package Data::MultiValued::UglySerializationHelperRole;
use Moose::Role;
use namespace::autoclean;

# ABSTRACT: only use this if you know what you're doing

=head1 SYNOPSIS

 package My::Class;
 use Moose;
 use Data::MultiValued::AttributeTrait::Tags;

 with 'Data::MultiValued::UglySerializationHelperRole';

 has tt => (
    is => 'rw',
    isa => 'Int',
    traits => ['MultiValued::Tags'],
    default => 3,
    predicate => 'has_tt',
    clearer => 'clear_tt',
 );

Later:

  my $json = JSON::XS->new->utf8;
  my $obj = My::Class->new(rr=>'foo');

  my $str = $json->encode($obj->as_hash);

  my $obj2 = My::Class->new_in_place($json->decode($str));

  # $obj and $obj2 have the same contents

=head1 DESCRIPTION

This is an ugly hack. It pokes inside the internals of your objects,
and will break if you're not careful. It assumes that your instances
are hashref-based. It mostly assumes that you're not storing blessed
refs inside the multi-value attributes. It goes to these lengths to
give a decent serialisation performance, without lots of unnecessary
copies. Oh, and on de-serialise it will skip all type constraint
checking and bypass the accessors, so it may well give you an unusable
object.

=method C<new_in_place>

  my $obj = My::Class->new_in_place($hashref);

Directly C<bless>es the hashref into the class, then calls
C<_rebless_slot> on any multi-value attribute.

This is very dangerous, don't try this at home without the supervision
of an adult.

=cut

sub new_in_place {
    my ($class,$hash) = @_;

    my $self = bless $hash,$class;

    for my $attr (@{$class->_dmv_multi_attrs}) {
        $attr->_rebless_slot($self);
    }
    return $self;
}

=method C<as_hash>

  my $hashref = $obj->as_hash;

Performs a shallow copy of the object's hash, then replaces the values
of all the multi-value slots with the results of calling C<_as_hash>
on the corresponding multi-value attribute.

This is very dangerous, don't try this at home without the supervision
of an adult.

=cut

sub as_hash {
    my ($self) = @_;

    my %ret = %$self;
    for my $attr (@{$self->_dmv_multi_attrs}) {
        my $st = $attr->_as_hash($self);
        if ($st) {
            $ret{$attr->full_storage_slot} = $st;
        }
        else {
            delete $ret{$attr->full_storage_slot};
        }
    }
    return \%ret;
}

{
my (
    %all_attrs_for_class,
    %tagged_attrs_for_class,
    %ranged_attrs_for_class,
    %multi_attrs_for_class,
);

sub _dmv_all_attrs {
    my ($class) = @_;$class=ref($class)||$class;

    return $all_attrs_for_class{$class} //= [$class->meta->get_all_attributes];
}
sub _dmv_tagged_attrs {
    my ($class) = @_;$class=ref($class)||$class;

    return $tagged_attrs_for_class{$class} //=
        [ grep { $_->does('Data::MultiValued::AttributeTrait::Tags') }
              @{$class->_dmv_all_attrs} ];
}
sub _dmv_ranged_attrs {
    my ($class) = @_;$class=ref($class)||$class;

    return $ranged_attrs_for_class{$class} //=
        [ grep { $_->does('Data::MultiValued::AttributeTrait::Ranges') }
              @{$class->_dmv_all_attrs} ];
}
sub _dmv_multi_attrs {
    my ($class) = @_;$class=ref($class)||$class;

    return $multi_attrs_for_class{$class} //=
        [ grep { $_->does('Data::MultiValued::AttributeTrait') }
              @{$class->_dmv_all_attrs} ];
}
}

=head1 FINAL WARNING

 my $obj_clone = My::Class->new_in_place($obj->as_hash);

This will create a shallow clone. Most internals will be
shared. Things may break. Just don't do it, C<dclone> the hashref, or
do something equivalent (as in the synopsis), instead.

=cut

1;