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

#define NBTH 4
#define NBLOOPS 4000

sem_t sem_ready;
sem_t mutex;
sem_t queue;

int nb_stark=0;
int nb_lannister=0;

int alea() {
  return (rand()%10);
}

void lannister(int my_id) {

  sem_wait(&mutex);
  {
    while(nb_stark > 0) {
      /* il y a un homme, il faut attendre */
      sem_post(&mutex);
      sem_wait(&queue);

      sem_wait(&mutex);
    }
    nb_lannister++;
  }

  assert(nb_lannister>0);
  assert(nb_stark==0);

  sem_post(&mutex);

  printf("Un Lannister (id=%d) entre\n", my_id);
  usleep(alea());

  sem_wait(&mutex);

  assert(nb_lannister>0);
  assert(nb_stark==0);

  {
    nb_lannister--;
    if(nb_lannister == 0)
      sem_post(&queue);
    printf("Un Lannister (id=%d) sort\n", my_id);
  }
  sem_post(&mutex);

}

void stark(int my_id) {

  sem_wait(&mutex);
  {
    while(nb_lannister > 0) {
      /* il y a un Lannister, il faut attendre */
      sem_post(&mutex);
      sem_wait(&queue);

      sem_wait(&mutex);
    }
    /* plus aucun Lannister en vue, on peut entrer */
    nb_stark++;
  }

  assert(nb_stark>0);
  assert(nb_lannister==0);

  sem_post(&mutex);


  printf("Un Stark (id=%d) entre\n", my_id);
  usleep(alea());

  sem_wait(&mutex);

  assert(nb_stark>0);
  assert(nb_lannister==0);

  {
    nb_stark--;
    if(nb_stark == 0)
      sem_post(&queue);
    printf("Un Stark (id=%d) sort\n", my_id);
  }
  sem_post(&mutex);

}


void* thread_func(void* arg) {
  int my_id = *(int*)arg;
  sem_post(&sem_ready);


  int i;
  for(i=0; i<NBLOOPS; i++) {
    int n = rand()%2;
    if(n) {
      lannister(my_id);
    } else {
      stark(my_id);
    }
  }
  return NULL;
}

int main(int argc, char**argv) {
  sem_init(&sem_ready, 0, 0);
  sem_init(&mutex, 0, 1);
  sem_init(&queue, 0, 0);

  int i;
  pthread_t tids[NBTH];

  for(i=0; i<NBTH; i++) {
    pthread_create(&tids[i], NULL, thread_func, &i);
    sem_wait(&sem_ready);
  }


  for(i=0; i<NBTH; i++) {
    pthread_join(tids[i], NULL);
  }
  return 0;
}