#define _POSIX_C_SOURCE 200809L

#include "timing.h"
#include <time.h>

double timing_get_seconds(void) {
  struct timespec ts;
  // We enforce monotonic clock so system daylight saving updates don't break
  // delta logic
  clock_gettime(CLOCK_MONOTONIC, &ts);
  return (double)ts.tv_sec + (double)ts.tv_nsec / 1.0e9;
}

void timing_sleep_us(unsigned int microseconds) {
  struct timespec req;
  req.tv_sec = microseconds / 1000000;
  req.tv_nsec = (microseconds % 1000000) * 1000L;
  nanosleep(&req, NULL);
}

void timing_limit_fps(double frame_start_time, int target_fps) {
  if (target_fps <= 0) {
    return;
  }

  double target_frame_time = 1.0 / (double)target_fps;
  double elapsed = timing_get_seconds() - frame_start_time;
  double sleep_time = target_frame_time - elapsed;

  // Attempt dynamic throttle
  if (sleep_time > 0.0) {
    unsigned int sleep_us = (unsigned int)(sleep_time * 1.0e6);
    timing_sleep_us(sleep_us);
  }
}