[readability] use event.StateKeyEquals where relevant and minor for-loop refactoring (#1339)

* use event.StateKeyEquals where relevant

Signed-off-by: Olivier Charvin <git@olivier.pfad.fr>

* use userID

federationapi/routing/join.go

@@ -165,7 +165,7 @@ func SendJoin(
 	}
 
 	// Check that a state key is provided.
-	if event.StateKey() == nil || (event.StateKey() != nil && *event.StateKey() == "") {
+	if event.StateKey() == nil || event.StateKeyEquals("") {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: jsonerror.BadJSON(
@@ -253,11 +253,12 @@ func SendJoin(
 	// there isn't much point in sending another join event into the room.
 	alreadyJoined := false
 	for _, se := range stateAndAuthChainResponse.StateEvents {
+		if !se.StateKeyEquals(*event.StateKey()) {
+			continue
+		}
 		if membership, merr := se.Membership(); merr == nil {
-			if se.StateKey() != nil && *se.StateKey() == *event.StateKey() {
-				alreadyJoined = (membership == "join")
-				break
-			}
+			alreadyJoined = (membership == gomatrixserverlib.Join)
+			break
 		}
 	}
 

federationapi/routing/leave.go

@@ -81,15 +81,16 @@ func MakeLeave(
 	// event. This means that /send_leave will be a no-op, which helps
 	// to reject invites multiple times - hopefully.
 	for _, state := range queryRes.StateEvents {
-		if state.Type() == gomatrixserverlib.MRoomMember && state.StateKeyEquals(userID) {
-			if mem, merr := state.Membership(); merr == nil && mem == gomatrixserverlib.Leave {
-				return util.JSONResponse{
-					Code: http.StatusOK,
-					JSON: map[string]interface{}{
-						"room_version": event.RoomVersion,
-						"event":        state,
-					},
-				}
+		if !state.StateKeyEquals(userID) {
+			continue
+		}
+		if mem, merr := state.Membership(); merr == nil && mem == gomatrixserverlib.Leave {
+			return util.JSONResponse{
+				Code: http.StatusOK,
+				JSON: map[string]interface{}{
+					"room_version": event.RoomVersion,
+					"event":        state,
+				},
 			}
 		}
 	}