1 files changed, 147 insertions, 0 deletions
diff --git a/src/crepe/api/LoopTimer.h b/src/crepe/api/LoopTimer.h
new file mode 100644
index 0000000..85687be
--- /dev/null
+++ b/src/crepe/api/LoopTimer.h
@@ -0,0 +1,147 @@
+#pragma once
+
+#include <chrono>
+#include <cstdint>
+
+namespace crepe {
+
+class LoopTimer {
+public:
+	/**
+     * \brief Get the singleton instance of LoopTimer.
+     *
+     * \return A reference to the LoopTimer instance.
+     */
+	static LoopTimer & get_instance();
+
+	/**
+     * \brief Get the current delta time for the current frame.
+     *
+     * \return Delta time in seconds since the last frame.
+     */
+	double get_delta_time() const;
+
+	/**
+     * \brief Get the current game time.
+     *
+     * \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.
+     */
+	double get_current_time() const;
+
+	/**
+     * \brief Set the target frames per second (FPS).
+     *
+     * \param fps The desired frames rendered per second.
+     */
+	void set_fps(int fps);
+
+	/**
+     * \brief Get the current frames per second (FPS).
+     *
+     * \return Current FPS.
+     */
+	int get_fps() const;
+
+	/**
+     * \brief Get the current game scale.
+     *
+     * \return The current game scale, where 0 = paused, 1 = normal speed, and values > 1 speed up the game.
+     */
+	double get_game_scale() const;
+
+	/**
+     * \brief Set the game scale.
+     *
+     * \param game_scale The desired game scale (0 = pause, 1 = normal speed, > 1 = speed up).
+     */
+	void set_game_scale(double game_scale);
+
+private:
+	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 fixed delta time for consistent updates.
+     *
+     * Fixed delta time is used for operations that require uniform time steps,
+     * such as physics calculations.
+     *
+     * \return Fixed delta time in seconds.
+     */
+	double get_fixed_delta_time() const;
+
+	/**
+     * \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.
+     */
+	double get_lag() const;
+
+	/**
+     * \brief Construct a new LoopTimer object.
+     *
+     * Private constructor for singleton pattern to restrict instantiation
+     * outside the class.
+     */
+	LoopTimer();
+
+	/**
+     * \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 Advance the game loop by a fixed update interval.
+     *
+     * This method progresses the game state by a consistent, fixed time step,
+     * allowing for stable updates independent of frame rate fluctuations.
+     */
+	void advance_fixed_update();
+
+private:
+	//! Current frames per second
+	int fps = 50;
+	//! Current game scale
+	double game_scale = 1;
+	//! Maximum delta time in seconds to avoid large jumps
+	std::chrono::duration<double> maximum_delta_time{0.25};
+	//! Delta time for the current frame in seconds
+	std::chrono::duration<double> delta_time{0.0};
+	//! Target time per frame in seconds
+	std::chrono::duration<double> frame_target_time
+		= std::chrono::seconds(1) / fps;
+	//! Fixed delta time for fixed updates in seconds
+	std::chrono::duration<double> fixed_delta_time
+		= std::chrono::seconds(1) / 50;
+	//! Total elapsed game time in seconds
+	std::chrono::duration<double> elapsed_time{0.0};
+	//! Total elapsed time for fixed updates in seconds
+	std::chrono::duration<double> elapsed_fixed_time{0.0};
+	//! Time of the last frame
+	std::chrono::steady_clock::time_point last_frame_time;
+};
+
+} // namespace crepe