#include <assert.h>
#include <fcntl.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "pingpong.h"

typedef struct pparg {
  sem_t *sem_ping; // Tell ping to wake up
  sem_t *sem_pong; // Tell pong to wake up
  size_t *shared;
} ppargs_t;

void *
pong (void * _args)
{
  ppargs_t *args = (ppargs_t *) _args;

  while (1)
    {
      sem_wait (args->sem_pong);

      printf ("PONG!\n");

      if (*(args->shared) == 0)
        {
          break;
        }
      else
        {
          sem_post (args->sem_ping);
        }
    }

  printf ("PONG: Game over\n");
  pthread_exit (NULL);
}

void
ping (size_t *count)
{
  pthread_t pong_thread;
  sem_t sem_ping;
  sem_t sem_pong;

  if (sem_init (&sem_ping, 0, 1) != 0)
    {
      perror ("sem_init sem_ping");
      return;
    }
  if (sem_init (&sem_pong, 0, 0) != 0)
    {
      perror ("sem_init sem_pong");
      sem_destroy (&sem_ping);
      return;
    }

  ppargs_t args;
  args.sem_ping = &sem_ping;
  args.sem_pong = &sem_pong;
  args.shared = count;

  if (pthread_create (&pong_thread, NULL, pong, (void *)&args) != 0)
    {
      perror ("pthread_create");
      sem_destroy (&sem_ping);
      sem_destroy (&sem_pong);
      return;
    }

  while (1)
    {
      sem_wait (&sem_ping);

      (*count)--;
      printf ("PING!\n");

      sem_post (&sem_pong);

      if (*count == 0)
          break;
    }

  // After PONG prints game over and exits, do the same for PING
  pthread_join (pong_thread, NULL);
  printf ("PING: Game over\n");

  sem_destroy (&sem_ping);
  sem_destroy (&sem_pong);
}