using System;
using System.Globalization;
using System.Security.Cryptography;
using System.Text;
using System.Windows;

namespace IoTKeyGen
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            if(string.IsNullOrEmpty(deviceNumber.Text))
            {
                MessageBox.Show("设备编号不能为空");
                return;
            }
            if (string.IsNullOrEmpty(this.days.Text))
            {
                MessageBox.Show("过期时间不能为空");
                return;
            }
            var sn = deviceNumber.Text;

            if(!int.TryParse(this.days.Text, out int days)||days<0)
            {
                MessageBox.Show("过期时间必须是非负整数");
                return;
            }
            var endTime = days == 0 ? 0 : new DateTimeOffset(DateTime.UtcNow.Date.AddDays(days + 1).AddSeconds(-1)).ToUnixTimeSeconds();
            keyCode.Text = DESEncrypt($"{sn}-{endTime}",sn);
        }

        public static string DESEncrypt(string value, string key)
        {
            using var des = new DESCryptoServiceProvider();
            var inputByteArray = Encoding.Default.GetBytes(value);
            var md5Key = Md5(key).Substring(0, 8);
            des.Key = ASCIIEncoding.ASCII.GetBytes(md5Key);
            des.IV = ASCIIEncoding.ASCII.GetBytes(md5Key);
            using var ms = new System.IO.MemoryStream();
            using var cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            var ret = new StringBuilder();
            foreach (var item in ms.ToArray())
            {
                ret.AppendFormat("{0:X2}", item);
            }
            return ret.ToString();
        }
        public static string Md5(string input)
        {
            using MD5 md5 = MD5.Create();
            byte[] hash = md5.ComputeHash(Encoding.UTF8.GetBytes(input));
            return BitConverter.ToString(hash).Replace("-", string.Empty, StringComparison.CurrentCulture).ToLower(CultureInfo.CurrentCulture);
        }
    }
}