/**
* Copyright (C) 2009 Orbeon, Inc.
*
* This program is free software; you can redistribute it and/or modify it under the terms of the
* GNU Lesser General Public License as published by the Free Software Foundation; either version
* 2.1 of the License, or (at your option) any later version.
*
* 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 Lesser General Public License for more details.
*
* The full text of the license is available at http://www.gnu.org/copyleft/lesser.html
*/
package org.orbeon.oxf.xforms.function;
import org.orbeon.saxon.expr.Expression;
import org.orbeon.saxon.expr.XPathContext;
import org.orbeon.saxon.om.Item;
import org.orbeon.saxon.trans.XPathException;
import org.orbeon.saxon.value.BooleanValue;
/**
* XForms is-card-number() function (XForms 1.1).
*/
public class IsCardNumber extends XFormsFunction {
public Item evaluateItem(XPathContext xpathContext) throws XPathException {
final Expression luhnnumberExpression = argument[0];
final String luhnnumber = luhnnumberExpression.evaluateAsString(xpathContext).toString();
int result = 0;
boolean alternation = false;
try {
for (int i = luhnnumber.length() - 1; i >= 0; i--) {
int n = Integer.parseInt(luhnnumber.substring(i, i + 1));
if (alternation) {
n *= 2;
if (n > 9) {
n = (n % 10) + 1;
}
}
result += n;
alternation = !alternation;
}
return BooleanValue.get(result % 10 == 0);
} catch(NumberFormatException e) {
return BooleanValue.FALSE;
}
}
}