draconisplusplus/include/rfl/parsing/Parser_rfl_variant.hpp

#ifndef RFL_PARSING_PARSER_RFL_VARIANT_HPP_
#define RFL_PARSING_PARSER_RFL_VARIANT_HPP_

#include <map>
#include <type_traits>
#include <variant>

#include "../Result.hpp"
#include "../Variant.hpp"
#include "../always_false.hpp"
#include "FieldVariantParser.hpp"
#include "Parser_base.hpp"
#include "schema/Type.hpp"

namespace rfl {
  namespace parsing {

    template <class R, class W, class... FieldTypes, class ProcessorsType>
      requires AreReaderAndWriter<R, W, rfl::Variant<FieldTypes...>>
    struct Parser<R, W, rfl::Variant<FieldTypes...>, ProcessorsType> {
      using InputVarType  = typename R::InputVarType;
      using OutputVarType = typename W::OutputVarType;

      /// Expresses the variables as type T.
      static Result<rfl::Variant<FieldTypes...>> read(
          const R& _r,
          const InputVarType& _var) noexcept {
        const auto to_rfl_variant = [](auto&& _var) {
          return rfl::Variant<FieldTypes...>(
              std::forward<std::variant<FieldTypes...>>(_var));
        };
        return Parser<R, W, std::variant<FieldTypes...>, ProcessorsType>::read(
                   _r, _var)
            .transform(to_rfl_variant);
      }

      template <class P>
      static void write(const W& _w,
                        const rfl::Variant<FieldTypes...>& _variant,
                        const P& _parent) noexcept {
        Parser<R, W, std::variant<FieldTypes...>, ProcessorsType>::write(
            _w, _variant.variant(), _parent);
      }

      static schema::Type to_schema(
          std::map<std::string, schema::Type>* _definitions) {
        return Parser<R, W, std::variant<FieldTypes...>,
                      ProcessorsType>::to_schema(_definitions);
      }
    };

  } // namespace parsing
} // namespace rfl

#endif