add random salt and result/error checksum

internal/server/rpc/writers.go

@@ -1,11 +1,40 @@
 package rpc
 
 import (
+	"crypto/md5"
 	"encoding/json"
+	"fmt"
 	"net/http"
+
+	"github.com/google/uuid"
 )
 
-func write(w http.ResponseWriter, msg *RPCResponse) error {
+func generateChecksum(result any) string {
+	if result == nil {
+		return ""
+	}
+	data, err := json.Marshal(result)
+	if err != nil {
+		return ""
+	}
+	return fmt.Sprintf("%x", md5.Sum(data))
+}
+
+func generateSalt() string {
+	return uuid.NewString()
+}
+
+func write(nid string, w http.ResponseWriter, msg *RPCResponse) error {
+	msg.Salt = generateSalt()
+	if msg.Result != nil {
+		msg.Checksum = generateChecksum(msg.Result)
+	} else {
+		msg.Checksum = generateChecksum(msg.Error)
+	}
+	
+	if nid != "" {
+		msg.ResponsibleNode = nid
+	}
 	data, err := json.Marshal(msg)
 	if err != nil {
 		return err
@@ -14,10 +43,10 @@ func write(w http.ResponseWriter, msg *RPCResponse) error {
 	return err
 }
 
-func WriteError(w http.ResponseWriter, errm *RPCResponse) error {
-	return write(w, errm)
+func WriteError(nid string, w http.ResponseWriter, errm *RPCResponse) error {
+	return write(nid, w, errm)
 }
 
-func WriteResponse(w http.ResponseWriter, response *RPCResponse) error {
-	return write(w, response)
+func WriteResponse(nid string, w http.ResponseWriter, response *RPCResponse) error {
+	return write(nid, w, response)
 }