#ifndef SPROUT_ITERATOR_COUNTING_ITERATOR_HPP
#define SPROUT_ITERATOR_COUNTING_ITERATOR_HPP

#include <cstddef>
#include <iterator>
#include <utility>
#include <type_traits>
#include <sprout/config.hpp>
#include <sprout/iterator/next.hpp>
#include <sprout/iterator/prev.hpp>
#include <sprout/iterator/distance.hpp>

namespace sprout {
	//
	// counting_iterator
	//
	template<typename Incrementable>
	class counting_iterator
		: public std::iterator<
			std::random_access_iterator_tag,
			Incrementable,
			std::ptrdiff_t,
			Incrementable*,
			Incrementable
		>
	{
	public:
		typedef std::random_access_iterator_tag iterator_category;
		typedef Incrementable value_type;
		typedef std::ptrdiff_t difference_type;
		typedef value_type* pointer;
		typedef value_type reference;
	private:
		value_type current_;
	private:
	public:
		counting_iterator() = default;
		counting_iterator(counting_iterator const&) = default;
		explicit SPROUT_CONSTEXPR counting_iterator(value_type const& v)
			: current_(v)
		{}
		template<typename U>
		SPROUT_CONSTEXPR counting_iterator(counting_iterator<U> const& it)
			: current_(it.current_)
		{}
		template<typename U>
		counting_iterator& operator=(counting_iterator<U> const& it) {
			counting_iterator temp(it);
			temp.swap(*this);
			return *this;
		}
		SPROUT_CONSTEXPR reference operator*() const {
			return current_;
		}
		SPROUT_CONSTEXPR pointer operator->() const {
			return &current_;
		}
		counting_iterator& operator++() {
			++current_;
			return *this;
		}
		counting_iterator operator++(int) {
			counting_iterator result(*this);
			++current_;
			return result;
		}
		counting_iterator& operator--() {
			--current_;
			return *this;
		}
		counting_iterator operator--(int) {
			counting_iterator temp(*this);
			--current_;
			return temp;
		}
		SPROUT_CONSTEXPR counting_iterator operator+(difference_type n) const {
			return counting_iterator(current_ + n);
		}
		SPROUT_CONSTEXPR counting_iterator operator-(difference_type n) const {
			return counting_iterator(current_ - n);
		}
		counting_iterator& operator+=(difference_type n) {
			counting_iterator temp(current_ + n);
			temp.swap(*this);
			return *this;
		}
		counting_iterator& operator-=(difference_type n) {
			counting_iterator temp(current_ - n);
			temp.swap(*this);
			return *this;
		}
		SPROUT_CONSTEXPR reference operator[](difference_type n) const {
			return current_ + n;
		}
		SPROUT_CONSTEXPR counting_iterator next() const {
			return counting_iterator(current_ + 1);
		}
		SPROUT_CONSTEXPR counting_iterator prev() const {
			return counting_iterator(current_ - 1);
		}
		void swap(counting_iterator& other) {
			using std::swap;
			swap(current_, other.current_);
		}
	};

	template<typename Incrementable1, typename Incrementable2>
	SPROUT_CONSTEXPR bool operator==(
		sprout::counting_iterator<Incrementable1> const& lhs,
		sprout::counting_iterator<Incrementable2> const& rhs
		)
	{
		return *lhs == *rhs;
	}
	template<typename Incrementable1, typename Incrementable2>
	SPROUT_CONSTEXPR bool operator!=(
		sprout::counting_iterator<Incrementable1> const& lhs,
		sprout::counting_iterator<Incrementable2> const& rhs
		)
	{
		return !(lhs == rhs);
	}
	template<typename Incrementable1, typename Incrementable2>
	SPROUT_CONSTEXPR bool operator<(
		sprout::counting_iterator<Incrementable1> const& lhs,
		sprout::counting_iterator<Incrementable2> const& rhs
		)
	{
		return *lhs < *rhs;
	}
	template<typename Incrementable1, typename Incrementable2>
	SPROUT_CONSTEXPR bool operator>(
		sprout::counting_iterator<Incrementable1> const& lhs,
		sprout::counting_iterator<Incrementable2> const& rhs
		)
	{
		return rhs < lhs;
	}
	template<typename Incrementable1, typename Incrementable2>
	SPROUT_CONSTEXPR bool operator<=(
		sprout::counting_iterator<Incrementable1> const& lhs,
		sprout::counting_iterator<Incrementable2> const& rhs
		)
	{
		return !(rhs < lhs);
	}
	template<typename Incrementable1, typename Incrementable2>
	SPROUT_CONSTEXPR bool operator>=(
		sprout::counting_iterator<Incrementable1> const& lhs,
		sprout::counting_iterator<Incrementable2> const& rhs
		)
	{
		return !(lhs < rhs);
	}
	template<typename Incrementable1, typename Incrementable2>
	SPROUT_CONSTEXPR typename sprout::counting_iterator<Incrementable1>::difference_type operator-(
		sprout::counting_iterator<Incrementable1> const& lhs,
		sprout::counting_iterator<Incrementable2> const& rhs
		)
	{
		return static_cast<typename sprout::counting_iterator<Incrementable1>::difference_type>(*lhs - *rhs);
	}
	template<typename Incrementable>
	SPROUT_CONSTEXPR sprout::counting_iterator<Incrementable> operator+(
		typename sprout::counting_iterator<Incrementable>::difference_type n,
		sprout::counting_iterator<Incrementable> const& it
		)
	{
		return it + n;
	}

	//
	// make_counting_iterator
	//
	template<typename Incrementable>
	SPROUT_CONSTEXPR sprout::counting_iterator<Incrementable>
	make_counting_iterator(Incrementable const& v) {
		return sprout::counting_iterator<Incrementable>(v);
	}

	//
	// swap
	//
	template<typename Incrementable>
	void swap(sprout::counting_iterator<Incrementable>& lhs, sprout::counting_iterator<Incrementable>& rhs)
	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
	{
		lhs.swap(rhs);
	}

	//
	// next
	//
	template<typename Incrementable>
	SPROUT_CONSTEXPR sprout::counting_iterator<Incrementable> next(
		sprout::counting_iterator<Incrementable> const& it
		)
	{
		return it.next();
	}
	template<typename Incrementable>
	SPROUT_CONSTEXPR sprout::counting_iterator<Incrementable> next(
		sprout::counting_iterator<Incrementable> const& it,
		typename sprout::counting_iterator<Incrementable>::difference_type n
		)
	{
		return it + n;
	}

	//
	// prev
	//
	template<typename Incrementable>
	SPROUT_CONSTEXPR sprout::counting_iterator<Incrementable> prev(
		sprout::counting_iterator<Incrementable> const& it
		)
	{
		return it.prev();
	}
	template<typename Incrementable>
	SPROUT_CONSTEXPR sprout::counting_iterator<Incrementable> prev(
		sprout::counting_iterator<Incrementable> const& it,
		typename sprout::counting_iterator<Incrementable>::difference_type n
		)
	{
		return it - n;
	}

	//
	// distance
	//
	template<typename Incrementable>
	SPROUT_CONSTEXPR typename std::iterator_traits<sprout::counting_iterator<Incrementable> >::difference_type
	distance(
		sprout::counting_iterator<Incrementable> first,
		sprout::counting_iterator<Incrementable> last
		)
	{
		return last - first;
	}
}	// namespace sprout

#endif	// #ifndef SPROUT_ITERATOR_COUNTING_ITERATOR_HPP