package auth

import (
	"crypto/rand"
	"encoding/hex"
	"time"

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

// Claims JWT claims
type Claims struct {
	Username string `json:"username"`
	jwt.RegisteredClaims
}

// JWTAuth JWT 认证管理器
type JWTAuth struct {
	secret     []byte
	expiration time.Duration
}

// NewJWTAuth 创建 JWT 认证管理器
func NewJWTAuth(secret string, expHours int) *JWTAuth {
	if secret == "" {
		secret = generateSecret()
	}
	return &JWTAuth{
		secret:     []byte(secret),
		expiration: time.Duration(expHours) * time.Hour,
	}
}

// GenerateToken 生成 JWT token
func (j *JWTAuth) GenerateToken(username string) (string, error) {
	claims := &Claims{
		Username: username,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(j.expiration)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Issuer:    "gotunnel",
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(j.secret)
}

// ValidateToken 验证 JWT token
func (j *JWTAuth) ValidateToken(tokenString string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		return j.secret, nil
	})
	if err != nil {
		return nil, err
	}

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

func generateSecret() string {
	b := make([]byte, 32)
	rand.Read(b)
	return hex.EncodeToString(b)
}