# $Id$
# Hash tied to restrict access to the specified keys list.
# Copyright (C) 2005 Jan Kratochvil <project-www.jankratochvil.net@jankratochvil.net>
# 
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; exactly version 2 of June 1991 is required
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


package My::Hash::RestrictTo;
our $VERSION=do { my @r=(q$Revision$=~/\d+/g); sprintf "%d.".("%03d"x$#r),@r; };
our $CVS_ID=q$Id$;
use strict;
use warnings;
use My::Web;	# for &Wrequire
Wrequire 'My::Hash';
our @ISA=qw(My::Hash);
use Carp qw(cluck confess);


sub TIEHASH($$@)
{
my($class,$parent,@keys)=@_;

	my $self=$class->SUPER::TIEHASH($parent);
	$self->{"keyshash"}={ map(($_=>1),@keys) };
	return $self;
}

sub STORE($$$)
{
my($this,$key,$value)=@_;

	confess "Key not permitted: $key" if !$this->{"keyshash"}{$key};
	return $this->pass("STORE",$key,$value);
}

sub FETCH($$)
{
my($this,$key)=@_;

	confess "Key not permitted: $key" if !$this->{"keyshash"}{$key};
	return $this->pass("FETCH",$key);
}

sub FIRSTKEY($)
{
my($this)=@_;

	my $a=keys(%{$this->{"keyshash"}});
	return $this->NEXTKEY($this,undef());
}

sub NEXTKEY($$)
{
my($this,$lastkey)=@_;

cluck "TODO: Enumeration may not be expected.";
	for (;;) {
		my $key=each(%{$this->{"keyshash"}});
		return if !defined $key;
		return $key if exists $this->{"parent"}{$key};
		}
}

sub EXISTS($$)
{
my($this,$key)=@_;

	confess "Key not permitted: $key" if !$this->{"keyshash"}{$key};
	return $this->pass("EXISTS",$key);
}

sub DELETE($$)
{
my($this,$key)=@_;

	confess "Key not permitted: $key" if !$this->{"keyshash"}{$key};
	return $this->pass("DELETE",$key);
}

sub CLEAR($)
{
my($this)=@_;

cluck "TODO: Enumeration may not be expected.";
	delete $this->{"parent"}{$_} for keys(%{$this->{"keyshash"}});
}

sub SCALAR
{
my($this)=@_;

confess "TODO: Not yet implemented.";
}

1;