/*
* 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
*
* http://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 uk.bl.wa.analyser.text.lang;
/*
* #%L
* warc-indexer
* %%
* Copyright (C) 2013 - 2015 The UK Web Archive
* %%
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as
* published by the Free Software Foundation, either version 2 of the
* License, or (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program. If not, see
* <http://www.gnu.org/licenses/gpl-2.0.html>.
* #L%
*/
import uk.bl.wa.util.Instrument;
import java.io.*;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
/**
* Identifier of the language that best matches a given content profile.
* The content profile is compared to generic language profiles based on
* material from various sources.
*
* @since Apache Tika 0.5
* @see <a href="http://www.iccs.inf.ed.ac.uk/~pkoehn/publications/europarl/">
* Europarl: A Parallel Corpus for Statistical Machine Translation</a>
* @see <a href="http://www.loc.gov/standards/iso639-2/php/code_list.php">
* ISO 639 Language Codes</a>
*/
public class LanguageIdentifier {
/**
* The available language profiles.
*/
private static final Map<String, LanguageProfile> PROFILES =
new HashMap<String, LanguageProfile>();
private static final String PROFILE_SUFFIX = ".ngp";
private static final String PROFILE_ENCODING = "UTF-8";
private static Properties props = new Properties();
private static String errors = "";
private static final String PROPERTIES_OVERRIDE_FILE = "tika.language.override.properties";
private static final String PROPERTIES_FILE = "tika.language.properties";
private static final String LANGUAGES_KEY = "languages";
private static final double CERTAINTY_LIMIT = 0.022;
private final String language;
private final double distance;
/*
* Always attempt initializing language profiles when class is loaded first time
*/
static {
initProfiles();
}
/*
* Add one language profile based on config in property file
*/
private static void addProfile(String language) throws Exception {
final long start = System.nanoTime();
try {
LanguageProfile profile = new LanguageProfile();
InputStream stream = getResourceAsStream(language + PROFILE_SUFFIX);
try {
BufferedReader reader =
new BufferedReader(new InputStreamReader(stream, PROFILE_ENCODING));
String line = reader.readLine();
while (line != null) {
if (line.length() > 0 && !line.startsWith("#")) {
int space = line.indexOf(' ');
profile.add(
line.substring(0, space),
Long.parseLong(line.substring(space + 1)));
}
line = reader.readLine();
}
} finally {
stream.close();
}
addProfile(language, profile);
} catch (Throwable t) {
throw new Exception("Failed trying to load language profile for language \""+language+"\". Error: "+t.getMessage());
} finally {
Instrument.timeRel("LanguageDetector.detectLanguage#li", "LanguageIdentifier.addProfile", start);
}
}
private static InputStream getResourceAsStream(String path) {
InputStream is;
return (is = Thread.currentThread().getContextClassLoader().getResourceAsStream(path)) != null ? is :
org.apache.tika.language.LanguageIdentifier.class.getResourceAsStream(path);
//return Thread.currentThread().getContextClassLoader().getResourceAsStream(path);
}
/**
* Adds a single language profile
* @param language an ISO 639 code representing language
* @param profile the language profile
*/
public static void addProfile(String language, LanguageProfile profile) {
PROFILES.put(language, profile);
}
/**
* Constructs a language identifier based on a LanguageProfile
* @param profile the language profile
*/
public LanguageIdentifier(LanguageProfile profile) {
final long start = System.nanoTime();
String minLanguage = "unknown";
double minDistance = 1.0;
for (Map.Entry<String, LanguageProfile> entry : PROFILES.entrySet()) {
double distance = profile.distance(entry.getValue());
if (distance < minDistance) {
minDistance = distance;
minLanguage = entry.getKey();
}
}
this.language = minLanguage;
this.distance = minDistance;
Instrument.timeRel("LanguageDetector.detectLanguage#li", "LanguageIdentifier#matchlanguageprofile", start);
}
/**
* Constructs a language identifier based on a String of text content
* @param content the text
*/
public LanguageIdentifier(String content) {
this(new LanguageProfile(content));
}
/**
* Gets the identified language
* @return an ISO 639 code representing the detected language
*/
public String getLanguage() {
return language;
}
/**
* Tries to judge whether the identification is certain enough
* to be trusted.
* WARNING: Will never return true for small amount of input texts.
* @return <code>true</code> if the distance is smaller then {@value #CERTAINTY_LIMIT}, <code>false</code> otherwise
*/
public boolean isReasonablyCertain() {
return distance < CERTAINTY_LIMIT;
}
/**
* Builds the language profiles.
* The list of languages are fetched from a property file named "tika.language.properties"
* If a file called "tika.language.override.properties" is found on classpath, this is used instead
* The property file contains a key "languages" with values being comma-separated language codes
*/
public static void initProfiles() {
clearProfiles();
errors = "";
InputStream stream;
stream = getResourceAsStream(PROPERTIES_OVERRIDE_FILE);
//stream = LanguageIdentifier.class.getResourceAsStream(PROPERTIES_OVERRIDE_FILE);
if(stream == null) {
stream = getResourceAsStream(PROPERTIES_FILE);
}
if (stream == null) {
throw new RuntimeException(
"Unable to locate a properties stream for either " + PROPERTIES_OVERRIDE_FILE + " or "
+ PROPERTIES_FILE);
}
if(stream != null){
try {
props = new Properties();
props.load(stream);
} catch (IOException e) {
errors += "IOException while trying to load property file. Message: " + e.getMessage() + "\n";
}
}
String[] languages = props.getProperty(LANGUAGES_KEY).split(",");
for(String language : languages) {
language = language.trim();
String name = props.getProperty("name."+language, "Unknown");
try {
addProfile(language);
} catch (Exception e) {
errors += "Language " + language + " (" + name + ") not initialized. Message: " + e.getMessage() + "\n";
}
}
}
/**
* Initializes the language profiles from a user supplied initialized Map.
* This overrides the default set of profiles initialized at startup,
* and provides an alternative to configuring profiles through property file
*
* @param profilesMap map of language profiles
*/
public static void initProfiles(Map<String, LanguageProfile> profilesMap) {
clearProfiles();
for(Map.Entry<String, LanguageProfile> entry : profilesMap.entrySet()) {
addProfile(entry.getKey(), entry.getValue());
}
}
/**
* Clears the current map of language profiles
*/
public static void clearProfiles() {
PROFILES.clear();
}
/**
* Tests whether there were errors initializing language config
* @return true if there are errors. Use getErrors() to retrieve.
*/
public static boolean hasErrors() {
return errors != "";
}
/**
* Returns a string of error messages related to initializing langauge profiles
* @return the String containing the error messages
*/
public static String getErrors() {
return errors;
}
/**
* Returns what languages are supported for language identification
* @return A set of Strings being the ISO 639 language codes
*/
public static Set<String> getSupportedLanguages() {
return PROFILES.keySet();
}
@Override
public String toString() {
return language + " (" + distance + ")";
}
}