package auth

import (
	"errors"
	"time"

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

// JWTService JWT服务
type JWTService struct {
	secretKey   string
	expireHours int
}

// NewJWTService 创建新的JWT服务
func NewJWTService(secretKey string, expireHours int) *JWTService {
	return &JWTService{
		secretKey:   secretKey,
		expireHours: expireHours,
	}
}

// Claims JWT声明
type Claims struct {
	UserID   int64  `json:"user_id"`
	Username string `json:"username"`
	Role     string `json:"role"`
	jwt.RegisteredClaims
}

// GenerateToken 生成JWT Token (使用UserID和基本信息)
func (j *JWTService) GenerateToken(userID int64, username, role string) (string, error) {
	claims := Claims{
		UserID:   userID,
		Username: username,
		Role:     role,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(time.Duration(j.expireHours) * time.Hour)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			NotBefore: jwt.NewNumericDate(time.Now()),
			Issuer:    "carrotskin",
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString([]byte(j.secretKey))
	if err != nil {
		return "", err
	}

	return tokenString, nil
}

// ValidateToken 验证JWT Token
func (j *JWTService) ValidateToken(tokenString string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		// 验证签名算法，防止algorithm confusion攻击
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("不支持的签名算法")
		}
		return []byte(j.secretKey), nil
	})

	if err != nil {
		return nil, err
	}

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

	return nil, errors.New("无效的token")
}