/* Copyright (c) 2018, Curtis McEnroe <programble@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/ioctl.h>
#include <sysexits.h>
#include <unistd.h>

static struct {
    int read;
    int write;
} fd;

static void sigwinch() {
    struct winsize window;
    int error = ioctl(STDERR_FILENO, TIOCGWINSZ, &window);
    if (error) err(EX_IOERR, "TIOCGWINSZ");

    ssize_t size = write(fd.write, &window, sizeof(window));
    if (size < 0) err(EX_IOERR, "write(%d)", fd.write);
    if ((size_t)size < sizeof(window)) errx(EX_IOERR, "short write(%d)", fd.write);
}

int winch(void) {
    int error = pipe((int *)&fd);
    if (error) err(EX_OSERR, "pipe");

    error = fcntl(fd.read, F_SETFD, FD_CLOEXEC);
    if (error) err(EX_IOERR, "fcntl");

    error = fcntl(fd.write, F_SETFD, FD_CLOEXEC);
    if (error) err(EX_IOERR, "fcntl");

    struct sigaction action = {
        .sa_handler = sigwinch,
        .sa_flags = SA_RESTART,
    };
    error = sigaction(SIGWINCH, &action, NULL);
    if (error) err(EX_OSERR, "sigaction");

    return fd.read;
}