package DBM_Filter ;

use strict;
use warnings;
our $VERSION = '0.01';

package Tie::Hash ;

use strict;
use warnings;

use Carp;


our %LayerStack = ();
our %origDESTROY = ();

our %Filters = map { $_, undef } qw(
            Fetch_Key
            Fetch_Value
            Store_Key
            Store_Value
	);

our %Options = map { $_, 1 } qw(
            fetch
            store
	);

#sub Filter_Enable
#{
#}
#
#sub Filter_Disable
#{
#}

sub Filtered
{
    my $this = shift;
    return defined $LayerStack{$this} ;
}

sub Filter_Pop
{
    my $this = shift;
    my $stack = $LayerStack{$this} || return undef ;
    my $filter = pop @{ $stack };

    # remove the filter hooks if this is the last filter to pop
    if ( @{ $stack } == 0 ) {
        $this->filter_store_key  ( undef );
        $this->filter_store_value( undef );
        $this->filter_fetch_key  ( undef );
        $this->filter_fetch_value( undef );
        delete $LayerStack{$this};
    }

    return $filter;
}

sub Filter_Key_Push
{
    &_do_Filter_Push;
}

sub Filter_Value_Push
{
    &_do_Filter_Push;
}


sub Filter_Push
{
    &_do_Filter_Push;
}

sub _do_Filter_Push
{
    my $this = shift;
    my %callbacks = ();
    my $caller = (caller(1))[3];
    $caller =~ s/^.*:://;
 
    croak "$caller: no parameters present" unless @_ ;

    if ( ! $Options{lc $_[0]} ) {
        my $class = shift;
        my @params = @_;

        # if $class already contains "::", don't prefix "DBM_Filter::"
        $class = "DBM_Filter::$class" unless $class =~ /::/;
    
        # does the "DBM_Filter::$class" exist?
	if ( ! defined %{ "${class}::"} ) {
	    # Nope, so try to load it.
            eval " require $class ; " ;
            croak "$caller: Cannot Load DBM Filter '$class': $@" if $@;
        }