using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;
using System.Security.Cryptography;

namespace BF
{
    /// <summary>
    /// rc4流式加密解密
    /// 加密是连续的,加密完成之后再解密
    /// 速度快,可以用在协议或日志
    /// </summary>
    public class Rc4Encrypt
    {
        private byte[] keyStream;
        public string Key
        {
            set
            {
                keyStream = Encoding.UTF8.GetBytes(value);
            }
        }

        private byte[] Encrypt(byte[] pwd, byte[] data)
        {
            if (ReferenceEquals(pwd, null))
            {
                return data;
            }
            if (pwd.Length <= 0 || data.Length <= 0)
            {
                return data;
            }
            int a, i, j, k, tmp;
            int[] key, box;
            byte[] cipher;

            key = new int[256];
            box = new int[256];
            cipher = new byte[data.Length];

            for (i = 0; i < 256; i++) {
                key[i] = pwd[i % pwd.Length];
                box[i] = i;
            }
            for (j = i = 0; i < 256; i++) {
                j = (j + box[i] + key[i]) % 256;
                tmp = box[i];
                box[i] = box[j];
                box[j] = tmp;
            }
            for (a = j = i = 0; i < data.Length; i++) {
                a++;
                a %= 256;
                j += box[a];
                j %= 256;
                tmp = box[a];
                box[a] = box[j];
                box[j] = tmp;
                k = box[((box[a] + box[j]) % 256)];
                cipher[i] = (byte)(data[i] ^ k);
            }
            return cipher;
        }

        private byte[] Decrypt(byte[] pwd, byte[] data) {
            return Encrypt(pwd, data);
        }

//        public static string EncryptBytes(byte[] data, bool toBase64 = false)
//        {
//            byte[] encryptData = Encrypt(keyStream, data);
//
//            var r = toBase64
//                ? Convert.ToBase64String(encryptData)
//                : Encoding.UTF8.GetString(Encoding.UTF8.GetBytes(Convert.ToBase64String(encryptData)));
//
//            return r;
//        }

//        public static string DecryptBytes(byte[] data)
//        {
//            return Encoding.UTF8.GetString(Decrypt(keyStream, data));
//        }

        public byte[] EncryptBytes(byte[] bytes)
        {
            return Encrypt(keyStream, bytes);
        }

        public byte[]DecryptBytes(byte[] bytes)
        {
            return Decrypt(keyStream, bytes);
        }

        public byte[] EncryptStr(string data)
        {
            byte[] bytes = Encoding.UTF8.GetBytes(data);
            return Encrypt(keyStream, bytes);
        }

        public byte[] DecryptStr(string data)
        {
            byte[] bytes = Encoding.UTF8.GetBytes(data); //Convert.FromBase64String(Encoding.UTF8.GetString(Encoding.UTF8.GetBytes(data)));
            return Decrypt(keyStream, bytes);
        }
    }
}