#!/usr/bin/perl -w
=head1 NAME

xterm-server-backend - TOD

=head1 SYNOPSIS

xterm-server-backend [options]

    --help
    --daemonize        (Default)
    --no-daemonize

=head1 DESCRIPTION

TODO

=cut

use strict;

# Seemingly socat doesn't seem to transmit STDERR automatically so
# re-route it myself.
#
*STDERR = *STDOUT;

# Option handling
# 
use Getopt::Long ();
Getopt::Long::GetOptions(
    help => \&pod2usage,
    'daemonize!' => \ my $daemonize,
)
    or pod2usage();
$daemonize = 1 if ! defined $daemonize;

# Daemonization by default
#
if ( $daemonize ) {
    fork && exit;
    fork && exit;
    umask 0;
    chdir '/';
}

# TODO: Add a socat readline proxy

# TODO: reduce the # of processes required here.
# 8105 pts/0    S      0:00 socat TCP-LISTEN:53505,fork,reuseaddr EXEC:/home/josh/src/xterm-server/xterm-server-backend,setsid,nofork
# 8110 pts/2    S+     0:00 telnet localhost 53505
# 8113 ?        S      0:00 /home/josh/perl5/perlbrew/perls/perl-5.12.1/bin/perl /home/josh/src/xterm-server/xterm-server-backend
# 8114 ?        S      0:00 sh -c 3>&1 xterm -title 'Perl 5 Debugger' -e sh -c "tty 1>&3;?sleep 10000000"
# 8115 ?        S      0:00 xterm -title Perl 5 Debugger -e sh -c tty 1>&3;?sleep 10000000
# 8116 pts/4    Ss+    0:00 sh -c tty 1>&3;?sleep 10000000
# 8118 ?        S      0:00 socat - FILE:/dev/pts/4
# 8119 pts/4    S+     0:00 sleep 10000000

# Launch xterm in a child process and have it write its tty to the
# STDOUT I'm reading from. It's going to sleep for approximately 115
# days.
#
my $cmd = q(3>&1 xterm -title 'Perl 5 Debugger' -e sh -c "tty 1>&3;
sleep 10000000"|);
my $xterm_pid = open my( $xterm_process ), $cmd;
if ( ! defined $xterm_pid ) {
    die "Can't [$cmd]: \$?=$?";
}

# Read the xterm's tty.
#
my $tty = <$xterm_process>;
chomp $tty;
if ( ! $tty ) {
    die "Couldn't get tty from xterm pid $xterm_pid";
}

# Launch socat to tie my STDIN, STDOUT, STDERR to the TTY that's in
# use by the xterm. We won't continue until the conversation is
# complete.
#
my @cmd = ( 'socat', '-', "FILE:$tty" );
system @cmd;
if ( $? ) {
    die "Can't [@cmd]: \$?=$?";
}

# Tell the xterm that the socket has closed. It's entirely possible
# that I can't talk to the tty anymore either so ignore any failures.
#
$^W = 0;
open my $tty_fh, '>', $tty;
if ( $tty_fh ) {
    syswrite $tty_fh, "Socket closed\n";
    close $tty_fh;
}

# Kill all our children, if they still exist
#
kill -2,  0; # SIGINT
kill -15, 0; # SIGTERM
kill -9,  0; # SIGKILL

sub pod2usage {
    require Pod::Usage;
    goto &Pod::Usage::pod2usage;
}