#ifndef ALSK_ALSK_SKELETON_TRAITS_H
#define ALSK_ALSK_SKELETON_TRAITS_H

#include <type_traits>

#include "tags.h"

namespace alsk {

/**
 * @brief true if the given type is a Skeleton
 */
template<typename T, typename = void>
struct IsSkeleton: std::false_type {};

template<typename T>
struct IsSkeleton<T, std::enable_if_t<std::is_same<typename std::decay_t<T>::IsSkeleton, tag::SkeletonTag>{}>>: std::true_type {};

template<typename T>
constexpr bool isSkeleton = IsSkeleton<T>::value;


/**
 * @brief class to determine a skeleton traits
 * @param serial true if the skeleton cannot be run in parallel
 */
template<template<typename...> class S>
struct SkeletonTraits {
	static constexpr bool serial = true;
};

template<typename> struct SkeletonTraitsTImpl;

template<template<typename...> class S, typename... Ts>
struct SkeletonTraitsTImpl<S<Ts...>> {
	using type = SkeletonTraits<S>;
};

template<typename S>
using SkeletonTraitsT = typename SkeletonTraitsTImpl<std::decay_t<S>>::type;

/**
 * @brief function to dynamically traverse a skeleton tree
 *
 * by default, do nothing (typically muscle case)
 */
template<typename Muscle, typename F,
	std::enable_if_t<not isSkeleton<std::decay_t<Muscle>>>* = nullptr
>
void skeletonTraversal(Muscle&&, F&&) {}

/**
 * @brief template to specialize to implement a bone
 */
template<typename Skeleton, typename Tag, typename Executor, typename Context> struct Impl;

/**
 * @brief template to specialize to define how to traverse a bone
 */
template<typename Skeleton, typename=void>
struct SkeletonTraversal;

/**
 * @brief returns steps between two instances of the skeleton
 */
template<typename Skeleton, std::enable_if_t<isSkeleton<Skeleton>>* = nullptr>
constexpr std::size_t skeletonStep(Skeleton const& s) {
	return s.step;
}

/**
 * @brief returns 0
 */
template<typename Skeleton, std::enable_if_t<not isSkeleton<Skeleton>>* = nullptr>
constexpr std::size_t skeletonStep(Skeleton const&) {
	return 0;
}

}

#endif