transitions.h

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#pragma once

#include "../base/type_traits.h"
#include "detail/handle_result.h"

namespace escad
{

template<class... S>
class transitions {
private:
    enum class result {
        not_handled,
        handled,
        transition
    };

public:
    constexpr transitions(transitions<> const& rhs) noexcept
        : idx {0}
        , outcome {rhs.outcome}
    {
    }

    template<class T>
    transitions(detail::transition<T>) noexcept
        : idx {mpl::type_list_index_v<T, list>}
        , outcome {result::transition}
    {
    }

    template<class T>
    transitions(transitions<T>) noexcept
        : idx {mpl::type_list_index_v<T, list>}
        , outcome {result::transition}
    {}

    transitions(detail::handled) noexcept
        : idx {sizeof...(S)}
        , outcome {result::handled}
    {}

    transitions(detail::not_handled) noexcept
        : idx {sizeof...(S)}
        , outcome {result::not_handled}
    {}

    bool is_transition() const {
        return outcome == result::transition;
    }

    bool is_handled() const {
        return outcome == result::handled;
    }

    using list = mpl::type_list<S...>;

    std::size_t const idx;
    result      const outcome;
};

} // namespace fsm