/* vi: set sw=4 ts=4: */
/*
 *  openvt.c - open a vt to run a command.
 *
 *  busyboxed by Quy Tonthat <quy@signal3.com>
 *  hacked by Tito <farmatito@tiscali.it>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

//usage:#define openvt_trivial_usage
//usage:       "[-c N] [-sw] [PROG ARGS]"
//usage:#define openvt_full_usage "\n\n"
//usage:       "Start PROG on a new virtual terminal\n"
//usage:     "\n        -c N    Use specified VT"
//usage:     "\n        -s      Switch to the VT"
/* //usage:     "\n     -l      Run PROG as login shell (by prepending '-')" */
//usage:     "\n        -w      Wait for PROG to exit"
//usage:
//usage:#define openvt_example_usage
//usage:       "openvt 2 /bin/ash\n"

#include <linux/vt.h>
#include "libbb.h"

/* "Standard" openvt's man page (we do not support all of this):

openvt [-c NUM] [-fsulv] [--] [command [args]]

Find the first available VT, and run command on it. Stdio is directed
to that VT. If no command is specified then $SHELL is used.

-c NUM
    Use the given VT number, not the first free one.
-f
    Force opening a VT: don't try to check if VT is already in use.
-s
    Switch to the new VT when starting the command.
    The VT of the new command will be made the new current VT.
-u
    Figure out the owner of the current VT, and run login as that user.
    Suitable to be called by init. Shouldn't be used with -c or -l.
-l
    Make the command a login shell: a "-" is prepended to the argv[0]
    when command is executed.
-v
    Verbose.
-w
    Wait for command to complete. If -w and -s are used together,
    switch back to the controlling terminal when the command completes.

bbox:
-u: not implemented
-f: always in effect
-l: not implemented, ignored
-v: ignored
-ws: does NOT switch back
*/

/* Helper: does this fd understand VT_xxx? */
static int not_vt_fd(int fd)
{
        struct vt_stat vtstat;
        return ioctl(fd, VT_GETSTATE, &vtstat); /* !0: error, it's not VT fd */
}

/* Helper: get a fd suitable for VT_xxx */
static int get_vt_fd(void)
{
        int fd;

        /* Do we, by chance, already have it? */
        for (fd = 0; fd < 3; fd++)
                if (!not_vt_fd(fd))
                        return fd;
        fd = open(DEV_CONSOLE, O_RDONLY | O_NONBLOCK);
        if (fd >= 0 && !not_vt_fd(fd))
                return fd;
        bb_error_msg_and_die("can't find open VT");
}

static int find_free_vtno(void)
{
        int vtno;
        int fd = get_vt_fd();

        errno = 0;
        /*xfunc_error_retval = 3; - do we need compat? */
        if (ioctl(fd, VT_OPENQRY, &vtno) != 0 || vtno <= 0)
                bb_perror_msg_and_die("can't find open VT");
// Not really needed, grep for DAEMON_ONLY_SANITIZE
//      if (fd > 2)
//              close(fd);
        return vtno;
}

/* vfork scares gcc, it generates bigger code.
 * Keep it away from main program.
 * TODO: move to libbb; or adapt existing libbb's spawn().
 */
static NOINLINE void vfork_child(char **argv)
{
        if (vfork() == 0) {
                /* CHILD */
                /* Try to make this VT our controlling tty */
                setsid(); /* lose old ctty */
                ioctl(STDIN_FILENO, TIOCSCTTY, 0 /* 0: don't forcibly steal */);
                //bb_error_msg("our sid %d", getsid(0));
                //bb_error_msg("our pgrp %d", getpgrp());
                //bb_error_msg("VT's sid %d", tcgetsid(0));
                //bb_error_msg("VT's pgrp %d", tcgetpgrp(0));
                BB_EXECVP_or_die(argv);
        }
}

int openvt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int openvt_main(int argc UNUSED_PARAM, char **argv)
{
        char vtname[sizeof(VC_FORMAT) + sizeof(int)*3];
        struct vt_stat vtstat;
        char *str_c;
        int vtno;
        int flags;
        enum {
                OPT_c = (1 << 0),
                OPT_w = (1 << 1),
                OPT_s = (1 << 2),
                OPT_l = (1 << 3),
                OPT_f = (1 << 4),
                OPT_v = (1 << 5),
        };

        /* "+" - stop on first non-option */
        flags = getopt32(argv, "+c:wslfv", &str_c);
        argv += optind;

        if (flags & OPT_c) {
                /* Check for illegal vt number: < 1 or > 63 */
                vtno = xatou_range(str_c, 1, 63);
        } else {
                vtno = find_free_vtno();
        }

        /* Grab new VT */
        sprintf(vtname, VC_FORMAT, vtno);
        /* (Try to) clean up stray open fds above fd 2 */
        bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS | DAEMON_ONLY_SANITIZE, NULL);
        close(STDIN_FILENO);
        /*setsid(); - BAD IDEA: after we exit, child is SIGHUPed... */
        xopen(vtname, O_RDWR);
        xioctl(STDIN_FILENO, VT_GETSTATE, &vtstat);

        if (flags & OPT_s) {
                console_make_active(STDIN_FILENO, vtno);
        }

        if (!argv[0]) {
                argv--;
                argv[0] = (char *) get_shell_name();
                /*argv[1] = NULL; - already is */
        }

        xdup2(STDIN_FILENO, STDOUT_FILENO);
        xdup2(STDIN_FILENO, STDERR_FILENO);

#ifdef BLOAT
        {
        /* Handle -l (login shell) option */
        const char *prog = argv[0];
        if (flags & OPT_l)
                argv[0] = xasprintf("-%s", argv[0]);
        }
#endif

        vfork_child(argv);
        if (flags & OPT_w) {
                /* We have only one child, wait for it */
                safe_waitpid(-1, NULL, 0); /* loops on EINTR */
                if (flags & OPT_s) {
                        console_make_active(STDIN_FILENO, vtstat.v_active);
                        // Compat: even with -c N (try to) disallocate:
                        // # /usr/app/kbd-1.12/bin/openvt -f -c 9 -ws sleep 5
                        // openvt: could not deallocate console 9
                        xioctl(STDIN_FILENO, VT_DISALLOCATE, (void*)(ptrdiff_t)vtno);
                }
        }
        return EXIT_SUCCESS;
}