package auth

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

// JWTClaims JWT声明
type JWTClaims struct {
	UserID uint     `json:"user_id"`
	Roles  []string `json:"roles"`
	jwt.RegisteredClaims
}

// JWTService JWT服务
type JWTService struct {
	secretKey string
	expire    int // 过期时间（秒）
}

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

// GenerateToken 生成JWT令牌
func (j *JWTService) GenerateToken(userID uint, roles []string) (string, error) {
	// 创建声明
	claims := JWTClaims{
		UserID: userID,
		Roles:  roles,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(time.Duration(j.expire) * time.Second)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			NotBefore: jwt.NewNumericDate(time.Now()),
			Issuer:    "web-training",
			Subject:   "user-auth",
		},
	}

	// 创建令牌
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)

	// 签名令牌
	tokenString, err := token.SignedString([]byte(j.secretKey))
	if err != nil {
		return "", err
	}

	return tokenString, nil
}

// ValidateToken 验证JWT令牌
func (j *JWTService) ValidateToken(tokenString string) (*JWTClaims, error) {
	// 解析令牌
	token, err := jwt.ParseWithClaims(tokenString, &JWTClaims{}, func(token *jwt.Token) (interface{}, error) {
		// 验证签名方法
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("unexpected signing method")
		}
		return []byte(j.secretKey), nil
	})

	if err != nil {
		return nil, err
	}

	// 验证令牌有效性
	if claims, ok := token.Claims.(*JWTClaims); ok && token.Valid {
		return claims, nil
	}

	return nil, errors.New("invalid token")
}

// RefreshToken 刷新JWT令牌
func (j *JWTService) RefreshToken(tokenString string) (string, error) {
	// 验证旧令牌
	claims, err := j.ValidateToken(tokenString)
	if err != nil {
		return "", err
	}

	// 生成新令牌
	return j.GenerateToken(claims.UserID, claims.Roles)
}

// ExtractTokenFromHeader 从请求头提取令牌
func ExtractTokenFromHeader(authHeader string) (string, error) {
	if authHeader == "" {
		return "", errors.New("authorization header is empty")
	}

	parts := strings.Split(authHeader, " ")
	if len(parts) != 2 || parts[0] != "Bearer" {
		return "", errors.New("authorization header format must be Bearer {token}")
	}

	return parts[1], nil
}