add jwt creating and parsing

internal/jwt/service.go

@@ -0,0 +1,49 @@
+package jwt
+
+import (
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/google/uuid"
+)
+
+type Service struct {
+	signer Signer
+	expiry time.Duration
+}
+
+func NewService(signer Signer, exp time.Duration) *Service {
+	return &Service{
+		signer: signer,
+		expiry: exp,
+	}
+}
+
+// Generate creates a new JWT token for a given user ID and
+// returns the token string along with its JTI(JWT IDentifier).
+func (s *Service) Generate(userID int) (string, string, error) {
+	jti := uuid.NewString()
+
+	claims := jwt.MapClaims{
+		"sub": userID,
+		"jti": jti,
+		"exp": time.Now().Add(s.expiry).Unix(),
+		"iat": time.Now().Unix(),
+	}
+
+	token, err := s.signer.Sign(claims)
+	return token, jti, err
+}
+
+// Validate verifies the JWT token and extracts the user ID and JTI(JWT IDentifier).
+func (s *Service) Validate(token string) (int, string, error) {
+	claims, err := s.signer.Verify(token)
+	if err != nil {
+		return 0, "", err
+	}
+
+	sub := int(claims.(jwt.MapClaims)["sub"].(float64))
+	jti := claims.(jwt.MapClaims)["jti"].(string)
+
+	return sub, jti, nil
+}