// service/jwt_service.go
package service

import (
	"errors"
	"fmt"
	"time"
	
	"github.com/golang-jwt/jwt/v5"
)

type JWTService interface {
	GenerateToken(userID uint, email string) (string, error)
	ValidateToken(tokenString string) (*jwt.Token, error)
	ExtractUserID(token *jwt.Token) (uint, error)
}

type jwtService struct {
	secretKey string
}

func NewJWTService(secretKey string) JWTService {
	return &jwtService{secretKey: secretKey}
}

type Claims struct {
	UserID uint   `json:"user_id"`
	Email  string `json:"email"`
	jwt.RegisteredClaims
}

func (j *jwtService) GenerateToken(userID uint, email string) (string, error) {
	claims := &Claims{
		UserID: userID,
		Email:  email,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(24 * time.Hour)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
		},
	}
	
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte(j.secretKey))
}

func (j *jwtService) ValidateToken(tokenString string) (*jwt.Token, error) {
	return jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		return []byte(j.secretKey), nil
	})
}

func (j *jwtService) ExtractUserID(token *jwt.Token) (uint, error) {
	claims, ok := token.Claims.(*Claims)
	if !ok {
		return 0, errors.New("invalid token claims")
	}
	return claims.UserID, nil
}