#ifndef CHAISCRIPT_FUNCTION_SIGNATURE_HPP
#define CHAISCRIPT_FUNCTION_SIGNATURE_HPP

#include <type_traits>

namespace chaiscript::dispatch::detail {

template<typename... Param>
struct Function_Params
{
};

template<typename Ret, typename Params, bool IsNoExcept = false, bool IsMember = false, bool IsMemberObject = false, bool IsObject = false>
struct Function_Signature
{
  using Param_Types = Params;
  using Return_Type = Ret;
  constexpr static const bool is_object = IsObject;
  constexpr static const bool is_member_object = IsMemberObject;
  constexpr static const bool is_noexcept = IsNoExcept;
  template<typename T>
  constexpr Function_Signature(T &&) noexcept {}
  constexpr Function_Signature() noexcept = default;
};

// Free functions

template<typename Ret, typename... Param>
Function_Signature(Ret (*f)(Param...))->Function_Signature<Ret, Function_Params<Param...>>;

template<typename Ret, typename... Param>
Function_Signature(Ret (*f)(Param...) noexcept)->Function_Signature<Ret, Function_Params<Param...>, true>;

// no reference specifier

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile)->Function_Signature<Ret, Function_Params<volatile Class &, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile noexcept)->Function_Signature<Ret, Function_Params<volatile Class &, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile const)->Function_Signature<Ret, Function_Params<volatile const Class &, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile const noexcept)->Function_Signature<Ret, Function_Params<volatile const Class &, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...))->Function_Signature<Ret, Function_Params<Class &, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) noexcept)->Function_Signature<Ret, Function_Params<Class &, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) const)->Function_Signature<Ret, Function_Params<const Class &, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) const noexcept)->Function_Signature<Ret, Function_Params<const Class &, Param...>, true, true>;

// & reference specifier

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile &)->Function_Signature<Ret, Function_Params<volatile Class &, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile &noexcept)->Function_Signature<Ret, Function_Params<volatile Class &, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile const &)->Function_Signature<Ret, Function_Params<volatile const Class &, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile const &noexcept)->Function_Signature<Ret, Function_Params<volatile const Class &, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) &)->Function_Signature<Ret, Function_Params<Class &, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) & noexcept)->Function_Signature<Ret, Function_Params<Class &, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) const &)->Function_Signature<Ret, Function_Params<const Class &, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) const &noexcept)->Function_Signature<Ret, Function_Params<const Class &, Param...>, true, true>;

// && reference specifier

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile &&)->Function_Signature<Ret, Function_Params<volatile Class &&, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile &&noexcept)->Function_Signature<Ret, Function_Params<volatile Class &&, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile const &&)->Function_Signature<Ret, Function_Params<volatile const Class &&, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) volatile const &&noexcept)->Function_Signature<Ret, Function_Params<volatile const Class &&, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) &&)->Function_Signature<Ret, Function_Params<Class &&, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) && noexcept)->Function_Signature<Ret, Function_Params<Class &&, Param...>, true, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) const &&)->Function_Signature<Ret, Function_Params<const Class &&, Param...>, false, true>;

template<typename Ret, typename Class, typename... Param>
Function_Signature(Ret (Class::*f)(Param...) const &&noexcept)->Function_Signature<Ret, Function_Params<const Class &&, Param...>, true, true>;

template<typename Ret, typename Class>
Function_Signature(Ret(Class::*f))->Function_Signature<Ret, Function_Params<Class &>, true, true, true>;

// primary template handles types that have no nested ::type member:
template<class, class = std::void_t<>>
struct has_call_operator : std::false_type
{
};

// specialization recognizes types that do have a nested ::type member:
template<class T>
struct has_call_operator<T, std::void_t<decltype(&T::operator())>> : std::true_type
{
};

template<typename Func>
auto function_signature(const Func &f)
{
  if constexpr (has_call_operator<Func>::value) {
    return Function_Signature<
      typename decltype(Function_Signature{ &std::decay_t<Func>::operator() })::Return_Type,
      typename decltype(Function_Signature{ &std::decay_t<Func>::operator() })::Param_Types,
      decltype(Function_Signature{ &std::decay_t<Func>::operator() })::is_noexcept,
      false,
      false,
      true>{};
  } else {
    return Function_Signature{ f };
  }
}

}// namespace chaiscript::dispatch::detail

#endif