convert_base.h

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/*  Copyright (c) SILVERCODERS Ltd, http://silvercoders.com                                                                                  */
/*  Project homepage: https://github.com/docwire/docwire                                                                                     */
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/*  SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-DocWire-Commercial                                                                  */
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#ifndef DOCWIRE_CONVERT_BASE_H
#define DOCWIRE_CONVERT_BASE_H
 
#include <optional>
#include <tuple>
#include "error_tags.h"
#include "make_error.h"
#include "source_location.h"
#include "type_name.h"

namespace docwire::convert
{

template<typename T>
struct dest_type_tag {};
 
template <typename To, typename From>
concept conversion_implementation_exists = requires(const From& from) {
    { convert_impl(from, convert::dest_type_tag<To>{}) } noexcept -> std::same_as<std::optional<To>>;
};
 
namespace detail
{
 
struct convert_cpo
{
    template<typename To, typename From>
    requires conversion_implementation_exists<To, From>
    constexpr std::optional<To> operator()(const From& from) const noexcept
    {
        return convert_impl(from, dest_type_tag<To>{});
    }
};
 
inline constexpr convert_cpo convert_cpo;
 
} // namespace detail

template<typename To, typename From>
requires conversion_implementation_exists<To, From>
constexpr std::optional<To> try_to(const From& from) noexcept
{
    return detail::convert_cpo.template operator()<To, From>(from);
}

template<typename To, typename From>
requires conversion_implementation_exists<To, From>
To to(const From& from)
{
    auto result = try_to<To>(from);
    if (!result.has_value())
    {
        auto context = std::make_tuple("Failed to convert value", "from_type"_v = type_name::pretty<From>(), "to_type"_v = type_name::pretty<To>(), errors::uninterpretable_data{});
        throw errors::make_error_from_tuple(source_location::current(), std::move(context));
    }
    return *result;
}
 
} // namespace docwire::convert
 
#endif // DOCWIRE_CONVERT_BASE_H