package utils

import (
	"crypto/hmac"
	"crypto/md5"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"time"

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

var jwtSecret = "please-change-this-secret-key"
var jwtExpire = 7 * time.Hour

// InitJWT 初始化JWT参数
func InitJWT(secret, expire string) {
	if secret != "" {
		jwtSecret = secret
	}
	if d, err := time.ParseDuration(expire); err == nil && d > 0 {
		jwtExpire = d
	}
}

// JWTClaims 自定义Claims
type JWTClaims struct {
	UserID   uint   `json:"user_id"`
	Username string `json:"username"`
	RoleCode string `json:"role_code"`
	jwt.RegisteredClaims
}

// GenerateToken 生成JWT Token
func GenerateToken(userID uint, username, roleCode string) (string, error) {
	claims := JWTClaims{
		UserID:   userID,
		Username: username,
		RoleCode: roleCode,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(jwtExpire)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			Issuer:    "filestoragesystem",
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte(jwtSecret))
}

// ParseToken 解析并校验JWT Token
func ParseToken(tokenStr string) (*JWTClaims, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &JWTClaims{}, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("非法的签名算法")
		}
		return []byte(jwtSecret), nil
	})
	if err != nil {
		return nil, err
	}
	if claims, ok := token.Claims.(*JWTClaims); ok && token.Valid {
		return claims, nil
	}
	return nil, errors.New("无效的Token")
}

// HashPassword bcrypt加密密码
func HashPassword(password string) (string, error) {
	bytes, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	return string(bytes), err
}

// CheckPassword 校验密码
func CheckPassword(hash, password string) bool {
	return bcrypt.CompareHashAndPassword([]byte(hash), []byte(password)) == nil
}

// MD5 计算字节串的MD5
func MD5(data []byte) string {
	h := md5.New()
	h.Write(data)
	return hex.EncodeToString(h.Sum(nil))
}

// RandomKey 生成指定长度的随机hex字符串
func RandomKey(n int) string {
	b := make([]byte, (n+1)/2)
	_, _ = rand.Read(b)
	return hex.EncodeToString(b)[:n]
}

// HMACSHA256 计算HMAC-SHA256签名(hex编码)
func HMACSHA256(secret, message string) string {
	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write([]byte(message))
	return hex.EncodeToString(mac.Sum(nil))
}