## chat.pl: chat with a server
## V2.01.alpha.2 91/04/10
## Randal L. Schwartz

package chat;
require 'sys/socket.ph';

$sockaddr = 'S n a4 x8';
chop($thishost = `hostname`); $thisaddr = (gethostbyname($thishost))[4];
$thisproc = pack($sockaddr, 2, 0, $thisaddr);

# *S = symbol for current I/O, gets assigned *chatsymbol....
$next = "chatsymbol000000"; # next one
$nextpat = "^chatsymbol"; # patterns that match next++, ++, ++, ++


## $handle = &chat'open_port("server.address",$port_number);
## opens a named or numbered TCP server


sub open_port { ## public
	local($server, $port) = @_;

	local($serveraddr,$serverproc);

	*S = ++$next;
	if ($server =~ /^(\d+)+\.(\d+)\.(\d+)\.(\d+)$/) {
		$serveraddr = pack('C4', $1, $2, $3, $4);
	} else {
		local(@x) = gethostbyname($server);
		return undef unless @x;
		$serveraddr = $x[4];
	}
	$serverproc = pack($sockaddr, 2, $port, $serveraddr);
	unless (socket(S, &AF_INET, &SOCK_STREAM, 'tcp')) {
	    print("Uh oh, can't make a socket!  What the hell?\n");
		# XXX hardwired $AF_SOCKET, $SOCK_STREAM, 'tcp'
		# but who the heck would change these anyway? (:-)
		($!) = ($!, close(S)); # close S while saving $!
		return undef;
	}
	unless (bind(S, $thisproc)) {
	    print("Uh oh, no bind\n");
		($!) = ($!, close(S)); # close S while saving $!
		return undef;
	}
	unless (connect(S, $serverproc)) {
	    print("Uh oh, no connec\n");
		($!) = ($!, close(S)); # close S while saving $!
		return undef;
	}
	select((select(S), $| = 1)[0]);
	$next; # return symbol for switcharound
}

## $handle = &chat'open_proc("command","arg1","arg2",...);
## opens a /bin/sh on a pseudo-tty

sub open_proc { ## public
	local(@cmd) = @_;

	*S = ++$next;
	local(*TTY) = "__TTY" . time;
	local($pty,$tty) = &_getpty(S,TTY);
	die "Cannot find a new pty" unless defined $pty;
	local($pid) = fork;
	die "Cannot fork: $!" unless defined $pid;
	unless ($pid) {
		close STDIN; close STDOUT; close STDERR;
		setpgrp(0,$$);
		if (open(DEVTTY, "/dev/tty")) {
		    ioctl(DEVTTY,0x20007471,0);		# XXX s/b &TIOCNOTTY
		    close DEVTTY;
		}
		open(STDIN,"<&TTY");
		open(STDOUT,">&TTY");
		open(STDERR,">&STDOUT");
		die "Oops" unless fileno(STDERR) == 2;	# sanity
		close(S);
		exec @cmd;
		die "Cannot exec @cmd: $!";
	}
	close(TTY);
	$next; # return symbol for switcharound
}

# $S is the read-ahead buffer

## $return = &chat'expect([$handle,] $timeout_time,
## 	$pat1, $body1, $pat2, $body2, ... )
## $handle is from previous &chat'open_*().
## $timeout_time is the time (either relative to the current time, or
## absolute, ala time(2)) at which a timeout event occurs.
## $pat1, $pat2, and so on are regexs which are matched against the input
## stream.  If a match is found, the entire matched string is consumed,
## and the corresponding body eval string is evaled.
##
## Each pat is a regular-expression (probably enclosed in single-quotes
## in the invocation).  ^ and $ will work, respecting the current value of $*.
## If pat is 'TIMEOUT', the body is executed if the timeout is exceeded.
## If pat is 'EOF', the body is executed if the process exits before
## the other patterns are seen.
##
## Pats are scanned in the order given, so later pats can contain
## general defaults that won't be examined unless the earlier pats
## have failed.
##
## The result of eval'ing body is returned as the result of
## the invocation.  Recursive invocations are not thought
## through, and may work only accidentally. :-)
##
## undef is returned if either a timeout or an eof occurs and no
## corresponding body has been defined.
## I/O errors of any sort are treated as eof.

sub expect { ## public
	if ($_[0] =~ /$nextpat/) {
		*S = shift;
	}
	local($endtime) = shift;

	$endtime += time if $endtime < 600_000_000;
	local($rmask, $nfound, $timeleft, $thisbuf);
	local($timeout,$eof) = (1,1);
	local($cases,$pattern,$action);
	local($caller) = caller;
	local($return,@return);
	local($returnvar) = wantarray ? '@return' : '$return';

	## strategy: create a giant block inside $cases
	$cases .= <<'ESQ';
	LOOP: {
ESQ
	while (@_) {
		($pattern,$action) = splice(@_,0,2);
		if ($pattern =~ /^eof$/i) {
			$cases .= <<"EDQ";
		if (\$eof) {
			$returnvar = do { package $caller; $action; };
			last LOOP;
		}
EDQ
			$eof = 0;
		} elsif ($pattern =~ /^timeout$/i) {
			$cases .= <<"EDQ";
		if (\$timeout) {
			$returnvar = do { package $caller; $action; };
			last LOOP;
		}
EDQ
			$timeout = 0;
		} else {
			$pattern =~ s#/#\\/#g;
			$cases .= <<"EDQ";
		if (\$S =~ /$pattern/) {
			\$S = \$';
			$returnvar = do { package $caller; $action; };
			last LOOP;
		}
EDQ
		}
	}
	$cases .= <<"EDQ" if $eof;
		if (\$eof) {
			$returnvar = undef;
			last LOOP;
		}
EDQ
	$cases .= <<"EDQ" if $timeout;
		if (\$timeout) {
			$returnvar = undef;
			last LOOP;
		}
EDQ
	$eof = $timeout = 0;
	$cases .= <<'ESQ';
		$rmask = "";
		vec($rmask,fileno(S),1) = 1;
		($nfound, $rmask) =
		 	select($rmask, undef, undef, $endtime - time);
		if ($nfound) {
			"<nfound = $nfound>";
			$nread = sysread(S, $thisbuf, 1024);
			if ($nread > 0) {
				$S .= $thisbuf;
			} else {
				$eof++, redo LOOP; # any error is also eof
			}
		} else {
			$timeout++, redo LOOP; # timeout
		}
		redo LOOP;
	}
ESQ
	eval $cases; die $@ if $@;
	if (wantarray) {
		return @return;
	} else {
		return $return;
	}
}

## &chat'print([$handle,] @data)
## $handle is from previous &chat'open().
## like print $handle @data

sub print { ## public
	if ($_[0] =~ /$nextpat/) {
		*S = shift;
	}
	print S @_;
}

## &chat'close([$handle,])
## $handle is from previous &chat'open().
## like close $handle

sub close { ## public
	if ($_[0] =~ /$nextpat/) {
	 	*S = shift;
	}
	close(S);
}

# ($pty,$tty) = $chat'_getpty(PTY,TTY):
# internal procedure to get the next available pty.
# opens pty on handle PTY, and matching tty on handle TTY.
# returns undef if can't find a pty.

sub _getpty { ## private
	local($_PTY,$_TTY) = @_;
	$_PTY =~ s/^([^']+)$/(caller)[$[]."'".$1/e;
	$_TTY =~ s/^([^']+)$/(caller)[$[]."'".$1/e;
	local($pty,$tty);
	for $bank (112..127) {
		next unless -e sprintf("/dev/pty%c0", $bank);
		for $unit (48..57) {
			$pty = sprintf("/dev/pty%c%c", $bank, $unit);
			open($_PTY,"+>$pty") || next;
			select((select($_PTY), $| = 1)[0]);
			($tty = $pty) =~ s/pty/tty/;
			open($_TTY,"+>$tty") || next;
			select((select($_TTY), $| = 1)[0]);
			system "stty nl>$tty";
			return ($pty,$tty);
		}
	}
	undef;
}

1;