Replace Game::initialize() with factory method

src/game/game.cppm

@@ -1,5 +1,6 @@
 module;
 
+#include <cassert>
 #include <memory>
 #include <SDL3/SDL.h>
 
@@ -15,35 +16,49 @@ export namespace game
 {
     class Game
     {
+        // Whether this class is currently instantiated (to prevent multiple instances)
+        static bool instantiated_;
+
+        // Reference to the engine
         core::Engine& engine_;
 
         // Sprite for testing
-        std::unique_ptr<Sprite> sprite_ = nullptr;
+        std::unique_ptr<Sprite> sprite_{nullptr};
+
+        // Private constructor
+        explicit Game(core::Engine& engine)
+            : engine_(engine)
+        {
+            // TODO: Texture should be a reference/pointer to an object managed by a ResourceManager or similar.
+            auto texture = sdl_image::LoadTexture(
+                engine_.get_renderer().get_sdl_renderer(),
+                "assets/neocat.png"
+            );
+
+            sprite_ = std::make_unique<Sprite>(std::move(texture), 100, 100);
+        }
 
         public:
             Game() = delete;
 
-            explicit Game(core::Engine& engine)
-                : engine_(engine)
-            {}
-
             // No copy or move operations because we have a reference to the engine
             Game(const Game&) = delete;
             Game& operator=(const Game&) = delete;
             Game(Game&&) = delete;
             Game& operator=(Game&&) = delete;
 
-            ~Game() = default;
-
-            void initialize()
+            ~Game()
             {
-                // TODO: Texture should be a reference/pointer to an object managed by a ResourceManager or similar.
-                auto texture = sdl_image::LoadTexture(
-                    engine_.get_renderer().get_sdl_renderer(),
-                    "assets/neocat.png"
-                );
+                instantiated_ = false;
+            }
 
-                sprite_ = std::make_unique<Sprite>(std::move(texture), 100, 100);
+            static std::unique_ptr<Game> create(core::Engine& engine)
+            {
+                // Prevent the class from being instantiated multiple times
+                assert(!instantiated_);
+                return std::unique_ptr<Game>{
+                    new Game(engine)
+                };
             }
 
             // Handles an SDL event. Returns true if the event has been handled.
@@ -75,4 +90,6 @@ export namespace game
             {
             }
     };
+
+    bool Game::instantiated_ = false;
 }