/// @file t_semop.c
/// @brief Tests semop between processes.
/// @copyright (c) 2014-2023 This file is distributed under the MIT License.
/// See LICENSE.md for details.

#include "sys/sem.h"
#include "stdio.h"
#include "sys/ipc.h"
#include "sys/errno.h"
#include "sys/wait.h"
#include "stdlib.h"
#include "sys/unistd.h"
#include "fcntl.h"

int main(int argc, char *argv[])
{
    struct sembuf sops[6];
    sops[0].sem_num = 0;
    sops[0].sem_op  = -1;
    sops[0].sem_flg = 0;

    sops[1].sem_num = 1;
    sops[1].sem_op  = -1;
    sops[1].sem_flg = 0;

    sops[2].sem_num = 2;
    sops[2].sem_op  = -1;
    sops[2].sem_flg = 0;

    sops[3].sem_num = 0;
    sops[3].sem_op  = 1;
    sops[3].sem_flg = 0;

    sops[4].sem_num = 1;
    sops[4].sem_op  = 1;
    sops[4].sem_flg = 0;

    sops[5].sem_num = 2;
    sops[5].sem_op  = 1;
    sops[5].sem_flg = 0;

    int status;

    //create a semaphore set
    int semid = semget(17, 4, IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);

    //set the values of the semaphores
    unsigned short values[] = { 0, 0, 0, 1 };

    union semun arg;
    arg.array = values;

    if (semctl(semid, 0, SETALL, &arg) == -1) {
        perror("Failed to set semaphores");
        return 1;
    }

    if (!fork()) {
        semop(semid, &sops[0], 1);
        printf("cheers!\n");
        exit(0);
    }
    if (!fork()) {
        semop(semid, &sops[1], 1);
        printf("course, ");
        semop(semid, &sops[3], 1);
        exit(0);
    }
    if (!fork()) {
        semop(semid, &sops[2], 1);
        printf("systems ");
        semop(semid, &sops[4], 1);
        exit(0);
    }
    if (!fork()) {
        printf("From the operating ");
        semop(semid, &sops[5], 1);
        exit(0);
    }
    for (int n = 0; n < 4; n++) {
        wait(&status);
    }
    if (semctl(semid, 0, IPC_RMID, 0) == -1) {
        perror("Failed to remove IPC");
        return 1;
    }
    return 0;
}