D-Net

/*

 * This file is part of CoAnSys project.

 * Copyright (c) 2012-2015 ICM-UW

 * 

 * CoAnSys is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Affero General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 * CoAnSys is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

 * GNU Affero General Public License for more details.

 * 

 * You should have received a copy of the GNU Affero General Public License

 * along with CoAnSys. If not, see <http://www.gnu.org/licenses/>.

 */

package eu.dnetlib.dhp.common.string;

import java.io.Serializable;

import java.util.List;

import org.apache.commons.lang3.StringUtils;

import com.google.common.collect.ImmutableList;

/**

 * An implementation of {@link StringNormalizer} that normalizes strings for non-strict comparisons

 * in which one does not care about characters other than letters and digits or about differently written diacritics.

 *

 * @author Łukasz Dumiszewski

 *

 */

public final class LenientComparisonStringNormalizer implements StringNormalizer, Serializable {

    private static final long serialVersionUID = 1L;

    private List<Character> whitelistCharacters;

    //------------------------ CONSTRUCTORS --------------------------

    public LenientComparisonStringNormalizer() {

        this(ImmutableList.of());

    }

    /**

     * @param whitelistCharacters - non alphanumeric characters that will not be removed

     *      during normalization

     */

    public LenientComparisonStringNormalizer(List<Character> whitelistCharacters) {

        this.whitelistCharacters = whitelistCharacters;

    }

    //------------------------ LOGIC --------------------------

    /**

     * Normalizes the given value. <br/>

     * The normalized strings are better suited for non-strict comparisons, in which one does NOT care about characters that are

     * neither letters nor digits; about accidental spaces or different diacritics etc. <br/><br/>

     * This method:

     * <ul>

     * <li>Replaces all characters that are not letters or digits with spaces (except those on whitelist characters list)</li>

     * <li>Replaces white spaces with spaces </li>

     * <li>Trims</li>

     * <li>Compacts multi-space gaps to one-space gaps</li>

     * <li>Removes diacritics</li>

     * <li>Changes characters to lower case</li>

     * </ul>

     * Returns "" if the passed value is null or blank

     *

     * @param value the string to normalize 

     * @see DiacriticsRemover#removeDiacritics(String, boolean)

     *

     *

     */

    public String normalize(String value) {

        if (StringUtils.isBlank(value)) {

            return "";

        }

        String result = value;

        result = DiacriticsRemover.removeDiacritics(result);

        result = removeNonLetterDigitCharacters(result);

        result = result.toLowerCase();

        result = result.trim().replaceAll(" +", " ");

        return result;

    }

    //------------------------ PRIVATE --------------------------

    private String removeNonLetterDigitCharacters(final String value) {

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < value.length(); ++i) {

            char c = value.charAt(i);

            if (Character.isLetterOrDigit(c) || whitelistCharacters.contains(c)) {

                sb.append(c);

            } else {

                sb.append(' ');

            }

        }

        return sb.toString();

    }

}