#! /usr/bin/perl
use warnings;
use strict;

use Tk;
use Tk::Dialog ();

my ($x,$y) = (320, 460); # start ship at that position
my @bulletRecycler = ();
my %monsters = ();
my @monsterRecycler = ();
my $monsterCount = 0;

my $mw = MainWindow->new();
$mw->protocol('WM_DELETE_WINDOW', \&ExitApplication);

my $canvas = $mw->Canvas(-background => '#000000', 
             -height => 480, -width => 640,
             -cursor => 'crosshair')
    ->pack(-side => 'top', -fill => 'both', -expand => 1);

my $ship = &GetNewShip($canvas);

for (my $i=100;$i<600;$i+=30) {
    for (my $j=40;$j<170;$j+=30) {
    &GetNewMonster($canvas, $i, $j);
    } # for
} # for

$canvas->Tk::bind("<Motion>",   [\&MoveShip, Ev('x'), Ev('y'), $ship]);
$canvas->Tk::bind("<Button-1>", [\&Fire,     Ev('x'), Ev('y'), $ship]);

&Tk::MainLoop;

# ------------------------------------------------------------
sub ExitApplication {
    my $dialog = $mw->Dialog(-text => 'Programm wirklich beenden?',
                             -bitmap => 'question',
                             -title => 'Programm beenden',
                             -default_button => 'Yes',
                             -buttons => [qw/Ja Nein/],
                             );

    my $answer = $dialog->Show(); # and display dialog
    if (lc($answer) eq 'ja'){  exit;  }

} # ExitApplication
# ------------------------------------------------------------
sub GetNewShip {
    my $canvas = shift;

    my $ship = $canvas->createPolygon($x-10,$y, $x-10,$y-10,
               
       $x-2,$y-14, $x,$y-10, 
               
       $x+2,$y-14,$x,$y-15, 
               
       $x+10,$y-10, $x+10,$y,
               
       -outline => '#ffffff',
               
       -fill    => '#ff0000');
    return $ship;
} # GetNewShip
# ------------------------------------------------------------
sub GetBullet {
    my ($canv, $x, $y) = @_;

    my $bullet;
    if (scalar @bulletRecycler) { 
    $bullet = shift(@bulletRecycler);
    $canvas->coords($bullet, $x-2, $y-18, $x+2,$y-28);
    } # if
    else { # if not possible, create new bullet
    $bullet = $canv->createRectangle($x-2,$y-18, $x+2,$y-28, 
               
       -fill => 'white');
    } # else

    return $bullet;
} # GetBullet
# ------------------------------------------------------------
sub GetNewMonster {
    my ($canvas, $x, $y) = @_;

    my $monster = $canvas->createOval($x-10,$y-10, $x+10,$y+20,
               
       -fill => '#ffff00',
               
       -outline => '#ffffff');
    $monsters{$monster} = 1;
    $monsterCount++;
    $canvas->after(50, [ \&MoveMonster, $canvas, $monster, $x, $y, 10 ]);

    return $monster;
} # GetNewMonster
# ------------------------------------------------------------
sub MoveShip {
    my ($canv, $x1, $y1, $ship) = @_;
    $x1 = $canv->canvasx($x1);

    # move ship to left or to right
    $canv->move($ship, $x1-$x, 0);
    $x = $x1;
} # MoveShip
# ------------------------------------------------------------
sub Fire {
    my ($canv, $x1, $y1, $ship) = @_;
    $x1 = $canv->canvasx($x1);

    # start firing bullet
    my $bullet = &GetBullet($canvas, $x, $y);
    $canv->after(10, [ \&FireUp, $bullet, $x1, $y-18 ]);

    #    print "BOOOMMMM $bullet at ($x1)\n";
} # Fire
# ------------------------------------------------------------
sub FireUp {
    my ($tag, $x2, $y2) = @_;
    $canvas->move($tag, 0, -8);

    my @items = $canvas->find("overlapping", $x2-2,$y2, $x2+2,$y2-10);
    local $" = "|";
    print "Found: @items\n" if scalar @items > 1;
    foreach (@items) {
    if (exists $monsters{$_}) {
#        print "Hit Monster $_\n";
        $monsterCount--;

        # add monster to recycler
        push (@monsterRecycler, $_);
        $canvas->coords($_, 1,1001, 21,1021);
    } # if
    } # foreach

    if ($monsterCount <= 0) {
    &RestartDialog();
    } # if

    if ($y2 < 10) { # if bullet out of screen

    # move bullet to recycler
    push (@bulletRecycler, $tag);
    $canvas->coords($tag, 1,1, 5,11); # dirty, I know
    } # if

    else { # continue moving bullet up
    $canvas->after(10, [\&FireUp, $tag, $x2, $y2-8]);
    } # else
} # FireUp
# ------------------------------------------------------------
sub MoveMonster {
    my ($canvas, $monster, $x, $y, $direction) = @_;
    my $down = 0;

    if ($direction < 0 and $x < 20) {
    $direction = -$direction; $down = 10; $y+= 10; 
    } # if
    elsif ($direction > 0 and $x > 620) {
    $direction = -$direction; $down = 10; $y+= 10; 
    } # elsif
    else {
    $x += $direction;
    } # else
    $canvas->move($monster, $direction, $down);

    $canvas->after(50, [ \&MoveMonster, $canvas, $monster, 
             $x, $y, $direction ]);
} # MoveMonster
# ------------------------------------------------------------
sub RestartDialog {
    my $dialog = $mw->Dialog(-text => "Gewonnen\nNoch mal?",
                             -bitmap => 'question',
                             -title => 'Programm beenden',
                             -default_button => 'Yes',
                             -buttons => [qw/Ja Nein/],
                             );

    my $answer = $dialog->Show(); # and display dialog
    if (lc($answer) eq 'ja'){
        exec($0); # dirty, i know
    } # if
    else {
    exit;
    } # else

} # RestartDialog
# ------------------------------------------------------------