From cc0688f048819febc571368fb9fc093ea066708c Mon Sep 17 00:00:00 2001
From: DH <dim@himro.ca>
Date: Fri, 27 Feb 2026 20:30:37 -0500
Subject: [PATCH] Final version with full refactoring.

---
 typefactory/typefactory.h | 186 +++++++++++++++++++-------------------
 1 file changed, 91 insertions(+), 95 deletions(-)

diff --git a/typefactory/typefactory.h b/typefactory/typefactory.h
index b7a0cd6..68e4dc1 100644
--- a/typefactory/typefactory.h
+++ b/typefactory/typefactory.h
@@ -1,120 +1,116 @@
 #ifndef TYPEFACTORY_H
 #define TYPEFACTORY_H
-#include <unordered_map>
-#include <type_traits>
+
 #include <memory>
+#include <type_traits>
+#include <unordered_map>
+#include <utility>   // std::move
 
 /**
  * @brief Registry-based factory for creating objects by runtime identifier.
  *
- * Allows registering derived types and instantiating them
- * using a ClassId key.
+ * Allows registering derived types and instantiating them using a ClassId key.
  *
- * @param ClassId - unique class identification class. For example string, or integer id.
- * @param BaseClass - all objects should have one base class. For example vehicle or parameter
- * @param Args - constructor arguments
+ * Notes:
+ * - Not thread-safe. Register types during initialization phase only.
+ * - Re-registering the same id overwrites the previous entry ("last wins").
+ * - ClassId must be hashable (std::hash<ClassId> specialization must exist).
+ *
+ * @tparam ClassId    Unique class identifier type (e.g. std::string, int, enum).
+ * @tparam BaseClass  Base type for all created objects.
+ * @tparam Args       Constructor arguments forwarded to registered derived types (by value).
  *
  * Usage example:
  * @code
- * class Base {
- *   public:
- *     virtual int get() = 0;
- * }
+ * #include <string>
  *
- * class Derived1 : public Base {
- *   public:
- *     Derived1 (int start) : m_start(start){}
- *     int get() override {
- *       return m_start + 1;
- *     }
- *   private:
- *     int m_start = 0;
- * }
+ * struct Base {
+ *   virtual ~Base() = default;
+ *   virtual int get() = 0;
+ * };
  *
- * class Derived2 : public Base {
- *   public:
- *     Derived2 (int start) : m_start(start){}
- *     int get() override {
- *       return m_start + 2;
- *     }
- *   private:
- *     int m_start = 0;
- * }
- * .
- * .
- * .
- * TypeFactory <std::string, Base, int> typefactory;
- * typefactory.registerType<Derived1>("one");
- * typefactory.registerType<Derived2>("2");
+ * struct Derived1 : Base {
+ *   explicit Derived1(int start) : m_start(start) {}
+ *   int get() override { return m_start + 1; }
+ *   int m_start = 0;
+ * };
  *
- * auto d1 = typefactory.creator ("one")(10);
- * auto d2 = typefactory.creator ("2")(10);
+ * struct Derived2 : Base {
+ *   explicit Derived2(int start) : m_start(start) {}
+ *   int get() override { return m_start + 2; }
+ *   int m_start = 0;
+ * };
  *
- * d1->get();
- * d2->get();
+ * TypeFactory<std::string, Base, int> factory;
+ * factory.registerType<Derived1>("one");
+ * factory.registerType<Derived2>("two");
+ *
+ * auto a = factory.create("one", 10);
+ * auto b = factory.creator("two")(10); // advanced API: get creator function
+ *
+ * (void)a->get();
+ * (void)b->get();
  * @endcode
  */
-template<class ClassId, class BaseClass, class ... Args>
+template <class ClassId, class BaseClass, class... Args>
 class TypeFactory {
-  public:
-    typedef std::shared_ptr<BaseClass> BaseClass_SP;
-    /**
-     * @brief typefactoryFunction - typefactory function pointer type. Generally speaking it is pointer to constructor.
-     */
-    typedef BaseClass_SP (*typefactoryFunction) (Args ...);
+public:
+  using BasePtr   = std::shared_ptr<BaseClass>;
+  using CreatorFn = BasePtr (*)(Args...);
 
-    TypeFactory() = default;
+  TypeFactory() = default;
 
-    /**
-     * @brief registerType - template function to register class in factory
-     * @param Derived - registering type
-     * @param id - unique class identification
-     *
-     * Usage example:
-     * @code
-     * typefactory.registerType<Derived1>("one");
-     * typefactory.registerType<Derived2>("2");
-     * @endcode
-     */
-    template<class Derived>
-    void registerType (const ClassId& id) {
-      /// Register Derived type by storing its constructor wrapper
-      static_assert(std::is_base_of_v<BaseClass, Derived>,
-                    "Derived must inherit from BaseClass");
-      static_assert(std::is_constructible_v<Derived, Args...>,
-                    "Derived must be constructible from Args...");
-      classes[id] = &typefactory<Derived>;
-    }
+  /**
+   * @brief Registers a Derived type under the given id.
+   *
+   * Requirements (checked at compile-time):
+   * - Derived must inherit from BaseClass
+   * - Derived must be constructible from Args...
+   *
+   * Re-registering the same id overwrites the previous entry ("last wins").
+   */
+  template <class Derived>
+  void registerType(const ClassId& id) {
+    static_assert(std::is_base_of_v<BaseClass, Derived>,
+                  "Derived must inherit from BaseClass");
+    static_assert(std::is_constructible_v<Derived, Args...>,
+                  "Derived must be constructible from Args...");
 
-    /**
-     * @brief creator - Returns creator function for id.
-     * @param id - unique class identification
-     * @returns creator function.
-     * @throws std::out_of_range when id not found in map
-     */
-    typefactoryFunction creator (const ClassId& id) const {
-      return classes.at (id);
-    }
-    BaseClass_SP create(const ClassId& id, Args... args) const {
-      return creator(id)(args...);
-    }
-  protected:
-    /**
-     * @brief classes - Not thread-safe. Register types during initialization phase only.
-     */
-    std::unordered_map<ClassId, typefactoryFunction> classes;
+    classes.insert_or_assign(id, &instantiate<Derived>);
+  }
 
-  private:
-    /**
-     * @brief typefactory - main functionality, creator registered object
-     * @param Derived - class type
-     * @param args - constructor arguments
-     * @return shared pointer to register Derived class
-     */
-    template<class Derived>
-    static BaseClass_SP typefactory (Args ... args) {
-      return std::make_shared<Derived> (args ...);
-    }
+  /**
+   * @brief Returns creator function for the given id.
+   * @throws std::out_of_range when id is not registered.
+   */
+  [[nodiscard]] CreatorFn creator(const ClassId& id) const {
+    return classes.at(id);
+  }
+
+  /**
+   * @brief Creates an instance for the given id using provided arguments.
+   * @throws std::out_of_range when id is not registered.
+   */
+  [[nodiscard]] BasePtr create(const ClassId& id, Args... args) const {
+    return creator(id)(std::move(args)...);
+  }
+
+  /**
+   * @brief Checks whether an id is registered.
+   */
+  [[nodiscard]] bool contains(const ClassId& id) const {
+    return classes.find(id) != classes.end();
+  }
+
+protected:
+  // Protected by design: derived factories may extend/inspect the registry.
+  std::unordered_map<ClassId, CreatorFn> classes;
+
+private:
+  template <class Derived>
+  static BasePtr instantiate(Args... args) {
+    return std::make_shared<Derived>(std::move(args)...);
+  }
 };
 
 #endif // TYPEFACTORY_H