From 203ef2d1adb19682ea7ce2e3ad3b8aba6f6e79d1 Mon Sep 17 00:00:00 2001
From: anhthii <nguyendanganhthi247@gmail.com>
Date: Mon, 2 Mar 2026 09:24:19 +0700
Subject: [PATCH] Add --peers flag to sync peers from JSON file to Consul on
 startup

Introduces a --peers CLI flag that loads peer definitions from a JSON file
and registers any new peers into Consul before the node starts. Existing
peers are skipped. Also extracts PeersPrefix constant to avoid hardcoded strings.
---
 cmd/mpcium/main.go  | 19 ++++++++++++++-
 pkg/config/peers.go | 56 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/cmd/mpcium/main.go b/cmd/mpcium/main.go
index 3c2c1a0..ad801ef 100644
--- a/cmd/mpcium/main.go
+++ b/cmd/mpcium/main.go
@@ -88,6 +88,10 @@ func main() {
 						Aliases: []string{"k"},
 						Usage:   "Path to file containing password for decrypting .age encrypted node private key",
 					},
+					&cli.StringFlag{
+						Name:  "peers",
+						Usage: "Path to peers.json file (syncs new peers to Consul on startup)",
+					},
 					&cli.BoolFlag{
 						Name:  "debug",
 						Usage: "Enable debug logging",
@@ -146,6 +150,19 @@ func runNode(ctx context.Context, c *cli.Command) error {
 
 	consulClient := infra.GetConsulClient(environment)
 	keyinfoStore := keyinfo.NewStore(consulClient.KV())
+
+	// If --peers flag is provided, sync new peers from file to Consul
+	peersFile := c.String("peers")
+	if peersFile != "" {
+		filePeers, err := config.LoadPeersFromFile(peersFile)
+		if err != nil {
+			logger.Fatal("Failed to load peers from file", err)
+		}
+		if err := config.SyncPeersToConsul(consulClient.KV(), filePeers); err != nil {
+			logger.Fatal("Failed to sync peers to Consul", err)
+		}
+	}
+
 	peers := LoadPeersFromConsul(consulClient)
 	nodeID := GetIDFromName(nodeName, peers)
 
@@ -474,7 +491,7 @@ func NewConsulClient(addr string) *api.Client {
 
 func LoadPeersFromConsul(consulClient *api.Client) []config.Peer { // Create a Consul Key-Value store client
 	kv := consulClient.KV()
-	peers, err := config.LoadPeersFromConsul(kv, "mpc_peers/")
+	peers, err := config.LoadPeersFromConsul(kv, config.PeersPrefix)
 	if err != nil {
 		logger.Fatal("Failed to load peers from Consul", err)
 	}
diff --git a/pkg/config/peers.go b/pkg/config/peers.go
index 34b87db..cec2290 100644
--- a/pkg/config/peers.go
+++ b/pkg/config/peers.go
@@ -1,7 +1,9 @@
 package config
 
 import (
+	"encoding/json"
 	"fmt"
+	"os"
 
 	"github.com/hashicorp/consul/api"
 )
@@ -33,6 +35,60 @@ func LoadPeersFromConsul(kv *api.KV, prefix string) ([]Peer, error) {
 	return peers, nil
 }
 
+// LoadPeersFromFile loads peers from a JSON file (map[string]string: name -> ID)
+func LoadPeersFromFile(path string) ([]Peer, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read peers file: %w", err)
+	}
+
+	var peersMap map[string]string
+	if err := json.Unmarshal(data, &peersMap); err != nil {
+		return nil, fmt.Errorf("failed to parse peers JSON: %w", err)
+	}
+
+	if len(peersMap) == 0 {
+		return nil, fmt.Errorf("no peers found in file %s", path)
+	}
+
+	peers := make([]Peer, 0, len(peersMap))
+	for name, id := range peersMap {
+		peers = append(peers, Peer{
+			ID:   id,
+			Name: name,
+		})
+	}
+
+	return peers, nil
+}
+
+const PeersPrefix = "mpc_peers/"
+
+// SyncPeersToConsul registers new peers from a file into Consul.
+// Existing peers are skipped. New peers are registered and logged.
+func SyncPeersToConsul(kv *api.KV, peers []Peer) error {
+	for _, peer := range peers {
+		key := PeersPrefix + peer.Name
+
+		existing, _, err := kv.Get(key, nil)
+		if err != nil {
+			return fmt.Errorf("failed to check existing key %s: %w", key, err)
+		}
+
+		if existing != nil {
+			continue
+		}
+
+		p := &api.KVPair{Key: key, Value: []byte(peer.ID)}
+		if _, err := kv.Put(p, nil); err != nil {
+			return fmt.Errorf("failed to register peer %s in Consul: %w", peer.Name, err)
+		}
+		fmt.Printf("New peer registered: %s with ID %s\n", peer.Name, peer.ID)
+	}
+
+	return nil
+}
+
 func GetNodeID(nodeName string, peers []Peer) string {
 	for _, peer := range peers {
 		if peer.Name == nodeName {