/*
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * resizewin
 *
 * Query terminal for size and inform the kernel
 *
 * Copyright 2015 EMC / Isilon Storage Division
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <termios.h>
#include <unistd.h>

/* screen doesn't support ESC[18t (return terminal size) so do it the hard way */
static const char query[] =
    "\0337"             /* Save cursor position */
    "\033[r"            /* Scroll whole screen */
    "\033[999;999H"     /* Move cursor */
    "\033[6n"           /* Get cursor position */
    "\0338";            /* Restore cursor position */

static void
usage(void)
{

        fprintf(stderr, "usage: resizewin [-z]\n");
        exit(1);
}

int
main(int argc, char **argv)
{
        struct termios old, new;
        struct winsize w;
        struct timeval then, now;
        char data[20];
        int ch, cnt, error, fd, ret, zflag;

        error = 0;
        zflag = 0;
        while ((ch = getopt(argc, argv, "z")) != -1) {
                switch (ch) {
                case 'z':
                        zflag = 1;
                        break;
                case '?':
                default:
                        usage();
                }
        }
        argc -= optind;
        if (argc != 0)
                usage();

        if ((fd = open("/dev/tty", O_RDWR | O_NONBLOCK)) == -1)
                exit(1);

        if (zflag) {
                if (ioctl(fd, TIOCGWINSZ, &w) == -1)
                        exit(1);
                if (w.ws_row != 0 && w.ws_col != 0)
                        exit(0);
        }

        /* Disable echo, flush the input, and drain the output */
        if (tcgetattr(fd, &old) == -1)
                exit(1);

        new = old;
        new.c_cflag |= (CLOCAL | CREAD);
        new.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
        if (tcsetattr(fd, TCSAFLUSH, &new) == -1)
                exit(1);

        if (write(fd, query, sizeof(query) - 1) != sizeof(query) - 1) {
                error = 1;
                goto out;
        }

        /* Read the response */
        bzero(data, sizeof(data));
        gettimeofday(&then, NULL);
        cnt = 0;
        while (1) {
                ret = read(fd, data + cnt, 1);

                if (ret == -1) {
                        if (errno == EAGAIN) {
                                gettimeofday(&now, NULL);
                                timersub(&now, &then, &now);
                                if (now.tv_sec >= 2) {
                                        warnx("timeout reading from terminal");
                                        error = 1;
                                        goto out;
                                }

                                usleep(20000);
                                continue;
                        }
                        error = 1;
                        goto out;
                }
                if (data[cnt] == 'R')
                        break;

                cnt++;
                if (cnt == sizeof(data) - 2) {
                        warnx("response too long");
                        error = 1;
                        goto out;
                }
        }

        /* Parse */
        if (sscanf(data, "\033[%hu;%huR", &w.ws_row, &w.ws_col) != 2) {
                error = 1;
                warnx("unable to parse response");
                goto out;
        }

        /* Finally, what we want */
        if (ioctl(fd, TIOCSWINSZ, &w) == -1)
                error = 1;
 out:
        /* Restore echo */
        tcsetattr(fd, TCSANOW, &old);

        close(fd);
        exit(error);
}