#ifndef BOOST_LEAF_DETAIL_OPTIONAL_HPP_INCLUDED
#define BOOST_LEAF_DETAIL_OPTIONAL_HPP_INCLUDED

// Copyright 2018-2024 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)

#include <boost/leaf/config.hpp>

#include <utility>
#include <new>

namespace boost { namespace leaf {

namespace detail
{
    template <class T>
    class optional
    {
        int key_;
        union { T value_; };

    public:

        typedef T value_type;

        BOOST_LEAF_CONSTEXPR optional() noexcept:
            key_(0)
        {
        }

        BOOST_LEAF_CONSTEXPR optional( optional const & x ):
            key_(x.key_)
        {
            if( x.key_ )
                (void) new (&value_) T( x.value_ );
        }

        BOOST_LEAF_CONSTEXPR optional( optional && x ) noexcept:
            key_(x.key_)
        {
            if( x.key_ )
            {
                (void) new (&value_) T( std::move(x.value_) );
                x.reset();
            }
        }

        BOOST_LEAF_CONSTEXPR optional( int key, T const & v ):
            key_(key),
            value_(v)
        {
            BOOST_LEAF_ASSERT(!empty());
        }

        BOOST_LEAF_CONSTEXPR optional( int key, T && v ) noexcept:
            key_(key),
            value_(std::move(v))
        {
            BOOST_LEAF_ASSERT(!empty());
        }

        BOOST_LEAF_CONSTEXPR optional & operator=( optional const & x )
        {
            reset();
            if( int key = x.key() )
            {
                load(key, x.value_);
                key_ = key;
            }
            return *this;
        }

        BOOST_LEAF_CONSTEXPR optional & operator=( optional && x ) noexcept
        {
            reset();
            if( int key = x.key() )
            {
                load(key, std::move(x.value_));
                x.reset();
            }
            return *this;
        }

        ~optional() noexcept
        {
            reset();
        }

        BOOST_LEAF_CONSTEXPR bool empty() const noexcept
        {
            return key_ == 0;
        }

        BOOST_LEAF_CONSTEXPR int key() const noexcept
        {
            return key_;
        }

        BOOST_LEAF_CONSTEXPR void reset() noexcept
        {
            if( key_ )
            {
                value_.~T();
                key_=0;
            }
        }

        BOOST_LEAF_CONSTEXPR T & load( int key )
        {
            BOOST_LEAF_ASSERT(key);
            reset();
            (void) new(&value_) T;
            key_=key;
            return value_;
        }

        BOOST_LEAF_CONSTEXPR T & load( int key, T const & v )
        {
            BOOST_LEAF_ASSERT(key);
            reset();
            (void) new(&value_) T(v);
            key_=key;
            return value_;
        }

        BOOST_LEAF_CONSTEXPR T & load( int key, T && v ) noexcept
        {
            BOOST_LEAF_ASSERT(key);
            reset();
            (void) new(&value_) T(std::move(v));
            key_=key;
            return value_;
        }

        BOOST_LEAF_CONSTEXPR T const * has_value_any_key() const noexcept
        {
            return key_ ? &value_ : nullptr;
        }

        BOOST_LEAF_CONSTEXPR T * has_value_any_key() noexcept
        {
            return key_ ? &value_ : nullptr;
        }

        BOOST_LEAF_CONSTEXPR T const * has_value(int key) const noexcept
        {
            BOOST_LEAF_ASSERT(key);
            return key_ == key ? &value_ : nullptr;
        }

        BOOST_LEAF_CONSTEXPR T * has_value(int key) noexcept
        {
            BOOST_LEAF_ASSERT(key);
            return key_ == key ? &value_ : nullptr;
        }

        BOOST_LEAF_CONSTEXPR T const & value(int key) const & noexcept
        {
            BOOST_LEAF_ASSERT(has_value(key) != 0);
            (void) key;
            return value_;
        }

        BOOST_LEAF_CONSTEXPR T & value(int key) & noexcept
        {
            BOOST_LEAF_ASSERT(has_value(key) != 0);
            (void) key;
            return value_;
        }

        BOOST_LEAF_CONSTEXPR T const && value(int key) const && noexcept
        {
            BOOST_LEAF_ASSERT(has_value(key) != 0);
            (void) key;
            return value_;
        }

        BOOST_LEAF_CONSTEXPR T value(int key) && noexcept
        {
            BOOST_LEAF_ASSERT(has_value(key) != 0);
            (void) key;
            T tmp(std::move(value_));
            reset();
            return tmp;
        }

        BOOST_LEAF_CONSTEXPR T & value_or_default(int key) noexcept
        {
            if( T * v = has_value(key) )
                return *v;
            else
                return load(key);
        }
    };

}

} }

#endif // BOOST_LEAF_DETAIL_OPTIONAL_HPP_INCLUDED
