Cow.hpp

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#pragma once
#include <concepts>
#include <variant>
 
namespace Thoth::Dsa {
    template<class RefT, class OwnT>
        requires std::constructible_from<OwnT, RefT>
    struct Cow {
        using ValueType = std::variant<RefT, OwnT>;
 
        using RefType = RefT;
        using OwnType = OwnT;
 
        // NOLINTBEGIN(*)
        constexpr Cow() = default;
        constexpr Cow(RefT) noexcept;
        constexpr Cow(Cow&&) noexcept = default;
        constexpr Cow(const Cow& other);
        // NOLINTEND(*)
 
        constexpr Cow& operator=(Cow&& other) noexcept = default;
        constexpr Cow& operator=(const Cow& other);
 
 
        static constexpr Cow FromRef(RefT ref);
        constexpr Cow& SetRef(RefT ref);
 
 
        [[nodiscard]] static constexpr bool IsRefType(const Cow& cow);
        [[nodiscard]] constexpr bool IsRef() const;
 
 
        static constexpr Cow FromOwned(const OwnT& own);
        static constexpr Cow FromOwned(OwnT&& own);
        constexpr Cow& SetOwned(const OwnT& own);
        constexpr Cow& SetOwned(OwnT&& own);
 
        constexpr OwnT& AsOwned();
        [[nodiscard]] constexpr OwnT AsCopy() const;
 
        [[nodiscard]] constexpr RefT AsRef() const;
 
        template<class Callable>
        constexpr decltype(auto) Visit(Callable&& callable);
 
        template<class Callable>
        [[nodiscard]] constexpr decltype(auto) Visit(Callable&& callable) const;
    private:
        ValueType _value;
    };
 
 
    template<class RefT, class OwnT>
        requires std::constructible_from<OwnT, RefT>
    constexpr bool operator==(const Cow<RefT, OwnT>& left, const Cow<RefT, OwnT>& right);
}
 
#include <Thoth/Dsa/Cow.tpp>