using System;
using System.IO;
using System.Text;
using System.Web.Security;
using System.Security.Cryptography;

namespace SHJX.Service.Common.Extend
{
    /// <summary>
    /// 加密
    /// </summary>
    public static class Encryption
    {
        /// <summary>
        /// MD5字符串加密
        /// </summary>
        /// <param name="str"></param>
        /// <returns>加密后字符串</returns>
        public static string GenerateMd5(this string str)
        {
            using var md = MD5.Create();
            var buffer = Encoding.Default.GetBytes(str);
            //开始加密
            var newBuffer = md.ComputeHash(buffer);
            var sb = new StringBuilder();
            foreach (var item in newBuffer)
            {
                sb.Append(item.ToString("x2"));
            }
            return sb.ToString();
        }

        /// <summary>
        /// MD5流加密
        /// </summary>
        /// <param name="inputStream"></param>
        /// <returns></returns>
        public static string GenerateMd5(this Stream inputStream)
        {
            using var md = MD5.Create();
            //开始加密
            var newBuffer = md.ComputeHash(inputStream);
            var sb = new StringBuilder();
            foreach (var item in newBuffer)
            {
                sb.Append(item.ToString("x2"));
            }
            return sb.ToString();
        }

        /// <summary>
        /// DES数据加密
        /// </summary>
        /// <param name="targetValue">目标值</param>
        /// <param name="key">密钥</param>
        /// <returns>加密值</returns>
        public static string Encrypt(this string targetValue, string key)
        {
            if (string.IsNullOrEmpty(targetValue)) return string.Empty;
            var returnValue = new StringBuilder();
            var des = new DESCryptoServiceProvider();
            var inputByteArray = Encoding.Default.GetBytes(targetValue);
            // 通过两次哈希密码设置对称算法的初始化向量  
            des.Key = Encoding.ASCII.GetBytes(FormsAuthentication.HashPasswordForStoringInConfigFile
                (FormsAuthentication.HashPasswordForStoringInConfigFile(key, "md5")?.Substring(0, 8)!, "sha1")?.Substring(0, 8)!);
            // 通过两次哈希密码设置算法的机密密钥  
            des.IV = Encoding.ASCII.GetBytes(FormsAuthentication.HashPasswordForStoringInConfigFile
                (FormsAuthentication.HashPasswordForStoringInConfigFile(key, "md5")?.Substring(0, 8)!, "md5")?.Substring(0, 8)!);
            var ms = new MemoryStream();
            var cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            foreach (byte b in ms.ToArray())
            {
                returnValue.AppendFormat("{0:X2}", b);
            }
            return returnValue.ToString();
        }


        /// <summary>
        /// DES数据解密
        /// </summary>
        /// <param name="targetValue"></param>
        /// <param name="key"></param>
        /// <returns></returns>
        public static string Decrypt(this string targetValue, string key)
        {
            if (string.IsNullOrEmpty(targetValue)) return string.Empty;
            // 定义DES加密对象
            var des = new DESCryptoServiceProvider();
            int len = targetValue.Length / 2;
            var inputByteArray = new byte[len];
            int x, i;
            for (x = 0; x < len; x++)
            {
                i = Convert.ToInt32(targetValue.Substring(x * 2, 2), 16);
                inputByteArray[x] = (byte)i;
            }
            // 通过两次哈希密码设置对称算法的初始化向量  
            des.Key = Encoding.ASCII.GetBytes(FormsAuthentication.HashPasswordForStoringInConfigFile
                (FormsAuthentication.HashPasswordForStoringInConfigFile(key, "md5")
                    ?.Substring(0, 8)!, "sha1")?.Substring(0, 8)!);
            // 通过两次哈希密码设置算法的机密密钥  
            des.IV = Encoding.ASCII.GetBytes(FormsAuthentication.HashPasswordForStoringInConfigFile
                (FormsAuthentication.HashPasswordForStoringInConfigFile(key, "md5")
                    ?.Substring(0, 8)!, "md5")?.Substring(0, 8)!);
            // 定义内存流
            var ms = new MemoryStream();
            // 定义加密流
            var cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            return Encoding.Default.GetString(ms.ToArray());
        }
    }
}