#define _GNU_SOURCE
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#define SLEEP_TIME  10
#define FIBER_STACK (1024 * 64)

int proc;

int thread_function(void* arg) {
    int thread = (int)((unsigned long)arg);
    printf("in process %d thread %d\n", proc, thread);
    for (int i = 0; i < SLEEP_TIME; i++) {
        printf("in process %d thread %d: %d\n", proc, thread, i);
        sleep(1);
    }
    return 0;
}

int main(int argc, char** argv) {
    int nprocs = 1, nthreads = 1;
    int thread;

    setvbuf(stdout, NULL, _IONBF, 0);

    for (int i = 1; i < argc; i++) {
        if (!strcmp(argv[i], "-n") && i + 1 < argc) {
            nprocs = atoi(argv[i + 1]);
            i++;
            continue;
        }

        if (!strcmp(argv[i], "-t") && i + 1 < argc) {
            nthreads = atoi(argv[i + 1]);
            i++;
            continue;
        }
    }

    for (proc = nprocs; proc > 1; proc--) {
        int ret = fork();

        if (ret < 0) {
            perror("fork");
            _exit(1);
        }

        if (!ret)
            break;
    }

    for (thread = 1; thread < nthreads; thread++) {
        void* stack = malloc(FIBER_STACK);
        if (!stack) {
            perror("malloc: could not allocate stack");
            _exit(1);
        }

        clone(&thread_function, (void*)stack + FIBER_STACK,
              CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_VM,
              (void*)((unsigned long)thread + 1));
    }

    for (int i = 0; i < SLEEP_TIME; i++) {
        printf("in process %d thread 1: %d\n", proc, i);
        sleep(1);
    }
    return 0;
}