package utils

import (
	"fmt"
	"time"

	"github.com/golang-jwt/jwt/v5"
	"golang.org/x/crypto/bcrypt"
)

// JWTClaims JWT声明结构体
type JWTClaims struct {
	UserID   uint   `json:"user_id"`
	Username string `json:"username"`
	IsAdmin  bool   `json:"is_admin"`
	jwt.RegisteredClaims
}

// GenerateToken 生成JWT令牌
func GenerateToken(userID uint, username string, isAdmin bool, secretKey string, expireTime time.Duration) (string, error) {
	// 创建声明
	claims := JWTClaims{
		UserID:   userID,
		Username: username,
		IsAdmin:  isAdmin,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(expireTime)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			NotBefore: jwt.NewNumericDate(time.Now()),
		},
	}

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

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

	return tokenString, nil
}

// ParseToken 解析JWT令牌
func ParseToken(tokenString string, secretKey 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, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}

		return []byte(secretKey), nil
	})

	if err != nil {
		return nil, err
	}

	// 验证令牌并获取声明
	if claims, ok := token.Claims.(*JWTClaims); ok && token.Valid {
		return claims, nil
	}

	return nil, fmt.Errorf("invalid token")
}

// HashPassword 密码加密
func HashPassword(password string) (string, error) {
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return "", err
	}

	return string(hash), nil
}

// VerifyPassword 密码验证
func VerifyPassword(hashedPassword, password string) error {
	return bcrypt.CompareHashAndPassword([]byte(hashedPassword), []byte(password))
}

// GenerateRandomString 生成随机字符串
func GenerateRandomString(length int) string {
	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	randomBytes := make([]byte, length)
	for i := range randomBytes {
		randomBytes[i] = charset[time.Now().UnixNano()%int64(len(charset))]
	}
	return string(randomBytes)
}