// Copyright (c) CypherCore <http://github.com/CypherCore> All rights reserved.
// Licensed under the GNU GENERAL PUBLIC LICENSE. See LICENSE file in the project root for full license information.

using System.Security.Cryptography;
using System;

namespace Game
{
    class SHA1Randx
    {
        public SHA1Randx(byte[] buff)
        {
            int halfSize = buff.Length / 2;
            Span<byte> span = buff;

            sh = SHA1.Create();
            o1 = sh.ComputeHash(buff, 0, halfSize);

            sh = SHA1.Create();
            o2 = sh.ComputeHash(span[halfSize..].ToArray(), 0, buff.Length - halfSize);

            FillUp();
        }

        public void Generate(byte[] buf, uint sz)
        {
            for (uint i = 0; i < sz; ++i)
            {
                if (taken == 20)
                    FillUp();

                buf[i] = o0[taken];
                taken++;
            }
        }


        void FillUp()
        {
            sh = SHA1.Create();
            sh.ComputeHash(o1, 0, 20);
            sh.ComputeHash(o0, 0, 20);
            o0 = sh.ComputeHash(o2, 0, 20);

            taken = 0;
        }

        SHA1 sh;
        uint taken;
        byte[] o0 = new byte[20];
        byte[] o1 = new byte[20];
        byte[] o2 = new byte[20];
    }

}