#pragma once

#include "meta19/nullptr_to.h"

#include <cstdint> // uint8_t

#include <new> // std::launder

#include <type_traits> // std::is_trivially_destructable_v

#include <utility>

namespace optional19 {

using meta19::nullptr_to;

struct Inplace;

constexpr static auto inplace = nullptr_to<Inplace>;

namespace details {

template<class T> struct OptionalStorage {

};

template<class T> requires(std::is_trivially_default_constructible_v<T> && std::is_trivially_destructible_v<T>)

struct OptionalStorage<T> {

T m_value{};

bool m_valid{};

constexpr OptionalStorage() = default;

constexpr OptionalStorage(T v) : m_value(std::move(v)), m_valid(true) {}

template<class... Args> OptionalStorage(Inplace*, Args&&... args) : m_value{(Args &&) args...}, m_valid(true) {}

template<class... Args> constexpr void emplace(Args&&... args) {

m_value = T{(Args &&) args...};

m_valid = true;

}

constexpr auto value() const -> const T& { return m_value; }

constexpr auto amend() -> T& { return m_value; }

};

} // namespace details

template<class T> struct Optional : private details::OptionalStorage<T> {

};

} // namespace optional19