draconisplusplus/include/rfl/internal/nt_to_ptr_named_tuple.hpp

#ifndef RFL_INTERNAL_NT_TO_PTR_NAMED_TUPLE_HPP_
#define RFL_INTERNAL_NT_TO_PTR_NAMED_TUPLE_HPP_

#include <tuple>

#include "../Field.hpp"
#include "../make_named_tuple.hpp"

namespace rfl {
  namespace internal {

    /// Generates a named tuple that contains pointers to the original values in
    /// the struct from a named tuple.
    template <class NamedTupleType, class... AlreadyExtracted>
    auto nt_to_ptr_named_tuple(NamedTupleType& _nt, AlreadyExtracted... _a) {
      using Fields = typename NamedTupleType::Fields;

      constexpr auto i          = sizeof...(AlreadyExtracted);
      constexpr auto num_fields = std::tuple_size_v<Fields>;

      if constexpr (i == num_fields) {
        return make_named_tuple(_a...);
      } else {
        using FieldType = typename std::tuple_element<i, Fields>::type;
        using T         = std::remove_cvref_t<typename FieldType::Type>;
        return nt_to_ptr_named_tuple(
            _nt, _a...,
            Field<FieldType::name_, T*>(&std::get<i>(_nt.values())));
      }
    }

    /// Generates a named tuple that contains pointers to the original values in
    /// the struct from a named tuple.
    template <class NamedTupleType, class... AlreadyExtracted>
    auto nt_to_ptr_named_tuple(const NamedTupleType& _nt,
                               AlreadyExtracted... _a) {
      using Fields = typename NamedTupleType::Fields;

      constexpr auto i          = sizeof...(AlreadyExtracted);
      constexpr auto num_fields = std::tuple_size_v<Fields>;

      if constexpr (i == num_fields) {
        return make_named_tuple(_a...);
      } else {
        using FieldType = typename std::tuple_element<i, Fields>::type;
        using T         = std::remove_cvref_t<typename FieldType::Type>;
        return nt_to_ptr_named_tuple(
            _nt, _a...,
            Field<FieldType::name_, const T*>(&std::get<i>(_nt.values())));
      }
    }

  } // namespace internal
} // namespace rfl

#endif