/*
 *  safetitle sets the title of the terminal window to the given string,
 *  if and only if the terminal is recognized via its device attributes.
 *
 *  If multiple terminals are attached to the same GNU screen session,
 *  the title is not set.  It is theoretically possible to check every
 *  terminal too see if it is recognized and, if so, set the title --
 *  but that would make the code more complex.
 */

#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <termios.h>
#include <unistd.h>

#define WSCONS_DA (char[]){27,91,62,50,52,59,50,48,59,48,99,0}
#define SCREEN_DA (char[]){27,91,62,56,51,59,52,48,56,48,48,59,48,99,0}

int debug = 0;

int
da(int fd, char *buf, int real)
{
	char c;
	fd_set fds;
	int i, r, responses;
	struct timeval timeout;

	FD_ZERO(&fds);
	FD_SET(fd, &fds);
	timeout.tv_sec = 0;
	timeout.tv_usec = 1;
	responses = 0;
	i = 0;

	if(real) write(fd, "\033P\033[>c\033\\", 8);
	else write(fd, "\033[>c", 4);

	while(r = read(fd, &c, 1)){
loop:
		if(r==-1){
			warn("read");
			return -1;
		}
		buf[i++] = c;
		if(c==99) break;
	}
	buf[i] = '\0';
	responses++;

	/* ensure there is only one real terminal */
check:
	if(real && select(fd+1, &fds, NULL, NULL, &timeout)>0){
		if ((r = read(fd, &c, 1)) && c==0) goto check; /* extra nul */
		else goto loop;
	}
	if(responses>1){
		if(debug) fprintf(stderr, "more than one attached terminal\n");
		return -1;
	}

	return i;
}

int
main(int argc, char *argv[])
{
	char *ap, *buf;
	int r, screen, ttyfd;
	struct termios term, restore;

	r = 1;

        /* parse arguments */
        if(argc==2)
                ap = argv[1];
        else if(argc==3){
                ap = argv[2];
                if(strcmp(argv[1], "-d")==0) debug = 1;
                else goto usage;
        }
        else goto usage;

	if((ttyfd = open("/dev/tty", O_RDWR))==-1)
		err(1, "open");
	if((buf = malloc(200*sizeof(char)))==NULL)
		err(1, "malloc");

	/* enter "raw" terminal mode */
	tcgetattr(ttyfd, &restore);
	tcgetattr(ttyfd, &term);
	term.c_lflag &= ~(ICANON|ECHO);
	tcsetattr(ttyfd, TCSANOW, &term);

	/* get device attributes for real terminal */
	if(da(ttyfd, buf, 0)==-1){
		goto end;
	}
	screen = strcmp(buf, SCREEN_DA)==0;
	if(screen && da(ttyfd, buf, screen)==-1){
		goto end;
	}

	/* set title */
	if(strcmp(buf, WSCONS_DA)==0){
		if(debug) fprintf(stderr, "wrong type of terminal\n");
		goto end;
	}
	else{
		if(screen) dprintf(ttyfd, "\033P\033]2;%s\007\033\\", ap);
		else dprintf(ttyfd, "\033]2;%s\007", ap);
	}

	r = 0;
end:
	tcsetattr(ttyfd, TCSANOW, &restore);
	return r;
usage:
        fprintf(stderr, "usage: %s [-d] title\n", argv[0]);
        return 1;
}