package SpiralSq;

use strict;

sub new
{
    my ($class, $size, $offset) = @_;
    $offset = 1 unless defined ($offset);

    my $self = { 'size'=>$size,
		 'offset' => $offset,
		 'nextoffset' => (4*($size - 1) + $offset)};
    bless $self, $class;
    return $self;
}

sub getInside
{
    my ($self) = @_;
    $self->{'inside'} = new SpiralSq($self->{'size'} - 2,
				     $self->{'nextoffset'}) 
	unless (defined $self->{'inside'});
    return $self->{'inside'};
}

sub getRow
{
    my ($self, $r) = @_;
    my $o = $self->{'offset'};
    my $s = $self->{'size'};
    my $n = $self->{'nextoffset'};
    my @row;

    if ($r == 0)
    {
	@row = ($o .. ($s - 1 + $o));
    }
    elsif ($r == $s - 1)
    {
	@row = ((2*($s - 1) + $o) .. (3*($s - 1) + $o));
	@row = reverse @row;
    }
    elsif ($r < $s)
    {
	@row = (($n - $r), 
		$self->getInside->getRow($r - 1), 
		($s -1 + $r + $o));
    }
    else
    {
	die "error!";
    }
    return @row;
}

1;