larra/library/include/larra/serialization/auto.hpp

#pragma once
#include <libxml++/libxml++.h>

#include <boost/pfr.hpp>
#include <larra/serialization.hpp>
#include <larra/serialization/error.hpp>
#include <utempl/constexpr_string.hpp>
#include <utempl/tuple.hpp>
#include <utempl/utils.hpp>
#include <variant>

namespace larra::xmpp::serialization {

template <typename T>
struct Tag {};

template <typename T>
inline constexpr auto kSerializationConfig = std::monostate{};

template <typename T>
inline constexpr auto kDeserializationConfig = kSerializationConfig<T>;

template <typename T>
constexpr auto Parse(xmlpp::Element* element, Tag<T> = {}) -> T
  requires(!std::same_as<std::decay_t<decltype(kDeserializationConfig<T>)>, std::monostate>);

template <typename T>
constexpr auto Parse(xmlpp::Element* element, Tag<T> = {}) -> T;

struct AttributeConfig {};

template <typename T>
struct MetaInfo {
  static constexpr std::size_t kSize = boost::pfr::tuple_size_v<T>;
  template <std::size_t I>
  using TupleElement = boost::pfr::tuple_element_t<I, T>;

  template <std::size_t I>
  static constexpr std::string_view kFieldName = boost::pfr::get_name<I, T>();

  template <typename Self, std::size_t I>
  static constexpr auto Get(Self&& self) -> decltype(auto) {
    return boost::pfr::get<I>(std::forward<Self>(self));
  }
};

template <typename MainT, std::size_t Element>
struct FieldInfo {
  using Main = MainT;
  using Info = MetaInfo<Main>;
  static inline const std::string kName = [] {
    if constexpr(requires { Info::template TupleElement<Element>::kDefaultName; }) {
      return Info::template TupleElement<Element>::kDefaultName;
    } else {
      return static_cast<std::string>(Info::template kFieldName<Element>);
    }
  }();
};

template <typename T>
struct Config {
  std::optional<T> defaultValue;
};

template <>
struct Config<std::string> {
  std::optional<std::string_view> defaultValue;
};

namespace impl {
template <typename T>
concept HasParse = requires(xmlpp::Element* e) {
  { T::Parse(e) } -> std::same_as<T>;
};

template <typename T, typename V>
struct Config : V {
  using V::V;
  constexpr Config()
    requires HasParse<T>
      : V(::larra::xmpp::serialization::Config<T>{}) {
  }

  constexpr Config()
    requires(!HasParse<T>)
      : V(AttributeConfig{}) {
  }
  constexpr auto Base() const -> const V& {
    return static_cast<const V&>(*this);
  }
  using type = T;
};

}  // namespace impl

template <typename T>
struct ElementConfig {
  using type = impl::Config<T, std::variant<AttributeConfig, Config<T>>>;
};

template <typename T, auto& Config, typename Info>
struct ElementSerializer {
  static constexpr auto Parse(xmlpp::Element* element) {
    auto node = element->get_first_child(Info::kName);
    if(!node) {
      throw ElementParsingError(std::format("[{}: {}] parsing error: [ Not found ]", Info::kName, nameof::nameof_full_type<T>()));
    }
    auto elementNode = dynamic_cast<xmlpp::Element*>(node);
    if(!node) {
      throw ElementParsingError(std::format("[{}: {}] parsing error: [ Invalid node ]", Info::kName, nameof::nameof_full_type<T>()));
    }
    try {
      return ::larra::xmpp::serialization::Parse(elementNode, Tag<T>{});
    } catch(const ParsingError& error) {
      throw ElementParsingError(std::format("[{}: {}] parsing error: [ {} ]", Info::kName, nameof::nameof_full_type<T>(), error.what()));
    }
  }
};

namespace impl {

template <typename T>
consteval auto FindElement(std::string_view field, utempl::TypeList<T> = {}) {
  auto fields = boost::pfr::names_as_array<T>();
  return std::ranges::find(fields, field) - fields.begin();
}

template <auto& Config, typename Info>
auto ParseField(xmlpp::Element* main) -> std::decay_t<decltype(Config)>::type {
  using Type = std::decay_t<decltype(Config)>::type;
  if constexpr(std::holds_alternative<AttributeConfig>(Config.Base())) {
    xmlpp::Attribute* node = main->get_attribute(Info::kName);
    if(!node) {
      throw AttributeParsingError(std::format("Attribute [{}: {}] parsing error", Info::kName, nameof::nameof_full_type<Type>()));
    }
    if constexpr(requires(std::string_view view) { Type::Parse(view); }) {
      return Type::Parse(node->get_value());
    } else {
      return node->get_value();
    }
  } else {
    return ElementSerializer<Type, Config, Info>::Parse(main);
  }
}

}  // namespace impl

template <typename T>
struct SerializationConfig {
  decltype([] {
    return [](auto... is) -> utempl::Tuple<typename ElementConfig<boost::pfr::tuple_element_t<*is, T>>::type...> {
      std::unreachable();
    } | utempl::kSeq<boost::pfr::tuple_size_v<T>>;
  }()) tuple{};
  template <std::size_t I, typename Self>  // NOLINTNEXTLINE
  consteval auto With(this Self&& self, ElementConfig<boost::pfr::tuple_element_t<I, T>>::type config) -> SerializationConfig {
    auto tuple = std::forward_like<Self>(self.tuple);
    Get<I>(tuple) = std::move(config);
    return {std::move(tuple)};
  }
  template <utempl::ConstexprString Name, typename Self>
  constexpr auto With(this Self&& self, ElementConfig<boost::pfr::tuple_element_t<impl::FindElement<T>(Name), T>>::type config)
      -> SerializationConfig {
    return std::forward<Self>(self).template With<impl::FindElement<T>(Name)>(std::move(config));
  }
};

template <typename T>
constexpr auto Parse(xmlpp::Element* element, Tag<T>) -> T {
  return Serialization<T>::Parse(element);
}
template <typename T>
constexpr auto Parse(xmlpp::Element* element, Tag<T>) -> T
  requires(!std::same_as<std::decay_t<decltype(kDeserializationConfig<T>)>, std::monostate>)
{
  static constexpr SerializationConfig config = kSerializationConfig<T>;
  constexpr auto tuple = utempl::Map(config.tuple, [](auto& ref) {
    return &ref;
  });
  return utempl::Unpack(utempl::PackConstexprWrapper<utempl::Enumerate(tuple)>(), [&](auto... configs) {
    try {
      return T{impl::ParseField<*((*configs).second), FieldInfo<T, (*configs).first>>(element)...};
    } catch(const ParsingError& error) {
      throw ElementParsingError(std::format("[{}] parsing error: [ {} ]", nameof::nameof_full_type<T>(), error.what()));
    }
  });
}

}  // namespace larra::xmpp::serialization