use strict;
use warnings;

package Test::Deep::Cache::Simple;
use Carp qw( confess );

use Scalar::Util qw( refaddr );

BEGIN
{
  if (grep /^weaken$/, @Scalar::Util::EXPORT_FAIL)
  {
    # we're running on a version of perl that has no weak refs, so we
    # just install a no-op sub for weaken instead of importing it
    *weaken = sub {};
  }
  else
  {
    Scalar::Util->import('weaken');
  }
}

sub new
{
  my $pkg = shift;

  my $self = bless {}, $pkg;

  return $self;
}

sub add
{
  my $self = shift;

  my ($d1, $d2) = @_;
  {
    local $SIG{__DIE__};

    local $@;

    # cannot weaken read only refs, no harm if we can't as they never
    # disappear
    eval{weaken($d1)};
    eval{weaken($d2)};
  }

  $self->{fn_get_key(@_)} = [$d1, $d2];
}

sub cmp
{
  my $self = shift;

  my $key = fn_get_key(@_);
  my $pair = $self->{$key};

  # are both weakened refs still valid, if not delete this entry
  if (ref($pair->[0]) and ref($pair->[1]))
  {
    return 1;
  }
  else
  {
    delete $self->{$key};
    return 0;
  }
}

sub absorb
{
  my $self = shift;

  my $other = shift;

  @{$self}{keys %$other} = values %$other;
}

sub fn_get_key
{
  return join(",", sort (map {refaddr($_)} @_));
}
1;