From 8673907e4e3f2f9ff6e8bd18aaf3ddc6d84c0e64 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Mon, 1 Jan 2024 22:20:21 +0800
Subject: NEED TEST: add support for pointer conversion in ObjectResolver.

---
 include/cru/common/SelfResolvable.h | 67 +++++++++++++++++++++++++++++++++++--
 1 file changed, 64 insertions(+), 3 deletions(-)

(limited to 'include/cru/common/SelfResolvable.h')

diff --git a/include/cru/common/SelfResolvable.h b/include/cru/common/SelfResolvable.h
index ce5b1628..84fa54f6 100644
--- a/include/cru/common/SelfResolvable.h
+++ b/include/cru/common/SelfResolvable.h
@@ -1,7 +1,9 @@
 #pragma once
 
 #include <cassert>
+#include <functional>
 #include <memory>
+#include <type_traits>
 
 namespace cru {
 template <typename T>
@@ -10,22 +12,74 @@ class SelfResolvable;
 template <typename T>
 class ObjectResolver {
   friend SelfResolvable<T>;
+  template <typename U>
+  friend class ObjectResolver;
 
  private:
-  explicit ObjectResolver(T* o) : shared_object_ptr_(new T*(o)) {}
+  template <typename U>
+  using Accessor_ = std::function<U*(const std::shared_ptr<void*>&)>;
+  using ThisAccessor_ = Accessor_<T>;
+
+  explicit ObjectResolver(T* o)
+      : shared_object_ptr_(new void*(o)),
+        accessor_([](const std::shared_ptr<void*>& ptr) {
+          return static_cast<T*>(*ptr);
+        }) {}
+  explicit ObjectResolver(std::shared_ptr<void*> ptr, ThisAccessor_ accessor)
+      : shared_object_ptr_(std::move(ptr)), accessor_(std::move(accessor)) {}
+
+  template <typename U>
+  static ThisAccessor_ CreateAccessor(Accessor_<U> parent_accessor) {
+    return [parent_accessor =
+                std::move(parent_accessor)](const std::shared_ptr<void*>& ptr) {
+      return static_cast<T*>(parent_accessor(ptr));
+    };
+  }
 
  public:
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U*, T*>>>
+  ObjectResolver(const ObjectResolver<U>& other)
+      : shared_object_ptr_(other.shared_object_ptr_),
+        accessor_(CreateAccessor(other.accessor_)) {}
+
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U*, T*>>>
+  ObjectResolver(ObjectResolver<U>&& other)
+      : shared_object_ptr_(std::move(other.shared_object_ptr_)),
+        accessor_(CreateAccessor(std::move(other.accessor_))) {}
+
   ObjectResolver(const ObjectResolver&) = default;
   ObjectResolver& operator=(const ObjectResolver&) = default;
   ObjectResolver(ObjectResolver&&) = default;
   ObjectResolver& operator=(ObjectResolver&&) = default;
   ~ObjectResolver() = default;
 
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U*, T*>>>
+  ObjectResolver& operator=(const ObjectResolver<U>& other) {
+    if (this != &other) {
+      this->shared_object_ptr_ = other.shared_object_ptr_;
+      this->accessor_ = CreateAccessor(other.accessor_);
+    }
+    return *this;
+  }
+
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U*, T*>>>
+  ObjectResolver& operator=(ObjectResolver<U>&& other) {
+    if (this != &other) {
+      this->shared_object_ptr_ = std::move(other.shared_object_ptr_);
+      this->accessor_ = CreateAccessor(std::move(other.shared_object_ptr_));
+    }
+    return *this;
+  }
+
   bool IsValid() const { return this->shared_object_ptr_ != nullptr; }
 
   T* Resolve() const {
     assert(IsValid());
-    return *this->shared_object_ptr_;
+    return this->accessor_(this->shared_object_ptr_);
   }
 
   /**
@@ -33,6 +87,12 @@ class ObjectResolver {
    */
   T* operator()() const { return Resolve(); }
 
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<T*, U*>>>
+  operator ObjectResolver<U>() const {
+    return ObjectResolver<U>(*this);
+  }
+
  private:
   void SetResolvedObject(T* o) {
     assert(IsValid());
@@ -40,7 +100,8 @@ class ObjectResolver {
   }
 
  private:
-  std::shared_ptr<T*> shared_object_ptr_;
+  std::shared_ptr<void*> shared_object_ptr_;
+  std::function<T*(const std::shared_ptr<void*>&)> accessor_;
 };
 
 /**
-- 
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