#include "apue.h"
#include <termios.h>
#include <errno.h>

static struct termios		save_termios;
static int					ttysavefd = -1;
static enum { RESET, RAW, CBREAK }	ttystate = RESET;

int
tty_cbreak(int fd)	/* put terminal into a cbreak mode */
{
	int				err;
	struct termios	buf;

	if (ttystate != RESET) {
		errno = EINVAL;
		return(-1);
	}
	if (tcgetattr(fd, &buf) < 0)
		return(-1);
	save_termios = buf;	/* structure copy */

	/*
	 * Echo off, canonical mode off.
	 */
	buf.c_lflag &= ~(ECHO | ICANON);

	/*
	 * Case B: 1 byte at a time, no timer.
	 */
	buf.c_cc[VMIN] = 1;
	buf.c_cc[VTIME] = 0;
	if (tcsetattr(fd, TCSAFLUSH, &buf) < 0)
		return(-1);

	/*
	 * Verify that the changes stuck.  tcsetattr can return 0 on
	 * partial success.
	 */
	if (tcgetattr(fd, &buf) < 0) {
		err = errno;
		tcsetattr(fd, TCSAFLUSH, &save_termios);
		errno = err;
		return(-1);
	}
	if ((buf.c_lflag & (ECHO | ICANON)) || buf.c_cc[VMIN] != 1 ||
	  buf.c_cc[VTIME] != 0) {
		/*
		 * Only some of the changes were made.  Restore the
		 * original settings.
		 */
		tcsetattr(fd, TCSAFLUSH, &save_termios);
		errno = EINVAL;
		return(-1);
	}

	ttystate = CBREAK;
	ttysavefd = fd;
	return(0);
}

int
tty_raw(int fd)		/* put terminal into a raw mode */
{
	int				err;
	struct termios	buf;

	if (ttystate != RESET) {
		errno = EINVAL;
		return(-1);
	}
	if (tcgetattr(fd, &buf) < 0)
		return(-1);
	save_termios = buf;	/* structure copy */

	/*
	 * Echo off, canonical mode off, extended input
	 * processing off, signal chars off.
	 */
	buf.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);

	/*
	 * No SIGINT on BREAK, CR-to-NL off, input parity
	 * check off, don't strip 8th bit on input, output
	 * flow control off.
	 */
	buf.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);

	/*
	 * Clear size bits, parity checking off.
	 */
	buf.c_cflag &= ~(CSIZE | PARENB);

	/*
	 * Set 8 bits/char.
	 */
	buf.c_cflag |= CS8;

	/*
	 * Output processing off.
	 */
	buf.c_oflag &= ~(OPOST);

	/*
	 * Case B: 1 byte at a time, no timer.
	 */
	buf.c_cc[VMIN] = 1;
	buf.c_cc[VTIME] = 0;
	if (tcsetattr(fd, TCSAFLUSH, &buf) < 0)
		return(-1);

	/*
	 * Verify that the changes stuck.  tcsetattr can return 0 on
	 * partial success.
	 */
	if (tcgetattr(fd, &buf) < 0) {
		err = errno;
		tcsetattr(fd, TCSAFLUSH, &save_termios);
		errno = err;
		return(-1);
	}
	if ((buf.c_lflag & (ECHO | ICANON | IEXTEN | ISIG)) ||
	  (buf.c_iflag & (BRKINT | ICRNL | INPCK | ISTRIP | IXON)) ||
	  (buf.c_cflag & (CSIZE | PARENB | CS8)) != CS8 ||
	  (buf.c_oflag & OPOST) || buf.c_cc[VMIN] != 1 ||
	  buf.c_cc[VTIME] != 0) {
		/*
		 * Only some of the changes were made.  Restore the
		 * original settings.
		 */
		tcsetattr(fd, TCSAFLUSH, &save_termios);
		errno = EINVAL;
		return(-1);
	}

	ttystate = RAW;
	ttysavefd = fd;
	return(0);
}

int
tty_reset(int fd)		/* restore terminal's mode */
{
	if (ttystate == RESET)
		return(0);
	if (tcsetattr(fd, TCSAFLUSH, &save_termios) < 0)
		return(-1);
	ttystate = RESET;
	return(0);
}

void
tty_atexit(void)		/* can be set up by atexit(tty_atexit) */
{
	if (ttysavefd >= 0)
		tty_reset(ttysavefd);
}

struct termios *
tty_termios(void)		/* let caller see original tty state */
{
	return(&save_termios);
}