#! /usr/bin/perl
use Glib qw/TRUE FALSE/;
use Gtk2 '-init';

sub exit_with_error
{
	my ($error)=@_;
	print STDERR "$error\n";
	exit(1);
}

sub process_one_packet
{
	$pos[$idx++]=tell(STDIN);
	while (<STDIN>) {
		if (!defined($match)) {
			syswrite(STDOUT,$_) or exit_with_error $!;
		} else {
			$buffer.=$_;
		}
		if (/^\$GPRMC/) {
			my($dummy,$time,$dummy)=split(/,/,$_);
			$entry->set_text($time);
			if (!defined($match)) {
				return;
			}
			if (substr($time,0,length($match)) eq $match) {
				undef $match;
				syswrite(STDOUT,$buffer) or exit_with_error $!;
				return;
			}
			$buffer='';
		}
	}
}

sub process_one_packet_at_idx
{
	($idx)=@_;
	seek(STDIN,$pos[$idx],SEEK_SET);
	process_one_packet();
}

sub forward
{
	process_one_packet();
	return 1;
}

sub backward
{
	if ($idx > 1) {
		process_one_packet_at_idx($idx-2);
	}
	return 1;
}

sub add_timeout
{
	my ($interval,$dir)=@_;

	if ($timeout > 0) {
		Glib::Source->remove($timeout);
	}
	if ($dir > 0) {
		forward();
		$timeout=Glib::Timeout->add ($interval, \&forward);
	}
	if ($dir < 0) {
		backward();
		$timeout=Glib::Timeout->add ($interval, \&backward);
	}
}

sub entry
{
	$match=$entry->get_text();
	seek(STDIN,0,SEEK_SET);
	process_one_packet();
}

$oldfh = select(STDOUT); $| = 1; select($oldfh);
$window = Gtk2::Window->new('toplevel');
$box = Gtk2::HBox->new();
$window->add($box);
$button = Gtk2::Button->new("Stop");
$button->signal_connect(clicked => sub { add_timeout(0,0) });
$box->add($button);
$button = Gtk2::Button->new("100 Hz");
$button->signal_connect(clicked => sub { add_timeout(10,-1); });
$box->add($button);
$button = Gtk2::Button->new("10 Hz");
$button->signal_connect(clicked => sub { add_timeout(100,-1); });
$box->add($button);
$button = Gtk2::Button->new("4 Hz");
$button->signal_connect(clicked => sub { add_timeout(250,-1); });
$box->add($button);
$button = Gtk2::Button->new("1 Hz");
$button->signal_connect(clicked => sub { add_timeout(1000,-1); });
$box->add($button);
$button = Gtk2::Button->new("-");
$button->signal_connect(clicked => sub { add_timeout(0,0) ; backward() });
$box->add($button);
$entry = Gtk2::Entry->new();
$entry->set_text("???");
$entry->signal_connect(activate => \&entry);
$box->add($entry);
$button = Gtk2::Button->new("+");
$button->signal_connect(clicked => sub { add_timeout(0,0) ; forward() });
$box->add($button);
$button = Gtk2::Button->new("1 Hz");
$button->signal_connect(clicked => sub { add_timeout(1000,1); });
$box->add($button);
$button = Gtk2::Button->new("4 Hz");
$button->signal_connect(clicked => sub { add_timeout(250,1); });
$box->add($button);
$button = Gtk2::Button->new("10 Hz");
$button->signal_connect(clicked => sub { add_timeout(100,1); });
$box->add($button);
$button = Gtk2::Button->new("100 Hz");
$button->signal_connect(clicked => sub { add_timeout(10,1); });
$box->add($button);
$button = Gtk2::Button->new("Max");
$button->signal_connect(clicked => sub { add_timeout(1,1); });
$box->add($button);
$window->show_all;
if ($ARGV[0]) {
	$match=$ARGV[0];
	process_one_packet();
}
Gtk2->main;
0;