#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <errno.h>
#include <string.h>

char *pidfile;

char *get_cronolog(void) {
	int len = 0;
	char *path, *tmp = NULL;
	struct stat st;

	path = strtok(getenv("PATH"), ":");
	while(path != NULL) {
		len = (strlen(path) + strlen("/cronolog") + 1);
		tmp = (char *)malloc(len);
		snprintf(tmp, len, "%s%s", path, "/cronolog");

		if(stat(tmp, &st) == -1) {
			if(errno == ENOENT) {
				free(tmp);
				path = strtok(NULL, ":");
				continue;
			}

			fprintf(stderr, "stat(): Error: %s\n", strerror(errno));
			free(tmp);
			return NULL;
		}

		if(st.st_mode & S_IFREG)
			return tmp;
		else {
			free(tmp);
			return NULL;
		}
	}

	if(tmp != NULL)
		free(tmp);

	return NULL;
}

void die(int sig) {
	/* kill off children */
	kill(0, SIGTERM);
	/* remove pid file, quit */
	unlink(pidfile);
	exit(0);
}

struct sigaction sigdie = { .sa_handler = die };

int main(int argc, char *argv[]) {
	time_t t = 0;
	pid_t pid = 0;
	int fd, pidfd, pidlen = 16;
	char *fifo, *log, *cronolog, pidstr[16];

	if (argc != 4) {
		fprintf(stderr, "Usage: %s /path/to/pidfile /path/to/fifo"
				" /path/to/logs/%%Y%%m%%d.log\n", argv[0]);
		exit(1);
	}

	pidfile = argv[1];
	fifo = argv[2];
	log = argv[3];

	cronolog = get_cronolog();
	if(cronolog == NULL) {
		fprintf(stderr, "cronolog not found in PATH\n");
		exit(1);
	}

	/* Test for fifo access, leave open for use */
	/* O_NONBLOCK allows us to fork into the background */
	fd = open(fifo, O_RDONLY|O_NONBLOCK);
	if (fd == -1) {
		fprintf(stderr, "Cannot open fifo %s: %s\n", fifo, strerror(errno));
		free(cronolog);
		exit(1);
	}

	pid = fork();

	if (pid == 0) {
		/* CHILD 0 */

		/* Record pid to pidfile */
		pidfd = open(pidfile, O_WRONLY|O_CREAT|O_EXCL, 0644);
		if (pidfd == -1) {
			fprintf(stderr, "Cannot create and open pid file %s: %s\n",
			pidfile, strerror(errno));
			free(cronolog);
			exit(1);
		} else {
			pidlen = snprintf(pidstr, pidlen, "%d\n", getpid());
			if(write(pidfd, pidstr, pidlen) == -1) {
				fprintf(stderr, "Cannot write pid file %s: %s\n", pidfile, strerror(errno));
				free(cronolog);
				exit(1);
			}
			close(pidfd);
		}

		/* close shell output */
		close(0);
		close(1);
		close(2);

		/* set a process group for easy cleanup */
		setpgrp();
		sigaction(SIGTERM, &sigdie, NULL);

		/* keep the cronolog process open */
		while (1) {
			t = time(NULL);
			pid = fork();
			if (pid == 0) {
				/* CHILD 1 */

				/* replace stdin with fifo */
				dup2(fd, 0);
				/* unset O_NONBLOCK */
				fcntl(0, F_SETFL, 0);
				/* exec cronolog */
				execl(cronolog, cronolog, log, (char *) 0);
				/* filure! give up on life */
				free(cronolog);
				exit(1);
			} else {
				/* PARENT 1 */
				/* watch child 1 */
				waitpid(pid, NULL, 0);
				if (time(NULL) - t < 2) {
					/* restarting too fast, wait 10 seconds */
					sleep(10);
				}
			}
		}
	}

	/* PARENT 0 exits */
	close(fd);

	free(cronolog);

	return 0;
}

/* vim: set ts=4 sw=4 tw=80: */