SedolCheckDigit.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.validator.routines.checkdigit;

/**
 * Modulus 10 <strong>SEDOL</strong> (UK Securities) Check Digit calculation/validation.
 *
 * <p>
 * SEDOL Numbers are 7 character alphanumeric codes used
 * to identify UK Securities (SEDOL stands for Stock Exchange Daily Official List).
 * </p>
 * <p>
 * Check digit calculation is based on <em>modulus 10</em> with digits being weighted
 * based on their position, from left to right, as follows:
 * </p>
 * <pre>{@code
 *      position:  1  2  3  4  5  6  7
 *     weighting:  1  3  1  7  3  9  1
 * }</pre>
 * <p>
 * See <a href="https://en.wikipedia.org/wiki/SEDOL">Wikipedia - SEDOL</a>
 * for more details.
 * </p>
 *
 * @since 1.4
 */
public final class SedolCheckDigit extends ModulusCheckDigit {

    private static final long serialVersionUID = -8976881621148878443L;

    /**
     * Singleton SEDOL check digit instance.
     */
    public static final CheckDigit SEDOL_CHECK_DIGIT = new SedolCheckDigit();

    /** Weighting given to digits depending on their right position. */
    private static final int[] POSITION_WEIGHT = {1, 3, 1, 7, 3, 9, 1};

    /**
     * Constructs a modulus 10 Check Digit routine for ISBN-10.
     */
    public SedolCheckDigit() {
    }

    /**
     * Calculate the modulus for an SEDOL code.
     *
     * @param code               The code to calculate the modulus for.
     * @param includesCheckDigit Whether the code includes the Check Digit or not.
     * @return The modulus value.
     * @throws CheckDigitException if an error occurs calculating the modulus for the specified code.
     */
    @Override
    protected int calculateModulus(final String code, final boolean includesCheckDigit) throws CheckDigitException {
        if (code.length() > POSITION_WEIGHT.length) {
            throw new CheckDigitException("Invalid Code Length = %d", code.length());
        }
        return super.calculateModulus(code, includesCheckDigit);
    }

    private boolean isVowel(final char character) {
        return "AEIOU".indexOf(Character.toUpperCase(character)) >= 0;
    }

    /**
     * Convert a character at a specified position to an integer value.
     *
     * @param character The character to convert.
     * @param leftPos   The position of the character in the code, counting from left to right.
     * @param rightPos  The position of the character in the code, counting from right to left.
     * @return The integer value of the character.
     * @throws CheckDigitException if character is not alphanumeric or a vowel.
     */
    @Override
    protected int toInt(final char character, final int leftPos, final int rightPos) throws CheckDigitException {
        final int charValue = Character.getNumericValue(character);
        // the check digit is only allowed to reach 9
        final int charValueMax = rightPos == 1 ? 9 : MAX_ALPHANUMERIC_VALUE; // CHECKSTYLE IGNORE MagicNumber
        // The SEDOL alphabet excludes the vowels A, E, I, O and U, and treats Y as a consonant.
        if (charValue > charValueMax || !isAsciiAlphaNum(character) || isVowel(character)) {
            throw new CheckDigitException("Invalid Character[%d,%d] = '%d' out of range 0 to %d, exclusing vowels.", leftPos, rightPos, charValue, charValueMax);
        }
        return charValue;
    }

    /**
     * Calculates the <em>weighted</em> value of a character in the code at a specified position.
     *
     * @param charValue The numeric value of the character.
     * @param leftPos   The position of the character in the code, counting from left to right.
     * @param rightPos  The position of the character in the code, counting from right to left.
     * @return The weighted value of the character.
     */
    @Override
    protected int weightedValue(final int charValue, final int leftPos, final int rightPos) {
        return charValue * POSITION_WEIGHT[leftPos - 1];
    }
}