using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace FAuth.Extensions.Decryptor
{
    /// <summary>
    /// 加密帮助类
    /// </summary>
    public class EncryptyWorker
    {
        /// <summary>
        /// 补位填充方式
        /// </summary>
        public PaddingMode Padding { get; set; }
        /// <summary>
        /// 加密算法模式
        /// </summary>
        public CipherMode Cipher { get; set; }
        /// <summary>
        /// 初始化向量
        /// </summary>
        public byte[] IV { get; set; }
        /// <summary>
        /// 加密字符串获取Base64密文
        /// </summary>
        /// <param name="key">加密key</param>
        /// <param name="str">要加密的字符串</param>
        public string Encrypty(string key,string str) {
            if(key.Length < 8) {
                throw new Exception("加密用的key长度为8位");
            }
            byte[] bKey = Encoding.UTF8.GetBytes(key.Substring(0,8));
            byte[] bStr = Encoding.UTF8.GetBytes(str);
            var desc = createProvider();
            using(var mStream = new MemoryStream()) {
                using(var cStream = new CryptoStream(mStream,desc.CreateEncryptor(bKey,IV),CryptoStreamMode.Write)) {
                    cStream.Write(bStr,0,bStr.Length);
                    cStream.FlushFinalBlock();
                    return Convert.ToBase64String(mStream.ToArray());
                }
            }
        }
        /// <summary>
        /// 从Base64密文解密，获取字符串
        /// </summary>
        /// <param name="key">加密键</param>
        /// <param name="str">密文</param>
        public string DesCrypty(string key,string str) {
            if(key.Length < 8) {
                throw new Exception("加密用的key长度为8位");
            }
            var bStr = Convert.FromBase64String(str);
            byte[] bKey = Encoding.UTF8.GetBytes(key.Substring(0,8));
            var desc = createProvider();
            using(var mStream = new MemoryStream()) {
                using(var cStream = new CryptoStream(mStream,desc.CreateDecryptor(bKey,IV),CryptoStreamMode.Write)) {
                    cStream.Write(bStr,0,bStr.Length);
                    cStream.FlushFinalBlock();
                    return Encoding.UTF8.GetString(mStream.ToArray());
                }
            }
        }

        private DESCryptoServiceProvider createProvider() {
            var desc = new DESCryptoServiceProvider();
            desc.Padding = this.Padding;
            desc.Mode = this.Cipher;
            return desc;
        }

        private static EncryptyWorker Deshelper { get; set; }

        private EncryptyWorker() { }

        /// <summary>
        /// 重用模式获取默认加密帮助器
        /// </summary>
        public static EncryptyWorker GetHelper() {
            if(Deshelper == null) {
                byte[] IV = { 0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08 };
                Deshelper = GetHelper(PaddingMode.PKCS7,CipherMode.CBC,IV);

            }
            return Deshelper;
        }
        /// <summary>
        /// 生成新的加密帮助器
        /// </summary>
        /// <param name="padding">补位方式</param>
        /// <param name="cipher">加密算法模式</param>
        /// <param name="IV">初始化向量</param>
        public static EncryptyWorker GetHelper(PaddingMode padding,CipherMode cipher,byte[] IV) {
            return new EncryptyWorker {
                Cipher = cipher,
                IV = IV,
                Padding = padding,
            };
        }
    }
}