Refactor code into classes

src/core/engine.cppm

@@ -0,0 +1,95 @@
+module;
+
+#include <cassert>
+#include <tuple>
+#include <SDL3/SDL.h>
+
+export module core.engine;
+
+import config;
+import core.renderer;
+import core.window;
+
+export namespace core
+{
+    class Engine
+    {
+        // Whether this class is currently instantiated (to prevent multiple instances)
+        static bool instantiated_;
+
+        // If this is set to false, the application will exit
+        bool keep_running_ = true;
+
+        Window window_;
+        Renderer renderer_;
+
+        public:
+            Engine()
+            {
+                // Prevent the class from being instantiated multiple times
+                assert(!instantiated_);
+                instantiated_ = true;
+            }
+
+            // No copy operations
+            Engine(const Engine&) = delete;
+            Engine& operator=(const Engine&) = delete;
+
+            // Default move operations
+            Engine(Engine&&) = default;
+            Engine& operator=(Engine&&) = default;
+
+            ~Engine()
+            {
+                instantiated_ = false;
+            }
+
+            bool keep_running() const
+            {
+                return keep_running_;
+            }
+
+            Window& get_window()
+            {
+                return window_;
+            }
+
+            Renderer& get_renderer()
+            {
+                return renderer_;
+            }
+
+            // TODO: Should this be moved to the constructor?
+            void initialize()
+            {
+                std::tie(window_, renderer_) = Window::create_window_and_renderer(
+                    config::get_window_title(),
+                    config::window_width,
+                    config::window_height,
+                    0
+                );
+            }
+
+            // Handles an SDL event. Returns true if the event has been handled.
+            bool handle_event(const SDL_Event* event)
+            {
+                if (event->type == SDL_EVENT_QUIT) {
+                    // Exit the application
+                    keep_running_ = false;
+                    return true;
+                }
+
+                return false;
+            }
+
+            void update()
+            {
+            }
+
+            void shutdown()
+            {
+            }
+    };
+
+    bool Engine::instantiated_ = false;
+}