#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <semaphore.h>

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

#include <err.h>
#include <errno.h>


int main() {
	pid_t pid;
	sem_t *sem1, *sem2;
	int error, saved_errno, status;
	int v1, v2;
	int pd[2];
	char er[1];
	char ok[1];
	char buf[1];
	size_t size;

	*er = 'X';
	*ok = 'O';

	if (pipe(pd) == -1)
		err(1, "Cannot create sync pipe");

	sem1 = sem_open("/test-sem", O_CREAT | O_EXCL, S_IRWXU, 1);
	if (sem1 == SEM_FAILED)
		err(1,"Cannot create test /test-sem semaphore");

	char c = getchar();
	pid = fork();

	if ( pid == -1)
		err(1, "Unable to fork test process");

	if (pid == 0) {

		close(pd[0]);

		error = sem_unlink("/test-sem");

		if (error) {
			perror("Cannot unlink semaphore /test-sem");
			goto error;
		}

		sem2 = sem_open("/test-sem", O_CREAT | O_EXCL, S_IRWXU, 2);

		if (sem2 == SEM_FAILED) {
			perror("Cannot re-create semaphore /test-sem");
			goto error;
		}

		write(pd[1], ok, 1);

		error = wait(&status);
		if (error && errno == EINTR)
			goto error;

		return(status);
error:
		write(pd[1], er, 1);
		close(pd[1]);
		error = wait(&status);
		if (error && errno == EINTR)
			goto error;

		errx(1, "TEST UNRESOLVED");

		return(1);

	} else {

		close(pd[1]);
		size = read(pd[0], buf, 1);

		if (size != 1)
			err(2, "process 2 cannot wait for process 1");

		if (*buf == *er)
			errx(2, "Test error");
		else {

			sem2 = sem_open("/test-sem", 0);

			if (sem2 == SEM_FAILED)
				err(2, "process 2 failed reopeing semaphore");

			// sem_unlink("/test-sem");

			sem_getvalue(sem1, &v1);
			sem_getvalue(sem2, &v2);
			printf("v1 = %d and v2 = %d\n", v1, v2);
			if (v1 == v2) {
				errx(2, "*** TEST FAILED. NOT POSIX ***");
			} else {
				errx(0, "*** TEST SUCCESS. POSIX CONFORMANT ***");
			}
		}

	}
}