package middleware

import (
	"fmt"
	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"
	"net/http"
	"strings"
	"time"
)

const (
	ApiSecret = "your-super-secret-key" // 预共享密钥
	TokenExp  = 1 * time.Hour           // Token有效期
)

type JWTService struct {
	secretKey []byte
	expiresIn time.Duration
}

func NewJWTService(secret string, expiresIn time.Duration) *JWTService {
	return &JWTService{
		secretKey: []byte(secret),
		expiresIn: expiresIn,
	}
}

// 生成带HMAC签名的Token
func (s *JWTService) GenerateToken() (string, error) {
	claims := jwt.MapClaims{
		"exp": time.Now().Add(s.expiresIn).Unix(),
		"iat": time.Now().Unix(),
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(s.secretKey)
}

// 验证HMAC签名的Token
func (s *JWTService) ValidateToken(tokenString string) (jwt.Claims, error) {
	token, err := jwt.Parse(tokenString, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, jwt.ErrSignatureInvalid
		}
		return s.secretKey, nil
	})

	if err != nil {
		return nil, err
	}

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

	return nil, jwt.ErrTokenInvalidClaims
}

// 鉴权中间件
func AuthMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		authHeader := c.GetHeader("Authorization")
		if authHeader == "" {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Authorization header required"})
			return
		}

		tokenString := strings.TrimPrefix(authHeader, "Bearer ")
		token, err := jwt.Parse(tokenString, func(t *jwt.Token) (interface{}, error) {
			if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
				return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
			}
			return []byte(ApiSecret), nil
		})

		if err != nil || !token.Valid {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
			return
		}

		c.Next()
	}
}