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 Digit routines.
025 * </p>
026 * <p>
027 * 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
028 * to implement/override the <code>toInt()</code> and <code>toChar()</code> methods.
029 * </p>
030 *
031 * @since 1.4
032 */
033public abstract class ModulusCheckDigit implements CheckDigit, Serializable {
034
035    static final int MODULUS_10 = 10;
036    static final int MODULUS_11 = 11;
037    private static final long serialVersionUID = 2948962251251528941L;
038
039    /**
040     * Add together the individual digits in a number.
041     *
042     * @param number The number whose digits are to be added
043     * @return The sum of the digits
044     */
045    public static int sumDigits(final int number) {
046        int total = 0;
047        int todo = number;
048        while (todo > 0) {
049            total += todo % 10; // CHECKSTYLE IGNORE MagicNumber
050            todo = todo / 10; // CHECKSTYLE IGNORE MagicNumber
051        }
052        return total;
053    }
054
055    /**
056     * The modulus can be greater than 10 provided that the implementing class overrides toCheckDigit and toInt (for example as in ISBN10CheckDigit).
057     */
058    private final int modulus;
059
060    /**
061     * Constructs a modulus 10 {@link CheckDigit} routine for a specified modulus.
062     */
063    ModulusCheckDigit() {
064        this(MODULUS_10);
065    }
066
067    /**
068     * Constructs a {@link CheckDigit} routine for a specified modulus.
069     *
070     * @param modulus The modulus value to use for the check digit calculation
071     */
072    public ModulusCheckDigit(final int modulus) {
073        this.modulus = modulus;
074    }
075
076    /**
077     * Calculate a modulus <i>Check Digit</i> for a code which does not yet have one.
078     *
079     * @param code The code for which to calculate the Check Digit;
080     * the check digit should not be included
081     * @return The calculated Check Digit
082     * @throws CheckDigitException if an error occurs calculating the check digit
083     */
084    @Override
085    public String calculate(final String code) throws CheckDigitException {
086        if (code == null || code.isEmpty()) {
087            throw new CheckDigitException("Code is missing");
088        }
089        final int modulusResult = calculateModulus(code, false);
090        final int charValue = (modulus - modulusResult) % modulus;
091        return toCheckDigit(charValue);
092    }
093
094    /**
095     * Calculate the modulus for a code.
096     *
097     * @param code The code to calculate the modulus for.
098     * @param includesCheckDigit Whether the code includes the Check Digit or not.
099     * @return The modulus value
100     * @throws CheckDigitException if an error occurs calculating the modulus
101     * for the specified code
102     */
103    protected int calculateModulus(final String code, final boolean includesCheckDigit) throws CheckDigitException {
104        int total = 0;
105        for (int i = 0; i < code.length(); i++) {
106            final int lth = code.length() + (includesCheckDigit ? 0 : 1);
107            final int leftPos = i + 1;
108            final int rightPos = lth - i;
109            final int charValue = toInt(code.charAt(i), leftPos, rightPos);
110            total += weightedValue(charValue, leftPos, rightPos);
111        }
112        if (total == 0) {
113            throw new CheckDigitException("Invalid code, sum is zero");
114        }
115        return total % modulus;
116    }
117
118    /**
119     * Return the modulus value this check digit routine is based on.
120     *
121     * @return The modulus value this check digit routine is based on
122     */
123    public int getModulus() {
124        return modulus;
125    }
126
127    /**
128     * Validate a modulus check digit for a code.
129     *
130     * @param code The code to validate
131     * @return {@code true} if the check digit is valid, otherwise
132     * {@code false}
133     */
134    @Override
135    public boolean isValid(final String code) {
136        if (code == null || code.isEmpty()) {
137            return false;
138        }
139        try {
140            final int modulusResult = calculateModulus(code, true);
141            return modulusResult == 0;
142        } catch (final CheckDigitException ex) {
143            return false;
144        }
145    }
146
147    /**
148     * Convert an integer value to a check digit.
149     * <p>
150     * <b>Note:</b> this implementation only handles single-digit numeric values
151     * For non-numeric characters, override this method to provide
152     * integer--&gt;character conversion.
153     *
154     * @param charValue The integer value of the character
155     * @return The converted character
156     * @throws CheckDigitException if integer character value
157     * doesn't represent a numeric character
158     */
159    protected String toCheckDigit(final int charValue)
160            throws CheckDigitException {
161        if (charValue >= 0 && charValue <= 9) { // CHECKSTYLE IGNORE MagicNumber
162            return Integer.toString(charValue);
163        }
164        throw new CheckDigitException("Invalid Check Digit Value =" +
165                + 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)
182            throws CheckDigitException {
183        if (Character.isDigit(character)) {
184            return Character.getNumericValue(character);
185        }
186        throw new CheckDigitException("Invalid Character[" +
187                leftPos + "] = '" + character + "'");
188    }
189
190    /**
191     * Calculates the <i>weighted</i> value of a character in the
192     * code at a specified position.
193     * <p>
194     * Some modulus routines weight the value of a character
195     * depending on its position in the code (e.g. ISBN-10), while
196     * others use different weighting factors for odd/even positions
197     * (e.g. EAN or Luhn). Implement the appropriate mechanism
198     * required by overriding this method.
199     *
200     * @param charValue The numeric value of the character
201     * @param leftPos The position of the character in the code, counting from left to right
202     * @param rightPos The positionof the character in the code, counting from right to left
203     * @return The weighted value of the character
204     * @throws CheckDigitException if an error occurs calculating
205     * the weighted value
206     */
207    protected abstract int weightedValue(int charValue, int leftPos, int rightPos)
208            throws CheckDigitException;
209
210}