Kernel/include_std/iterator

/*
	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

namespace std
{
	struct input_iterator_tag
	{
	};

	struct output_iterator_tag
	{
	};

	struct forward_iterator_tag : public input_iterator_tag
	{
	};

	struct bidirectional_iterator_tag : public forward_iterator_tag
	{
	};

	struct random_access_iterator_tag : public bidirectional_iterator_tag
	{
	};

	struct contiguous_iterator_tag : public random_access_iterator_tag
	{
	};

	template <class Iter>
	class reverse_iterator
	{
	public:
		/* FIXME: missing implementation */
	};

	template <class Iter>
	struct iterator_traits
	{
	public:
		typedef Iter::difference_type difference_type;

		/* FIXME: missing implementation */
	};

	template <class It>
	constexpr typename std::iterator_traits<It>::difference_type __do_distance(It first, It last, std::input_iterator_tag)
	{
		typename std::iterator_traits<It>::difference_type result = 0;
		while (first != last)
		{
			++first;
			++result;
		}
		return result;
	}

	template <class It>
	constexpr typename std::iterator_traits<It>::difference_type __do_distance(It first, It last, std::random_access_iterator_tag)
	{
		return last - first;
	}

	template <class InputIt>
	constexpr typename std::iterator_traits<InputIt>::difference_type distance(InputIt first, InputIt last)
	{
		return __do_distance(first, last, typename std::iterator_traits<InputIt>::iterator_category());
	}
}