draconisplusplus/include/rfl/parsing/NamedTupleParser.hpp

#ifndef RFL_PARSING_NAMEDTUPLEPARSER_HPP_
#define RFL_PARSING_NAMEDTUPLEPARSER_HPP_

#include <array>
#include <map>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <utility>

#include "../NamedTuple.hpp"
#include "../Result.hpp"
#include "../always_false.hpp"
#include "../internal/Memoization.hpp"
#include "../internal/is_array.hpp"
#include "../internal/is_attribute.hpp"
#include "../internal/is_basic_type.hpp"
#include "../internal/is_skip.hpp"
#include "../internal/strings/replace_all.hpp"
#include "../to_view.hpp"
#include "AreReaderAndWriter.hpp"
#include "Parent.hpp"
#include "Parser_base.hpp"
#include "ViewReader.hpp"
#include "is_empty.hpp"
#include "is_required.hpp"
#include "schema/Type.hpp"
#include "to_single_error_message.hpp"

namespace rfl {
  namespace parsing {

    template <
        class R,
        class W,
        bool _ignore_empty_containers,
        bool _all_required,
        class ProcessorsType,
        class... FieldTypes>
      requires AreReaderAndWriter<R, W, NamedTuple<FieldTypes...>>
    struct NamedTupleParser {
      using InputObjectType = typename R::InputObjectType;
      using InputVarType    = typename R::InputVarType;

      using OutputObjectType = typename W::OutputObjectType;
      using OutputVarType    = typename W::OutputVarType;

      using ParentType = Parent<W>;

      using NamedTupleType = NamedTuple<FieldTypes...>;

      static constexpr size_t size_ = NamedTupleType::size();

     public:
      /// The way this works is that we allocate space on the stack in this size
      /// of the named tuple in which we then write the individual fields using
      /// views and placement new. This is how we deal with the fact that some
      /// fields might not be default-constructible.
      static Result<NamedTuple<FieldTypes...>>
      read(const R& _r, const InputVarType& _var) noexcept {
        alignas(NamedTuple<FieldTypes...>) unsigned char
             buf[sizeof(NamedTuple<FieldTypes...>)];
        auto ptr       = reinterpret_cast<NamedTuple<FieldTypes...>*>(buf);
        auto view      = rfl::to_view(*ptr);
        using ViewType = std::remove_cvref_t<decltype(view)>;
        const auto err =
            Parser<R, W, ViewType, ProcessorsType>::read_view(_r, _var, &view);
        if (err) [[unlikely]] { return *err; }
        return *ptr;
      }

      /// Reads the data into a view.
      static std::optional<Error> read_view(
          const R&                   _r,
          const InputVarType&        _var,
          NamedTuple<FieldTypes...>* _view
      ) noexcept {
        auto obj = _r.to_object(_var);
        if (!obj) [[unlikely]] { return obj.error(); }
        return read_object(_r, *obj, _view);
      }

      /// For writing, we do not need to make the distinction between
      /// default-constructible and non-default constructible fields.
      template <class P>
      static void write(
          const W&                         _w,
          const NamedTuple<FieldTypes...>& _tup,
          const P&                         _parent
      ) noexcept {
        auto obj = ParentType::add_object(_w, _tup.size(), _parent);
        build_object_recursively(_w, _tup, &obj);
        _w.end_object(&obj);
      }

      /// For generating the schema, we also do not need to make the distinction
      /// between default-constructible and non-default constructible fields.
      template <size_t _i = 0>
      static schema::Type to_schema(
          std::map<std::string, schema::Type>* _definitions,
          std::map<std::string, schema::Type>  _values = {}
      ) {
        using Type            = schema::Type;
        using T               = NamedTuple<FieldTypes...>;
        constexpr size_t size = T::size();
        if constexpr (_i == size) {
          return Type {Type::Object {_values}};
        } else {
          using F = std::tuple_element_t<
              _i, typename NamedTuple<FieldTypes...>::Fields>;
          using U = typename F::Type;
          if constexpr (!internal::is_skip_v<U>) {
            _values[std::string(F::name())] =
                Parser<R, W, U, ProcessorsType>::to_schema(_definitions);
          }
          return to_schema<_i + 1>(_definitions, _values);
        }
      };

     private:
      template <int _i = 0>
      static void build_object_recursively(
          const W&                         _w,
          const NamedTuple<FieldTypes...>& _tup,
          OutputObjectType*                _ptr
      ) noexcept {
        if constexpr (_i >= sizeof...(FieldTypes)) {
          return;
        } else {
          using FieldType =
              typename std::tuple_element<_i, std::tuple<FieldTypes...>>::type;
          using ValueType      = std::remove_cvref_t<typename FieldType::Type>;
          const auto&    value = rfl::get<_i>(_tup);
          constexpr auto name  = FieldType::name_.string_view();
          const auto     new_parent = typename ParentType::Object {name, _ptr};
          if constexpr (!_all_required &&
                        !is_required<ValueType, _ignore_empty_containers>()) {
            if (!is_empty(value)) {
              if constexpr (internal::is_attribute_v<ValueType>) {
                Parser<R, W, ValueType, ProcessorsType>::write(
                    _w, value, new_parent.as_attribute()
                );
              } else {
                Parser<R, W, ValueType, ProcessorsType>::write(
                    _w, value, new_parent
                );
              }
            }
          } else {
            if constexpr (internal::is_attribute_v<ValueType>) {
              Parser<R, W, ValueType, ProcessorsType>::write(
                  _w, value, new_parent.as_attribute()
              );
            } else {
              Parser<R, W, ValueType, ProcessorsType>::write(
                  _w, value, new_parent
              );
            }
          }
          return build_object_recursively<_i + 1>(_w, _tup, _ptr);
        }
      }

      /// Generates error messages for when fields are missing.
      template <int _i>
      static void handle_one_missing_field(
          const std::array<bool, size_>& _found,
          const NamedTupleType&          _view,
          std::array<bool, size_>*       _set,
          std::vector<Error>*            _errors
      ) noexcept {
        using FieldType =
            std::tuple_element_t<_i, typename NamedTupleType::Fields>;
        using ValueType = std::remove_reference_t<
            std::remove_pointer_t<typename FieldType::Type>>;

        if (!std::get<_i>(_found)) {
          if constexpr (_all_required ||
                        is_required<ValueType, _ignore_empty_containers>()) {
            constexpr auto current_name =
                std::tuple_element_t<_i, typename NamedTupleType::Fields>::name(
                );
            _errors->emplace_back(Error(
                "Field named '" + std::string(current_name) + "' not found."
            ));
          } else {
            if constexpr (!std::is_const_v<ValueType>) {
              ::new (rfl::get<_i>(_view)) ValueType();
            } else {
              using NonConstT = std::remove_const_t<ValueType>;
              ::new (const_cast<NonConstT*>(rfl::get<_i>(_view))) NonConstT();
            }
            std::get<_i>(*_set) = true;
          }
        }
      }

      /// Generates error messages for when fields are missing.
      template <int... _is>
      static void
      handle_missing_fields(const std::array<bool, size_>& _found, const NamedTupleType& _view, std::array<bool, size_>* _set, std::vector<Error>* _errors, std::integer_sequence<int, _is...>) noexcept {
        (handle_one_missing_field<_is>(_found, _view, _set, _errors), ...);
      }

      static std::optional<Error> read_object(
          const R&               _r,
          const InputObjectType& _obj,
          NamedTupleType*        _view
      ) noexcept {
        auto found = std::array<bool, NamedTupleType::size()>();
        found.fill(false);
        auto set = std::array<bool, NamedTupleType::size()>();
        set.fill(false);
        std::vector<Error> errors;
        const auto         object_reader =
            ViewReader<R, W, NamedTupleType, ProcessorsType>(
                &_r, _view, &found, &set, &errors
            );
        const auto err = _r.read_object(object_reader, _obj);
        if (err) { return *err; }
        handle_missing_fields(
            found, *_view, &set, &errors,
            std::make_integer_sequence<int, size_>()
        );
        if (errors.size() != 0) {
          object_reader.call_destructors_where_necessary();
          return to_single_error_message(errors);
        }
        return std::nullopt;
      }
    };

  } // namespace parsing
} // namespace rfl

#endif