    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 *      http://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 * Abstract <b>Modulus</b> Check digit calculation/validation.
    023 * <p>
    024 * Provides a <i>base</i> class for building <i>modulus</i> Check
    025 * Digit routines.
    026 * <p>
    027 * This implementation only handles <i>single-digit numeric</i> codes, such as
    028 * <b>EAN-13</b>. For <i>alphanumeric</i> codes such as <b>EAN-128</b> you
    029 * will need to implement/override the <code>toInt()</code> and
    030 * <code>toChar()</code> methods.
    031 * <p>
    032 *
    033 * @version $Revision$
    034 * @since Validator 1.4
    035 */
    036public abstract class ModulusCheckDigit implements CheckDigit, Serializable {
    037
    038    private static final long serialVersionUID = 2948962251251528941L;
    039
    040    // N.B. The modulus can be > 10 provided that the implementing class overrides toCheckDigit and toInt
    041    // (for example as in ISBN10CheckDigit)
    042    private final int modulus;
    043
    044    /**
    045     * Construct a {@link CheckDigit} routine for a specified modulus.
    046     *
    047     * @param modulus The modulus value to use for the check digit calculation
    048     */
    049    public ModulusCheckDigit(int modulus) {
    050        this.modulus = modulus;
    051    }
    052
    053    /**
    054     * Return the modulus value this check digit routine is based on.
    055     *
    056     * @return The modulus value this check digit routine is based on
    057     */
    058    public int getModulus() {
    059        return modulus;
    060    }
    061
    062    /**
    063     * Validate a modulus check digit for a code.
    064     *
    065     * @param code The code to validate
    066     * @return <code>true</code> if the check digit is valid, otherwise
    067     * <code>false</code>
    068     */
    069    @Override
    070    public boolean isValid(String code) {
    071        if (code == null || code.length() == 0) {
    072            return false;
    073        }
    074        try {
    075            int modulusResult = calculateModulus(code, true);
    076            return (modulusResult == 0);
    077        } catch (CheckDigitException  ex) {
    078            return false;
    079        }
    080    }
    081
    082    /**
    083     * Calculate a modulus <i>Check Digit</i> for a code which does not yet have one.
    084     *
    085     * @param code The code for which to calculate the Check Digit;
    086     * the check digit should not be included
    087     * @return The calculated Check Digit
    088     * @throws CheckDigitException if an error occurs calculating the check digit
    089     */
    090    @Override
    091    public String calculate(String code) throws CheckDigitException {
    092        if (code == null || code.length() == 0) {
    093            throw new CheckDigitException("Code is missing");
    094        }
    095        int modulusResult = calculateModulus(code, false);
    096        int charValue = (modulus - modulusResult) % modulus;
    097        return toCheckDigit(charValue);
    098    }
    099
    100    /**
    101     * Calculate the modulus for a code.
    102     *
    103     * @param code The code to calculate the modulus for.
    104     * @param includesCheckDigit Whether the code includes the Check Digit or not.
    105     * @return The modulus value
    106     * @throws CheckDigitException if an error occurs calculating the modulus
    107     * for the specified code
    108     */
    109    protected int calculateModulus(String code, boolean includesCheckDigit) throws CheckDigitException {
    110        int total = 0;
    111        for (int i = 0; i < code.length(); i++) {
    112            int lth = code.length() + (includesCheckDigit ? 0 : 1);
    113            int leftPos  = i + 1;
    114            int rightPos = lth - i;
    115            int charValue = toInt(code.charAt(i), leftPos, rightPos);
    116            total += weightedValue(charValue, leftPos, rightPos);
    117        }
    118        if (total == 0) {
    119            throw new CheckDigitException("Invalid code, sum is zero");
    120        }
    121        return total % modulus;
    122    }
    123
    124    /**
    125     * Calculates the <i>weighted</i> value of a character in the
    126     * code at a specified position.
    127     * <p>
    128     * Some modulus routines weight the value of a character
    129     * depending on its position in the code (e.g. ISBN-10), while
    130     * others use different weighting factors for odd/even positions
    131     * (e.g. EAN or Luhn). Implement the appropriate mechanism
    132     * required by overriding this method.
    133     *
    134     * @param charValue The numeric value of the character
    135     * @param leftPos The position of the character in the code, counting from left to right
    136     * @param rightPos The positionof the character in the code, counting from right to left
    137     * @return The weighted value of the character
    138     * @throws CheckDigitException if an error occurs calculating
    139     * the weighted value
    140     */
    141    protected abstract int weightedValue(int charValue, int leftPos, int rightPos)
    142            throws CheckDigitException;
    143
    144
    145    /**
    146     * Convert a character at a specified position to an integer value.
    147     * <p>
    148     * <b>Note:</b> this implementation only handlers numeric values
    149     * For non-numeric characters, override this method to provide
    150     * character--&gt;integer conversion.
    151     *
    152     * @param character The character to convert
    153     * @param leftPos The position of the character in the code, counting from left to right (for identifiying the position in the string)
    154     * @param rightPos The position of the character in the code, counting from right to left (not used here)
    155     * @return The integer value of the character
    156     * @throws CheckDigitException if character is non-numeric
    157     */
    158    protected int toInt(char character, int leftPos, int rightPos)
    159            throws CheckDigitException {
    160        if (Character.isDigit(character)) {
    161            return Character.getNumericValue(character);
    162        }
    163        throw new CheckDigitException("Invalid Character[" +
    164                leftPos + "] = '" + character + "'");
    165    }
    166
    167    /**
    168     * Convert an integer value to a check digit.
    169     * <p>
    170     * <b>Note:</b> this implementation only handles single-digit numeric values
    171     * For non-numeric characters, override this method to provide
    172     * integer--&gt;character conversion.
    173     *
    174     * @param charValue The integer value of the character
    175     * @return The converted character
    176     * @throws CheckDigitException if integer character value
    177     * doesn't represent a numeric character
    178     */
    179    protected String toCheckDigit(int charValue)
    180            throws CheckDigitException {
    181        if (charValue >= 0 && charValue <= 9) { // CHECKSTYLE IGNORE MagicNumber
    182            return Integer.toString(charValue);
    183        }
    184        throw new CheckDigitException("Invalid Check Digit Value =" +
    185                + charValue);
    186    }
    187
    188    /**
    189     * Add together the individual digits in a number.
    190     *
    191     * @param number The number whose digits are to be added
    192     * @return The sum of the digits
    193     */
    194    public static int sumDigits(int number) {
    195        int total = 0;
    196        int todo = number;
    197        while (todo > 0) {
    198            total += todo % 10; // CHECKSTYLE IGNORE MagicNumber
    199            todo  = todo / 10; // CHECKSTYLE IGNORE MagicNumber
    200        }
    201        return total;
    202    }
    203
    204}