#ifndef BOOST_LEAF_DETAIL_FUNCTION_TRAITS_HPP_INCLUDED
#define BOOST_LEAF_DETAIL_FUNCTION_TRAITS_HPP_INCLUDED

// Copyright (c) 2018-2020 Emil Dotchevski and Reverge Studios, Inc.

// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_LEAF_ENABLE_WARNINGS
#   if defined(__clang__)
#       pragma clang system_header
#   elif (__GNUC__*100+__GNUC_MINOR__>301)
#       pragma GCC system_header
#   elif defined(_MSC_VER)
#       pragma warning(push,1)
#   endif
#endif

#include <boost/leaf/detail/mp11.hpp>
#include <tuple>

namespace boost { namespace leaf {

    namespace leaf_detail
    {
        template<class...>
        struct gcc49_workaround //Thanks Glen Fernandes
        {
            using type = void;
        };

        template<class... T>
        using void_t = typename gcc49_workaround<T...>::type;

        template<class F,class V=void>
        struct function_traits
        {
            constexpr static int arity = -1;
        };

        template<class F>
        struct function_traits<F, void_t<decltype(&F::operator())>>
        {
        private:

            using tr = function_traits<decltype(&F::operator())>;

        public:

            using return_type = typename tr::return_type;
            static constexpr int arity = tr::arity - 1;

            using mp_args = typename leaf_detail_mp11::mp_rest<typename tr::mp_args>;

            template <int I>
            struct arg:
                tr::template arg<I+1>
            {
            };
        };

        template<class R, class... A>
        struct function_traits<R(A...)>
        {
            using return_type = R;
            static constexpr int arity = sizeof...(A);

            using mp_args = leaf_detail_mp11::mp_list<A...>;

            template <int I>
            struct arg
            {
                static_assert(I < arity, "I out of range");
                using type = typename std::tuple_element<I,std::tuple<A...>>::type;
            };
        };

        template<class F> struct function_traits<F&> : function_traits<F> { };
        template<class F> struct function_traits<F&&> : function_traits<F> { };
        template<class R, class... A> struct function_traits<R(*)(A...)> : function_traits<R(A...)> { };
        template<class R, class... A> struct function_traits<R(* &)(A...)> : function_traits<R(A...)> { };
        template<class R, class... A> struct function_traits<R(* const &)(A...)> : function_traits<R(A...)> { };
        template<class C, class R, class... A> struct function_traits<R(C::*)(A...)> : function_traits<R(C&,A...)> { };
        template<class C, class R, class... A> struct function_traits<R(C::*)(A...) const> : function_traits<R(C const &,A...)> { };
        template<class C, class R> struct function_traits<R(C::*)> : function_traits<R(C&)> { };

        template <class F>
        using fn_return_type = typename function_traits<F>::return_type;

        template <class F, int I>
        using fn_arg_type = typename function_traits<F>::template arg<I>::type;

        template <class F>
        using fn_mp_args = typename function_traits<F>::mp_args;

    }

} }

#endif