package utils

import (
	"errors"
	"time"

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

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

// JWTClaims JWT声明
type JWTClaims struct {
	UserID   int    `json:"user_id"`
	Username string `json:"username"`
	jwt.RegisteredClaims
}

// GenerateToken 生成JWT Token
func GenerateToken(userID int, username, secret string, expiresInHours int) (string, error) {
	claims := JWTClaims{
		UserID:   userID,
		Username: username,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(time.Duration(expiresInHours) * time.Hour)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			NotBefore: jwt.NewNumericDate(time.Now()),
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte(secret))
}

// ParseToken 解析JWT Token
func ParseToken(tokenString, secret string) (*JWTClaims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &JWTClaims{}, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("签名方法无效")
		}
		return []byte(secret), nil
	})

	if err != nil {
		return nil, err
	}

	if claims, ok := token.Claims.(*JWTClaims); ok && token.Valid {
		return claims, nil
	}

	return nil, ErrTokenInvalid
}

// ValidateToken 验证Token是否有效
func ValidateToken(tokenString, secret string) error {
	claims, err := ParseToken(tokenString, secret)
	if err != nil {
		return err
	}

	if claims.ExpiresAt != nil && claims.ExpiresAt.Time.Before(time.Now()) {
		return ErrTokenExpired
	}

	return nil
}