001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.validator.routines.checkdigit;
018
019import java.io.Serializable;
020
021/**
022 * <strong>IBAN</strong> (International Bank Account Number) Check Digit calculation/validation.
023 * <p>
024 * This routine is based on the ISO 7064 Mod 97,10 check digit calculation routine.
025 * <p>
026 * The two check digit characters in a IBAN number are the third and fourth characters
027 * in the code. For <em>check digit</em> calculation/validation the first four characters are moved
028 * to the end of the code.
029 *  So {@code CCDDnnnnnnn} becomes {@code nnnnnnnCCDD} (where
030 *  {@code CC} is the country code and {@code DD} is the check digit). For
031 *  check digit calculation the check digit value should be set to zero (such as
032 *  {@code CC00nnnnnnn} in this example).
033 * <p>
034 * Note: the class does not check the format of the IBAN number, only the check digits.
035 * <p>
036 * For further information see
037 *  <a href="https://en.wikipedia.org/wiki/International_Bank_Account_Number">Wikipedia -
038 *  IBAN number</a>.
039 *
040 * @since 1.4
041 */
042public final class IBANCheckDigit extends AbstractCheckDigit implements Serializable {
043
044    private static final int MIN_CODE_LEN = 5;
045
046    private static final long serialVersionUID = -3600191725934382801L;
047
048    /**
049     * Singleton IBAN Number Check Digit instance.
050     */
051    public static final CheckDigit IBAN_CHECK_DIGIT = new IBANCheckDigit();
052
053    private static final long MAX = 999999999;
054
055    private static final long MODULUS = 97;
056
057    /**
058     * Constructs Check Digit routine for IBAN Numbers.
059     */
060    public IBANCheckDigit() {
061    }
062
063    /**
064     * Calculate the <em>Check Digit</em> for an IBAN code.
065     * <p>
066     * <strong>Note:</strong> The check digit is the third and fourth characters and is set to the value "{@code 00}".
067     * </p>
068     *
069     * @param code The code to calculate the Check Digit for,
070     * @return The calculated Check Digit as 2 numeric decimal characters, for example, "42",
071     * @throws CheckDigitException if an error occurs calculating the check digit for the specified code,
072     */
073    @Override
074    public String calculate(String code) throws CheckDigitException {
075        if (code == null || code.length() < MIN_CODE_LEN) {
076            throw new CheckDigitException("Invalid Code length=%,d", code == null ? 0 : code.length());
077        }
078        code = code.substring(0, 2) + "00" + code.substring(4); // CHECKSTYLE IGNORE MagicNumber
079        final int modulusResult = calculateModulus(code);
080        final int charValue = 98 - modulusResult; // CHECKSTYLE IGNORE MagicNumber
081        final String checkDigit = Integer.toString(charValue);
082        return charValue > 9 ? checkDigit : "0" + checkDigit; // CHECKSTYLE IGNORE MagicNumber
083    }
084
085    /**
086     * Calculate the modulus for a code.
087     *
088     * @param code The code to calculate the modulus for.
089     * @return The modulus value,
090     * @throws CheckDigitException if an error occurs calculating the modulus for the specified code,
091     */
092    private int calculateModulus(final String code) throws CheckDigitException {
093        final String reformattedCode = code.substring(4) + code.substring(0, 4); // CHECKSTYLE IGNORE MagicNumber
094        long total = 0;
095        for (int i = 0; i < reformattedCode.length(); i++) {
096            final char ch = reformattedCode.charAt(i);
097            final int charValue = Character.getNumericValue(ch);
098            if (!isAsciiAlphaNum(reformattedCode.charAt(i))) {
099                throw new CheckDigitException("Invalid Character[%d] = '%d'", i, charValue);
100            }
101            total = (charValue > 9 ? total * 100 : total * 10) + charValue; // CHECKSTYLE IGNORE MagicNumber
102            if (total > MAX) {
103                total %= MODULUS;
104            }
105        }
106        return (int) (total % MODULUS);
107    }
108
109    /**
110     * Validate the check digit of an IBAN code.
111     *
112     * @param code The code to validate.
113     * @return {@code true} if the check digit is valid, otherwise {@code false}.
114     */
115    @Override
116    public boolean isValid(final String code) {
117        if (code == null || code.length() < MIN_CODE_LEN) {
118            return false;
119        }
120        final String check = code.substring(2, 4); // CHECKSTYLE IGNORE MagicNumber
121        if ("00".equals(check) || "01".equals(check) || "99".equals(check)) {
122            return false;
123        }
124        try {
125            return calculateModulus(code) == 1;
126        } catch (final CheckDigitException ex) {
127            return false;
128        }
129    }
130}