using System;
using System.Collections.Generic;
using System.Text;

namespace CP.Common
{
    /// <summary>
    /// xxtea加解密
    /// </summary>
    public class XXTEA
    {
        /// <summary>
        /// 加/解密KEY
        /// </summary>
        private const string PASSKEY = "01F4FD6F4CB96EA4";

        /// <summary>
        /// 加密字符串
        /// </summary>
        /// <param name="Str"></param>
        /// <returns></returns>
        public static string Encode(string Str)
        {
            System.Text.Encoding encoder = System.Text.Encoding.UTF8;
            Byte[] data = Encrypt(encoder.GetBytes(Str), encoder.GetBytes(PASSKEY));
            return System.Convert.ToBase64String(data);
        }

        /// <summary>
        /// 解密码字符串
        /// </summary>
        /// <param name="Str"></param>
        /// <returns></returns>
        public static string Decode(string Str)
        {
            System.Text.Encoding encoder = System.Text.Encoding.UTF8;
            string DeStr = string.Empty;
            try
            {
                DeStr = encoder.GetString(Decrypt(System.Convert.FromBase64String(Str), encoder.GetBytes(PASSKEY)));
            }
            catch
            {
                return "";
            }
            return DeStr;
        }


        private static Byte[] Encrypt(Byte[] Data, Byte[] Key)
        {
            if (Data.Length == 0)
            {
                return Data;
            }
            return ToByteArray(Encrypt(ToUInt32Array(Data, true), ToUInt32Array(Key, false)), false);
        }

        private static Byte[] Decrypt(Byte[] Data, Byte[] Key)
        {
            if (Data.Length == 0)
            {
                return Data;
            }
            return ToByteArray(Decrypt(ToUInt32Array(Data, false), ToUInt32Array(Key, false)), true);
        }

        private static UInt32[] Encrypt(UInt32[] v, UInt32[] k)
        {
            Int32 n = v.Length - 1;
            if (n < 1)
            {
                return v;
            }
            if (k.Length < 4)
            {
                UInt32[] Key = new UInt32[4];
                k.CopyTo(Key, 0);
                k = Key;
            }
            UInt32 z = v[n], y = v[0], delta = 0x9E3779B9, sum = 0, e;
            Int32 p, q = 6 + 52 / (n + 1);
            while (q-- > 0)
            {
                sum = unchecked(sum + delta);
                e = sum >> 2 & 3;
                for (p = 0; p < n; p++)
                {
                    y = v[p + 1];
                    z = unchecked(v[p] += (z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z));
                }
                y = v[0];
                z = unchecked(v[n] += (z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z));
            }
            return v;
        }

        private static UInt32[] Decrypt(UInt32[] v, UInt32[] k)
        {
            Int32 n = v.Length - 1;
            if (n < 1)
            {
                return v;
            }
            if (k.Length < 4)
            {
                UInt32[] Key = new UInt32[4];
                k.CopyTo(Key, 0);
                k = Key;
            }
            UInt32 z = v[n], y = v[0], delta = 0x9E3779B9, sum, e;
            Int32 p, q = 6 + 52 / (n + 1);
            sum = unchecked((UInt32)(q * delta));
            while (sum != 0)
            {
                e = sum >> 2 & 3;
                for (p = n; p > 0; p--)
                {
                    z = v[p - 1];
                    y = unchecked(v[p] -= (z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z));
                }
                z = v[n];
                y = unchecked(v[0] -= (z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z));
                sum = unchecked(sum - delta);
            }
            return v;
        }

        private static UInt32[] ToUInt32Array(Byte[] Data, Boolean IncludeLength)
        {
            Int32 n = (((Data.Length & 3) == 0) ? (Data.Length >> 2) : ((Data.Length >> 2) + 1));
            UInt32[] Result;
            if (IncludeLength)
            {
                Result = new UInt32[n + 1];
                Result[n] = (UInt32)Data.Length;
            }
            else
            {
                Result = new UInt32[n];
            }
            n = Data.Length;
            for (Int32 i = 0; i < n; i++)
            {
                Result[i >> 2] |= (UInt32)Data[i] << ((i & 3) << 3);
            }
            return Result;
        }
        private static Byte[] ToByteArray(UInt32[] Data, Boolean IncludeLength)
        {
            Int32 n;
            if (IncludeLength)
            {
                n = (Int32)Data[Data.Length - 1];
            }
            else
            {
                n = Data.Length << 2;
            }
            Byte[] Result = new Byte[n];
            for (Int32 i = 0; i < n; i++)
            {
                Result[i] = (Byte)(Data[i >> 2] >> ((i & 3) << 3));
            }
            return Result;
        }
    }
}