    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 */
    017
    018package org.apache.commons.validator.routines.checkdigit;
    019
    020import java.io.Serializable;
    021
    022import org.apache.commons.validator.GenericValidator;
    023
    024/**
    025 * Abstracts <strong>Modulus</strong> Check digit calculation/validation.
    026 * <p>
    027 * Provides a <em>base</em> class for building <em>modulus</em> Check Digit routines.
    028 * </p>
    029 * <p>
    030 * This implementation only handles <em>single-digit numeric</em> codes, such as <strong>EAN-13</strong>. For <em>alphanumeric</em> codes such as
    031 * <strong>EAN-128</strong> you will need to implement/override the {@code toInt()} and {@code toChar()} methods.
    032 * </p>
    033 *
    034 * @since 1.4
    035 */
    036public abstract class ModulusCheckDigit extends AbstractCheckDigit implements Serializable {
    037
    038    static final int MODULUS_10 = 10;
    039    static final int MODULUS_11 = 11;
    040    private static final long serialVersionUID = 2948962251251528941L;
    041
    042    /**
    043     * Adds together the individual digits in a number.
    044     *
    045     * @param number The number whose digits are to be added.
    046     * @return The sum of the digits.
    047     */
    048    public static int sumDigits(final int number) {
    049        int total = 0;
    050        int todo = number;
    051        while (todo > 0) {
    052            total += todo % 10; // CHECKSTYLE IGNORE MagicNumber
    053            todo /= 10; // CHECKSTYLE IGNORE MagicNumber
    054        }
    055        return total;
    056    }
    057
    058    /**
    059     * The modulus can be greater than 10 provided that the implementing class overrides toCheckDigit and toInt (for example as in ISBN10CheckDigit).
    060     */
    061    private final int modulus;
    062
    063    /**
    064     * Constructs a modulus 10 {@link CheckDigit} routine for a specified modulus.
    065     */
    066    ModulusCheckDigit() {
    067        this(MODULUS_10);
    068    }
    069
    070    /**
    071     * Constructs a {@link CheckDigit} routine for a specified modulus.
    072     *
    073     * @param modulus The modulus value to use for the check digit calculation.
    074     */
    075    public ModulusCheckDigit(final int modulus) {
    076        this.modulus = modulus;
    077    }
    078
    079    /**
    080     * Calculates a modulus <em>Check Digit</em> for a code which does not yet have one.
    081     *
    082     * @param code The code for which to calculate the Check Digit; 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     * Calculates 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 for the specified code.
    103     */
    104    protected int calculateModulus(final String code, final boolean includesCheckDigit) throws CheckDigitException {
    105        int total = 0;
    106        for (int i = 0; i < code.length(); i++) {
    107            final int lth = code.length() + (includesCheckDigit ? 0 : 1);
    108            final int leftPos = i + 1;
    109            final int rightPos = lth - i;
    110            final int charValue = toInt(code.charAt(i), leftPos, rightPos);
    111            total += weightedValue(charValue, leftPos, rightPos);
    112        }
    113        if (total == 0) {
    114            throw new CheckDigitException("Invalid code, sum is zero");
    115        }
    116        return total % modulus;
    117    }
    118
    119    /**
    120     * Gets the modulus value this check digit routine is based on.
    121     *
    122     * @return The modulus value this check digit routine is based on.
    123     */
    124    public int getModulus() {
    125        return modulus;
    126    }
    127
    128    /**
    129     * Tests if the code is of the specified length.
    130     *
    131     * @param code The code to test.
    132     * @param length The length to test for.
    133     * @return {@code true} if the code is of the specified length, otherwise {@code false}.
    134     */
    135    boolean isLength(final String code, final int length) {
    136        return code != null && code.length() == length;
    137    }
    138
    139    /**
    140     * Validates a modulus check digit for a code.
    141     *
    142     * @param code The code to validate.
    143     * @return {@code true} if the check digit is valid, otherwise {@code false}.
    144     */
    145    @Override
    146    public boolean isValid(final String code) {
    147        if (GenericValidator.isBlankOrNull(code)) {
    148            return false;
    149        }
    150        try {
    151            return calculateModulus(code, true) == 0;
    152        } catch (final CheckDigitException ex) {
    153            return false;
    154        }
    155    }
    156
    157    /**
    158     * Converts an integer value to a check digit.
    159     * <p>
    160     * <strong>Note:</strong> this implementation only handles single-digit numeric values For non-numeric characters, override this method to provide
    161     * integer--&gt;character conversion.
    162     * </p>
    163     *
    164     * @param charValue The integer value of the character.
    165     * @return The converted character.
    166     * @throws CheckDigitException if integer character value. doesn't represent a numeric character.
    167     */
    168    protected String toCheckDigit(final int charValue) throws CheckDigitException {
    169        if (isAsciiDigit(charValue)) {
    170            return Integer.toString(charValue);
    171        }
    172        throw new CheckDigitException("Invalid Check Digit Value =%d", charValue);
    173    }
    174
    175    /**
    176     * Converts a character at a specified position to an integer value.
    177     * <p>
    178     * <strong>Note:</strong> this implementation only handlers numeric values For non-numeric characters, override this method to provide
    179     * character--&gt;integer conversion.
    180     * </p>
    181     *
    182     * @param character The character to convert.
    183     * @param leftPos   The position of the character in the code, counting from left to right (for identifying the position in the string).
    184     * @param rightPos  The position of the character in the code, counting from right to left (not used here).
    185     * @return The integer value of the character.
    186     * @throws CheckDigitException if character is non-numeric.
    187     */
    188    protected int toInt(final char character, final int leftPos, final int rightPos) throws CheckDigitException {
    189        if (isAsciiDigit(character)) {
    190            return character - '0';
    191        }
    192        throw new CheckDigitException("Invalid Character[%d,%d] = '%c'", leftPos, rightPos, character);
    193    }
    194
    195    /**
    196     * Calculates the <em>weighted</em> value of a character in the code at a specified position.
    197     * <p>
    198     * Some modulus routines weight the value of a character depending on its position in the code (for example, ISBN-10), while others use different weighting
    199     * factors for odd/even positions (for example, EAN or Luhn). Implement the appropriate mechanism required by overriding this method.
    200     * </p>
    201     *
    202     * @param charValue The numeric value of the character.
    203     * @param leftPos   The position of the character in the code, counting from left to right.
    204     * @param rightPos  The position of the character in the code, counting from right to left.
    205     * @return The weighted value of the character.
    206     * @throws CheckDigitException if an error occurs calculating. the weighted value.
    207     */
    208    protected abstract int weightedValue(int charValue, int leftPos, int rightPos) throws CheckDigitException;
    209}