named.h

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/*  Copyright (c) SILVERCODERS Ltd, http://silvercoders.com                                                                                  */
/*  Project homepage: https://github.com/docwire/docwire                                                                                     */
/*                                                                                                                                           */
/*  SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-DocWire-Commercial                                                                  */
/*********************************************************************************************************************************************/
#ifndef DOCWIRE_NAMED_H
#define DOCWIRE_NAMED_H
#include <string_view>
#include <utility>
#include <tuple>
#include <type_traits>
 
namespace docwire::named
{
    template <typename T>
    struct value
    {
        std::string_view name;
        T value;
    };
 
    template <size_t I, typename T>
    [[nodiscard]] constexpr decltype(auto) get(value<T>& v) noexcept
    {
        if constexpr (I == 0) return (v.name);
        else return (v.value);
    }
 
    template <size_t I, typename T>
    [[nodiscard]] constexpr decltype(auto) get(const value<T>& v) noexcept
    {
        if constexpr (I == 0) return (v.name);
        else return (v.value);
    }
 
    template <size_t I, typename T>
    [[nodiscard]] constexpr decltype(auto) get(value<T>&& v) noexcept
    {
        if constexpr (I == 0) return std::move(v.name);
        else return std::move(v.value);
    }
 
    struct variable
    {
        const std::string_view name;
 
        template <typename T>
        [[nodiscard]] constexpr auto operator=(T&& val) const noexcept(noexcept(value<std::decay_t<T>>{name, std::forward<T>(val)}))
        {
            return value<std::decay_t<T>>{name, std::forward<T>(val)};
        }
    };
 
    inline namespace literals
    {
        [[nodiscard]] constexpr variable operator""_v(const char* str, size_t len) noexcept
        {
            return {std::string_view{str, len}};
        }
    }
}
 
namespace docwire
{
    // Bring the _v literal into the docwire namespace for convenience.
    using namespace docwire::named::literals;
}
 
namespace std
{
    template <typename T>
    struct tuple_size<docwire::named::value<T>> : std::integral_constant<size_t, 2> {};
 
    template <size_t I, typename T>
    struct tuple_element<I, docwire::named::value<T>>
    {
        static_assert(I < 2, "index out of range for docwire::named::value");
        using type = std::conditional_t<I == 0, std::string_view, T>;
    };
}
 
#endif // DOCWIRE_NAMED_H