daw_json_boost_pfr_mapping.h

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// Copyright (c) Darrell Wright
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/beached/daw_json_link
//
 
#pragma once
 
#include "daw/daw_tuple_forward.h"
#include "daw/json/daw_json_link.h"
 
#include <daw/daw_attributes.h>
#include <daw/daw_consteval.h>
 
#include <boost/pfr.hpp>
#include <daw/stdinc/tuple_traits.h>
#include <type_traits>
#include <utility>
 
namespace daw::json {
  template<typename T>
  requires( std::is_aggregate_v<T> and std::is_class_v<T> and
            not std::is_empty_v<T> ) //
    inline constexpr bool use_boost_pfr = false;
 
  namespace pfr_details {
    template<typename T, std::size_t Idx>
    DAW_CONSTEVAL auto get_member_name( ) {
      DAW_CPP23_STATIC_LOCAL constexpr auto name =
        boost::pfr::get_name<Idx, T>( );
      static_assert( not name.empty( ) );
      return json_name<name.size( ) + 1>(
        name.data( ), std::make_index_sequence<name.size( ) + 1>{ } );
    }
 
    template<typename, typename>
    struct make_data_contract;
 
    template<typename T, std::size_t... Is>
    struct make_data_contract<T, std::index_sequence<Is...>> {
    private:
      using member_types = DAW_TYPEOF(
        boost::pfr::structure_to_tuple( std::declval<T const &>( ) ) );
 
    public:
      using type =
        json_member_list<json_link<get_member_name<T, Is>( ),
                                   std::tuple_element_t<Is, member_types>>...>;
 
      DAW_ATTRIB_INLINE static constexpr auto to_json_data( T const &value ) {
        return boost::pfr::structure_tie( value );
      }
    };
  } // namespace pfr_details
 
  template<typename T>
  requires use_boost_pfr<T> //
    struct json_data_contract<T>
    : pfr_details::make_data_contract<
        T, std::make_index_sequence<boost::pfr::tuple_size_v<T>>> {};
} // namespace daw::json