/*
    pthreads_sample.c
    Jeff Ondich, 6 March 2022

    A simple threaded program that lets us see a typical use of
    threads. One thread is an extremely simple user interface
    thread (printing a prompt and waiting for a newline), while
    the other is a trivial "computational" thread, counting
    until the UI thread tells it to stop.

    The two threads communicate through the global variable
    time_to_quit.
    

    To compile on mantis:

        gcc -Wall -o pthreads_sample pthreads_sample.c -lpthread

    On some systems, you don't need to link the pthread library
    explicitly, so it looks like this instead:

        gcc -Wall -o pthreads_sample pthreads_sample.c
*/

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

bool time_to_quit = false;

void *ui_thread_main(void *arg);
void *worker_thread_main(void *arg);

int main() {
    pthread_t ui_thread, worker_thread;

    // Spawn the threads
    if (pthread_create(&ui_thread, NULL, ui_thread_main, 0) != 0) {
        perror("Can't create UI thread");
        exit(1);
    }

    if (pthread_create(&worker_thread, NULL, worker_thread_main, 0) != 0) {
        perror("Can't create worker thread");
        exit(1);
    }

    // Detach the worker thread. This means that once the worker thread finishes,
    // all its associated resources will get cleaned up automatically.
    if (pthread_detach(worker_thread) != 0) {
        fprintf(stderr, "Failed to detach worker thread. I'm going to go pout.\n");
        exit(1);
    }

    // Wait for the UI thread to return. If you don't wait for it,
    // we will return from main(), and thus shut down the whole
    // process, including the threads.
    pthread_join(ui_thread, NULL);

    return 0;
}

void *ui_thread_main(void *arg) {
    char buffer[100];
    printf("[UI thread] Hit Enter when you're ready to be done\n");
    fgets(buffer, 100, stdin);
    time_to_quit = true;
    return NULL;
}

void *worker_thread_main(void *arg) {
    long counter = 0;
    while(!time_to_quit) {
        counter++;
    }

    printf("[Worker thread] I counted this high: %ld\n", counter);
    return NULL;
}