.

library/include/larra/serialization.hpp

@@ -2,6 +2,7 @@
 #include <libxml++/libxml++.h>
 #include <spdlog/spdlog.h>
 
+#include <larra/serialization/error.hpp>
 #include <nameof.hpp>
 #include <string>
 #include <utempl/utils.hpp>
@@ -96,7 +97,8 @@ template <typename T>
 struct Serialization : SerializationBase<T> {
   [[nodiscard]] static constexpr auto Parse(xmlpp::Element* element) -> T {
     if(!Serialization::StartCheck(element)) {
-      throw std::runtime_error("StartCheck failed");
+      throw serialization::SerializationError{
+          std::format("[{}: {}] serialization error: [ StartCheck failed ]", Serialization::kDefaultName, nameof::nameof_full_type<T>())};
     }
     return T::Parse(element);
   }

library/include/larra/serialization/auto.hpp

@@ -0,0 +1,175 @@
+#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, typename V>
+struct Config : V {
+  using V::V;
+  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 ElementSerializationError(
+          std::format("[{}: {}] serialization error: [ Not found ]", Info::kName, nameof::nameof_full_type<T>()));
+    }
+    auto elementNode = dynamic_cast<xmlpp::Element*>(node);
+    if(!node) {
+      throw ElementSerializationError(
+          std::format("[{}: {}] serialization error: [ Invalid node ]", Info::kName, nameof::nameof_full_type<T>()));
+    }
+    try {
+      return ::larra::xmpp::serialization::Parse(elementNode, Tag<T>{});
+    } catch(const SerializationError& error) {
+      throw ElementSerializationError(
+          std::format("[{}: {}] serialization 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) {
+  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 AttributeSerializationError(std::format("Attribute [{}] serialization error", Info::kName));
+    }
+    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 SerializationError& error) {
+      throw ElementSerializationError(std::format("[{}] serialization error: [ {} ]", nameof::nameof_full_type<T>(), error.what()));
+    }
+  });
+}
+
+}  // namespace larra::xmpp::serialization

library/include/larra/serialization/error.hpp

@@ -0,0 +1,18 @@
+#pragma once
+#include <stdexcept>
+
+namespace larra::xmpp::serialization {
+
+struct SerializationError : std::runtime_error {
+  using std::runtime_error::runtime_error;
+};
+
+struct AttributeSerializationError : SerializationError {
+  using SerializationError::SerializationError;
+};
+
+struct ElementSerializationError : SerializationError {
+  using SerializationError::SerializationError;
+};
+
+}  // namespace larra::xmpp::serialization

tests/serialization.cpp

@@ -1,8 +1,12 @@
 #include <gtest/gtest.h>
 
 #include <larra/serialization.hpp>
+#include <larra/serialization/auto.hpp>
+#include <larra/serialization/error.hpp>
 #include <larra/stream_error.hpp>
 
+using namespace std::literals;
+
 namespace larra::xmpp {
 
 TEST(Parse, Variant) {
@@ -21,8 +25,83 @@ TEST(Serialize, Variant) {
   auto node = doc.create_root_node("stream:error");
   S::Serialize(node, data);
   EXPECT_EQ(doc.write_to_string(),
-            std::string_view{"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<stream:error><unsupported-stanza-type "
+            "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<stream:error><unsupported-stanza-type "
-                             "xmlns=\"urn:ietf:params:xml:ns:xmpp-streams\"/></stream:error>\n"});
+            "xmlns=\"urn:ietf:params:xml:ns:xmpp-streams\"/></stream:error>\n"sv);
+}
+
+namespace tests::serialization {
+
+struct SomeStruct {
+  static constexpr auto kDefaultName = "some";
+  std::string value;
+  [[nodiscard]] static auto Parse(xmlpp::Element* element) -> SomeStruct;
+};
+
+struct SomeStruct2 {
+  static constexpr auto kDefaultName = "some2";
+  SomeStruct value;
+  [[nodiscard]] static auto Parse(xmlpp::Element* element) -> SomeStruct2;
+};
+
+struct SomeStruct3 {
+  static constexpr auto kDefaultName = "some3";
+  int value;
+  [[nodiscard]] static auto Parse(xmlpp::Element* element) -> SomeStruct3;
+};
+
+struct SomeStruct4 {
+  static constexpr auto kDefaultName = "some4";
+  SomeStruct3 value;
+  [[nodiscard]] static auto Parse(xmlpp::Element* element) -> SomeStruct4;
+};
+
+}  // namespace tests::serialization
+
+namespace serialization {
+
+template <>
+constexpr auto kSerializationConfig<tests::serialization::SomeStruct> = SerializationConfig<tests::serialization::SomeStruct>{};
+
+template <>
+constexpr auto kSerializationConfig<tests::serialization::SomeStruct2> =
+    SerializationConfig<tests::serialization::SomeStruct2>{}.With<"value">(serialization::Config<tests::serialization::SomeStruct>{});
+
+template <>
+constexpr auto kSerializationConfig<tests::serialization::SomeStruct4> =
+    SerializationConfig<tests::serialization::SomeStruct4>{}.With<"value">(serialization::Config<tests::serialization::SomeStruct3>{});
+
+}  // namespace serialization
+
+auto tests::serialization::SomeStruct::Parse(xmlpp::Element* element) -> SomeStruct {
+  return ::larra::xmpp::serialization::Parse<tests::serialization::SomeStruct>(element);
+}
+
+auto tests::serialization::SomeStruct2::Parse(xmlpp::Element* element) -> SomeStruct2 {
+  return ::larra::xmpp::serialization::Parse<tests::serialization::SomeStruct2>(element);
+}
+
+auto tests::serialization::SomeStruct3::Parse(xmlpp::Element*) -> SomeStruct3 {
+  return {.value = 42};  // NOLINT
+}
+
+auto tests::serialization::SomeStruct4::Parse(xmlpp::Element* element) -> SomeStruct4 {
+  return ::larra::xmpp::serialization::Parse<tests::serialization::SomeStruct4>(element);
+}
+
+TEST(Parse, Auto) {
+  xmlpp::Document doc;
+  auto node = doc.create_root_node("some2");
+  node = node->add_child_element("some");
+  node->set_attribute("value", "Hello");
+  auto a = Serialization<tests::serialization::SomeStruct>::Parse(node);
+  EXPECT_EQ(a.value, "Hello"sv);
+  auto b = Serialization<tests::serialization::SomeStruct2>::Parse(doc.get_root_node());
+  EXPECT_EQ(b.value.value, "Hello"sv);
+  EXPECT_THROW(std::ignore = tests::serialization::SomeStruct2::Parse(node), serialization::SerializationError);
+  auto node2 = node->add_child_element("some4");
+  node2->add_child_element("some3");
+  auto c = Serialization<tests::serialization::SomeStruct4>::Parse(node2);
+  EXPECT_EQ(c.value.value, 42);
 }
 
 }  // namespace larra::xmpp