// Keccak-256 (Ethereum's pre-standard SHA-3) via BouncyCastle, plus hex helpers.

using System;
using Org.BouncyCastle.Crypto.Digests;

namespace Nethermind.AerePqc.Qbft;

public static class Keccak256
{
    public static byte[] Hash(byte[] data)
    {
        var d = new KeccakDigest(256);
        d.BlockUpdate(data, 0, data.Length);
        var outp = new byte[32];
        d.DoFinal(outp, 0);
        return outp;
    }
}

public static class Hex
{
    public static byte[] Decode(string s)
    {
        if (s.StartsWith("0x") || s.StartsWith("0X")) s = s.Substring(2);
        if (s.Length == 0) return Array.Empty<byte>();
        if ((s.Length & 1) != 0) s = "0" + s;
        var b = new byte[s.Length / 2];
        for (int i = 0; i < b.Length; i++)
            b[i] = Convert.ToByte(s.Substring(i * 2, 2), 16);
        return b;
    }

    public static string Encode(byte[] b) => "0x" + Convert.ToHexString(b).ToLowerInvariant();
}