package Auth;

use CGI qw(:standard);
use CGI::Cookie ();
use MD5 ();
use Crypt::CBC ();

use constant COOKIE_NAME => 'Cname';
use constant SECRET => '0mn1um ex 0vum';

$CIPHER ||= Crypt::CBC->new(SECRET, 'IDEA');

sub set_cookie {
my $usrname=shift;
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time);
$year = $year + 1900;
$mon++;
my $time = "$year$mon$mday$hour$min$sec";
$state=initialize($state,$time,$usrname);

print header(-cookie => save_state($state));

}


sub initialize {
    my $state = shift;
	my $time=shift;
	my $usrname=shift;

	$state = {} unless $state;
  	$state->{TIME}     =$time ;

    $state->{USRNAME}  = $usrname;
	return $state;
}




# Check or generate the MAC authentication information
sub MAC {
    my($state, $action) = @_;
    return undef unless ref($state);
    my @fields = @{$state}{qw(TIME USRNAME)};
    my ($newmac) = MD5->hexhash(SECRET .
				MD5->hexhash(join '', SECRET, @fields));
    return $newmac eq $state->{MAC} if $action eq 'check';
    return $state->{MAC} = $newmac if $action eq 'generate';
    undef;
}

# Save the current state
sub save_state {
    my $state = shift;
    MAC($state, 'generate');  # add MAC to the state
    # encrypt the cookie
    my $encrypted = $CIPHER->encrypt_hex(join ':', %{$state});
    return CGI::Cookie->new(-name => COOKIE_NAME,
			    -value => $encrypted,
			    );
}


# Retrieve an existing state
sub get_state {
    my $cookie =  CGI::cookie(COOKIE_NAME);
    return undef unless $cookie;
    # decrypt the cookie
    my %state = split ':', $CIPHER->decrypt_hex($cookie);
    authentication_error() unless MAC(\%state, 'check');
    return \%state;
}

sub authentication_error {
print"<h4> Authentication error </h4>";


}



1;