1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.codec.language.bm;
19
20 import java.util.ArrayList;
21 import java.util.Arrays;
22 import java.util.Collections;
23 import java.util.EnumMap;
24 import java.util.HashSet;
25 import java.util.List;
26 import java.util.Locale;
27 import java.util.Map;
28 import java.util.Scanner;
29 import java.util.Set;
30 import java.util.regex.Pattern;
31
32 import org.apache.commons.codec.Resources;
33
34 /**
35 * Language guessing utility.
36 * <p>
37 * This class encapsulates rules used to guess the possible languages that a word originates from. This is
38 * done by reference to a whole series of rules distributed in resource files.
39 * </p>
40 * <p>
41 * Instances of this class are typically managed through the static factory method instance().
42 * Unless you are developing your own language guessing rules, you will not need to interact with this class directly.
43 * </p>
44 * <p>
45 * This class is intended to be immutable and thread-safe.
46 * </p>
47 * <h2>Lang resources</h2>
48 * <p>
49 * Language guessing rules are typically loaded from resource files. These are UTF-8 encoded text files.
50 * They are systematically named following the pattern:
51 * </p>
52 * <blockquote>org/apache/commons/codec/language/bm/lang.txt</blockquote>
53 * <p>
54 * The format of these resources is the following:
55 * </p>
56 * <ul>
57 * <li><b>Rules:</b> whitespace separated strings.
58 * There should be 3 columns to each row, and these will be interpreted as:
59 * <ol>
60 * <li>pattern: a regular expression.</li>
61 * <li>languages: a '+'-separated list of languages.</li>
62 * <li>acceptOnMatch: 'true' or 'false' indicating if a match rules in or rules out the language.</li>
63 * </ol>
64 * </li>
65 * <li><b>End-of-line comments:</b> Any occurrence of '//' will cause all text following on that line to be
66 * discarded as a comment.</li>
67 * <li><b>Multi-line comments:</b> Any line starting with '/*' will start multi-line commenting mode.
68 * This will skip all content until a line ending in '*' and '/' is found.</li>
69 * <li><b>Blank lines:</b> All blank lines will be skipped.</li>
70 * </ul>
71 * <p>
72 * Port of lang.php
73 * </p>
74 *
75 * @since 1.6
76 */
77 public class Lang {
78 // Implementation note: This class is divided into two sections. The first part is a static factory interface that
79 // exposes the LANGUAGE_RULES_RN resource as a Lang instance. The second part is the Lang instance methods that
80 // encapsulate a particular language-guessing rule table and the language guessing itself.
81 //
82 // It may make sense in the future to expose the private constructor to allow power users to build custom language-
83 // guessing rules, perhaps by marking it protected and allowing sub-classing. However, the vast majority of users
84 // should be strongly encouraged to use the static factory {@code instance} method to get their Lang instances.
85
86 private static final class LangRule {
87 private final boolean acceptOnMatch;
88 private final Set<String> languages;
89 private final Pattern pattern;
90
91 private LangRule(final Pattern pattern, final Set<String> languages, final boolean acceptOnMatch) {
92 this.pattern = pattern;
93 this.languages = languages;
94 this.acceptOnMatch = acceptOnMatch;
95 }
96
97 public boolean matches(final String txt) {
98 return this.pattern.matcher(txt).find();
99 }
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 }