#include <semaphore.h>
#include <stdatomic.h>

#include "atomic.h"
#include "threads_impl.h"

int sem_timedwait(sem_t* restrict sem, const struct timespec* restrict at) {
  if (!sem_trywait(sem))
    return 0;

  int spins = 100;
  while (spins-- && atomic_load(&sem->_s_value) <= 0 && !atomic_load(&sem->_s_waiters))
    a_spin();

  while (sem_trywait(sem)) {
    atomic_fetch_add(&sem->_s_waiters, 1);
    a_cas_shim(&sem->_s_value, 0, -1);
    int r = __timedwait(&sem->_s_value, -1, CLOCK_REALTIME, at);
    if (r) {
      errno = r;
      return -1;
    }
  }
  return 0;
}