#! perl -slw
use strict;
use Time::HiRes qw[ time ];
use Tk::Canvas;

our $TIME ||= 10;

## Fudge factor! using 850 instead of a 1000 works
## reasonably well for timeperiods of 5 to 30 seconds
## on my machine. Adjust to suit processor speed.
my $repeatTime = int( 850 * $TIME / 360 );
print $repeatTime;

my $mw = MainWindow->new;
my $canvas = $mw->Canvas(
    -width => 640,
    -height => 480,
    -bg => 'white',
)->pack;

## Create 360 tagged segments white (invisible).
for my $tag ( 0 .. 359 ) {
    $canvas->createArc(
        80, 0, 560, 480,
        -fill => 'white', -outline => undef,
        -start => $tag + 90, -extent => 1,
        -tag => "t$tag",
    );
}

## Bind action to space bar
$mw->bind( '<space>', sub {
    ## remove previous alphanumeric code
    $canvas->delete( 'code' );
    print time();
    
    ## make circle visible by setting the color of the segments
    $canvas->itemconfigure( "t$_", -fill => 'black' ) for 0 .. 359;
    
    my $tag = 359; ## Start with the first tag to 'remove'.
    my $rep;
    
    ## Set up the repeating callback with the delay calculated earlier
    $rep = $mw->repeat( $repeatTime, sub {
        
        ## if the last segment has been removed
        ## beep, display the code and cancel the timer.
        if( $tag < 0 ) {
            printf "\a";
            $canvas->createText( 300, 240, 
                -text => 'AN ALPHA-NUMERIC CODE', -tag => 'code' 
            );
            $rep->cancel;
            print time();
        }
        ## If a quater of the circle left, beep and change the color to red
        if( $tag == 90 ) {
            printf "\a";
            $canvas->itemconfigure( "t$_", -fill => 'red' ) for 0 .. 90;
        }
        ## make the next segment invisible.        
        $canvas->itemconfigure( "t$tag", -fill => 'white' );
        --$tag; ## Next segment to remove.
    });
});

$mw->MainLoop;