    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
    021import org.apache.commons.validator.GenericValidator;
    022
    023/**
    024 * Abstract <b>Modulus</b> Check digit calculation/validation.
    025 * <p>
    026 * Provides a <i>base</i> class for building <i>modulus</i> Check Digit routines.
    027 * </p>
    028 * <p>
    029 * This implementation only handles <i>single-digit numeric</i> codes, such as <b>EAN-13</b>. For <i>alphanumeric</i> codes such as <b>EAN-128</b> you will need
    030 * to implement/override the <code>toInt()</code> and <code>toChar()</code> methods.
    031 * </p>
    032 *
    033 * @since 1.4
    034 */
    035public abstract class ModulusCheckDigit extends AbstractCheckDigit implements Serializable {
    036
    037    static final int MODULUS_10 = 10;
    038    static final int MODULUS_11 = 11;
    039    private static final long serialVersionUID = 2948962251251528941L;
    040
    041    /**
    042     * Add together the individual digits in a number.
    043     *
    044     * @param number The number whose digits are to be added
    045     * @return The sum of the digits
    046     */
    047    public static int sumDigits(final int number) {
    048        int total = 0;
    049        int todo = number;
    050        while (todo > 0) {
    051            total += todo % 10; // CHECKSTYLE IGNORE MagicNumber
    052            todo /= 10; // CHECKSTYLE IGNORE MagicNumber
    053        }
    054        return total;
    055    }
    056
    057    /**
    058     * The modulus can be greater than 10 provided that the implementing class overrides toCheckDigit and toInt (for example as in ISBN10CheckDigit).
    059     */
    060    private final int modulus;
    061
    062    /**
    063     * Constructs a modulus 10 {@link CheckDigit} routine for a specified modulus.
    064     */
    065    ModulusCheckDigit() {
    066        this(MODULUS_10);
    067    }
    068
    069    /**
    070     * Constructs a {@link CheckDigit} routine for a specified modulus.
    071     *
    072     * @param modulus The modulus value to use for the check digit calculation
    073     */
    074    public ModulusCheckDigit(final int modulus) {
    075        this.modulus = modulus;
    076    }
    077
    078    /**
    079     * Calculate a modulus <i>Check Digit</i> for a code which does not yet have one.
    080     *
    081     * @param code The code for which to calculate the Check Digit;
    082     * the check digit should not be included
    083     * @return The calculated Check Digit
    084     * @throws CheckDigitException if an error occurs calculating the check digit
    085     */
    086    @Override
    087    public String calculate(final String code) throws CheckDigitException {
    088        if (GenericValidator.isBlankOrNull(code)) {
    089            throw new CheckDigitException("Code is missing");
    090        }
    091        final int modulusResult = calculateModulus(code, false);
    092        final int charValue = (modulus - modulusResult) % modulus;
    093        return toCheckDigit(charValue);
    094    }
    095
    096    /**
    097     * Calculate the modulus for a code.
    098     *
    099     * @param code The code to calculate the modulus for.
    100     * @param includesCheckDigit Whether the code includes the Check Digit or not.
    101     * @return The modulus value
    102     * @throws CheckDigitException if an error occurs calculating the modulus
    103     * for the specified code
    104     */
    105    protected int calculateModulus(final String code, final boolean includesCheckDigit) throws CheckDigitException {
    106        int total = 0;
    107        for (int i = 0; i < code.length(); i++) {
    108            final int lth = code.length() + (includesCheckDigit ? 0 : 1);
    109            final int leftPos = i + 1;
    110            final int rightPos = lth - i;
    111            final int charValue = toInt(code.charAt(i), leftPos, rightPos);
    112            total += weightedValue(charValue, leftPos, rightPos);
    113        }
    114        if (total == 0) {
    115            throw new CheckDigitException("Invalid code, sum is zero");
    116        }
    117        return total % modulus;
    118    }
    119
    120    /**
    121     * Gets the modulus value this check digit routine is based on.
    122     *
    123     * @return The modulus value this check digit routine is based on
    124     */
    125    public int getModulus() {
    126        return modulus;
    127    }
    128
    129    /**
    130     * Validate a modulus check digit for a code.
    131     *
    132     * @param code The code to validate
    133     * @return {@code true} if the check digit is valid, otherwise
    134     * {@code false}
    135     */
    136    @Override
    137    public boolean isValid(final String code) {
    138        if (GenericValidator.isBlankOrNull(code)) {
    139            return false;
    140        }
    141        try {
    142            final int modulusResult = calculateModulus(code, true);
    143            return modulusResult == 0;
    144        } catch (final CheckDigitException ex) {
    145            return false;
    146        }
    147    }
    148
    149    /**
    150     * Convert an integer value to a check digit.
    151     * <p>
    152     * <b>Note:</b> this implementation only handles single-digit numeric values
    153     * For non-numeric characters, override this method to provide
    154     * integer--&gt;character conversion.
    155     *
    156     * @param charValue The integer value of the character
    157     * @return The converted character
    158     * @throws CheckDigitException if integer character value
    159     * doesn't represent a numeric character
    160     */
    161    protected String toCheckDigit(final int charValue) throws CheckDigitException {
    162        if (charValue >= 0 && charValue <= 9) { // CHECKSTYLE IGNORE MagicNumber
    163            return Integer.toString(charValue);
    164        }
    165        throw new CheckDigitException("Invalid Check Digit Value =" + +charValue);
    166    }
    167
    168    /**
    169     * Convert a character at a specified position to an integer value.
    170     * <p>
    171     * <b>Note:</b> this implementation only handlers numeric values
    172     * For non-numeric characters, override this method to provide
    173     * character--&gt;integer conversion.
    174     *
    175     * @param character The character to convert
    176     * @param leftPos The position of the character in the code, counting from left to right (for identifiying the position in the string)
    177     * @param rightPos The position of the character in the code, counting from right to left (not used here)
    178     * @return The integer value of the character
    179     * @throws CheckDigitException if character is non-numeric
    180     */
    181    protected int toInt(final char character, final int leftPos, final int rightPos) throws CheckDigitException {
    182        if (Character.isDigit(character)) {
    183            return Character.getNumericValue(character);
    184        }
    185        throw new CheckDigitException("Invalid Character[" + leftPos + "] = '" + character + "'");
    186    }
    187
    188    /**
    189     * Calculates the <i>weighted</i> value of a character in the
    190     * code at a specified position.
    191     * <p>
    192     * Some modulus routines weight the value of a character
    193     * depending on its position in the code (e.g. ISBN-10), while
    194     * others use different weighting factors for odd/even positions
    195     * (e.g. EAN or Luhn). Implement the appropriate mechanism
    196     * required by overriding this method.
    197     *
    198     * @param charValue The numeric value of the character
    199     * @param leftPos The position of the character in the code, counting from left to right
    200     * @param rightPos The positionof the character in the code, counting from right to left
    201     * @return The weighted value of the character
    202     * @throws CheckDigitException if an error occurs calculating
    203     * the weighted value
    204     */
    205    protected abstract int weightedValue(int charValue, int leftPos, int rightPos) throws CheckDigitException;
    206
    207}