#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <err.h>
#include <string.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/wait.h>

#include "status.h"

char *const run_path[] = { "./run", NULL };

void
start_proc()
{
	pid_t p = fork();
	if (p == 0) {
		execv(run_path[0], run_path);
	} else if (p > 0) {
		waitpid(p, NULL, 0);
	} else {
		err(1, "fork()");
	}
}

int
acquire_lock()
{
	int lock_fd;

	if ((lock_fd = open("supervise/lock", O_CREAT | O_TRUNC | O_RDONLY, 0600)) == -1)
		err(1, "open()");

	if (flock(lock_fd, LOCK_EX | LOCK_NB) == -1) {
		if (errno == EWOULDBLOCK) {
			fprintf(stderr, "Could not acquire lock\n");
			exit(1);
		} else {
			err(1, "flock()");
		}
	}

	return lock_fd;
}

void
update_status()
{
	int fd, r;
	unsigned char status[18];

	if ((fd = open("supervise/status.new", O_CREAT | O_TRUNC | O_WRONLY | 0644)) == -1) {
		perror("open()");
		return;
	}

	if ((r = write(fd, status, sizeof(status))) == -1)
		perror("write()");

	if (close(fd) == -1)
		perror("close()");

	if (r < sizeof(status)) {
		fprintf(stderr, "Failed to fully write status.new\n");

		if (unlink("supervise/status.new") == -1)
			perror("unlink()");

		return;
	}

	if (rename("supervise/status.new", "supervise/status") == -1)
		perror("rename()");
}

void
setup_signals()
{
	struct sigaction act;
	memset(&act, 0, sizeof(act));

	act.sa_handler = SIG_IGN;
	if (sigaction(SIGHUP, &act, NULL) == -1)
		err(1, "sigaction()");
	if (sigaction(SIGINT, &act, NULL) == -1)
		err(1, "sigaction()");
	if (sigaction(SIGTERM, &act, NULL) == -1)
		err(1, "sigaction()");
}

void
reset_signals()
{
	struct sigaction act;
	memset(&act, 0, sizeof(act));

	act.sa_handler = SIG_DFL;
	if (sigaction(SIGHUP, &act, NULL) == -1)
		err(1, "sigaction()");
	if (sigaction(SIGINT, &act, NULL) == -1)
		err(1, "sigaction()");
	if (sigaction(SIGTERM, &act, NULL) == -1)
		err(1, "sigaction()");
}

int
main(int argc, char **argv)
{
	int ctrl_fd, ok_fd, lock_fd, kq;
	struct kevent evt[6], revt[6];

	if (argc != 2)
		errx(1, "Usage: %s <dir>\n", argv[0]);

	if (chdir(argv[1]) == -1)
		err(1, "chdir()");

	if (mkdir("supervise", 0700) == -1 && errno != EEXIST)
		err(1, "mkdir()");

	lock_fd = acquire_lock();

	if (mkfifo("supervise/control", 0600) == -1 && errno != EEXIST)
		err(1, "mkfifo()");

	if (mkfifo("supervise/ok", 0600) == -1 && errno != EEXIST)
		err(1, "mkfifo()");

	setup_signals();

	kq = kqueue();
	if (kq == -1)
		err(1, "kqueue()");

	if ((ctrl_fd = open("supervise/control", O_RDONLY | O_NONBLOCK | O_CLOEXEC)) == -1)
		err(1, "open()");

	if ((ok_fd = open("supervise/ok", O_RDONLY | O_NONBLOCK | O_CLOEXEC)) == -1)
		err(1, "open()");

	EV_SET(&evt[0], SIGHUP,  EVFILT_SIGNAL, EV_ADD | EV_ENABLE, 0, 0, 0);
	EV_SET(&evt[1], SIGINT,  EVFILT_SIGNAL, EV_ADD | EV_ENABLE, 0, 0, 0);
	EV_SET(&evt[2], SIGTERM, EVFILT_SIGNAL, EV_ADD | EV_ENABLE, 0, 0, 0);
	EV_SET(&evt[3], SIGCHLD, EVFILT_SIGNAL, EV_ADD | EV_ENABLE, 0, 0, 0);
	EV_SET(&evt[4], ctrl_fd, EVFILT_READ,   EV_ADD | EV_ENABLE, 0, 0, 0);
	//EV_SET(&evt[5], ok_fd,   EVFILT_READ,   EV_ADD | EV_ENABLE, 0, 0, 0);

	if (kevent(kq, evt, 5, NULL, 0, NULL) == -1)
		err(1, "kevent()");

	for (;;) {
		start_proc();
		break;

		kevent(kq, NULL, 0, revt, 5, NULL);
	}

	if (close(ctrl_fd) == -1)
		perror("close()");

	if (close(lock_fd) == -1)
		perror("close()");

	reset_signals();

	return 0;
}