utility

/*
	This file is part of Fennix Kernel.

	Fennix Kernel 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.

	Fennix Kernel 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 Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
*/

#pragma once

#include <type_traits>
#include <algorithm>
#include <tuple>

namespace std
{
	struct piecewise_construct_t
	{
		explicit piecewise_construct_t() = default;
	};

	inline constexpr std::piecewise_construct_t piecewise_construct{};

	template <typename T>
	typename std::remove_reference<T>::type &&move(T &&arg)
	{
		return static_cast<typename std::remove_reference<T>::type &&>(arg);
	}

	template <typename T>
	void __utility_swap(T &a, T &b)
	{
		T temp = std::move(a);
		a = std::move(b);
		b = std::move(temp);
	}

	template <class T, T... Ints>
	class integer_sequence
	{
	public:
		typedef T value_type;

		static constexpr std::size_t size() noexcept { return sizeof...(Ints); }
	};

	template <std::size_t... Ints>
	using index_sequence = std::integer_sequence<std::size_t, Ints...>;

	template <class T, T N>
	using make_integer_sequence = std::integer_sequence<T, N>;

	template <std::size_t N>
	using make_index_sequence = std::make_integer_sequence<std::size_t, N>;

	template <class... T>
	using index_sequence_for = std::make_index_sequence<sizeof...(T)>;

	template <class T>
	constexpr T &&forward(std::remove_reference_t<T> &t) noexcept
	{
		return static_cast<T &&>(t);
	}

	template <class T>
	constexpr T &&forward(std::remove_reference_t<T> &&t) noexcept
	{
		static_assert(!std::is_lvalue_reference<T>::value, "Can't forward an rvalue as an lvalue.");
		return static_cast<T &&>(t);
	}

	template <typename T1, typename T2>
	struct pair
	{
		typedef T1 first_type;
		typedef T2 second_type;

		first_type first;
		second_type second;

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<std::is_default_constructible<U1>::value &&
											  std::is_default_constructible<U2>::value,
										  int>::type = true>
		constexpr pair()
			: first(),
			  second()
		{
		}

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<!std::is_default_constructible<U1>::value ||
											  !std::is_default_constructible<U2>::value,
										  int>::type = false>
		explicit constexpr pair()
			: first(),
			  second()
		{
		}

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<std::is_copy_constructible<U1>::value &&
											  std::is_copy_constructible<U2>::value,
										  int>::type = true>
		constexpr pair(const T1 &x, const T2 &y)
			: first(x),
			  second(y)
		{
		}

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<!std::is_copy_constructible<U1>::value ||
											  !std::is_copy_constructible<U2>::value,
										  int>::type = false>
		explicit constexpr pair(const T1 &x, const T2 &y)
			: first(x),
			  second(y)
		{
		}

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<std::is_move_constructible<U1>::value &&
											  std::is_move_constructible<U2>::value,
										  int>::type = true>
		constexpr pair(U1 &&x, U2 &&y)
			: first(std::forward<U1>(x)),
			  second(std::forward<U2>(y))
		{
		}

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<!std::is_move_constructible<U1>::value ||
											  !std::is_move_constructible<U2>::value,
										  int>::type = false>
		explicit constexpr pair(T1 &&x, T2 &&y)
			: first(std::forward<T1>(x)),
			  second(std::forward<T2>(y)){};

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<std::is_copy_constructible<U1>::value &&
											  std::is_copy_constructible<U2>::value,
										  int>::type = true>
		constexpr pair(const pair<U1, U2> &p)
			: first(p.first),
			  second(p.second)
		{
		}

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<!std::is_copy_constructible<U1>::value ||
											  !std::is_copy_constructible<U2>::value,
										  int>::type = false>
		explicit constexpr pair(const pair<U1, U2> &p)
			: first(p.first),
			  second(p.second)
		{
		}

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<std::is_move_constructible<U1>::value &&
											  std::is_move_constructible<U2>::value,
										  int>::type = true>
		constexpr pair(pair<U1, U2> &&p)
			: first(std::forward<U1>(p.first)),
			  second(std::forward<U2>(p.second))
		{
		}

		template <typename U1 = T1,
				  typename U2 = T2,
				  typename std::enable_if<!std::is_move_constructible<U1>::value ||
											  !std::is_move_constructible<U2>::value,
										  int>::type = false>
		explicit constexpr pair(pair<U1, U2> &&p)
			: first(std::forward<U1>(p.first)),
			  second(std::forward<U2>(p.second))
		{
		}

		template <class... Args1, class... Args2>
		constexpr pair(std::piecewise_construct_t, std::tuple<Args1...> first_args, std::tuple<Args2...> second_args)
			: pair(first_args, second_args, std::index_sequence_for<Args1...>(), std::index_sequence_for<Args2...>())
		{
		}

		pair(const pair &p) = default;
		pair(pair &&p) = default;

		constexpr pair &operator=(const pair &other)
		{
			first = other.first;
			second = other.second;
			return *this;
		}

		template <class U1, class U2>
		constexpr pair &operator=(const pair<U1, U2> &other)
		{
			first = other.first;
			second = other.second;
			return *this;
		}

		constexpr pair &operator=(pair &&other) noexcept(std::is_nothrow_move_assignable<T1>::value && std::is_nothrow_move_assignable<T2>::value)
		{
			first = std::move(other.first);
			second = std::move(other.second);
			return *this;
		}

		template <class U1, class U2>
		constexpr pair &operator=(pair<U1, U2> &&p)
		{
			first = std::forward<U1>(p.first);
			second = std::forward<U2>(p.second);
			return *this;
		}

		constexpr void swap(pair &other) noexcept(std::is_nothrow_swappable_v<first_type> && std::is_nothrow_swappable_v<second_type>)
		{
			__utility_swap(first, other.first);
			__utility_swap(second, other.second);
		}
	};

	template <class T1, class T2>
	std::pair<typename std::decay<T1>::type, typename std::decay<T2>::type> make_pair(T1 &&t, T2 &&u)
	{
		typedef typename std::decay<T1>::type first_type;
		typedef typename std::decay<T2>::type second_type;
		typedef pair<first_type, second_type> pair_type;
		return pair_type(std::forward<T1>(t), std::forward<T2>(u));
	}
}