package Numbers;

use strict;
use warnings;
use IO::File;
use Carp;
use Fcntl ':flock';
use Tie::Hash;
our @ISA = qw(Tie::StdHash);
use Storable qw(fd_retrieve store_fd);

# VARs intern
my $fh = new IO::File; # LOCK_EX
my $init = 0;


# Constructor
sub TIEHASH{
	my $class = shift;
	my $ref = shift or return;
	croak "No ref HASH in Arg" if ref $ref ne 'HASH';
	croak "No file is given, use {-file => \$file} in Args" if not exists $ref->{-file};
	
	my $self = _initialize($ref->{-file}) or return; # IO-Error

	# apply autoincrement for custom keys like 'foo', 'bar'
	if(exists $ref->{-auto}){
		if(ref $ref->{-auto} eq 'ARRAY'){
			foreach my $k(@{$ref->{-auto}}){
				$self->{$k}++;
			}
		}
		else{ carp "Second Arg must be a ARRAY-Ref ['foo','bar']" }
	}
	return bless $self, $class;
}

# hash from $file
sub _initialize{
	my $file = shift;
	return if $init == 1;
	$init = 1;
	$fh->open($file, O_CREAT|O_BINARY|O_RDWR) or return;
	flock($fh, LOCK_EX) or carp "Your system does not support flock()!";
	binmode $fh, ':raw';
	my $ref = {};
	eval { $ref = fd_retrieve($fh) }; 
	# caught exception: file is void
	if($@){ return {} }
	else { return $ref }
}

# hash to file
sub _serialize{
	my $ref = shift;
	seek $fh, 0, 0;
	truncate $fh, 0;
	store_fd($ref, $fh);
	undef $fh;
}

# Overload method, make sure that value is numeric
sub STORE{
	my $self = shift;
	my $key = shift;
	my $value = shift;
	if($value =~ /^\d+$/){
		$self->{$key} = $value;
	}
	else{
		carp "Value is not numeric";
	}
}

sub DESTROY{
	my $self = shift;
	_serialize($self); 
}
###########################################################################
1; ########################################################################
###########################################################################

package main;

my $file = 'd:/tmp/storednumbers.bin';
tie my %h, 'Numbers', {-file => $file, -auto => ['foo','bar']} or die $!;

foreach my $k(keys %h){
	print "$k => $h{$k}\n";
}