using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Numerics;
using System.Text;

namespace Chop.Game.Encryption
{
    class Crypto
    {
        public RC4 RC4Decode;
        private BigInteger _prime;
        private BigInteger _publicKey;
        private BigInteger _privateKey;

        public void InitRc4(byte[] tKey)
        {
            RC4Decode = new RC4();
            RC4Decode.Init(tKey);
        }

        public void InitDh(BigInteger p, BigInteger generator, string bigrand)
        {
            _prime = p;
            _privateKey = new BigInteger(bigrand, 16);
            _publicKey = generator.modPow(_privateKey, _prime);
        }

        public String GenerateSharedKey(string cKey)
        {
            return (new BigInteger(cKey, 10).modPow(_privateKey, _prime).ToString(16)).ToUpper();
        }

        public String GetPublicKey()
        {
            return _publicKey.ToString(10);
        }

        public String GenerateRandomHexString(int len)
        {
            var result = "";

            var rnd = new Random();

            for (var i = 0; i < len; i++)
            {
                var rand = 1 + (int)(rnd.NextDouble() * 254);
                result += int.Parse(rand.ToString(), (NumberStyles)16);
            }
            return result;
        }

        public byte[] HextoBytes(String hexString)
        {
            if ((hexString.Length % 2) != 0)
            {
                hexString = ("0" + hexString);
            }
            var bytes = new byte[hexString.Length / 2];
            var j = 0;
            for (var i = 0; i < bytes.Length; i++)
            {
                bytes[i] = (byte)int.Parse(hexString.Substring(j, j + 2), (NumberStyles)16);
                j += 2;
            }
            return bytes;
        }
    }
}