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#pragma once
#include "asl/assert.hpp"
#include "asl/meta.hpp"
#include "asl/maybe_uninit.hpp"
namespace asl
{
struct nullopt_t {};
static constexpr nullopt_t nullopt{};
// @Todo(option) Niche
// @Todo(option) Reference
// @Todo(option) Function
// @Todo(option) Arrays
template<is_object T>
class option
{
maybe_uninit<T> m_payload;
bool m_has_value = false;
template<typename... Args>
constexpr void construct(Args&&... args) &
{
ASL_ASSERT(!m_has_value);
m_payload.init_unsafe(ASL_FWD(args)...);
m_has_value = true;
}
template<typename Arg>
constexpr void assign(Arg&& arg) &
{
ASL_ASSERT(m_has_value);
m_payload.as_init_unsafe() = ASL_FWD(arg);
}
public:
constexpr option() = default;
constexpr option(nullopt_t) {} // NOLINT(*-explicit-conversions)
constexpr option(const option& other) requires copy_constructible<T>
{
if (other.m_has_value)
{
construct(other.m_payload.as_init_unsafe());
}
}
constexpr option(option&& other) requires move_constructible<T>
{
if (other.m_has_value)
{
construct(ASL_MOVE(other.m_payload.as_init_unsafe()));
}
}
constexpr option& operator=(const option& other) & requires copy_assignable<T> && copy_constructible<T>
{
if (&other == this) { return *this; }
if (other.m_has_value)
{
if (m_has_value)
{
assign(other.m_payload.as_init_unsafe());
}
else
{
construct(other.m_payload.as_init_unsafe());
}
}
else if (m_has_value)
{
reset();
}
return *this;
}
constexpr option& operator=(option&& other) & requires move_assignable<T> && move_constructible<T>
{
if (&other == this) { return *this; }
if (other.m_has_value)
{
if (m_has_value)
{
assign(ASL_MOVE(other.m_payload.as_init_unsafe()));
}
else
{
construct(ASL_MOVE(other.m_payload.as_init_unsafe()));
}
}
else if (m_has_value)
{
reset();
}
return *this;
}
constexpr ~option() = default;
constexpr ~option() requires (!trivially_destructible<T>)
{
reset();
}
constexpr void reset()
{
if (m_has_value)
{
m_payload.uninit_unsafe();
m_has_value = false;
}
}
};
} // namespace asl
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