#!/usr/bin/perl

use strict;
use warnings;

{   package Encapsulate;
    use Scalar::Util;

    BEGIN {
        my $Secrets = {};
        use overload
            '%{}' => sub {
                my $id = Scalar::Util::refaddr( shift );
                my $package = caller;
                return $Secrets->{ $id }->{ $package } ||= {};
            },
            fallback => 1;

        sub DESTROY {
            my $id = Scalar::Util::refaddr( shift );
            delete $Secrets->{ $id };
        };

    }
}

{   package Foo;
    use base qw( Encapsulate );

    sub new {
        my $class = shift;
        return bless {}, $class;
    }

    sub foo {
        my $self = shift;
        $self->{ secret } = shift if @_;
        return $self->{ secret };
    }
}

{   package Bar;
    use base qw( Foo );

    sub bar {
        my $self = shift;
        $self->{ secret } = shift if @_;
        return $self->{ secret };
    }
}

use Test::More tests => 6;

isa_ok my $o = Bar->new, 'Bar';

$o->foo( 42 );
is $o->foo, 42, "can set and get value of Foo's secret";

Bar->new->foo( 24 );
is $o->foo, 42, "different objects get different secrets";

$o->bar( 99 );
is $o->bar, 99, "can set and get value of Bar's secret";

is $o->foo, 42, "secrets of different classes do not interfere";

ok !defined $o->{secret}, 'cannot reach into objects';