path: root/src/sexpr/variant.hpp

#pragma once
//    variant.hpp - A single value, multiple type container. Better than boost's.
//
//    Copyright © 2012 Ben Longbons <b.r.longbons@gmail.com>
//
//    This file is part of The Mana World (Athena server)
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    (at your option) any later version.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU General Public License for more details.
//
//    You should have received a copy of the GNU General Public License
//    along with this program.  If not, see <http://www.gnu.org/licenses/>.

#include <type_traits>
#include <cstdint>
#include <cstddef>
#include <utility>

#include "union.hpp"
#include "void.hpp"

#include "fwd.hpp"


namespace tmwa
{
namespace sexpr
{
#define MATCH_BEGIN(expr)                                           \
    {                                                               \
        auto&& _match_var = (expr);                                 \
        switch (tmwa::sexpr::VariantFriend::get_state(_match_var))  \
        {                                                           \
            {                                                       \
                {                                                   \
    /* }}}} */
#define MATCH_END()         \
    /* {{{{ */              \
                }           \
            }               \
        }                   \
        (void) _match_var;  \
    }

#define MATCH_CASE(ty, v)                                                                           \
    /* {{{{ */                                                                                      \
        }                                                                                           \
        break;                                                                                      \
    }                                                                                               \
    {                                                                                               \
        using _match_case_type = std::remove_const<std::remove_reference<ty>::type>::type;          \
        case tmwa::sexpr::VariantFriend::get_state_for<_match_case_type, decltype(_match_var)>():   \
        {                                                                                           \
            ty v = tmwa::sexpr::VariantFriend::unchecked_get<_match_case_type>(_match_var);
    /* }}}} */
#define MATCH_DEFAULT() \
    /* {{{{ */          \
        }               \
        break;          \
    }                   \
    {                   \
        default:        \
        {               \
    /* }}}} */

    template<class... T>
    class Variant
    {
        static_assert(sizeof...(T), "A variant must not be empty");
    };
    template<class D, class... T>
    class Variant<D, T...>
    {
        constexpr static size_t state_count = 1 + sizeof...(T);

        // simplify things immensely
        friend class VariantFriend;

        typedef Union<D, T...> DataType;
        DataType data;
        size_t state;

        void do_destruct();
        template<class C, class... A>
        void do_construct(A&&... a);
    public:
        Variant();
        ~Variant();

        void reset();
        template<class C, class... A>
        void emplace(A&&... a);

        Variant(const Variant& r);
        Variant(Variant&& r);
        Variant& operator = (const Variant& r);
        Variant& operator = (Variant&& r);

        template<class E>
        Variant(E e)
        {
            do_construct<E, E>(std::move(e));
        }

        template<class E>
        Variant& operator = (E e)
        {
            emplace<E, E>(std::move(e));
            return *this;
        }

        // use these ONLY if only one type makes sense
        // otherwise use apply
        template<class E>
        bool is() const;

        template<class E>
        E *get_if();

        template<class E>
        const E *get_if() const;
    };

    template<class R, class F>
    void apply(R& r, F&& f);
    template<class R, class F, class V1, class... V>
    void apply(R& r, F&& f, V1&& v1, V&&... v);
    template<class F, class... V>
    void apply(Void&& r, F&& f, V&&... v);
} // namespace sexpr
using sexpr::Variant;
} // namespace tmwa

#include "variant.tcc"