#pragma once

#include "util.hpp"

#include "../type/type.hpp"

namespace util {

// <functional>

// clang-format off

namespace detail {

template <typename> constexpr bool is_reference_wrapper_v = false;
template <typename U> constexpr bool is_reference_wrapper_v<reference_wrapper<U>> = true;

template <typename T, typename Type, typename T1, typename... Args>
constexpr decltype(auto) INVOKE(Type T::*f, T1 &&t1, Args &&... args)
{
	if constexpr (type::is_member_function_pointer_v<decltype(f)>) {
		if constexpr (type::is_base_of_v<T, type::decay_t<T1>>)
			return (util::forward<T1>(t1).*f)(util::forward<Args>(args)...);
		else if constexpr (is_reference_wrapper_v<type::decay_t<T1>>)
			return (t1.get().*f)(util::forward<Args>(args)...);
		else
			return ((*util::forward<T1>(t1)).*f)(util::forward<Args>(args)...);
	} else {
		static_assert(type::is_member_object_pointer_v<decltype(f)>);
		static_assert(sizeof...(args) == 0);
		if constexpr (type::is_base_of_v<T, type::decay_t<T1>>)
			return util::forward<T1>(t1).*f;
		else if constexpr (is_reference_wrapper_v<type::decay_t<T1>>)
			return t1.get().*f;
		else
			return (*util::forward<T1>(t1)).*f;
	}
}

template <typename Fn, typename... Args>
constexpr decltype(auto) INVOKE(Fn &&f, Args &&... args)
{
	return util::forward<Fn>(f)(util::forward<Args>(args)...);
}

template <typename T> constexpr T &FUN(T &t) noexcept { return t; }
template <typename T> void FUN(T &&) = delete;

} // namespace detail

template <typename Fn, typename... Args>
constexpr type::invoke_result_t<Fn, Args...> invoke(Fn &&f, Args &&... args)
	noexcept(type::is_nothrow_invocable_v<Fn, Args...>)
{
	return detail::INVOKE(util::forward<Fn>(f), util::forward<Args>(args)...);
}

template <typename T>
class reference_wrapper {
  public:
	// construct/copy/destroy
	template <typename U,
	          typename = decltype(detail::FUN<T>(util::declval<U>()),
	                              type::enable_if_t<!type::is_same_v<reference_wrapper, type::remove_cvref_t<U>>>())>
	constexpr reference_wrapper(U &&u) noexcept(noexcept(detail::FUN<T>(util::forward<U>(u))))
	    : _ptr(util::addressof(detail::FUN<T>(util::forward<U>(u))))
	{}
	reference_wrapper(const reference_wrapper &) noexcept = default;

	// assignment
	reference_wrapper &operator=(const reference_wrapper &) noexcept = default;

	// access
	constexpr operator T &() const noexcept	{ return *_ptr; }
	constexpr T &get() const noexcept { return *_ptr; }

	template <typename... ArgTypes>
	constexpr type::invoke_result_t<T &, ArgTypes...> operator()(ArgTypes &&... args) const
	{
		return invoke(get(), util::forward<ArgTypes>(args)...);
	}

	// types
	using type = T;

  private:
	T *_ptr;
};

// deduction guides
template <typename T> reference_wrapper(T &) -> reference_wrapper<T>;

// clang-format on

} // namespace util