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lib/Data/CircularList/Iterator.pm  view on Meta::CPAN

package Data::CircularList::Iterator;

use 5.006;
use strict;
use warnings FATAL => 'all';
use parent qw/Class::Accessor/;
__PACKAGE__->mk_accessors(qw/p header rotate rotate_count/);
use Scalar::Util qw/blessed/;
use Carp;
sub DEBUG() {0}; # {0} when done

=head1 NAME

Data::CircularList::Iterator - iterator for Data::CircularList's object.

=head1 VERSION

Version 0.03

=cut

our $VERSION = '0.03';

=head1 SYNOPSIS

You can see Data::CircularList module's SYNOPSIS as a example.

=cut

=head1 SUBROUTINES/METHODS

=head2 new

constructor. reguire one argument (not necessary) as rotate.

=cut

sub new {
    my ($class, $circular_list, $rotate) = @_;
    my $self = {
        p => $circular_list->header,
        header => $circular_list->header,
        rotate => defined $rotate ? $rotate : undef,
        rotate_count => 0,
    };
    bless $self => $class;
    return $self;
}

=head2 has_next

return boolean value(1 or 0).
If the linkedList has next cell, this method return 1.
If the linkedList has not next cell, this method return 0.

=cut

sub has_next {
    my $self = shift;

    # if rotate is not defined, return true eternary.
    return 1 if (!defined($self->rotate));

    if ( ! blessed($self->p->next->data) ) {
            $self->rotate_count($self->rotate_count + 1);
    }

    # case of the rotate is defined
    if ( $self->rotate_count < $self->rotate ) {
        # skip header
        return 1;
    } else {
        return 0;
    }
}

=head2 next

return next cell(Data::CircularList::Cell) of the CircularList.

=head3 caution

If next method called, iterator progresses next cell.
So you should generally call has_next method and next method alternately each once respectively.

    my $list = Data::CircularList->new;
    my $iter = $list->iterator;
    while ($iter->has_next) {
       print $iter->next->data . "\n";
    }

=cut

sub next {
    my $self = shift;

    if ( ! defined($self->p->next) ) {
        return undef;
    }

    if ( ! blessed($self->p->next->data) ) {
        # skip header
        $self->p($self->p->next->next);
    } else {
        $self->p($self->p->next);
    }