/*

Copyright (C) 2017-2026 Topological Manifold

This program 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.

This program 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 this program. If not, see <http://www.gnu.org/licenses/>.

*/

#pragma once

#include "error.h"

#include <cstddef>

#include <random>

#include <tuple>

namespace ns

{

// Donald Knuth. The Art of Computer Programming. Second edition. Addison-Wesley, 1981.

// Volume 2. Seminumerical Algorithms. 3.4.2. Random Sampling and Shuffling.

template <typename RandomEngine, typename T>

void shuffle_dimension(RandomEngine&& engine, const std::size_t dimension, T* const data)

{

ASSERT(dimension < std::tuple_size_v<typename T::value_type>);

if (data->size() < 2)

{

return;

}

for (std::size_t i = data->size() - 1; i > 0; --i)

{

const std::size_t j = std::uniform_int_distribution<std::size_t>(0, i)(engine);

std::swap((*data)[i][dimension], (*data)[j][dimension]);

}

}

template <typename RandomEngine, typename... T>

void shuffle(RandomEngine&& engine, T* const... data)

{

static_assert(sizeof...(T) >= 1);

ASSERT((data && ...));

const std::size_t size = std::get<0>(std::make_tuple(data->size()...));

if constexpr (sizeof...(T) >= 2)

{

ASSERT(((data->size() == size) && ...));

}

if (size < 2)

{

return;

}

for (std::size_t i = size - 1; i > 0; --i)

{

const std::size_t j = std::uniform_int_distribution<std::size_t>(0, i)(engine);

(std::swap((*data)[i], (*data)[j]), ...);

}

}

}