package jwt

import (
	"errors"
	"time"

	"github.com/golang-jwt/jwt/v5"
)

var (
	// ErrTokenExpired token 已过期
	ErrTokenExpired = errors.New("token已过期")
	// ErrTokenInvalid token 无效
	ErrTokenInvalid = errors.New("token无效")
)

// JWT JWT工具
type JWT struct {
	secretKey []byte
	expiresIn time.Duration
}

// NewJWT 创建JWT实例
func NewJWT(secretKey string, expiresIn time.Duration) *JWT {
	return &JWT{
		secretKey: []byte(secretKey),
		expiresIn: expiresIn,
	}
}

// GenerateToken 生成token
func (j *JWT) GenerateToken(claims jwt.Claims) (string, error) {
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(j.secretKey)
}

// ParseToken 解析token
func (j *JWT) ParseToken(tokenString string, claims jwt.Claims) error {
	token, err := jwt.ParseWithClaims(tokenString, claims, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("unexpected signing method")
		}
		return j.secretKey, nil
	})

	if err != nil {
		if errors.Is(err, jwt.ErrTokenExpired) {
			return ErrTokenExpired
		}
		return ErrTokenInvalid
	}

	if !token.Valid {
		return ErrTokenInvalid
	}

	return nil
}