// Copyright 2008 The Apache Software Foundation

 //

 // Licensed 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.tapestry5.internal.util;

 import java.util.Locale;

 /**

  * Contains code borrowed from <a href="http://commons.apache.org/lang/">commons-lang</a>.

  */

 public class LocaleUtils

 {

     /**

      * <p>Converts a String to a Locale.</p> <p/> <p>This method takes the string format of a locale and creates the

      * locale object from it.</p> <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/> <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/> <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 input 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(String input)

     {

         if (input == null)

             return null;

         int len = input.length();

         if (len != 2 && len != 5 && len < 7)

             fail(input);

         char ch0 = input.charAt(0);

         char ch1 = input.charAt(1);

         if (ch0 < 'a' || ch0 > 'z' || ch1 < 'a' || ch1 > 'z')

             fail(input);

         if (len == 2)

             return new Locale(input, "");

         if (input.charAt(2) != '_')

             fail(input);

         char ch3 = input.charAt(3);

         if (ch3 == '_')

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

         char ch4 = input.charAt(4);

         if (ch3 < 'A' || ch3 > 'Z' || ch4 < 'A' || ch4 > 'Z')

             fail(input);

         if (len == 5)

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

         if (input.charAt(5) != '_')

             fail(input);

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

     }

     private static void fail(String input)

     {

         throw new IllegalArgumentException(String.format("Unable to convert '%s' to a Locale instance.", input));

     }

 }