daw_json_reflection.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_pipelines.h"
#include "daw_json_link.h"
 
#include <cstddef>
#include <experimental/meta>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>
 
// This gets around clang-format issues
#define DAW_REFLECT( ... ) ^^__VA_ARGS__
#define DAW_SPLICE( ... ) [:__VA_ARGS__:]
#define DAW_SPLICE( ... ) [:__VA_ARGS__:]
 
namespace daw::json::inline DAW_JSON_VER {
  inline namespace experimental {
    template<typename E, json_options_t Options = json_custom_opts_def>
    requires std::is_enum_v<E> struct enum_string;
 
    struct refl_map_as {
      std::meta::info type;
    };
 
    struct refl_rename {
      char const *name;
    };
 
    struct refl_enum_string {
      json_options_t Options;
    };
 
    struct refl_ignore_with_default {};
 
    template<typename T>
    struct refl_ignore_with_value {
      T value;
    };
 
    namespace refl_details {
      template<auto... vals>
      struct replicator_type {
        template<typename F>
        constexpr void operator>>( F body ) const {
          ( body.template operator( )<vals>( ), ... );
        }
      };
 
      template<auto... vals>
      replicator_type<vals...> replicator = { };
 
      consteval std::vector<std::meta::info>
      pub_nsdm_of( std::meta::info type_class ) {
        auto members = std::meta::nonstatic_data_members_of(
          type_class, std::meta::access_context::unprivileged( ) );
        std::erase_if( members, []( std::meta::info const &i ) {
          return not std::meta::is_public( i );
        } );
        return members;
      }
 
      template<typename R>
      consteval auto expand( R range ) {
        auto args = std::vector<std::meta::info>( );
        for( auto r : range ) {
          args.push_back( std::meta::reflect_constant( r ) );
        }
        return std::meta::substitute( DAW_REFLECT( replicator ), args );
      }
 
      template<typename T>
      consteval std::optional<T> get_annotaion( std::meta::info r ) {
        for( std::meta::info a : std::meta::annotations_of( r ) ) {
          if( std::meta::type_of( a ) == DAW_REFLECT( T ) ) {
            return std::meta::extract<T>( a );
          }
        }
        return std::nullopt;
      }
 
      template<typename T>
      consteval bool has_annotation( std::meta::info r, T const &value ) {
        auto expected = std::meta::reflect_constant( value );
        for( std::meta::info a : std::meta::annotations_of( r ) ) {
          if( constant_of( a ) == expected ) {
            return true;
          }
        }
        return false;
      }
 
      template<typename T, std::size_t... Is>
      consteval auto to_tuple( T const &value, std::index_sequence<Is...> )
        -> decltype( std::tuple{
          value.DAW_SPLICE( pub_nsdm_of( DAW_REFLECT( T ) )[Is] )... } ) {
        return std::tuple{
          value.DAW_SPLICE( pub_nsdm_of( DAW_REFLECT( T ) )[Is] )... };
      }
 
      template<typename T>
      consteval auto to_tuple( T const &value )
        -> decltype( refl_details::to_tuple(
          value, std::make_index_sequence<
                   pub_nsdm_of( DAW_REFLECT( T ) ).size( )>{ } ) ) {
        return refl_details::to_tuple(
          value, std::make_index_sequence<
                   pub_nsdm_of( DAW_REFLECT( T ) ).size( )>{ } );
      }
 
      template<JSONNAMETYPE Name, typename T>
      using deduce_t = typename json_details::ensure_mapped_t<
        json_details::json_deduced_type<T>>::template with_name<Name>;
 
      template<typename T, std::size_t Idx>
      using submember_type_t =
        std::tuple_element_t<Idx, DAW_TYPEOF( refl_details::to_tuple(
                                    std::declval<T>( ) ) )>;
 
      template<typename T, std::size_t Idx>
      consteval auto get_member_link_func( ) {
        static constexpr auto member_info =
          pub_nsdm_of( DAW_REFLECT( T ) )[Idx];
        static constexpr auto annot_rename =
          get_annotaion<daw::json::refl_rename>( member_info );
 
        static constexpr std::string_view name =
          annot_rename ? std::string_view( annot_rename->name )
                       : std::meta::identifier_of( member_info );
        static_assert( not name.empty( ), "Unexpected empty name" );
 
        static constexpr auto annot_map_as = [] {
          static constexpr auto refl_map_as_annot =
            get_annotaion<refl_map_as>( member_info );
          static constexpr auto refl_enum_string_annot =
            get_annotaion<refl_enum_string>( member_info );
          if constexpr( refl_map_as_annot ) {
            static_assert( not refl_enum_string_annot,
                           "Do not use reflect.enum_string and reflect.map_as "
                           "at the same time" );
            return refl_map_as_annot;
          } else if constexpr( refl_enum_string_annot ) {
            using json_member_no_name =
              daw::json::enum_string<typename DAW_SPLICE(
                                       std::meta::type_of( member_info ) ),
                                     refl_enum_string_annot->Options>;
            static constexpr auto info =
              DAW_REFLECT( typename json_member_no_name::template with_name<
                           json_name<name.size( ) + 1>(
                             name.data( ),
                             std::make_index_sequence<name.size( ) + 1>{ } )> );
            return std::optional<refl_map_as>{ refl_map_as{ info } };
          } else {
            return false;
          }
        }( );
 
        if constexpr( annot_map_as ) {
          static_assert(
            not annot_rename,
            "Do not use reflect.rename and reflect.map_as at the same time" );
          static constexpr auto result =
            daw::traits::identity<typename DAW_SPLICE( annot_map_as->type )>{ };
          return result;
        } else {
          return daw::traits::identity<deduce_t<
            json_name<name.size( ) + 1>(
              name.data( ), std::make_index_sequence<name.size( ) + 1>{ } ),
            submember_type_t<T, Idx>>>{ };
        }
      }
 
      template<typename T, std::size_t Idx>
      using get_member_link_t =
        typename DAW_TYPEOF( get_member_link_func<T, Idx>( ) )::type;
 
      template<typename, typename>
      struct make_data_contract;
 
      template<typename, typename...>
      inline constexpr bool construction_test_v = false;
 
      template<typename T, typename... Ts>
      inline constexpr bool construction_test_v<T, std::tuple<Ts...>> =
        requires {
        T{ std::declval<Ts>( )... };
      };
 
      template<typename T>
      concept Reflectable =
        not std::is_empty_v<T> and std::is_class_v<T> and requires {
        refl_details::to_tuple( std::declval<T>( ) );
      }
      and construction_test_v<T, DAW_TYPEOF( refl_details::to_tuple(
                                   std::declval<T>( ) ) )>;
 
      template<Reflectable T, std::size_t... Is>
      struct make_data_contract<T, std::index_sequence<Is...>> {
        using type = json_member_list<get_member_link_t<T, Is>...>;
 
        DAW_ATTRIB_INLINE static constexpr auto to_json_data( T const &value ) {
          return daw::forward_nonrvalue_as_tuple(
            value.DAW_SPLICE( pub_nsdm_of( DAW_REFLECT( T ) )[Is] )... );
        }
      };
 
      template<typename E>
      requires std::is_enum_v<E> constexpr E
      enum_from_string( std::string_view name ) {
        template for( constexpr auto enumerator :
                      std::meta::enumerators_of( DAW_REFLECT( E ) ) ) {
          if( name == std::meta::identifier_of( enumerator ) ) {
            return DAW_SPLICE( enumerator );
          }
        }
        daw_json_error( ErrorReason::InvalidString );
      }
 
      /*
      template<typename E>
        requires std::is_enum_v<E>
      constexpr std::string_view enum_to_string( E value ) {
        template for( constexpr auto enumerator: std::meta::enumerators_of(
      DAW_REFLECT( E ) ) ) { if( value == DAW_SPLICE( enumerator ) ) { return
      std::meta::identifier_of( enumerator );
          }
        }
        return std::string_view{ };
      }
      */
      template<typename E>
      requires std::is_enum_v<E> constexpr std::string_view
      enum_to_string( E value ) {
        auto result = std::string_view{ };
        DAW_SPLICE( expand( std::meta::enumerators_of( DAW_REFLECT( E ) ) ) ) >>
          [&]<auto e> {
            if( value == DAW_SPLICE( e ) ) {
              result = std::meta::identifier_of( e );
            }
          };
        return result;
      }
 
      template<typename E>
      requires std::is_enum_v<E> struct reflect_enum_as_string {
        static constexpr E operator( )( std::string_view name ) {
          return enum_from_string<E>( name );
        }
 
        static constexpr std::string_view operator( )( E value ) {
          return enum_to_string( value );
        }
      };
    } // namespace refl_details
 
    template<typename E, json_options_t Options>
    requires std::is_enum_v<E> struct enum_string
      : json_custom_no_name<E, refl_details::reflect_enum_as_string<E>,
                            refl_details::reflect_enum_as_string<E>, Options> {
    };
 
    inline constexpr struct reflect_t {
      static consteval refl_rename rename( char const *name ) {
        return refl_rename{ name };
      }
 
      template<typename JsonMember>
      static consteval auto map_as( ) {
        return refl_map_as{ DAW_REFLECT( JsonMember ) };
      }
 
      static constexpr auto ignore_with_default =
        daw::json::refl_ignore_with_default{ };
 
      template<typename T>
      static consteval auto ignore_with_value( T &&v ) {
        return refl_ignore_with_value{ DAW_FWD( v ) };
      }
 
      template<json_options_t Options>
      static constexpr auto enum_string_with_opt =
        daw::json::refl_enum_string{ Options };
 
      static constexpr auto enum_string =
        enum_string_with_opt<json_custom_opts_def>;
    } reflect{ };
 
    // Trait that specifies a type is to be reflected on for parse info
    template<refl_details::Reflectable T>
    inline constexpr bool is_reflectible_type_v =
      refl_details::has_annotation( DAW_REFLECT( T ), reflect );
  } // namespace experimental
 
  template<typename T>
  requires is_reflectible_type_v<T> //
    struct json_data_contract<T>
    : refl_details::make_data_contract<
        T, std::make_index_sequence<
             refl_details::pub_nsdm_of( DAW_REFLECT( T ) ).size( )>> {};
 
} // namespace daw::json::inline DAW_JSON_VER
 
#undef DAW_SPLICE