#pragma once

#include <cstdint>

namespace crepe{
class LoopTimer {
public:
/**
 * \brief Get the singleton instance of LoopTimer.
 *
 * \return A reference to the LoopTimer instance.
 */
static LoopTimer& getInstance();

/**
 * \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 the real-world elapsed time.
 * It is the cumulative sum of each frame's delta time.
 *
 * \return Elapsed game time in milliseconds.
 */
int get_current_time() const;

/**
 * \brief Set the target frames per second (FPS).
 *
 * \param fps The number of frames that should be 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;
void start();
void enforce_frame_rate();
double get_fixed_delta_time() const;
double get_lag() const;
LoopTimer();
void update();
void advance_fixed_update();
private:
int fps = 50;                       ///< Current frames per second
double game_scale = 1;              ///< Current game scale
double maximum_delta_time = 0.25;   ///< Maximum delta time to avoid large jumps
double delta_time = 0;              ///< Delta time for the current frame
double frame_target_time = 1.0 / fps; ///< Target time per frame in seconds
double fixed_delta_time = 0.02;     ///< Fixed delta time for fixed updates
double elapsed_time = 0;             ///< Total elapsed game time
double elapsed_fixed_time = 0;      ///< Total elapsed time for fixed updates
uint64_t last_frame_time = 0;       ///< Time of the last frame
};

} // namespace crepe::api