using System;
using System.IO;
using System.Security.Cryptography;

namespace Common.Helper.Encryption
{
    public class DesHelper
    {
        private const string Key = "Blue2021";
        private const string Iv = "Flag2021";

        /// <summary>
        /// DES加密
        /// </summary>
        /// <param name="data">加密数据</param>
        /// <returns></returns>
        public static string DesEncrypt(string data)
        {
            var byKey = System.Text.Encoding.ASCII.GetBytes(Key);
            var byIv = System.Text.Encoding.ASCII.GetBytes(Iv);

            var cryptoProvider = new DESCryptoServiceProvider();
            var ms = new MemoryStream();
            var cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(byKey, byIv), CryptoStreamMode.Write);

            var sw = new StreamWriter(cst);
            sw.Write(data);
            sw.Flush();
            cst.FlushFinalBlock();
            sw.Flush();
            return Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
        }

        /// <summary>
        /// DES解密
        /// </summary>
        /// <param name="data">解密数据</param>
        /// <returns></returns>
        public static string DesDecrypt(string data)
        {
            var byKey = System.Text.Encoding.ASCII.GetBytes(Key);
            var byIv = System.Text.Encoding.ASCII.GetBytes(Iv);

            byte[] byEnc;
            try
            {
                byEnc = Convert.FromBase64String(data);
            }
            catch
            {
                return null;
            }

            var cryptoProvider = new DESCryptoServiceProvider();
            var ms = new MemoryStream(byEnc);
            var cst = new CryptoStream(ms, cryptoProvider.CreateDecryptor(byKey, byIv), CryptoStreamMode.Read);
            var sr = new StreamReader(cst);
            return sr.ReadToEnd();
        }
    }
}