7 files changed, 285 insertions, 26 deletions

diff --git a/src/crepe/manager/CMakeLists.txt b/src/crepe/manager/CMakeLists.txt
index 480c8ee..f73e165 100644
--- a/src/crepe/manager/CMakeLists.txt
+++ b/src/crepe/manager/CMakeLists.txt
@@ -4,6 +4,7 @@ target_sources(crepe PUBLIC
 	Manager.cpp
 	SaveManager.cpp
 	SceneManager.cpp
+	LoopTimerManager.cpp
 	ResourceManager.cpp
 )
 
@@ -17,6 +18,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	SaveManager.h
 	SceneManager.h
 	SceneManager.hpp
+	LoopTimerManager.h
 	ResourceManager.h
 	ResourceManager.hpp
 )
diff --git a/src/crepe/manager/EventManager.cpp b/src/crepe/manager/EventManager.cpp
index 20f0dd3..6aa49ee 100644
--- a/src/crepe/manager/EventManager.cpp
+++ b/src/crepe/manager/EventManager.cpp
@@ -3,11 +3,9 @@
 using namespace crepe;
 using namespace std;
 
-EventManager & EventManager::get_instance() {
-	static EventManager instance;
-	return instance;
+EventManager::EventManager(Mediator & mediator) : Manager(mediator) {
+	this->mediator.event_manager = *this;
 }
-
 void EventManager::dispatch_events() {
 	for (auto & event : this->events_queue) {
 		this->handle_event(event.type, event.channel, *event.event.get());
diff --git a/src/crepe/manager/EventManager.h b/src/crepe/manager/EventManager.h
index ba5e98b..639e37f 100644
--- a/src/crepe/manager/EventManager.h
+++ b/src/crepe/manager/EventManager.h
@@ -8,6 +8,8 @@
 #include "../api/Event.h"
 #include "../api/EventHandler.h"
 
+#include "Manager.h"
+
 namespace crepe {
 
 //! Event listener unique ID
@@ -22,27 +24,19 @@ typedef size_t subscription_t;
 typedef size_t event_channel_t;
 
 /**
- * \class EventManager
  * \brief Manages event subscriptions, triggers, and queues, enabling decoupled event handling.
  *
  * The `EventManager` acts as a centralized event system. It allows for registering callbacks
  * for specific event types, triggering events synchronously, queueing events for later
  * processing, and managing subscriptions via unique identifiers.
  */
-class EventManager {
+class EventManager : public Manager {
 public:
 	static constexpr const event_channel_t CHANNEL_ALL = -1;
-
 	/**
-	 * \brief Get the singleton instance of the EventManager.
-	 *
-	 * This method returns the unique instance of the EventManager, creating it if it
-	 * doesn't already exist. Ensures only one instance is active in the program.
-	 *
-	 * \return Reference to the singleton instance of the EventManager.
+	 * \param mediator A reference to a Mediator object used for transfering managers.
 	 */
-	static EventManager & get_instance();
-
+	EventManager(Mediator & mediator);
 	/**
 	 * \brief Subscribe to a specific event type.
 	 *
@@ -108,13 +102,6 @@ public:
 
 private:
 	/**
-	 * \brief Default constructor for the EventManager.
-	 *
-	 * Constructor is private to enforce the singleton pattern.
-	 */
-	EventManager() = default;
-
-	/**
 	 * \struct QueueEntry
 	 * \brief Represents an entry in the event queue.
 	 */
diff --git a/src/crepe/manager/LoopTimerManager.cpp b/src/crepe/manager/LoopTimerManager.cpp
new file mode 100644
index 0000000..a306eb7
--- /dev/null
+++ b/src/crepe/manager/LoopTimerManager.cpp
@@ -0,0 +1,94 @@
+#include <chrono>
+#include <thread>
+
+#include "../util/Log.h"
+
+#include "LoopTimerManager.h"
+
+using namespace crepe;
+using namespace std::chrono_literals;
+LoopTimerManager::LoopTimerManager(Mediator & mediator) : Manager(mediator) {
+	this->mediator.loop_timer = *this;
+	dbg_trace();
+}
+
+void LoopTimerManager::start() {
+	this->last_frame_time = std::chrono::steady_clock::now();
+
+	this->elapsed_time = 0s;
+	// by starting the elapsed_fixed_time at (0 - fixed_delta_time) in milliseconds it calls a fixed update at the start of the loop.
+	this->elapsed_fixed_time
+		= -std::chrono::duration_cast<ElapsedTime_t>(this->fixed_delta_time);
+	this->delta_time = 0s;
+}
+
+void LoopTimerManager::update() {
+	TimePoint_t current_frame_time
+		= std::chrono::steady_clock::now();
+	// Convert to duration in seconds for delta time
+	this->delta_time = current_frame_time - last_frame_time;
+
+	if (this->delta_time > this->maximum_delta_time) {
+		this->delta_time = this->maximum_delta_time;
+	}
+	if (this->delta_time > 0s) {
+		this->actual_fps = 1.0 / this->delta_time.count();
+	} else {
+		this->actual_fps = 0;
+	}
+	this->elapsed_time += std::chrono::duration_cast<ElapsedTime_t>(this->delta_time);
+	this->last_frame_time = current_frame_time;
+}
+
+Duration_t LoopTimerManager::get_delta_time() const {return this->delta_time * this->time_scale;}
+
+ElapsedTime_t LoopTimerManager::get_elapsed_time() const { return this->elapsed_time; }
+
+void LoopTimerManager::advance_fixed_elapsed_time() {
+	this->elapsed_fixed_time += std::chrono::duration_cast<ElapsedTime_t>(this->fixed_delta_time);
+}
+
+void LoopTimerManager::set_target_framerate(unsigned fps) {
+	this->target_fps = fps;
+	//check if fps is lower or equals 0
+	if (fps <= 0) return;
+	// target time per frame in seconds
+	this->frame_target_time = Duration_t(1s) / this->target_fps;
+}
+
+unsigned LoopTimerManager::get_fps() const { return this->actual_fps; }
+
+void LoopTimerManager::set_time_scale(double value) { this->time_scale = value; }
+
+float LoopTimerManager::get_time_scale() const { return this->time_scale; }
+
+void LoopTimerManager::enforce_frame_rate() {
+	TimePoint_t current_frame_time
+		= std::chrono::steady_clock::now();
+	Duration_t frame_duration = current_frame_time - this->last_frame_time;
+	// Check if frame duration is less than the target frame time
+	if (frame_duration < this->frame_target_time) {
+		std::chrono::microseconds delay_time
+			= std::chrono::duration_cast<std::chrono::microseconds>(this->frame_target_time
+																	- frame_duration);
+
+		if (delay_time.count() > 0) {
+			std::this_thread::sleep_for(delay_time);
+		}
+	}
+}
+
+Duration_t LoopTimerManager::get_lag() const {
+	return (this->elapsed_time - this->elapsed_fixed_time);
+}
+
+Duration_t LoopTimerManager::get_scaled_fixed_delta_time() const {
+	return this->fixed_delta_time * this->time_scale;
+}
+void LoopTimerManager::set_fixed_delta_time(float seconds) {
+	this->fixed_delta_time = Duration_t(seconds);
+}
+
+Duration_t LoopTimerManager::get_fixed_delta_time() const {
+	return this->fixed_delta_time;
+}
diff --git a/src/crepe/manager/LoopTimerManager.h b/src/crepe/manager/LoopTimerManager.h
new file mode 100644
index 0000000..c5f3cb0
--- /dev/null
+++ b/src/crepe/manager/LoopTimerManager.h
@@ -0,0 +1,173 @@
+#pragma once
+
+#include <chrono>
+
+#include "Manager.h"
+
+namespace crepe {
+typedef std::chrono::duration<float> Duration_t;
+typedef std::chrono::duration<unsigned long long, std::micro> ElapsedTime_t;
+typedef std::chrono::steady_clock::time_point TimePoint_t;
+/**
+ * \brief Manages timing and frame rate for the game loop.
+ * 
+ * The LoopTimerManager class is responsible for calculating and managing timing functions 
+ * such as delta time, frames per second (FPS), fixed time steps, and time scaling. It ensures 
+ * consistent frame updates and supports game loop operations, such as handling fixed updates 
+ * for physics and other time-sensitive operations.
+ */
+class LoopTimerManager : public Manager {
+public:
+	/**
+	 * \param mediator A reference to a Mediator object used for transfering managers.
+	 */
+	LoopTimerManager(Mediator & mediator);
+	/**
+	 * \brief Get the current delta time for the current frame.
+	 *	
+	 * This value represents the estimated frame duration of the current frame.
+	 * This value can be used in the frame_update to convert pixel based values to time based values.
+	 * 
+	 * \return Delta time in seconds since the last frame.
+	 */
+	Duration_t get_delta_time() const;
+
+	/**
+	 * \brief Get the current elapsed time (total time passed )
+	 *
+	 * \note The current game time may vary from real-world elapsed time. It is the cumulative
+	 * sum of each frame's delta time.
+	 *
+	 * \return Elapsed game time in seconds.
+	 */
+	ElapsedTime_t get_elapsed_time() const;
+
+	/**
+	 * \brief Set the target frames per second (FPS).
+	 *
+	 * \param fps The desired frames rendered per second.
+	 */
+	void set_target_framerate(unsigned fps);
+
+	/**
+	 * \brief Get the current frames per second (FPS).
+	 *
+	 * \return Current FPS.
+	 */
+	unsigned get_fps() const;
+
+	/**
+	 * \brief Get the current time scale.
+	 *
+	 * \return The current time scale, where (0 = pause, < 1 = slow down, 1 = normal speed, > 1 = speed up).
+	 * up the game.
+	 */
+	float get_time_scale() const;
+
+	/**
+	 * \brief Set the time scale.
+	 *
+	 * time_scale is a value that changes the delta time that can be retrieved using get_delta_time function. 
+	 * 
+	 * \param time_scale The desired time scale (0 = pause, < 1 = slow down, 1 = normal speed, > 1 = speed up).
+	 */
+	void set_time_scale(double time_scale);
+
+	/**
+	 * \brief Get the fixed delta time in seconds without scaling by the time scale.
+	 *
+	 * This value is used in the LoopManager to determine how many times 
+	 * the fixed_update should be called within a given interval.
+	 *
+	 * \return The unscaled fixed delta time in seconds.
+	 */
+	Duration_t get_fixed_delta_time() const;
+
+	/**
+	 * \brief Set the fixed_delta_time in seconds.
+	 * 
+	 * \param seconds fixed_delta_time in seconds.
+	 * 
+	 * The fixed_delta_time value is used to determine how many times per second the fixed_update and process_input functions are called.
+	 * 
+	 */
+	void set_fixed_delta_time(float seconds);
+
+	/**
+	 * \brief Retrieves the scaled fixed delta time in seconds.
+	 *
+	 * The scaled fixed delta time is the timing value used within the `fixed_update` function. 
+	 * It is adjusted by the time_scale to account for any changes in the simulation's 
+	 * speed.
+	 *
+	 * \return The fixed delta time, scaled by the current time scale, in seconds.
+	 */
+	Duration_t get_scaled_fixed_delta_time() const;
+
+private:
+	//! Friend relation to use start,enforce_frame_rate,get_lag,update,advance_fixed_update.
+	friend class LoopManager;
+	/**
+	 * \brief Start the loop timer.
+	 *
+	 * Initializes the timer to begin tracking frame times.
+	 */
+	void start();
+	/**
+	 * \brief Enforce the frame rate limit.
+	 *
+	 * Ensures that the game loop does not exceed the target FPS by delaying frame updates as
+	 * necessary.
+	 */
+	void enforce_frame_rate();
+	/**
+	 * \brief Get the accumulated lag in the game loop.
+	 *
+	 * Lag represents the difference between the target frame time and the actual frame time,
+	 * useful for managing fixed update intervals.
+	 *
+	 * \return Accumulated lag in seconds.
+	 */
+	Duration_t get_lag() const;
+
+	/**
+	 * \brief Update the timer to the current frame.
+	 *
+	 * Calculates and updates the delta time for the current frame and adds it to the cumulative
+	 * game time.
+	 */
+	void update();
+
+	/**
+	 * \brief Progress the elapsed fixed time by the fixed delta time interval.
+	 *
+	 * This method advances the game's fixed update loop by adding the fixed_delta_time 
+	 * to elapsed_fixed_time, ensuring the fixed update catches up with the elapsed time.
+	 */
+	void advance_fixed_elapsed_time();
+
+private:
+	//! Target frames per second.
+	int target_fps = 60;
+	//! Actual frames per second.
+	int actual_fps = 0;
+	//! Time scale for speeding up or slowing down the game (0 = pause, < 1 = slow down, 1 = normal speed, > 1 = speed up).
+	float time_scale = 1;
+	//! Maximum delta time in seconds to avoid large jumps.
+	Duration_t maximum_delta_time{0.25};
+	//! Delta time for the current frame in seconds.
+	Duration_t delta_time{0.0};
+	//! Target time per frame in seconds
+	Duration_t frame_target_time
+		= Duration_t(1.0) / target_fps;
+	//! Fixed delta time for fixed updates in seconds.
+	Duration_t fixed_delta_time = Duration_t(1.0) / 50.0;
+	//! Total elapsed game time in microseconds.
+	ElapsedTime_t elapsed_time{0};
+	//! Total elapsed time for fixed updates in microseconds.
+	ElapsedTime_t elapsed_fixed_time{0};
+	//! Time of the last frame.
+	TimePoint_t last_frame_time;
+};
+
+} // namespace crepe
diff --git a/src/crepe/manager/Mediator.h b/src/crepe/manager/Mediator.h
index 35ac181..dfb37dc 100644
--- a/src/crepe/manager/Mediator.h
+++ b/src/crepe/manager/Mediator.h
@@ -4,8 +4,8 @@
 
 // TODO: remove these singletons:
 #include "../facade/SDLContext.h"
-#include "EventManager.h"
-#include "api/LoopTimer.h"
+
+#include "SaveManager.h"
 
 namespace crepe {
 
@@ -14,6 +14,8 @@ class SceneManager;
 class SaveManager;
 class ResourceManager;
 
+class LoopTimerManager;
+class EventManager;
 /**
  * Struct to pass references to classes that would otherwise need to be singletons down to
  * other classes within the engine hierarchy. Made to prevent constant changes to subclasses to
@@ -29,11 +31,11 @@ class ResourceManager;
 struct Mediator {
 	OptionalRef<ComponentManager> component_manager;
 	OptionalRef<SceneManager> scene_manager;
+	OptionalRef<EventManager> event_manager;
+	OptionalRef<LoopTimerManager> loop_timer;
 	OptionalRef<SaveManager> save_manager;
-	OptionalRef<EventManager> event_manager = EventManager::get_instance();
 	OptionalRef<ResourceManager> resource_manager;
 	OptionalRef<SDLContext> sdl_context = SDLContext::get_instance();
-	OptionalRef<LoopTimer> timer = LoopTimer::get_instance();
 };
 
 } // namespace crepe
diff --git a/src/crepe/manager/SceneManager.cpp b/src/crepe/manager/SceneManager.cpp
index 50a9fbb..d4ca90b 100644
--- a/src/crepe/manager/SceneManager.cpp
+++ b/src/crepe/manager/SceneManager.cpp
@@ -32,4 +32,7 @@ void SceneManager::load_next_scene() {
 
 	// Load the new scene
 	scene->load_scene();
+
+	//clear the next scene
+	next_scene.clear();
 }