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}