✨ Support build jwk from jwt reader

pkg/nex/sec/jwt_reader.go

@@ -3,9 +3,11 @@ package sec
 import (
 	"crypto/rsa"
 	"crypto/x509"
+	"encoding/base64"
 	"encoding/pem"
 	"fmt"
 	"github.com/golang-jwt/jwt/v5"
+	"math/big"
 	"os"
 )
 
@@ -40,8 +42,8 @@ func NewJwtReader(fp string) (*JwtReader, error) {
 }
 
 // ReadJwt is the helper method to help me validate and parse jwt.
-// To use it, pass the initialized jwt reader which contains public key.
-// And pass the token string, and a pointer struct (you must initialize it, which it cannot be nil) of your claims
+// To use it, pass the initialized jwt reader which contains a public key.
+// And pass the token string and a pointer struct (you must initialize it, which it cannot be nil) of your claims
 func ReadJwt[T jwt.Claims](v *JwtReader, in string, out T) (T, error) {
 	token, err := jwt.ParseWithClaims(in, out, func(token *jwt.Token) (interface{}, error) {
 		if _, ok := token.Method.(*jwt.SigningMethodRSA); !ok {
@@ -61,3 +63,18 @@ func ReadJwt[T jwt.Claims](v *JwtReader, in string, out T) (T, error) {
 		return out, err
 	}
 }
+
+func (v *JwtReader) BuildJwk(kid string) map[string]any {
+	encodeBigInt := func(i *big.Int) string {
+		return base64.RawURLEncoding.EncodeToString(i.Bytes())
+	}
+
+	return map[string]any{
+		"kid": kid,
+		"kty": "RSA",
+		"use": "sig",
+		"alg": "RS256",
+		"n":   encodeBigInt(v.key.N),
+		"e":   encodeBigInt(big.NewInt(int64(v.key.E))),
+	}
+}