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

/* the number of threads */
int num_threads;

/* our counter and condition */
int counter = 0;
pthread_cond_t condition;
pthread_mutex_t condition_mutex;

/* the function called for each thread */
void* worker(void* idp) {
    /* get our thread id */
    int id = * (int*) idp;

    /* we start to work */
    printf("Thread %d starting!\n", id);

    /* simulate the threads taking slightly different amounts of time by sleeping
     * for our thread id seconds */
    sleep(id);
    printf("Thread %d is done its work!\n", id);


    /***************** begin barrier here *****************/
    /* lock the condition and increment the counter */
    pthread_mutex_lock(&condition_mutex);
    counter++;

    /* if all the threads have incremented counter */
    if (counter == num_threads) {
        /* reset the counter and broadcast the event to all waiting threads */
        counter = 0;
        pthread_cond_broadcast(&condition);
    } else {
        /* otherwise not all threads are here yet, so we need to wait */
        pthread_cond_wait(&condition, &condition_mutex);
    }
    /* unlock the condition mutex */
    pthread_mutex_unlock(&condition_mutex);
    /***************** end barrier here *****************/




    printf("Thread %d is past the barrier!\n", id); 
    pthread_exit(NULL);
}

int main (int argc, char** argv) {
    /* get the number of threads */
    if (argc < 2) {
        printf("Pass the number of threads to use!\n");
        pthread_exit(0);
    } else {
        num_threads = atoi(argv[1]);
    }

    /* initialize the mutex and condition */
    pthread_mutex_init(&condition_mutex, NULL);
    pthread_cond_init(&condition, NULL);

    /* an array of threads */
    pthread_t threads[num_threads];
    int ids[num_threads];
    int i;

    /* spawn all threads */
    for (i = 0; i < num_threads; i++) {
        ids[i] = i;
        pthread_create(&threads[i], NULL, worker, &ids[i]);
    }

    /* join all threads */
    for (i = 0; i < num_threads; i++) {
        pthread_join(threads[i], NULL);
    }

    pthread_exit(0);
}