<?php
	/**
	 * Copyright 2000, 2001, 2002 Philipp von Klitzing
	 * Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009 Wim van Ravesteijn
	 *
	 * This file is part of AEGEE-Europe Statutory Event Applications.
	 *
	 * AEGEE-Europe Statutory Event Applications 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, either
	 * version 3 of the License, or (at your option) any later version.
	 *
	 * AEGEE-Europe Statutory Event Applications 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 AEGEE-Europe Statutory Event Applications.  If not, see
	 * <http://www.gnu.org/licenses/>.
	 */
//#########################################
//### File:         CSNcheck.php        ###
//### Author:       Wim van Ravesteijn  ###
//#########################################
//### Created:      2002.08.10          ###
//### Last changed: 2002.09.08          ###
//### Version:      1.10                ###
//#########################################

	function CSN_check ($CSN) {
		# *** Written in LotusScript for Notes/Domino 5.x [by P v Klitzing] ***
		# *** Translated to PHP and extended functionality [by Wim van Ravesteijn] ***
		# *** *** 
		# *** Aim: Compute the last character of the CSN (card serial number) ***
		# *** introduced by AEGEE-Europe in spring 2000 (AGORA Utrecht) ***
		# *** This last character has the function of a check digit ***
		# *** ***
		# *** As input, you send a full CSN number, with or without dash (-), ***
		# *** upper or lower case letters ***
		# *** ***
		# *** The return of the function is the following: ***
		# ***   ok: CSN number valid ***
		# ***   no: CSN number invalid ***
		# ***   error: unrecognised characters
		#
		# ord() : Return the ASCII code for this character
		# substr() : Extract x charcacters from a string, starting at position i
		# strlen() : Length of a string
		# % : Modula operation
		
		$stringtemp = strtoupper(substr($CSN, 0, strlen($CSN)-1));
		$CSN_check = strtoupper(substr($CSN, strlen($CSN)-1,1));
		
		if( strlen($stringtemp)>0 ) {
			for( $i=0;$i<strlen($stringtemp);$i++ ) {
				# Treat anything except 0 to 9
				# The idea is to turn A to Z into numbers, even though this results in two digits
				if( (ord( substr($stringtemp, $i, 1) )>=65) AND (ord( substr($stringtemp, $i, 1) )<=90) ) {
					$newwork = $newwork . ord( substr($stringtemp, $i, 1) );
				}else if( substr($stringtemp, $i, 1)=="-" ) {
					# Dealing with -
					# -> Do nothing
				}else if( (ord(substr($stringtemp, $i, 1))>=48) AND (ord(substr($stringtemp, $i, 1))<=57) ) {
					# Dealing with 0-9
					$newwork = $newwork . substr($stringtemp, $i, 1);
				}else {
					return "error";
				}
			}
		}
		
		for($i=0;$i<strlen($newwork);$i++) {
			$add = substr($newwork, $i, 1) * pow(2,(strlen($newwork) - $i));
			$result = $result + $add;
		}
		// Also check if the format is correct.
		$re="/(^[A-Za-z]\d{5}-?\d{5}[0-9X]$)/";
		if( (preg_match($re,$CSN)) AND (( (($result % 11)==10) AND ($CSN_check=="X") ) OR (($result % 11)==$CSN_check)) ) {
			return "ok";
		}else {
			return "no";
		}
	}
?>