/*

  * 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 org.apache.commons.lang3;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.Collections;

 import java.util.HashSet;

 import java.util.List;

 import java.util.Locale;

 import java.util.Set;

 import java.util.concurrent.ConcurrentHashMap;

 import java.util.concurrent.ConcurrentMap;

 /**

  * <p>Operations to assist when working with a {@link Locale}.</p>

  *

  * <p>This class tries to handle {@code null} input gracefully.

  * An exception will not be thrown for a {@code null} input.

  * Each method documents its behaviour in more detail.</p>

  *

  * @since 2.2

  * @version $Id: LocaleUtils.java 1436770 2013-01-22 07:09:45Z ggregory $

  */

 public class LocaleUtils {

     /** Concurrent map of language locales by country. */

     private static final ConcurrentMap<String, List<Locale>> cLanguagesByCountry = 

         new ConcurrentHashMap<String, List<Locale>>();

     /** Concurrent map of country locales by language. */

     private static final ConcurrentMap<String, List<Locale>> cCountriesByLanguage = 

         new ConcurrentHashMap<String, List<Locale>>();

     /**

      * <p>{@code LocaleUtils} instances should NOT be constructed in standard programming.

      * Instead, the class should be used as {@code LocaleUtils.toLocale("en_GB");}.</p>

      *

      * <p>This constructor is public to permit tools that require a JavaBean instance

      * to operate.</p>

      */

     public LocaleUtils() {

       super();

     }

     //-----------------------------------------------------------------------

     /**

      * <p>Converts a String to a Locale.</p>

      *

      * <p>This method takes the string format of a locale and creates the

      * locale object from it.</p>

      *

      * <pre>

      *   LocaleUtils.toLocale("en")         = new Locale("en", "")

      *   LocaleUtils.toLocale("en_GB")      = new Locale("en", "GB")

      *   LocaleUtils.toLocale("en_GB_xxx")  = new Locale("en", "GB", "xxx")   (#)

      * </pre>

      *

      * <p>(#) The behaviour of the JDK variant constructor changed between JDK1.3 and JDK1.4.

      * In JDK1.3, the constructor upper cases the variant, in JDK1.4, it doesn't.

      * Thus, the result from getVariant() may vary depending on your JDK.</p>

      *

      * <p>This method validates the input strictly.

      * The language code must be lowercase.

      * The country code must be uppercase.

      * The separator must be an underscore.

      * The length must be correct.

      * </p>

      *

      * @param str  the locale String to convert, null returns null

      * @return a Locale, null if null input

      * @throws IllegalArgumentException if the string is an invalid format

      */

     public static Locale toLocale(final String str) {

         if (str == null) {

             return null;

         }

         final int len = str.length();

         if (len < 2) {

             throw new IllegalArgumentException("Invalid locale format: " + str);

         }

         final char ch0 = str.charAt(0);

         if (ch0 == '_') {

             if (len < 3) {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             final char ch1 = str.charAt(1);

             final char ch2 = str.charAt(2);

             if (!Character.isUpperCase(ch1) || !Character.isUpperCase(ch2)) {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             if (len == 3) {

                 return new Locale("", str.substring(1, 3));

             }

             if (len < 5) {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             if (str.charAt(3) != '_') {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             return new Locale("", str.substring(1, 3), str.substring(4));

         } else {

             final char ch1 = str.charAt(1);

             if (!Character.isLowerCase(ch0) || !Character.isLowerCase(ch1)) {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             if (len == 2) {

                 return new Locale(str);

             }

             if (len < 5) {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             if (str.charAt(2) != '_') {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             final char ch3 = str.charAt(3);

             if (ch3 == '_') {

                 return new Locale(str.substring(0, 2), "", str.substring(4));

             }

             final char ch4 = str.charAt(4);

             if (!Character.isUpperCase(ch3) || !Character.isUpperCase(ch4)) {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             if (len == 5) {

                 return new Locale(str.substring(0, 2), str.substring(3, 5));

             }

             if (len < 7) {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             if (str.charAt(5) != '_') {

                 throw new IllegalArgumentException("Invalid locale format: " + str);

             }

             return new Locale(str.substring(0, 2), str.substring(3, 5), str.substring(6));

         }

     }

     //-----------------------------------------------------------------------

     /**

      * <p>Obtains the list of locales to search through when performing

      * a locale search.</p>

      *

      * <pre>

      * localeLookupList(Locale("fr","CA","xxx"))

      *   = [Locale("fr","CA","xxx"), Locale("fr","CA"), Locale("fr")]

      * </pre>

      *

      * @param locale  the locale to start from

      * @return the unmodifiable list of Locale objects, 0 being locale, not null

      */

     public static List<Locale> localeLookupList(final Locale locale) {

         return localeLookupList(locale, locale);

     }

     //-----------------------------------------------------------------------

     /**

      * <p>Obtains the list of locales to search through when performing

      * a locale search.</p>

      *

      * <pre>

      * localeLookupList(Locale("fr", "CA", "xxx"), Locale("en"))

      *   = [Locale("fr","CA","xxx"), Locale("fr","CA"), Locale("fr"), Locale("en"]

      * </pre>

      *

      * <p>The result list begins with the most specific locale, then the

      * next more general and so on, finishing with the default locale.

      * The list will never contain the same locale twice.</p>

      *

      * @param locale  the locale to start from, null returns empty list

      * @param defaultLocale  the default locale to use if no other is found

      * @return the unmodifiable list of Locale objects, 0 being locale, not null

      */

     public static List<Locale> localeLookupList(final Locale locale, final Locale defaultLocale) {

         final List<Locale> list = new ArrayList<Locale>(4);

         if (locale != null) {

             list.add(locale);

             if (locale.getVariant().length() > 0) {

                 list.add(new Locale(locale.getLanguage(), locale.getCountry()));

             }

             if (locale.getCountry().length() > 0) {

                 list.add(new Locale(locale.getLanguage(), ""));

             }

             if (list.contains(defaultLocale) == false) {

                 list.add(defaultLocale);

             }

         }

         return Collections.unmodifiableList(list);

     }

     //-----------------------------------------------------------------------

     /**

      * <p>Obtains an unmodifiable list of installed locales.</p>

      * 

      * <p>This method is a wrapper around {@link Locale#getAvailableLocales()}.

      * It is more efficient, as the JDK method must create a new array each

      * time it is called.</p>

      *

      * @return the unmodifiable list of available locales

      */

     public static List<Locale> availableLocaleList() {

         return SyncAvoid.AVAILABLE_LOCALE_LIST;

     }

     //-----------------------------------------------------------------------

     /**

      * <p>Obtains an unmodifiable set of installed locales.</p>

      * 

      * <p>This method is a wrapper around {@link Locale#getAvailableLocales()}.

      * It is more efficient, as the JDK method must create a new array each

      * time it is called.</p>

      *

      * @return the unmodifiable set of available locales

      */

     public static Set<Locale> availableLocaleSet() {

         return SyncAvoid.AVAILABLE_LOCALE_SET;

     }

     //-----------------------------------------------------------------------

     /**

      * <p>Checks if the locale specified is in the list of available locales.</p>

      *

      * @param locale the Locale object to check if it is available

      * @return true if the locale is a known locale

      */

     public static boolean isAvailableLocale(final Locale locale) {

         return availableLocaleList().contains(locale);

     }

     //-----------------------------------------------------------------------

     /**

      * <p>Obtains the list of languages supported for a given country.</p>

      *

      * <p>This method takes a country code and searches to find the

      * languages available for that country. Variant locales are removed.</p>

      *

      * @param countryCode  the 2 letter country code, null returns empty

      * @return an unmodifiable List of Locale objects, not null

      */

     public static List<Locale> languagesByCountry(final String countryCode) {

         if (countryCode == null) {

             return Collections.emptyList();

         }

         List<Locale> langs = cLanguagesByCountry.get(countryCode);

         if (langs == null) {

             langs = new ArrayList<Locale>();

             final List<Locale> locales = availableLocaleList();

             for (int i = 0; i < locales.size(); i++) {

                 final Locale locale = locales.get(i);

                 if (countryCode.equals(locale.getCountry()) &&

                         locale.getVariant().isEmpty()) {

                     langs.add(locale);

                 }

             }

             langs = Collections.unmodifiableList(langs);

             cLanguagesByCountry.putIfAbsent(countryCode, langs);

             langs = cLanguagesByCountry.get(countryCode);

         }

         return langs;

     }

     //-----------------------------------------------------------------------

     /**

      * <p>Obtains the list of countries supported for a given language.</p>

      * 

      * <p>This method takes a language code and searches to find the

      * countries available for that language. Variant locales are removed.</p>

      *

      * @param languageCode  the 2 letter language code, null returns empty

      * @return an unmodifiable List of Locale objects, not null

      */

     public static List<Locale> countriesByLanguage(final String languageCode) {

         if (languageCode == null) {

             return Collections.emptyList();

         }

         List<Locale> countries = cCountriesByLanguage.get(languageCode);

         if (countries == null) {

             countries = new ArrayList<Locale>();

             final List<Locale> locales = availableLocaleList();

             for (int i = 0; i < locales.size(); i++) {

                 final Locale locale = locales.get(i);

                 if (languageCode.equals(locale.getLanguage()) &&

                         locale.getCountry().length() != 0 &&

                         locale.getVariant().isEmpty()) {

                     countries.add(locale);

                 }

             }

             countries = Collections.unmodifiableList(countries);

             cCountriesByLanguage.putIfAbsent(languageCode, countries);

             countries = cCountriesByLanguage.get(languageCode);

         }

         return countries;

     }

     //-----------------------------------------------------------------------

     // class to avoid synchronization (Init on demand)

     static class SyncAvoid {

         /** Unmodifiable list of available locales. */

         private static final List<Locale> AVAILABLE_LOCALE_LIST;

         /** Unmodifiable set of available locales. */

         private static final Set<Locale> AVAILABLE_LOCALE_SET;

         static {

             final List<Locale> list = new ArrayList<Locale>(Arrays.asList(Locale.getAvailableLocales()));  // extra safe

             AVAILABLE_LOCALE_LIST = Collections.unmodifiableList(list);

             AVAILABLE_LOCALE_SET = Collections.unmodifiableSet(new HashSet<Locale>(list));

         }

     }

 }