// Copyright (c) 2020 The Bitcoin Core developers
// Copyright (c) 2016-2024 The Hush developers
// Distributed under the GPLv3 software license, see the accompanying
// file COPYING or https://www.gnu.org/licenses/gpl-3.0.en.html

#ifndef HUSH_CRYPTO_SHA3_H
#define HUSH_CRYPTO_SHA3_H

#include "span.h"

#include <stdint.h>
#include <stdlib.h>

//! The Keccak-f[1600] transform.
void KeccakF(uint64_t (&st)[25]);

class SHA3_256_
{
private:
    uint64_t m_state[25] = {0};
    unsigned char m_buffer[8];
    unsigned m_bufsize = 0;
    unsigned m_pos = 0;

    //! Sponge rate in bits.
    static constexpr unsigned RATE_BITS = 1088;

    //! Sponge rate expressed as a multiple of the buffer size.
    static constexpr unsigned RATE_BUFFERS = RATE_BITS / (8 * sizeof(m_buffer));

    static_assert(RATE_BITS % (8 * sizeof(m_buffer)) == 0, "Rate must be a multiple of 8 bytes");

public:
    static constexpr size_t OUTPUT_SIZE = 32;

    SHA3_256_() {}
    SHA3_256_& Write(Span<const unsigned char> data);
    SHA3_256_& Finalize(Span<unsigned char> output);
    SHA3_256_& Reset();
};

#endif // HUSH_CRYPTO_SHA3_H