/* Copyright (C) 2018  Causal Agent June <june@causal.agency>
 *
 * 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 <sys/types.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/event.h>
#include <sys/ioctl.h>
#include <sysexits.h>
#include <termios.h>
#include <unistd.h>

static void nop() { }

static struct {
    int remote;
    int local;
    int input;
} fd = { -1, STDOUT_FILENO, STDIN_FILENO };

static struct termios saveTerm;
static void restoreTerm(void) {
    tcsetattr(fd.input, TCSADRAIN, &saveTerm);
}

int main(int argc, char *argv[]) {
    int error;

    if (argc < 2) errx(EX_USAGE, "missing public id");
    if (!isatty(fd.local)) errx(EX_USAGE, "no terminal (use ssh -t)");

    const char *path = argv[1];
    fd.remote = open(path, O_RDONLY);
    if (fd.remote < 0) err(EX_NOINPUT, "%s", path);

    error = tcgetattr(fd.input, &saveTerm);
    if (error) err(EX_IOERR, "tcgetattr");
    atexit(restoreTerm);

    struct termios term = saveTerm;
    term.c_lflag &= ~(ICANON | ECHO);
    error = tcsetattr(fd.input, TCSADRAIN, &term);
    if (error) err(EX_IOERR, "tcsetattr");

    signal(SIGWINCH, nop);

    int kq = kqueue();
    if (kq < 0) err(EX_OSERR, "kqueue");

    struct kevent events[2] = {
        { .ident = fd.input, .filter = EVFILT_READ, .flags = EV_ADD },
        { .ident = fd.remote, .filter = EVFILT_READ, .flags = EV_ADD },
    };
    int nevents = kevent(kq, events, 2, NULL, 0, NULL);
    if (nevents < 0) err(EX_OSERR, "kevent");

    for (;;) {
        off_t off = lseek(fd.remote, 0, SEEK_SET);
        if (off < 0) err(EX_IOERR, "%s", path);

        struct winsize localWindow;
        error = ioctl(fd.local, TIOCGWINSZ, &localWindow);
        if (error) err(EX_IOERR, "TIOCGWINSZ");

        // FIXME: Hack spin waiting for remote window.
        struct winsize remoteWindow;
        ssize_t size;
        for (int i = 0; i < 100; ++i, usleep(100)) {
            size = read(fd.remote, &remoteWindow, sizeof(remoteWindow));
            if (size < 0) err(EX_IOERR, "read(%d)", fd.remote);
            if (size) break;
        }
        if ((size_t)size < sizeof(remoteWindow)) {
            errx(EX_DATAERR, "no window size (stream not started)");
        }

        if (
            localWindow.ws_col < remoteWindow.ws_col
            || localWindow.ws_row < remoteWindow.ws_row
        ) {
            warnx(
                "resize window %hux%hu to at least %hux%hu",
                localWindow.ws_col, localWindow.ws_row,
                remoteWindow.ws_col, remoteWindow.ws_row
            );
            sigset_t mask;
            sigemptyset(&mask);
            sigsuspend(&mask);
            continue;
        }

        char buf[4096];
        for (;;) {
            struct kevent event;
            int nevents = kevent(kq, NULL, 0, &event, 1, NULL);
            if (nevents < 0) {
                if (errno == EINTR) break;
                err(EX_OSERR, "kevent");
            }

            if (event.ident == (uintptr_t)fd.input) {
                ssize_t size = read(fd.input, buf, sizeof(buf));
                if (size < 0) err(EX_IOERR, "read(%d)", fd.input);
                if (size == 1 && buf[0] == 'q') return EX_OK;
            }

            if (event.ident == (uintptr_t)fd.remote) {
                if (event.data < 0) break;

                ssize_t readSize = read(fd.remote, buf, sizeof(buf));
                if (readSize < 0) err(EX_IOERR, "read(%d)", fd.remote);

                ssize_t writeSize = write(fd.local, buf, readSize);
                if (writeSize < 0) err(EX_IOERR, "write(%d)", fd.local);
                if (writeSize < readSize) errx(EX_IOERR, "short write(%d)", fd.local);
            }
        }
    }
}