/*

  This file is part of solidity.

  solidity is free software: you can redistribute it and/or modify

  it under the terms of the GNU General Public License as published by

  the Free Software Foundation, either version 3 of the License, or

  (at your option) any later version.

  solidity is distributed in the hope that it will be useful,

  but WITHOUT ANY WARRANTY; without even the implied warranty of

  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License

  along with solidity.  If not, see <http://www.gnu.org/licenses/>.

*/

// SPDX-License-Identifier: GPL-3.0

/** @file SwarmHash.cpp

 */

#include <libsolutil/SwarmHash.h>

#include <libsolutil/Keccak256.h>

using namespace std;

using namespace solidity;

using namespace solidity::util;

namespace

{

bytes toLittleEndian(uint64_t _size)

{

  bytes encoded(8);

  for (size_t i = 0; i < 8; ++i)

    encoded[i] = (_size >> (8 * i)) & 0xff;

  return encoded;

}

h256 swarmHashSimple(bytesConstRef _data, size_t _size)

{

  return keccak256(toLittleEndian(_size) + _data.toBytes());

}

h256 swarmHashIntermediate(string const& _input, size_t _offset, size_t _length)

{

  bytesConstRef ref;

  bytes innerNodes;

  if (_length <= 0x1000)

    ref = bytesConstRef(_input).cropped(_offset, _length);

  else

  {

    size_t maxRepresentedSize = 0x1000;

    while (maxRepresentedSize * (0x1000 / 32) < _length)

      maxRepresentedSize *= (0x1000 / 32);

    for (size_t i = 0; i < _length; i += maxRepresentedSize)

    {

      size_t size = std::min(maxRepresentedSize, _length - i);

      innerNodes += swarmHashIntermediate(_input, _offset + i, size).asBytes();

    }

    ref = bytesConstRef(&innerNodes);

  }

  return swarmHashSimple(ref, _length);

}

h256 bmtHash(bytesConstRef _data)

{

  if (_data.size() <= 64)

    return keccak256(_data);

  size_t midPoint = _data.size() / 2;

  return keccak256(

    bmtHash(_data.cropped(0, midPoint)).asBytes() +

    bmtHash(_data.cropped(midPoint)).asBytes()

  );

}

h256 chunkHash(bytesConstRef const _data, bool _forceHigherLevel = false)

{

  bytes dataToHash;

  if (_data.size() < 0x1000)

    dataToHash = _data.toBytes();

  else if (_data.size() == 0x1000 && !_forceHigherLevel)

    dataToHash = _data.toBytes();

  else

  {

    size_t maxRepresentedSize = 0x1000;

    while (maxRepresentedSize * (0x1000 / 32) < _data.size())

      maxRepresentedSize *= (0x1000 / 32);

    // If remaining size is 0x1000, but maxRepresentedSize is not,

    // we have to still do one level of the chunk hashes.

    bool forceHigher = maxRepresentedSize > 0x1000;

    for (size_t i = 0; i < _data.size(); i += maxRepresentedSize)

    {

      size_t size = std::min(maxRepresentedSize, _data.size() - i);

      dataToHash += chunkHash(_data.cropped(i, size), forceHigher).asBytes();

    }

  }

  dataToHash.resize(0x1000, 0);

  return keccak256(toLittleEndian(_data.size()) + bmtHash(&dataToHash).asBytes());

}

}

h256 solidity::util::bzzr0Hash(string const& _input)

{

  return swarmHashIntermediate(_input, 0, _input.size());

}

h256 solidity::util::bzzr1Hash(bytes const& _input)

{

  if (_input.empty())

    return h256{};

  return chunkHash(&_input);

}