// SPDX-License-Identifier: GPL-2.0
/*
 * Simple poll on a file.
 *
 * Copyright (c) 2024 Google LLC.
 */

#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define BUFSIZE 4096

/*
 * Usage:
 *  poll [-I|-P] [-t timeout] FILE
 */
int main(int argc, char *argv[])
{
        struct pollfd pfd = {.events = POLLIN};
        char buf[BUFSIZE];
        int timeout = -1;
        int ret, opt;

        while ((opt = getopt(argc, argv, "IPt:")) != -1) {
                switch (opt) {
                case 'I':
                        pfd.events = POLLIN;
                        break;
                case 'P':
                        pfd.events = POLLPRI;
                        break;
                case 't':
                        timeout = atoi(optarg);
                        break;
                default:
                        fprintf(stderr, "Usage: %s [-I|-P] [-t timeout] FILE\n",
                                argv[0]);
                        return -1;
                }
        }
        if (optind >= argc) {
                fprintf(stderr, "Error: Polling file is not specified\n");
                return -1;
        }

        pfd.fd = open(argv[optind], O_RDONLY);
        if (pfd.fd < 0) {
                fprintf(stderr, "failed to open %s", argv[optind]);
                perror("open");
                return -1;
        }

        /* Reset poll by read if POLLIN is specified. */
        if (pfd.events & POLLIN)
                do {} while (read(pfd.fd, buf, BUFSIZE) == BUFSIZE);

        ret = poll(&pfd, 1, timeout);
        if (ret < 0 && errno != EINTR) {
                perror("poll");
                return -1;
        }
        close(pfd.fd);

        /* If timeout happned (ret == 0), exit code is 1 */
        if (ret == 0)
                return 1;

        return 0;
}