.Sprintf("!%s:%s", util.RandomString(16), cfg.Matrix.ServerName)
+	// Generate a room ID and reserve it.
+	// Keep trying until we have one which is unused.
+	var roomID string
+	for roomID == "" {
+		checkRoomID := util.RandomString(16)
+		checkRoomID = fmt.Sprintf("!%s:%s", checkRoomID, cfg.Matrix.ServerName)
+
+		queryReq := api.QueryReserveRoomIDRequest{RoomID: checkRoomID}
+		var queryResp api.QueryReserveRoomIDResponse
+		queryAPI.QueryReserveRoomID(req.Context(), &queryReq, &queryResp)
+
+		if queryResp.Success {
+			roomID = checkRoomID
+		}
+	}
+
 	return createRoom(req, device, cfg, roomID, producer, accountDB, aliasAPI)
 }
 
diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go b/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
index 0b9e4172a..586646937 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
@@ -71,7 +71,7 @@ func Setup(
 
 	r0mux.Handle("/createRoom",
 		common.MakeAuthAPI("createRoom", deviceDB, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
-			return CreateRoom(req, device, cfg, producer, accountDB, aliasAPI)
+			return CreateRoom(req, device, cfg, producer, accountDB, aliasAPI, queryAPI)
 		}),
 	).Methods("POST", "OPTIONS")
 	r0mux.Handle("/join/{roomIDOrAlias}",
diff --git a/src/github.com/matrix-org/dendrite/roomserver/api/query.go b/src/github.com/matrix-org/dendrite/roomserver/api/query.go
index 36961d383..578cfe444 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/api/query.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/api/query.go
@@ -209,6 +209,13 @@ type RoomserverQueryAPI interface {
 		request *QueryServerAllowedToSeeEventRequest,
 		response *QueryServerAllowedToSeeEventResponse,
 	) error
+
+	// Query if a room ID is available and reserve it.
+	QueryReserveRoomID(
+		ctx context.Context,
+		request *QueryReserveRoomIDRequest,
+		response *QueryReserveRoomIDResponse,
+	) error
 }
 
 // RoomserverQueryLatestEventsAndStatePath is the HTTP path for the QueryLatestEventsAndState API.