use strict;
use warnings;

use Tk;
use Tk::WorldCanvas;
use Physics::Springs;

my $sim = Physics::Springs->new();

use Data::Dumper;

my $mw = MainWindow->new();
my $worldcanvas = $mw->WorldCanvas(-width=>400,-height=>400);
my $i = 1;
$worldcanvas->configure(-bandColor => 'purple');
$worldcanvas->CanvasBind('<3>'               => sub {$worldcanvas->CanvasFocus;
													 $worldcanvas->rubberBand(0)
													});

my $spring_start = undef;													
$worldcanvas->CanvasBind('<1>' =>
	sub {
		my ($x,$y) = $worldcanvas->eventLocation;
		my $name = "Sun_" . $i++;
		print "Inserting at $name ($x,$y)\n";
		
		$worldcanvas->createOval( $x-5,$y-5,$x+5,$y+5, -fill=>'yellow', -tag=> $name);
		my $spring_end = $sim->add_particle( x=> $x, y=> $y, z=>0, xv => 1, yv => 0, m=>10_000, n => $name);
		$sim->add_spring(k=>1,p1=>$spring_start, p2=>$spring_end,l=>undef) if defined $spring_start;
		$spring_start = $spring_end;
	}
);

$worldcanvas->CanvasBind('<2>' =>
	sub {
		my ($x,$y) = $worldcanvas->eventLocation;
		my $name = "Vertex_" . $i++;
		print "Inserting at $name ($x,$y)\n";
		$worldcanvas->createOval( $x-5,$y-5,$x+5,$y+5, -fill=>'red', -tag=> $name);
		
		my $spring_end = $sim->add_particle( x=> $x, y=> $y, z=>0, xv => 1, yv => 0, m=>50, n => $name);
		$sim->add_spring(k=>1,p1=>$spring_start, p2=>$spring_end, l=>50) if defined $spring_start;
		$spring_start = $spring_end;
	}
);

$worldcanvas->CanvasBind('<B3-Motion>'       => sub {$worldcanvas->rubberBand(1)});
$worldcanvas->CanvasBind('<ButtonRelease-3>' => sub {my @box = $worldcanvas->rubberBand(2);
													 my @ids = $worldcanvas->find('enclosed', @box);
													 foreach my $id (@ids) {$worldcanvas->delete($id)}
													});
$worldcanvas->CanvasBind('<Up>' => sub {$worldcanvas->rubberBand(1);});
$worldcanvas->CanvasBind('<Down>' => sub {$worldcanvas->rubberBand(1);});
$worldcanvas->CanvasBind('<Left>' => sub {$worldcanvas->rubberBand(1);});
$worldcanvas->CanvasBind('<Right>' => sub {$worldcanvas->rubberBand(1);});
$worldcanvas->CanvasBind('<i>' => sub {$worldcanvas->zoom(1.25); $worldcanvas->rubberBand(1);});
$worldcanvas->CanvasBind('<o>' => sub {$worldcanvas->zoom(0.8);  $worldcanvas->rubberBand(1);});
$worldcanvas->pack();
$worldcanvas->CanvasFocus;
$worldcanvas->repeat(100, 
		sub {
			$sim->iterate_step(1);
			foreach my $p (@{ $sim->{p} }) {
				$worldcanvas->coords($p->{n},  $p->{x} - 5 , $p->{y} - 5, $p->{x} + 5 , $p->{y} + 5 );
			}
			foreach my $spring (@{$sim->{_PhSprings_springs}}) {
				my $p1 = $sim->{p}[$spring->{p1}];
				my $p2 = $sim->{p}[$spring->{p2}];
				my $spring_name = 'spring_' . $spring;
				if ($worldcanvas->find('withtag',$spring_name)) {
					$worldcanvas->coords($spring_name, $p1->{x}, $p1->{y}, $p2->{x}, $p2->{y});
					#print "$spring_name ", $spring->{strech}, "\n";
				} else {
					$worldcanvas->createLine($p1->{x}, $p1->{y}, $p2->{x}, $p2->{y}, -tag=>$spring_name);
				}
			}		
				
		});
MainLoop;

##</code><code>##

	foreach my $spring (@{$self->{_PhSprings_springs}}) {
		my $p1 = $self->{p}[$spring->{p1}];
		my $p2 = $self->{p}[$spring->{p2}];
		my $l  = $spring->{len};
		my $k  = $spring->{k};

		my $dist =  sqrt(
			( ($p1->{x} - $p2->{x}) )**2 +
			( ($p1->{y} - $p2->{y}) )**2 +
			( ($p1->{z} - $p2->{z}) )**2
		);

		my $force1 = $k * ($dist-$l);
		my $force2 = -$force1;

		my $dx = ($p2->{x} - $p1->{x}) / $dist;
		my $dy = ($p2->{y} - $p1->{y}) / $dist;
		my $dz = ($p2->{z} - $p1->{z}) / $dist;

		$p1->{_fx} += $force1 * $dx;
		$p1->{_fy} += $force1 * $dy;
		$p1->{_fz} += $force1 * $dz;

		$p2->{_fx} += $force2 * $dx;
		$p2->{_fy} += $force2 * $dy;
		$p2->{_fz} += $force2 * $dz;
	}