#ifndef SPROUT_DARKROOM_RAYS_RAY_HPP
#define SPROUT_DARKROOM_RAYS_RAY_HPP

#include <sprout/config.hpp>
#include <sprout/tuple/tuple.hpp>
#include <sprout/utility/forward.hpp>
#include <sprout/darkroom/access/access.hpp>
#include <sprout/darkroom/coords/vector.hpp>

namespace sprout {
	namespace darkroom {
		namespace rays {
			//
			// position
			// direction
			//
			template<typename T>
			SPROUT_CONSTEXPR auto position(
				T&& t
				) SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::darkroom::access::get<0>(sprout::forward<T>(t))))
				-> decltype(sprout::darkroom::access::get<0>(sprout::forward<T>(t)))
			{
				return sprout::darkroom::access::get<0>(sprout::forward<T>(t));
			}
			template<typename T>
			SPROUT_CONSTEXPR auto direction(
				T&& t
				) SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::darkroom::access::get<1>(sprout::forward<T>(t))))
				-> decltype(sprout::darkroom::access::get<1>(sprout::forward<T>(t)))
			{
				return sprout::darkroom::access::get<1>(sprout::forward<T>(t));
			}

			//
			// make_ray
			//
			template<typename Position, typename Direction>
			SPROUT_CONSTEXPR sprout::tuples::tuple<Position, Direction>
			make_ray(Position const& pos, Direction const& dir) {
				return sprout::tuples::make_tuple(pos, dir);
			}

			//
			// ray
			//
			typedef sprout::tuples::tuple<sprout::darkroom::coords::vector3d, sprout::darkroom::coords::vector3d> ray;

			//
			// point_of_intersection
			//
			template<typename Ray, typename Distance>
			SPROUT_CONSTEXPR inline typename sprout::darkroom::access::unit<Ray>::type
			point_of_intersection(Ray const& ray, Distance const& dist) {
				return sprout::darkroom::coords::add(
					sprout::darkroom::rays::position(ray),
					sprout::darkroom::coords::scale(sprout::darkroom::rays::direction(ray), dist)
					);
			}
		}	// namespace ray
	}	// namespace darkroom
}	// namespace sprout

#endif	// #ifndef SPROUT_DARKROOM_RAYS_RAY_HPP