use warnings;
use strict;

use IO::Pty;
use IO::Select;
use POSIX ":sys_wait_h";


if (@ARGV < 2)
{
	die "Arguments: logfile executable ...";
}

exit if (fork);

my $logfile;

POSIX::setsid() or die "Can't start a new session: $!\n";

sub signal_handler
{
	my $signame = shift;
	logMsg($logfile, "ERROR: caught signal $signame, exiting.");
}

$SIG{INT} = $SIG{TERM} = $SIG{HUP} = \&signal_handler;

sub terminate
{
	my $pid = shift;
	my $signal = shift;

	kill $signal, $pid;
	my ($r, $starttime);

	$starttime = time;

	do
	{
		$r = waitpid($pid, &WNOHANG);
	}
	until ($r == $pid || (time - $starttime > 5));

	if ($r == $pid)
	{
		return 1;
	}
	else
	{
		return undef;
	}
}

sub logMsg
{
	my $fh = shift;
	my $msg = shift;
	my $t = scalar localtime;
	my $oldfh = select($fh);
	
	$|=1;
	print $fh "$t [$$]: $msg\n";
	select($oldfh);
}
	


my $logfileName = shift @ARGV;
$logfile = new IO::File ">>$logfileName" || die "Unable to open logfile $logfileName";

while (1)
{
	my $pty = new IO::Pty;
	my ($readerr, $writeerr);
	pipe($readerr, $writeerr) || die "pipe $!\n";

	if (my $pid = fork)
	{
		close($writeerr);
		my $select = new IO::Select;
		$select->add($pty);
		$select->add($readerr);

		my $run = 1;
		my $runtime = time;
		

		while ($run)
		{
			foreach my $fh ($select->can_read(0.25))
			{
				my $buf;
				if (sysread($fh, $buf, 4096))
				{
					logMsg($logfile, "child reports \"$buf\"");
				}
			}

			my $r = waitpid($pid, &WNOHANG);
			if ($r == $pid)
			{
				logMsg($logfile, "Warning: $pid died unexpectedly, restarting.\n");
				$run = 0;
			}
			else
			{
				my @times = localtime(time);
				if ($times[2] == 7 && $times[1] == 0 && ($times[0] > 0 && $times[0] < 05))
				{
					sleep 5;

					unless (terminate($pid, 15))
					{
						unless (terminate($pid, 9))
						{
							die "Unable to kill process $pid with SIGTERM or SIGKILL!";
						}
						else
						{
							logMsg($logfile, "Warning: had to resort to SIGKILL to remove $pid.\n");
						}
					}
					else
					{
						logMsg($logfile, "Info: killed $pid with SIGTERM.\n");
					}
					$run = 0;
				}
			}
		}

		close($readerr);
		close($pty);
	}
	else
	{
		logMsg($logfile, "Info: starting " . join(" ", @ARGV));
		close($readerr);
		my $slave = $pty->slave();
		close $pty;
		$slave->set_raw();
		
		open(STDOUT, ">&" . $slave->fileno);
		open(STDERR, ">&" . $writeerr->fileno);
		close($slave);
		
		exec(@ARGV) || die "exec: $!\n";
	}
}