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package Abstract::Meta::Attribute;

use strict;
use warnings;
use Carp 'confess';
use base 'Abstract::Meta::Attribute::Method';
use vars qw($VERSION);

$VERSION = 0.04;

=head1 NAME

Abstract::Meta::Attribute - Meta object attribute.

=head1 SYNOPSIS

    use Abstract::Meta::Class ':all';
    has '$.attr1' => (default => 0);    

=head1 DESCRIPTION

An object that describes an attribute.
It includes required, data type, association validation, default value, lazy retrieval.
Name of attribute must begin with one of the follwoing prefix:
    $. => Scalar,
    @. => Array,
    %. => Hash,
    &. => Code,


=head1 EXPORT

None.

=head2 METHODS

=over

=item new

=cut


sub new {
    my $class = shift;
    unshift @_, $class;
    bless {&initialise}, $class;
}


=item initialise

Initialises attribute

=cut

{
   my %supported_type = (
      '$' => 'Scalar',
      '@' => 'Array',
      '%' => 'Hash',
      '&' => 'Code',
    );

    sub initialise {
        my ($class, %args) = @_;
        foreach my $k (keys %args) {
            confess "unknown attribute $k"
            unless Abstract::Meta::Attribute->can($k);
        }
        my $name = $args{name} or confess "name is requried";
        my $storage_type = $args{storage_type} = $args{transistent} ? 'Hash' : $args{storage_type} || '';
        
        my $attribute_index = 0;
        if($storage_type  eq 'Array')  {
            my $meta_class= Abstract::Meta::Class::meta_class($args{class});
            $attribute_index = $#{$meta_class->all_attributes} + 1;
        }
        
        my ($type, $accessor_name) = ($name =~ /^([\$\@\%\&])\.(.*)$/);
        confess "invalid attribute defintion ${class}::" .($accessor_name || $name) .", supported prefixes are \$.,%.,\@.,&."
          if ! $type || ! $supported_type{$type};