rpcsrv: do not store nil Oracle service

And simplify atomic service value stored by RPC server. It's unwanted
to use reflection, thus we can directly check for the typed nil service
value. Otherwise `submitoracleresponse` RPC handler doesn't work properly.

Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>

cli/server/server.go

@@ -359,7 +359,14 @@ func resetDB(ctx *cli.Context) error {
 	return nil
 }
 
-func mkOracle(config config.OracleConfiguration, magic netmode.Magic, chain *core.Blockchain, serv *network.Server, log *zap.Logger) (*oracle.Oracle, error) {
+// OracleService is an interface representing Oracle service with network.Service
+// capabilities and ability to submit oracle responses.
+type OracleService interface {
+	rpcsrv.OracleHandler
+	network.Service
+}
+
+func mkOracle(config config.OracleConfiguration, magic netmode.Magic, chain *core.Blockchain, serv *network.Server, log *zap.Logger) (OracleService, error) {
 	if !config.Enabled {
 		return nil, nil
 	}

pkg/services/rpcsrv/server.go

@@ -254,7 +254,8 @@ var invalidBlockHeightError = func(index int, height int) *neorpc.Error {
 	return neorpc.NewRPCError("Invalid block height", fmt.Sprintf("param at index %d should be greater than or equal to 0 and less then or equal to current block height, got: %d", index, height))
 }
 
-// New creates a new Server struct.
+// New creates a new Server struct. Pay attention that orc is expected to be either
+// untyped nil or non-nil structure implementing OracleHandler interface.
 func New(chain Ledger, conf config.RPC, coreServer *network.Server,
 	orc OracleHandler, log *zap.Logger, errChan chan<- error) Server {
 	addrs := conf.GetAddresses()
@@ -293,7 +294,7 @@ func New(chain Ledger, conf config.RPC, coreServer *network.Server,
 	}
 	var oracleWrapped = new(atomic.Value)
 	if orc != nil {
-		oracleWrapped.Store(&orc)
+		oracleWrapped.Store(orc)
 	}
 	var wsOriginChecker func(*http.Request) bool
 	if conf.EnableCORSWorkaround {
@@ -445,7 +446,9 @@ func (s *Server) Shutdown() {
 
 // SetOracleHandler allows to update oracle handler used by the Server.
 func (s *Server) SetOracleHandler(orc OracleHandler) {
-	s.oracle.Store(&orc)
+	if orc != nil {
+		s.oracle.Store(orc)
+	}
 }
 
 func (s *Server) handleHTTPRequest(w http.ResponseWriter, httpRequest *http.Request) {
@@ -2461,10 +2464,11 @@ func getRelayResult(err error, hash util.Uint256) (any, *neorpc.Error) {
 }
 
 func (s *Server) submitOracleResponse(ps params.Params) (any, *neorpc.Error) {
-	oracle := s.oracle.Load().(*OracleHandler)
-	if oracle == nil || *oracle == nil {
+	oraclePtr := s.oracle.Load()
+	if oraclePtr == nil {
 		return nil, neorpc.NewRPCError("Oracle is not enabled", "")
 	}
+	oracle := oraclePtr.(OracleHandler)
 	var pub *keys.PublicKey
 	pubBytes, err := ps.Value(0).GetBytesBase64()
 	if err == nil {
@@ -2489,7 +2493,7 @@ func (s *Server) submitOracleResponse(ps params.Params) (any, *neorpc.Error) {
 	if !pub.Verify(msgSig, hash.Sha256(data).BytesBE()) {
 		return nil, neorpc.NewRPCError("Invalid request signature", "")
 	}
-	(*oracle).AddResponse(pub, uint64(reqID), txSig)
+	(oracle).AddResponse(pub, uint64(reqID), txSig)
 	return json.RawMessage([]byte("{}")), nil
 }