// Copyright (c) 2020-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

// Based on https://github.com/mjosaarinen/tiny_sha3/blob/master/sha3.c

// by Markku-Juhani O. Saarinen <mjos@iki.fi>

#include <crypto/sha3.h>

#include <crypto/common.h>

#include <algorithm>

#include <bit>

#include <cassert>

#include <iterator>

#include <span>

void KeccakF(uint64_t (&st)[25])

{

    static constexpr uint64_t RNDC[24] = {

        0x0000000000000001, 0x0000000000008082, 0x800000000000808a, 0x8000000080008000,

        0x000000000000808b, 0x0000000080000001, 0x8000000080008081, 0x8000000000008009,

        0x000000000000008a, 0x0000000000000088, 0x0000000080008009, 0x000000008000000a,

        0x000000008000808b, 0x800000000000008b, 0x8000000000008089, 0x8000000000008003,

        0x8000000000008002, 0x8000000000000080, 0x000000000000800a, 0x800000008000000a,

        0x8000000080008081, 0x8000000000008080, 0x0000000080000001, 0x8000000080008008

    };

    static constexpr int ROUNDS = 24;

    for (int round = 0; round < ROUNDS; ++round) {

        uint64_t bc0, bc1, bc2, bc3, bc4, t;

        // Theta

        bc0 = st[0] ^ st[5] ^ st[10] ^ st[15] ^ st[20];

        bc1 = st[1] ^ st[6] ^ st[11] ^ st[16] ^ st[21];

        bc2 = st[2] ^ st[7] ^ st[12] ^ st[17] ^ st[22];

        bc3 = st[3] ^ st[8] ^ st[13] ^ st[18] ^ st[23];

        bc4 = st[4] ^ st[9] ^ st[14] ^ st[19] ^ st[24];

        t = bc4 ^ std::rotl(bc1, 1); st[0] ^= t; st[5] ^= t; st[10] ^= t; st[15] ^= t; st[20] ^= t;

        t = bc0 ^ std::rotl(bc2, 1); st[1] ^= t; st[6] ^= t; st[11] ^= t; st[16] ^= t; st[21] ^= t;

        t = bc1 ^ std::rotl(bc3, 1); st[2] ^= t; st[7] ^= t; st[12] ^= t; st[17] ^= t; st[22] ^= t;

        t = bc2 ^ std::rotl(bc4, 1); st[3] ^= t; st[8] ^= t; st[13] ^= t; st[18] ^= t; st[23] ^= t;

        t = bc3 ^ std::rotl(bc0, 1); st[4] ^= t; st[9] ^= t; st[14] ^= t; st[19] ^= t; st[24] ^= t;

        // Rho Pi

        t = st[1];

        bc0 = st[10]; st[10] = std::rotl(t, 1); t = bc0;

        bc0 = st[7]; st[7] = std::rotl(t, 3); t = bc0;

        bc0 = st[11]; st[11] = std::rotl(t, 6); t = bc0;

        bc0 = st[17]; st[17] = std::rotl(t, 10); t = bc0;

        bc0 = st[18]; st[18] = std::rotl(t, 15); t = bc0;

        bc0 = st[3]; st[3] = std::rotl(t, 21); t = bc0;

        bc0 = st[5]; st[5] = std::rotl(t, 28); t = bc0;

        bc0 = st[16]; st[16] = std::rotl(t, 36); t = bc0;

        bc0 = st[8]; st[8] = std::rotl(t, 45); t = bc0;

        bc0 = st[21]; st[21] = std::rotl(t, 55); t = bc0;

        bc0 = st[24]; st[24] = std::rotl(t, 2); t = bc0;

        bc0 = st[4]; st[4] = std::rotl(t, 14); t = bc0;

        bc0 = st[15]; st[15] = std::rotl(t, 27); t = bc0;

        bc0 = st[23]; st[23] = std::rotl(t, 41); t = bc0;

        bc0 = st[19]; st[19] = std::rotl(t, 56); t = bc0;

        bc0 = st[13]; st[13] = std::rotl(t, 8); t = bc0;

        bc0 = st[12]; st[12] = std::rotl(t, 25); t = bc0;

        bc0 = st[2]; st[2] = std::rotl(t, 43); t = bc0;

        bc0 = st[20]; st[20] = std::rotl(t, 62); t = bc0;

        bc0 = st[14]; st[14] = std::rotl(t, 18); t = bc0;

        bc0 = st[22]; st[22] = std::rotl(t, 39); t = bc0;

        bc0 = st[9]; st[9] = std::rotl(t, 61); t = bc0;

        bc0 = st[6]; st[6] = std::rotl(t, 20); t = bc0;

        st[1] = std::rotl(t, 44);

        // Chi Iota

        bc0 = st[0]; bc1 = st[1]; bc2 = st[2]; bc3 = st[3]; bc4 = st[4];

        st[0] = bc0 ^ (~bc1 & bc2) ^ RNDC[round];

        st[1] = bc1 ^ (~bc2 & bc3);

        st[2] = bc2 ^ (~bc3 & bc4);

        st[3] = bc3 ^ (~bc4 & bc0);

        st[4] = bc4 ^ (~bc0 & bc1);

        bc0 = st[5]; bc1 = st[6]; bc2 = st[7]; bc3 = st[8]; bc4 = st[9];

        st[5] = bc0 ^ (~bc1 & bc2);

        st[6] = bc1 ^ (~bc2 & bc3);

        st[7] = bc2 ^ (~bc3 & bc4);

        st[8] = bc3 ^ (~bc4 & bc0);

        st[9] = bc4 ^ (~bc0 & bc1);

        bc0 = st[10]; bc1 = st[11]; bc2 = st[12]; bc3 = st[13]; bc4 = st[14];

        st[10] = bc0 ^ (~bc1 & bc2);

        st[11] = bc1 ^ (~bc2 & bc3);

        st[12] = bc2 ^ (~bc3 & bc4);

        st[13] = bc3 ^ (~bc4 & bc0);

        st[14] = bc4 ^ (~bc0 & bc1);

        bc0 = st[15]; bc1 = st[16]; bc2 = st[17]; bc3 = st[18]; bc4 = st[19];

        st[15] = bc0 ^ (~bc1 & bc2);

        st[16] = bc1 ^ (~bc2 & bc3);

        st[17] = bc2 ^ (~bc3 & bc4);

        st[18] = bc3 ^ (~bc4 & bc0);

        st[19] = bc4 ^ (~bc0 & bc1);

        bc0 = st[20]; bc1 = st[21]; bc2 = st[22]; bc3 = st[23]; bc4 = st[24];

        st[20] = bc0 ^ (~bc1 & bc2);

        st[21] = bc1 ^ (~bc2 & bc3);

        st[22] = bc2 ^ (~bc3 & bc4);

        st[23] = bc3 ^ (~bc4 & bc0);

        st[24] = bc4 ^ (~bc0 & bc1);

    }

}

SHA3_256& SHA3_256::Write(std::span<const unsigned char> data)

{

    if (m_bufsize && data.size() >= sizeof(m_buffer) - m_bufsize) {

        // Fill the buffer and process it.

        std::copy(data.begin(), data.begin() + (sizeof(m_buffer) - m_bufsize), m_buffer + m_bufsize);

        data = data.subspan(sizeof(m_buffer) - m_bufsize);

        m_state[m_pos++] ^= ReadLE64(m_buffer);

        m_bufsize = 0;

        if (m_pos == RATE_BUFFERS) {

            KeccakF(m_state);

            m_pos = 0;

        }

    }

    while (data.size() >= sizeof(m_buffer)) {

        // Process chunks directly from the buffer.

        m_state[m_pos++] ^= ReadLE64(data.data());

        data = data.subspan(8);

        if (m_pos == RATE_BUFFERS) {

            KeccakF(m_state);

            m_pos = 0;

        }

    }

    if (data.size()) {

        // Keep the remainder in the buffer.

        std::copy(data.begin(), data.end(), m_buffer + m_bufsize);

        m_bufsize += data.size();

    }

    return *this;

}

SHA3_256& SHA3_256::Finalize(std::span<unsigned char> output)

{

    assert(output.size() == OUTPUT_SIZE);

    std::fill(m_buffer + m_bufsize, m_buffer + sizeof(m_buffer), 0);

    m_buffer[m_bufsize] ^= 0x06;

    m_state[m_pos] ^= ReadLE64(m_buffer);

    m_state[RATE_BUFFERS - 1] ^= 0x8000000000000000;

    KeccakF(m_state);

    for (unsigned i = 0; i < 4; ++i) {

        WriteLE64(output.data() + 8 * i, m_state[i]);

    }

    return *this;

}

SHA3_256& SHA3_256::Reset()

{

    m_bufsize = 0;

    m_pos = 0;

    std::fill(std::begin(m_state), std::end(m_state), 0);

    return *this;

}