/* vi: set sw=4 ts=4: */
/*
 * bare bones 'talk to modem' program - similar to 'cu -l $device'
 * inspired by mgetty's microcom
 *
 * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

//usage:#define microcom_trivial_usage
//usage:       "[-d DELAY] [-t TIMEOUT] [-s SPEED] [-X] TTY"
//usage:#define microcom_full_usage "\n\n"
//usage:       "Copy bytes for stdin to TTY and from TTY to stdout\n"
//usage:     "\n        -d      Wait up to DELAY ms for TTY output before sending every"
//usage:     "\n                next byte to it"
//usage:     "\n        -t      Exit if both stdin and TTY are silent for TIMEOUT ms"
//usage:     "\n        -s      Set serial line to SPEED"
//usage:     "\n        -X      Disable special meaning of NUL and Ctrl-X from stdin"

#include "libbb.h"

// set raw tty mode
static void xget1(int fd, struct termios *t, struct termios *oldt)
{
        tcgetattr(fd, oldt);
        *t = *oldt;
        cfmakeraw(t);
//      t->c_lflag &= ~(ISIG|ICANON|ECHO|IEXTEN);
//      t->c_iflag &= ~(BRKINT|IXON|ICRNL);
//      t->c_oflag &= ~(ONLCR);
//      t->c_cc[VMIN]  = 1;
//      t->c_cc[VTIME] = 0;
}

static int xset1(int fd, struct termios *tio, const char *device)
{
        int ret = tcsetattr(fd, TCSAFLUSH, tio);

        if (ret) {
                bb_perror_msg("can't tcsetattr for %s", device);
        }
        return ret;
}

int microcom_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int microcom_main(int argc UNUSED_PARAM, char **argv)
{
        int sfd;
        int nfd;
        struct pollfd pfd[2];
        struct termios tio0, tiosfd, tio;
        char *device_lock_file;
        enum {
                OPT_X = 1 << 0, // do not respect Ctrl-X, Ctrl-@
                OPT_s = 1 << 1, // baudrate
                OPT_d = 1 << 2, // wait for device response, ms
                OPT_t = 1 << 3, // timeout, ms
        };
        speed_t speed = 9600;
        int delay = -1;
        int timeout = -1;
        unsigned opts;

        // fetch options
        opt_complementary = "=1:s+:d+:t+"; // exactly one arg, numeric options
        opts = getopt32(argv, "Xs:d:t:", &speed, &delay, &timeout);
//      argc -= optind;
        argv += optind;

        // try to create lock file in /var/lock
        device_lock_file = (char *)bb_basename(argv[0]);
        device_lock_file = xasprintf("/var/lock/LCK..%s", device_lock_file);
        sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
        if (sfd < 0) {
                // device already locked -> bail out
                if (errno == EEXIST)
                        bb_perror_msg_and_die("can't create '%s'", device_lock_file);
                // can't create lock -> don't care
                if (ENABLE_FEATURE_CLEAN_UP)
                        free(device_lock_file);
                device_lock_file = NULL;
        } else {
                // %4d to make concurrent mgetty (if any) happy.
                // Mgetty treats 4-bytes lock files as binary,
                // not text, PID. Making 5+ char file. Brrr...
                fdprintf(sfd, "%4d\n", getpid());
                close(sfd);
        }

        // setup signals
        bb_signals(0
                + (1 << SIGHUP)
                + (1 << SIGINT)
                + (1 << SIGTERM)
                + (1 << SIGPIPE)
                , record_signo);

        // error exit code if we fail to open the device
        bb_got_signal = 1;

        // open device
        sfd = open_or_warn(argv[0], O_RDWR | O_NOCTTY | O_NONBLOCK);
        if (sfd < 0)
                goto done;
        fcntl(sfd, F_SETFL, O_RDWR);

        // put device to "raw mode"
        xget1(sfd, &tio, &tiosfd);
        // set device speed
        cfsetspeed(&tio, tty_value_to_baud(speed));
        if (xset1(sfd, &tio, argv[0]))
                goto done;

        // put stdin to "raw mode" (if stdin is a TTY),
        // handle one character at a time
        if (isatty(STDIN_FILENO)) {
                xget1(STDIN_FILENO, &tio, &tio0);
                if (xset1(STDIN_FILENO, &tio, "stdin"))
                        goto done;
        }

        // main loop: check with poll(), then read/write bytes across
        pfd[0].fd = sfd;
        pfd[0].events = POLLIN;
        pfd[1].fd = STDIN_FILENO;
        pfd[1].events = POLLIN;

        bb_got_signal = 0;
        nfd = 2;
        // Not safe_poll: we want to exit on signal
        while (!bb_got_signal && poll(pfd, nfd, timeout) > 0) {
                if (nfd > 1 && pfd[1].revents) {
                        char c;
                        // read from stdin -> write to device
                        if (safe_read(STDIN_FILENO, &c, 1) < 1) {
                                // don't poll stdin anymore if we got EOF/error
                                nfd--;
                                goto skip_write;
                        }
                        // do we need special processing?
                        if (!(opts & OPT_X)) {
                                // ^@ sends Break
                                if (VINTR == c) {
                                        tcsendbreak(sfd, 0);
                                        goto skip_write;
                                }
                                // ^X exits
                                if (24 == c)
                                        break;
                        }
                        write(sfd, &c, 1);
                        if (delay >= 0)
                                safe_poll(pfd, 1, delay);
skip_write: ;
                }
                if (pfd[0].revents) {
#define iobuf bb_common_bufsiz1
                        ssize_t len;
                        // read from device -> write to stdout
                        len = safe_read(sfd, iobuf, sizeof(iobuf));
                        if (len > 0)
                                full_write(STDOUT_FILENO, iobuf, len);
                        else {
                                // EOF/error -> bail out
                                bb_got_signal = SIGHUP;
                                break;
                        }
                }
        }

        // restore device mode
        tcsetattr(sfd, TCSAFLUSH, &tiosfd);

        if (isatty(STDIN_FILENO))
                tcsetattr(STDIN_FILENO, TCSAFLUSH, &tio0);

done:
        if (device_lock_file)
                unlink(device_lock_file);

        return bb_got_signal;
}