/*

  * 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.io.comparator;

 import java.io.File;

 import java.io.Serializable;

 import java.util.Comparator;

 import org.apache.commons.io.FilenameUtils;

 import org.apache.commons.io.IOCase;

 /**

  * Compare the file name <b>extensions</b> for order

  * (see {@link FilenameUtils#getExtension(String)}).

  * <p>

  * This comparator can be used to sort lists or arrays of files

  * by their file extension either in a case-sensitive, case-insensitive or

  * system dependent case sensitive way. A number of singleton instances

  * are provided for the various case sensitivity options (using {@link IOCase})

  * and the reverse of those options.

  * <p>

  * Example of a <i>case-sensitive</i> file extension sort using the

  * {@link #EXTENSION_COMPARATOR} singleton instance:

  * <pre>

  *       List<File> list = ...

  *       ((AbstractFileComparator) ExtensionFileComparator.EXTENSION_COMPARATOR).sort(list);

  * </pre>

  * <p>

  * Example of a <i>reverse case-insensitive</i> file extension sort using the

  * {@link #EXTENSION_INSENSITIVE_REVERSE} singleton instance:

  * <pre>

  *       File[] array = ...

  *       ((AbstractFileComparator) ExtensionFileComparator.EXTENSION_INSENSITIVE_REVERSE).sort(array);

  * </pre>

  * <p>

  *

  * @version $Id: ExtensionFileComparator.java 1469107 2013-04-17 23:45:53Z sebb $

  * @since 1.4

  */

 public class ExtensionFileComparator extends AbstractFileComparator implements Serializable {

     /** Case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */

     public static final Comparator<File> EXTENSION_COMPARATOR = new ExtensionFileComparator();

     /** Reverse case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */

     public static final Comparator<File> EXTENSION_REVERSE = new ReverseComparator(EXTENSION_COMPARATOR);

     /** Case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */

     public static final Comparator<File> EXTENSION_INSENSITIVE_COMPARATOR

                                                 = new ExtensionFileComparator(IOCase.INSENSITIVE);

     /** Reverse case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */

     public static final Comparator<File> EXTENSION_INSENSITIVE_REVERSE

                                                 = new ReverseComparator(EXTENSION_INSENSITIVE_COMPARATOR);

     /** System sensitive extension comparator instance (see {@link IOCase#SYSTEM}) */

     public static final Comparator<File> EXTENSION_SYSTEM_COMPARATOR = new ExtensionFileComparator(IOCase.SYSTEM);

     /** Reverse system sensitive path comparator instance (see {@link IOCase#SYSTEM}) */

     public static final Comparator<File> EXTENSION_SYSTEM_REVERSE = new ReverseComparator(EXTENSION_SYSTEM_COMPARATOR);

     /** Whether the comparison is case sensitive. */

     private final IOCase caseSensitivity;

     /**

      * Construct a case sensitive file extension comparator instance.

      */

     public ExtensionFileComparator() {

         this.caseSensitivity = IOCase.SENSITIVE;

     }

     /**

      * Construct a file extension comparator instance with the specified case-sensitivity.

      *

      * @param caseSensitivity how to handle case sensitivity, null means case-sensitive

      */

     public ExtensionFileComparator(final IOCase caseSensitivity) {

         this.caseSensitivity = caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity;

     }

     /**

      * Compare the extensions of two files the specified case sensitivity.

      * 

      * @param file1 The first file to compare

      * @param file2 The second file to compare

      * @return a negative value if the first file's extension

      * is less than the second, zero if the extensions are the

      * same and a positive value if the first files extension

      * is greater than the second file.

      * 

      */

     public int compare(final File file1, final File file2) {

         final String suffix1 = FilenameUtils.getExtension(file1.getName());

         final String suffix2 = FilenameUtils.getExtension(file2.getName());

         return caseSensitivity.checkCompareTo(suffix1, suffix2);

     }

     /**

      * String representation of this file comparator.

      *

      * @return String representation of this file comparator

      */

     @Override

     public String toString() {

         return super.toString() + "[caseSensitivity=" + caseSensitivity + "]";

     }

 }