######################
# SESSION MANAGEMENT
# create the session or if avaible load the session
#######################
my $q = CGI->new();
my $session = CGI::Session->new("driver:File", $q, {Directory => "$tmp_dir"});
$session->expire('15m');

if ($session->is_new ) {
	my $cookie = $q->cookie(CGISESSID => $session->id);
	print $q->redirect( -url => 'admin.cgi', -cookie => $cookie);
}
#########################
# DISPATCH PART - GET THE ACTIONS
# if action is login, do the login
#########################
my $action = '';
$action = $q->url_param('action') if ($q->url_param('action'));

if ($action eq 'login') {
	login($q, $session);
}

# Check the Login Status and if the user is logged in, start the chosen action
my $login = $session->param("login");

###############
# secret pages (only visible if logged in)
###############
if ($login) {
[...]
     #hier sind die verschiedenen möglichen Aktionen, die nur nach Login zugänglich sein sollen. Wichtig ist wohl nur:
     elsif ($action eq 'logout') {
		logout($q, $session);
	}
[...]

# Die Login Funktion
sub login {
	my ($q, $session) = @_;
	my $username = $q->param('user');
	my $password = $q->param('password');
	
	open my $fh, "<:encoding(utf-8)", $conffile or die "Could not open $conffile: $!";
	my $yaml ='';
	while (my $line = <$fh>) {$yaml .= $line}
	close $fh;
	my $config = Load($yaml);
	$password = sha256_hex($password, $config->{'secret'});
	if ($username eq $config->{'user'} and $password eq $config->{'password'}) {
		$session->param("login", "can_access");	
		print $q->redirect(-url => 'admin.cgi?action=show_pages');
	}
}
[...]
# Und schließlich die Logout Funktion
sub logout {
	my ($q, $session) =  @_;
	# Delete the current session
        $session->delete();
	$session->flush();
	
	# Delete all expired Sessions
	CGI::Session->find( undef, \&purge , {Directory=> "$tmp_dir"} );
	sub purge {
	    my ($session) = @_;
	    if ( $session->is_expired )  {
	        $session->delete();
	        $session->flush(); # Recommended practice says use flush() after delete().
	    }
	}


	print_template('logout.tmpl');

}