From 5c5d1a37d51e821f2fa2418ab83476871b26c500 Mon Sep 17 00:00:00 2001
From: sha512sum <linuxnyasha@tutanota.com>
Date: Fri, 30 Aug 2024 18:50:25 +0000
Subject: [PATCH] Update field set helpers

---
 library/include/larra/utils.hpp | 105 +++++++++++++++++++++++---------
 tests/set.cpp                   |  24 ++++++++
 2 files changed, 101 insertions(+), 28 deletions(-)

diff --git a/library/include/larra/utils.hpp b/library/include/larra/utils.hpp
index 59a5081..507458e 100644
--- a/library/include/larra/utils.hpp
+++ b/library/include/larra/utils.hpp
@@ -3,8 +3,26 @@
 
 namespace larra::xmpp::utils {
 
+namespace impl {
+
 template <typename T, typename R>
-constexpr auto GetType(R(T::* ptr)) -> R;
+constexpr auto GetType(R(T::*ptr)) -> R;
+
+template <typename T>
+using GetTypeT = decltype(GetType(std::declval<T>()));
+
+template <typename Self, typename Type, typename... Fs>
+concept SetConcept =
+    (std::conditional_t<std::same_as<GetTypeT<Fs>, Type>,
+                        std::true_type,
+                        std::integral_constant<
+                            bool,
+                            std::is_reference_v<Self>
+                                ? std::copy_constructible<GetTypeT<Fs>>
+                                : std::move_constructible<GetTypeT<Fs>>&& requires { std::declval<Self>().*std::declval<Fs>(); }>>::value &&
+     ...);
+
+}  // namespace impl
 
 // Fields description
 // struct SomeStruct {
@@ -34,12 +52,13 @@ struct FieldsDescription {
    */
   template <std::size_t I, typename Self, typename Value>
   constexpr auto With(Self&& self, Value&& value) const
-    requires([] {
-      if constexpr(I < sizeof...(Fs)) {
-        return std::is_constructible_v<decltype(GetType(Get<I>(tuple))), decltype(value)>;
-      };
-      return false;
-    }())
+    requires(std::is_constructible_v<T, impl::GetTypeT<Fs>...> && impl::SetConcept<Self, std::decay_t<Value>, Fs...> &&
+             [] {
+               if constexpr(I < sizeof...(Fs)) {
+                 return std::is_constructible_v<impl::GetTypeT<decltype(Get<I>(tuple))>, decltype(value)>;
+               };
+               return false;
+             }())
 
   {
     return [&](auto... is) -> T {
@@ -61,8 +80,9 @@ struct FieldsDescription {
    * \return T with new field value and values from self
    */
   template <typename Self, typename Value, typename Type>
-  constexpr auto With(Type(T::* ptr), Self&& self, Value&& value) const
-    requires std::is_constructible_v<Type, decltype(value)>
+  constexpr auto With(Type(T::*ptr), Self&& self, Value&& value) const
+    requires(std::is_constructible_v<T, impl::GetTypeT<Fs>...> && std::is_constructible_v<Type, decltype(value)> &&
+             impl::SetConcept<Self, Type, Fs...>)
   {
     return utempl::Unpack(this->tuple, [&](auto... fs) -> T {
       return {[&] {
@@ -75,7 +95,7 @@ struct FieldsDescription {
       }()...};
     });
   };
-};
+};  // namespace larra::xmpp::utils
 
 namespace impl {
 
@@ -118,47 +138,76 @@ struct FieldSetHelper {
   /* Method accepting field index, self and new value for field and returns object with new field value
    *
    * \param I field index for object T
+   * \param T Type for return and pfr reflection
    * \param self old object
    * \param value new value for field
    * \return T with new field value and values from self
    */
-  template <std::size_t I, typename Self, typename Value>
-  static constexpr auto With(Self&& self, Value&& value)
-    requires([] {
-      if constexpr(I < boost::pfr::tuple_size_v<std::decay_t<Self>>) {
-        return std::is_constructible_v<std::decay_t<decltype(boost::pfr::get<I>(std::declval<Self&>()))>, decltype(value)>;
-      };
-      return false;
-    }())
+  template <std::size_t I,
+            typename T = void,
+            typename Self,
+            typename Value,
+            typename...,
+            typename Type = std::conditional_t<std::same_as<T, void>, std::decay_t<Self>, T>,
+            typename TT = decltype([] -> decltype(auto) {
+              if constexpr(std::same_as<T, void>) {
+                return [] -> Self {
+                  std::unreachable();
+                }();
+              } else {
+                return [] -> std::remove_reference_t<decltype(std::forward_like<Self>(std::declval<T>()))> {
+                  std::unreachable();
+                }();
+              }
+            }())>
+  static constexpr auto With(Self&& self, Value&& value) -> Type
+    requires(
+        std::is_aggregate_v<Type> && (std::same_as<T, void> || requires { static_cast<T&>(self); }) &&
+        [] {
+          if constexpr(I < boost::pfr::tuple_size_v<Type>) {
+            return std::is_constructible_v<std::decay_t<decltype(boost::pfr::get<I>(std::declval<TT>()))>, decltype(value)>;
+          };
+          return false;
+        }() &&
+        [](auto... is) {
+          return ((*is == I                    ? true
+                   : std::is_reference_v<Self> ? std::copy_constructible<decltype(boost::pfr::get<*is>(std::declval<TT>()))>
+                                               : std::move_constructible<decltype(boost::pfr::get<*is>(std::declval<TT>()))>) &&
+                  ...) &&
+                 std::is_constructible_v<Type, decltype(boost::pfr::get<*is>(std::declval<TT>()))...>;
+        } | utempl::kSeq<boost::pfr::tuple_size_v<Type>>)
   {
-    using T = std::decay_t<Self>;
-    return [&](auto... is) -> T {
+    return [&](auto... is) -> Type {
       return {[&] -> decltype(auto) {
         if constexpr(I == *is) {
           return std::forward<Value>(value);
         } else {
-          return std::forward_like<Self>(boost::pfr::get<*is>(self));
-        };
+          return std::forward_like<Self>(boost::pfr::get<*is>(static_cast<TT&>(self)));
+        }
       }()...};
-    } | utempl::kSeq<boost::pfr::tuple_size_v<T>>;
+    } | utempl::kSeq<boost::pfr::tuple_size_v<TT>>;
   };
 
+  // clang-format off
   /* Method accepting field name, self and new value for field and returns object with new field value
    *
    * \param FieldName field name for object T
+   * \param T Type for return and pfr reflection
    * \param self old object
    * \param value new value for field
    * \return T with new field value and values from self
    */
-  template <utempl::ConstexprString FieldName, typename Self, typename Value>
+  template <utempl::ConstexprString FieldName, typename T = void, typename Self, typename Value>
   static constexpr auto With(Self&& self, Value&& value) -> decltype(With<[] {
-    auto names = boost::pfr::names_as_array<std::decay_t<Self>>();
+    constexpr auto names = boost::pfr::names_as_array<std::conditional_t<std::same_as<T, void>, std::decay_t<Self>, T>>();
     return std::ranges::find(names, static_cast<std::string_view>(FieldName)) - names.begin();
-  }()>(std::forward<Self>(self), std::forward<Value>(value))) {
-    constexpr auto names = boost::pfr::names_as_array<std::decay_t<Self>>();
+  }(),
+  T>(std::forward<Self>(self), std::forward<Value>(value))) {
+    constexpr auto names = boost::pfr::names_as_array<std::conditional_t<std::same_as<T, void>, std::decay_t<Self>, T>>();
     constexpr auto id = std::ranges::find(names, static_cast<std::string_view>(FieldName)) - names.begin();
-    return With<id>(std::forward<Self>(self), std::forward<Value>(value));
+    return With<id, T>(std::forward<Self>(self), std::forward<Value>(value));
   };
+  // clang-format on
 };
 
 }  // namespace larra::xmpp::utils
diff --git a/tests/set.cpp b/tests/set.cpp
index 6fba1e3..699a579 100644
--- a/tests/set.cpp
+++ b/tests/set.cpp
@@ -84,4 +84,28 @@ TEST(NonPfrSet, NonCopyable) {
   auto obj = SomeStruct5{}.Field1({}).Field2({});
 }
 
+struct SomeStruct6 {
+  std::string field1;
+  std::string field2;
+  template <typename Self>
+  auto Field1(this Self&& self, std::string field1) -> std::decay_t<Self> {
+    return utils::FieldSetHelper::With<"field1", SomeStruct6>(std::forward<Self>(self), std::move(field1));
+  }
+  template <typename Self>
+  auto Field2(this Self&& self, std::string field2) -> std::decay_t<Self> {
+    return utils::FieldSetHelper::With<"field2", SomeStruct6>(std::forward<Self>(self), std::move(field2));
+  }
+};
+
+struct SomeStruct7 : SomeStruct6 {
+  SomeStruct7(SomeStruct6&& obj) : SomeStruct6(std::move(obj)) {};
+  using SomeStruct6::SomeStruct6;
+};
+
+TEST(Set, Inheritance) {
+  const SomeStruct7 obj = SomeStruct7{}.Field1("Hello").Field2("World");
+  ASSERT_EQ(obj.field1, "Hello");
+  ASSERT_EQ(obj.field2, "World");
+}
+
 }  // namespace larra::xmpp