using System;
using System.Collections.Generic;
using System.Text;
using System.Security.Cryptography;
using System.IO;

namespace Zhaizj.Framework.Utils
{
    /// <summary>
    /// 证书加密解密
    /// </summary>
    public class LicenseEncry
    {
        
        private SymmetricAlgorithm _algthm;
        private string _key;
        private string _IV;

        /// <summary>
        /// 对称加密算法构造函数
        /// </summary>
        public LicenseEncry()
        {
            Inital();
        }

        /// <summary>
        /// 对称加密算法构造函数，需要传入密钥字符串
        /// </summary>
        /// <param name="Key">密钥字符串</param>
        public LicenseEncry(string Key)
        {
            Inital();
            _key = EncryKey(Key);
        }

        /// <summary>
        /// 对称加密算法构造函数，需要传入密钥字符串和初始化向量字符串
        /// </summary>
        /// <param name="Key">密钥字符串</param>
        /// <param name="IV">初始向量字符串</param>
        public LicenseEncry(string Key,string IV)
        {
            Inital();
            _key = EncryKey(Key);
            _IV = IV;
        }

        /// <summary>
        /// 基本配置初始化
        /// </summary>
        private void Inital()
        {
            _algthm = new RijndaelManaged();
            //128位的key
            _key = "*)L7uaDdsl#@(*&873JKLF(*#klj*)L7uaDdsl#@(*&873JKLF(*#kljsdsfhjskldf789#()RU*(h9oa9#*w7R(Q#U(*)L7*)L7uaDdsl#@(*&873JKLF(*#kljsdsfhjskldf789#()RU*(h9oa9#*w7R(Q#U(uaDdsl#@(*&873JKLF(*#kljsdsfhjskldf789#()RU*(h9oa9#*w7R(Q#U(sdsfhjskldf789#()RU*(h9oa9#*w7R(Q#U(";
            _IV = "FG&^lsdlkjsdojslkad3240897&^9o34ly89f(*&#(!@_@_dfskldfhjks5d4f";
            //_algthm.KeySize = 256;
        }

        private string EncryKey(string key)
        {
            //32位MD5加密
            string longKey = MD5Encrp.MD5(key);
            //将key变成64位的长密钥
            while(longKey.Length<256)
            {
                longKey += longKey;
            }
            return longKey;
        }

        /// <summary>
        /// 对原文进行加密后返回加密文
        /// </summary>
        /// <param name="Source"></param>
        /// <returns></returns>
        public string Encrypt(string Source)
        {
            //原文字节
            byte[] byteIn = UTF8Encoding.UTF8.GetBytes(Source);
            //密文流
            MemoryStream ms = new MemoryStream();

            //加密算法转换器生成
            _algthm.Key = GetLegalKey();
            _algthm.IV = GetLegalIV();
            ICryptoTransform crypto = _algthm.CreateEncryptor();

            //执行加密转换
            CryptoStream cs = new CryptoStream(ms, crypto, CryptoStreamMode.Write);
            cs.Write(byteIn, 0, byteIn.Length);
            cs.FlushFinalBlock();
            ms.Close();
            cs.Close();

            //返回编码后的字符串结果
            byte[] byteOut = ms.ToArray();
            return Convert.ToBase64String(byteOut);
        }

        /// <summary>
        /// 对密文进行解密后返回加原文
        /// </summary>
        /// <param name="Source"></param>
        /// <returns></returns>
        public string Decrypt(string Source)
        {
            //密文字节
            byte[] byteIn = Convert.FromBase64String(Source);
            //密文流
            MemoryStream ms = new MemoryStream(byteIn, 0, byteIn.Length);

            //解密算法转换器生成
            _algthm.Key = GetLegalKey();
            _algthm.IV = GetLegalIV();
            ICryptoTransform crypto = _algthm.CreateDecryptor();

            //执行解密转换
            CryptoStream cs = new CryptoStream(ms, crypto, CryptoStreamMode.Read);

            //返回编码后的字符串结果
            StreamReader sr = new StreamReader(cs);
            return sr.ReadToEnd();
        }



        /// <summary>
        /// 比较现有密钥与算法密钥的长度，使得现有密钥此成为合法长度
        /// </summary>
        /// <returns></returns>
        private byte[] GetLegalKey()
        {
            string tmpKey = _key;
            _algthm.GenerateKey();

            int okLen = _algthm.Key.Length;
            if (tmpKey.Length > okLen)
            {
                //_key过长则截取
                tmpKey = tmpKey.Substring(0, okLen);
            }
            else if (tmpKey.Length < okLen)
            {
                //_key过短则补充
                tmpKey = tmpKey.PadRight(okLen, ' ');
            }

            return ASCIIEncoding.ASCII.GetBytes(tmpKey);
        }

        /// <summary>
        /// 比较现有IV与算法IV的长度，使得现有密钥此成为合法长度
        /// </summary>
        /// <returns></returns>
        private byte[] GetLegalIV()
        {
            string tmpIV = _IV;
            _algthm.GenerateIV();
            int okLen = _algthm.IV.Length;
            if (tmpIV.Length > okLen)
            {
                //_IV过长则截取
                tmpIV = tmpIV.Substring(0, okLen);
            }
            else if (tmpIV.Length < okLen)
            {
                //_IV过短则补充
                tmpIV = tmpIV.PadRight(okLen, ' ');
            }
            return ASCIIEncoding.ASCII.GetBytes(tmpIV);
        }
    }

    /// <summary>
    /// MD5加密算法
    /// </summary>
    public static class MD5Encrp
    {
        /// <summary>
        /// MD5函数
        /// </summary>
        /// <param name="str">原始字符串</param>
        /// <returns>MD5结果</returns>
        public static string MD5(string str)
        {
            byte[] b = Encoding.Default.GetBytes(str);
            b = new MD5CryptoServiceProvider().ComputeHash(b);
            string ret = "";
            for (int i = 0; i < b.Length; i++)
                ret += b[i].ToString("x").PadLeft(2, '0');

            return ret;
        }
    }
}