    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 */
    017
    018package org.apache.commons.codec.language.bm;
    019
    020import java.util.ArrayList;
    021import java.util.Arrays;
    022import java.util.Collections;
    023import java.util.EnumMap;
    024import java.util.HashSet;
    025import java.util.List;
    026import java.util.Locale;
    027import java.util.Map;
    028import java.util.Scanner;
    029import java.util.Set;
    030import java.util.regex.Pattern;
    031
    032import org.apache.commons.codec.Resources;
    033
    034/**
    035 * Language guessing utility.
    036 * <p>
    037 * This class encapsulates rules used to guess the possible languages that a word originates from. This is
    038 * done by reference to a whole series of rules distributed in resource files.
    039 * </p>
    040 * <p>
    041 * Instances of this class are typically managed through the static factory method instance().
    042 * Unless you are developing your own language guessing rules, you will not need to interact with this class directly.
    043 * </p>
    044 * <p>
    045 * This class is intended to be immutable and thread-safe.
    046 * </p>
    047 * <h2>Lang resources</h2>
    048 * <p>
    049 * Language guessing rules are typically loaded from resource files. These are UTF-8 encoded text files.
    050 * They are systematically named following the pattern:
    051 * </p>
    052 * <blockquote>org/apache/commons/codec/language/bm/lang.txt</blockquote>
    053 * <p>
    054 * The format of these resources is the following:
    055 * </p>
    056 * <ul>
    057 * <li><b>Rules:</b> whitespace separated strings.
    058 * There should be 3 columns to each row, and these will be interpreted as:
    059 * <ol>
    060 * <li>pattern: a regular expression.</li>
    061 * <li>languages: a '+'-separated list of languages.</li>
    062 * <li>acceptOnMatch: 'true' or 'false' indicating if a match rules in or rules out the language.</li>
    063 * </ol>
    064 * </li>
    065 * <li><b>End-of-line comments:</b> Any occurrence of '//' will cause all text following on that line to be
    066 * discarded as a comment.</li>
    067 * <li><b>Multi-line comments:</b> Any line starting with '/*' will start multi-line commenting mode.
    068 * This will skip all content until a line ending in '*' and '/' is found.</li>
    069 * <li><b>Blank lines:</b> All blank lines will be skipped.</li>
    070 * </ul>
    071 * <p>
    072 * Port of lang.php
    073 * </p>
    074 *
    075 * @since 1.6
    076 */
    077public class Lang {
    078    // Implementation note: This class is divided into two sections. The first part is a static factory interface that
    079    // exposes the LANGUAGE_RULES_RN resource as a Lang instance. The second part is the Lang instance methods that
    080    // encapsulate a particular language-guessing rule table and the language guessing itself.
    081    //
    082    // It may make sense in the future to expose the private constructor to allow power users to build custom language-
    083    // guessing rules, perhaps by marking it protected and allowing sub-classing. However, the vast majority of users
    084    // should be strongly encouraged to use the static factory {@code instance} method to get their Lang instances.
    085
    086    private static final class LangRule {
    087        private final boolean acceptOnMatch;
    088        private final Set<String> languages;
    089        private final Pattern pattern;
    090
    091        private LangRule(final Pattern pattern, final Set<String> languages, final boolean acceptOnMatch) {
    092            this.pattern = pattern;
    093            this.languages = languages;
    094            this.acceptOnMatch = acceptOnMatch;
    095        }
    096
    097        public boolean matches(final String txt) {
    098            return this.pattern.matcher(txt).find();
    099        }
    100    }
    101
    102    private static final Map<NameType, Lang> LANGS = new EnumMap<>(NameType.class);
    103
    104    private static final String LANGUAGE_RULES_RN = "org/apache/commons/codec/language/bm/%s_lang.txt";
    105
    106    static {
    107        for (final NameType s : NameType.values()) {
    108            LANGS.put(s, loadFromResource(String.format(LANGUAGE_RULES_RN, s.getName()), Languages.getInstance(s)));
    109        }
    110    }
    111
    112    /**
    113     * Gets a Lang instance for one of the supported NameTypes.
    114     *
    115     * @param nameType
    116     *            the NameType to look up
    117     * @return a Lang encapsulating the language guessing rules for that name type
    118     */
    119    public static Lang instance(final NameType nameType) {
    120        return LANGS.get(nameType);
    121    }
    122
    123    /**
    124     * Loads language rules from a resource.
    125     * <p>
    126     * In normal use, you will obtain instances of Lang through the {@link #instance(NameType)} method.
    127     * You will only need to call this yourself if you are developing custom language mapping rules.
    128     * </p>
    129     *
    130     * @param languageRulesResourceName
    131     *            the fully-qualified resource name to load
    132     * @param languages
    133     *            the languages that these rules will support
    134     * @return a Lang encapsulating the loaded language-guessing rules.
    135     */
    136    public static Lang loadFromResource(final String languageRulesResourceName, final Languages languages) {
    137        final List<LangRule> rules = new ArrayList<>();
    138        try (final Scanner scanner = new Scanner(Resources.getInputStream(languageRulesResourceName),
    139                ResourceConstants.ENCODING)) {
    140            boolean inExtendedComment = false;
    141            while (scanner.hasNextLine()) {
    142                final String rawLine = scanner.nextLine();
    143                String line = rawLine;
    144                if (inExtendedComment) {
    145                    // check for closing comment marker, otherwise discard doc comment line
    146                    if (line.endsWith(ResourceConstants.EXT_CMT_END)) {
    147                        inExtendedComment = false;
    148                    }
    149                } else if (line.startsWith(ResourceConstants.EXT_CMT_START)) {
    150                    inExtendedComment = true;
    151                } else {
    152                    // discard comments
    153                    final int cmtI = line.indexOf(ResourceConstants.CMT);
    154                    if (cmtI >= 0) {
    155                        line = line.substring(0, cmtI);
    156                    }
    157
    158                    // trim leading-trailing whitespace
    159                    line = line.trim();
    160
    161                    if (line.isEmpty()) {
    162                        continue; // empty lines can be safely skipped
    163                    }
    164
    165                    // split it up
    166                    final String[] parts = line.split("\\s+");
    167
    168                    if (parts.length != 3) {
    169                        throw new IllegalArgumentException("Malformed line '" + rawLine +
    170                                "' in language resource '" + languageRulesResourceName + "'");
    171                    }
    172
    173                    final Pattern pattern = Pattern.compile(parts[0]);
    174                    final String[] langs = parts[1].split("\\+");
    175                    final boolean accept = parts[2].equals("true");
    176
    177                    rules.add(new LangRule(pattern, new HashSet<>(Arrays.asList(langs)), accept));
    178                }
    179            }
    180        }
    181        return new Lang(rules, languages);
    182    }
    183
    184    private final Languages languages;
    185
    186    private final List<LangRule> rules;
    187
    188    private Lang(final List<LangRule> rules, final Languages languages) {
    189        this.rules = Collections.unmodifiableList(rules);
    190        this.languages = languages;
    191    }
    192
    193    /**
    194     * Guesses the language of a word.
    195     *
    196     * @param text
    197     *            the word
    198     * @return the language that the word originates from or {@link Languages#ANY} if there was no unique match
    199     */
    200    public String guessLanguage(final String text) {
    201        final Languages.LanguageSet ls = guessLanguages(text);
    202        return ls.isSingleton() ? ls.getAny() : Languages.ANY;
    203    }
    204
    205    /**
    206     * Guesses the languages of a word.
    207     *
    208     * @param input
    209     *            the word
    210     * @return a Set of Strings of language names that are potential matches for the input word
    211     */
    212    public Languages.LanguageSet guessLanguages(final String input) {
    213        final String text = input.toLowerCase(Locale.ENGLISH);
    214        final Set<String> langs = new HashSet<>(this.languages.getLanguages());
    215        rules.forEach(rule -> {
    216            if (rule.matches(text)) {
    217                if (rule.acceptOnMatch) {
    218                    langs.retainAll(rule.languages);
    219                } else {
    220                    langs.removeAll(rule.languages);
    221                }
    222            }
    223        });
    224        final Languages.LanguageSet ls = Languages.LanguageSet.from(langs);
    225        return ls.equals(Languages.NO_LANGUAGES) ? Languages.ANY_LANGUAGE : ls;
    226    }
    227}