    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.text.similarity;
    018
    019import java.util.Locale;
    020
    021/**
    022 * A matching algorithm that is similar to the searching algorithms implemented in editors such
    023 * as Sublime Text, TextMate, Atom and others.
    024 *
    025 * <p>
    026 * One point is given for every matched character. Subsequent matches yield two bonus points. A higher score
    027 * indicates a higher similarity.
    028 * </p>
    029 *
    030 * <p>
    031 * This code has been adapted from Apache Commons Lang 3.3.
    032 * </p>
    033 *
    034 * @since 1.0
    035 */
    036public class FuzzyScore {
    037
    038    /**
    039     * Locale used to change the case of text.
    040     */
    041    private final Locale locale;
    042
    043
    044    /**
    045     * <p>This returns a {@link Locale}-specific {@link FuzzyScore}.</p>
    046     *
    047     * @param locale The string matching logic is case insensitive.
    048                     A {@link Locale} is necessary to normalize both Strings to lower case.
    049     * @throws IllegalArgumentException
    050     *         This is thrown if the {@link Locale} parameter is {@code null}.
    051     */
    052    public FuzzyScore(final Locale locale) {
    053        if (locale == null) {
    054            throw new IllegalArgumentException("Locale must not be null");
    055        }
    056        this.locale = locale;
    057    }
    058
    059    /**
    060     * <p>
    061     * Find the Fuzzy Score which indicates the similarity score between two
    062     * Strings.
    063     * </p>
    064     *
    065     * <pre>
    066     * score.fuzzyScore(null, null)                          = IllegalArgumentException
    067     * score.fuzzyScore("not null", null)                    = IllegalArgumentException
    068     * score.fuzzyScore(null, "not null")                    = IllegalArgumentException
    069     * score.fuzzyScore("", "")                              = 0
    070     * score.fuzzyScore("Workshop", "b")                     = 0
    071     * score.fuzzyScore("Room", "o")                         = 1
    072     * score.fuzzyScore("Workshop", "w")                     = 1
    073     * score.fuzzyScore("Workshop", "ws")                    = 2
    074     * score.fuzzyScore("Workshop", "wo")                    = 4
    075     * score.fuzzyScore("Apache Software Foundation", "asf") = 3
    076     * </pre>
    077     *
    078     * @param term a full term that should be matched against, must not be null
    079     * @param query the query that will be matched against a term, must not be
    080     *            null
    081     * @return result score
    082     * @throws IllegalArgumentException if the term or query is {@code null}
    083     */
    084    public Integer fuzzyScore(final CharSequence term, final CharSequence query) {
    085        if (term == null || query == null) {
    086            throw new IllegalArgumentException("CharSequences must not be null");
    087        }
    088
    089        // fuzzy logic is case insensitive. We normalize the Strings to lower
    090        // case right from the start. Turning characters to lower case
    091        // via Character.toLowerCase(char) is unfortunately insufficient
    092        // as it does not accept a locale.
    093        final String termLowerCase = term.toString().toLowerCase(locale);
    094        final String queryLowerCase = query.toString().toLowerCase(locale);
    095
    096        // the resulting score
    097        int score = 0;
    098
    099        // the position in the term which will be scanned next for potential
    100        // query character matches
    101        int termIndex = 0;
    102
    103        // index of the previously matched character in the term
    104        int previousMatchingCharacterIndex = Integer.MIN_VALUE;
    105
    106        for (int queryIndex = 0; queryIndex < queryLowerCase.length(); queryIndex++) {
    107            final char queryChar = queryLowerCase.charAt(queryIndex);
    108
    109            boolean termCharacterMatchFound = false;
    110            for (; termIndex < termLowerCase.length()
    111                    && !termCharacterMatchFound; termIndex++) {
    112                final char termChar = termLowerCase.charAt(termIndex);
    113
    114                if (queryChar == termChar) {
    115                    // simple character matches result in one point
    116                    score++;
    117
    118                    // subsequent character matches further improve
    119                    // the score.
    120                    if (previousMatchingCharacterIndex + 1 == termIndex) {
    121                        score += 2;
    122                    }
    123
    124                    previousMatchingCharacterIndex = termIndex;
    125
    126                    // we can leave the nested loop. Every character in the
    127                    // query can match at most one character in the term.
    128                    termCharacterMatchFound = true;
    129                }
    130            }
    131        }
    132
    133        return score;
    134    }
    135
    136    /**
    137     * Gets the locale.
    138     *
    139     * @return The locale
    140     */
    141    public Locale getLocale() {
    142        return locale;
    143    }
    144
    145}