use strict;
use warnings;
use Tk;

my $fh;

my $mw = MainWindow->new;

$mw->withdraw;
if (! open $fh, '<', "COM4:") {
    $mw->messageBox (
        -message => 'GPS unit not available',
        -title => 'Time and location', -type => 'Ok',
        -icon => 'info',
        );
    exit;
}

my $location;
while (<$fh>) {
    next if ! /^\$GPGGA,/;
    chomp;
    
    my ($hour, $min, $sec, $latDeg, $latMin, $latHemi, $longDeg, $longMin, $longHem) =
        /(\d\d)(\d\d)(\d\d),(\d\d)([\d.]+),(\S),(\d\d)([\d.]+),(\S),/;

    next if ! defined ($longHem);
    
    $latMin = toMS ($latMin);
    $longMin = toMS ($longMin);
    $location = sprintf "%s", "$hour:$min:$sec, $latDeg $latMin$latHemi, $longDeg $longMin$longHem";
    last;
}


$mw->messageBox (
    -message => $location, -title => 'Time and location', -type => 'Ok'
    );

sub toMS {
    my $x = shift;
    my $min = int ($x);
    $x = ($x - $min) * 60;
    return sprintf "%d %.2f", $min, $x;
}