Add message serialization and deserialization

library/include/larra/message.hpp

@@ -1,31 +1,133 @@
 #pragma once
-#include <libxml++/libxml++.h>
-
 #include <larra/serialization/auto.hpp>
 #include <larra/xml_language.hpp>
 #include <string>
 
 namespace larra::xmpp {
 
+namespace message {
+struct Body {
+  std::string content;
+  std::optional<XmlLanguage> language;
+  static constexpr auto kDefaultName = "body";
+  constexpr auto operator==(const Body& other) const -> bool = default;
+  friend constexpr auto operator<<(xmlpp::Element* node, const Body& message) -> void {
+    node->add_child_text(message.content);
+  }
+  static constexpr auto Parse(xmlpp::Element* node) -> Body {
+    auto ptr = node->get_first_child_text();
+    if(!ptr) {
+      throw std::runtime_error("Message::Body: [ Text node not found ]");
+    }
+    auto lang = node->get_attribute("lang", "xml");
+    return {
+        .content = ptr->get_content(),                                                          //
+        .language = lang ? std::optional{XmlLanguage::Parse(lang->get_value())} : std::nullopt  //
+    };
+  }
+};
+
+namespace type {
+
+struct Chat {
+  static constexpr auto TryParse(std::string_view value) -> std::optional<Chat> {
+    return value == "chat" ? std::optional{Chat{}} : std::nullopt;
+  }
+  friend constexpr auto ToString(const Chat&) -> std::string {
+    return "chat";
+  }
+  constexpr auto operator==(const Chat&) const -> bool {
+    return true;
+  };
+};
+
+static constexpr auto kChat = Chat{};
+
+struct Error {
+  static constexpr auto TryParse(std::string_view value) -> std::optional<Error> {
+    return value == "error" ? std::optional{Error{}} : std::nullopt;
+  }
+  friend constexpr auto ToString(const Error&) -> std::string {
+    return "error";
+  }
+  constexpr auto operator==(const Error&) const -> bool {
+    return true;
+  };
+};
+
+static constexpr auto kError = Error{};
+
+struct GroupChat {
+  static constexpr auto TryParse(std::string_view value) -> std::optional<GroupChat> {
+    return value == "groupchat" ? std::optional{GroupChat{}} : std::nullopt;
+  }
+  friend constexpr auto ToString(const GroupChat&) -> std::string {
+    return "groupchat";
+  }
+  constexpr auto operator==(const GroupChat&) const -> bool {
+    return true;
+  };
+};
+
+static constexpr auto kGroupChat = GroupChat{};
+
+struct Headline {
+  static constexpr auto TryParse(std::string_view value) -> std::optional<Headline> {
+    return value == "headline" ? std::optional{Headline{}} : std::nullopt;
+  }
+  friend constexpr auto ToString(const Headline&) -> std::string {
+    return "headline";
+  }
+  constexpr auto operator==(const Headline&) const -> bool {
+    return true;
+  };
+};
+
+static constexpr auto kHeadline = Headline{};
+
+struct Normal {
+  static constexpr auto Parse(std::string_view value) -> Normal {
+    return value == "normal" ? Normal{}
+                             : throw std::runtime_error(
+                                   std::format(R"(message::type::Normal Parsing error: [ expected "normal" but "{}" found ])", value));
+  }
+  friend constexpr auto ToString(const Normal&) -> std::string {
+    return "normal";
+  }
+  constexpr auto operator==(const Normal&) const -> bool {
+    return true;
+  };
+};
+
+static constexpr auto kNormal = Normal{};
+
+}  // namespace type
+
+using TypeVariant = std::variant<type::Chat, type::GroupChat, type::Headline, type::Error, type::Normal>;
+
+struct Type : TypeVariant {
+  using TypeVariant::variant;
+  constexpr Type(TypeVariant variant) : TypeVariant(std::move(variant)) {
+  }
+
+  static constexpr auto GetDefault() -> Type {
+    return type::kNormal;
+  }
+
+  friend constexpr auto ToString(const Type& value) -> std::string {
+    return std::visit(
+        [](const auto& value) {
+          return ToString(value);
+        },
+        value);
+  }
+};
+
+}  // namespace message
+
 template <typename From, typename To>
 struct Message {
   static constexpr auto kDefaultName = "message";
-  struct Body : std::string {
-    using std::string::basic_string;
-    constexpr Body(std::string str) : std::string{std::move(str)} {
-    }
-    static constexpr auto kDefaultName = "body";
-    friend constexpr auto operator<<(xmlpp::Element* node, const Body& message) -> void {
-      node->add_child_text(message);
-    }
-    static constexpr auto Parse(xmlpp::Element* node) -> Body {
-      auto ptr = node->get_first_child_text();
-      if(!ptr) {
-        throw std::runtime_error("Message::Body: [ Text node not found ]");
-      }
-      return {ptr->get_content()};
-    }
-  };
   static auto Parse(xmlpp::Element* element) -> Message {
     return serialization::Parse<Message>(element);
   }
@@ -35,15 +137,20 @@ struct Message {
   constexpr auto operator==(const Message& other) const -> bool = default;
   From from;
   To to;
-  std::string type;
+  message::Type type;
   std::optional<std::string> id;
   XmlLanguage language;
-  Body body;
+  std::vector<message::Body> body;
 };
 
 template <typename From, typename To>
 struct serialization::SerializationConfigT<Message<From, To>> {
-  static constexpr auto kValue = serialization::SerializationConfig<Message<From, To>>{};
+  static constexpr auto kValue = serialization::SerializationConfig<Message<From, To>>{}  //
+                                     .template With<"type">(serialization::AttributeConfig{})
+                                     .template With<"body">(serialization::Config<std::vector<message::Body>>{});
 };
 
+template <typename Info>
+struct serialization::AttributeSerializer<message::Type, Info> : serialization::AttributeSerializer<message::TypeVariant, Info> {};
+
 }  // namespace larra::xmpp

library/include/larra/serialization/auto.hpp

@@ -64,10 +64,24 @@ struct MetaInfo {
   }
 };
 
+template <typename T>
+struct DefaultValue {};
+
+template <typename T>
+  requires requires {
+    { T::GetDefault() } -> std::convertible_to<T>;
+  }
+struct DefaultValue<T> {
+  static constexpr auto Default() {
+    return T::GetDefault();
+  }
+};
+
 template <typename MainT, std::size_t Element>
 struct FieldInfo {
   using Main = MainT;
   using Info = MetaInfo<Main>;
+  using Type = Info::template TupleElement<Element>;
   static inline const std::string kName = [] {
     if constexpr(requires { Info::template TupleElement<Element>::kDefaultName; }) {
       return Info::template TupleElement<Element>::kDefaultName;
@@ -234,6 +248,9 @@ struct AttributeSerializer {
   static constexpr auto Parse(xmlpp::Element* element) -> T {
     auto node = element->get_attribute(Info::kName, Info::kNamespace);
     if(!node) {
+      if constexpr(requires { DefaultValue<T>::Default(); }) {
+        return DefaultValue<T>::Default();
+      }
       throw AttributeParsingError(std::format("Attribute [{}{}{}: {}] parsing error",
                                               Info::kNamespace,
                                               Info::kNamespace == std::string{} ? "" : ":",
@@ -246,6 +263,19 @@ struct AttributeSerializer {
       return node->get_value();
     }
   }
+  static constexpr auto TryParse(xmlpp::Element* element) -> std::optional<T>
+    requires requires { T::TryParse(std::string_view{}); }
+  {
+    auto node = element->get_attribute(Info::kName, Info::kNamespace);
+    if(!node) {
+      throw AttributeParsingError(std::format("Attribute [{}{}{}: {}] parsing error",
+                                              Info::kNamespace,
+                                              Info::kNamespace == std::string{} ? "" : ":",
+                                              Info::kName,
+                                              nameof::nameof_full_type<T>()));
+    }
+    return T::TryParse(node->get_value());
+  }
   static constexpr auto Serialize(xmlpp::Element* element, const T& obj) {
     if constexpr(requires {
                    { ToString(obj) } -> std::convertible_to<const std::string&>;
@@ -261,7 +291,12 @@ template <typename T, typename Info>
 struct AttributeSerializer<std::optional<T>, Info> {
   static constexpr auto Parse(xmlpp::Element* element) -> std::optional<T> {
     auto node = element->get_attribute(Info::kName, Info::kNamespace);
-    return node ? std::optional{AttributeSerializer<T, Info>::Parse(element)} : std::nullopt;
+    return node ? std::optional{AttributeSerializer<T, Info>::Parse(element)} : [] -> std::optional<T> {
+      if constexpr(requires { DefaultValue<T>::Default(); }) {
+        return DefaultValue<T>::Default();
+      }
+      return std::nullopt;
+    }();
   }
   static constexpr auto Serialize(xmlpp::Element* element, const std::optional<T>& obj) {
     if(obj) {
@@ -270,6 +305,52 @@ struct AttributeSerializer<std::optional<T>, Info> {
   }
 };
 
+template <typename... Ts, typename Info>
+struct AttributeSerializer<std::variant<Ts...>, Info> {
+  template <typename T>
+  static constexpr auto FunctionForType(xmlpp::Element* element) {
+    return [=] -> std::optional<T> {
+      if constexpr(requires { AttributeSerializer<T, Info>::TryParse(element); }) {
+        return AttributeSerializer<T, Info>::TryParse(element);
+      } else {
+        try {
+          return AttributeSerializer<T, Info>::Parse(element);
+        } catch(...) {
+          return std::nullopt;
+        }
+      }
+    };
+  }
+  static constexpr auto Parse(xmlpp::Element* element) -> std::variant<Ts...> {
+    using T = Info::Type;
+    auto node = element->get_attribute(Info::kName, Info::kNamespace);
+    if(!node) {
+      if constexpr(requires { DefaultValue<T>::Default(); }) {
+        return DefaultValue<T>::Default();
+      }
+      throw AttributeParsingError(std::format("Attribute [{}{}{}: {}] parsing error",
+                                              Info::kNamespace,
+                                              Info::kNamespace == std::string{} ? "" : ":",
+                                              Info::kName,
+                                              nameof::nameof_full_type<T>()));
+    }
+    return [&]<typename... TTs>(utempl::TypeList<TTs...>) {
+      // operator* is safe because in or_else Parse returns Ts...[sizeof...(Ts) - 1] (not optional)
+      return *utempl::FirstOf(utempl::Tuple{FunctionForType<TTs>(element)...}, std::optional<std::variant<Ts...>>{})
+                  .or_else([&] -> std::optional<std::variant<Ts...>> {
+                    return AttributeSerializer<decltype(utempl::Get<sizeof...(Ts) - 1>(utempl::kTypeList<Ts...>)), Info>::Parse(element);
+                  });
+    }(utempl::TakeFrom<sizeof...(Ts) - 1>(utempl::kTypeList<Ts...>));
+  }
+  static constexpr auto Serialize(xmlpp::Element* element, const std::variant<Ts...>& obj) {
+    std::visit(
+        [&]<typename T>(const T& value) {
+          AttributeSerializer<T, Info>::Serialize(element, value);
+        },
+        obj);
+  }
+};
+
 namespace impl {
 
 template <typename T>

tests/message.cpp

@@ -21,13 +21,13 @@ auto CreateTestData() {
   return doc;
 }
 
-constexpr Message<BareJid, BareJid> kMessage{
+const Message<BareJid, BareJid> kMessage{
     .from = {.username = "user1", .server = "server.i2p"},
     .to = {.username = "user2", .server = "server.i2p"},
-    .type = "chat",
+    .type = message::type::kChat,
     .id = "1",
     .language = "en",
-    .body = "hello"  //
+    .body = {message::Body{.content = "hello"}}  //
 };
 
 }  // namespace