/*

  * 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.monitor;

 import java.io.File;

 import java.io.Serializable;

 /**

  * {@link FileEntry} represents the state of a file or directory, capturing

  * the following {@link File} attributes at a point in time.

  * <ul>

  *   <li>File Name (see {@link File#getName()})</li>

  *   <li>Exists - whether the file exists or not (see {@link File#exists()})</li>

  *   <li>Directory - whether the file is a directory or not (see {@link File#isDirectory()})</li>

  *   <li>Last Modified Date/Time (see {@link File#lastModified()})</li>

  *   <li>Length (see {@link File#length()}) - directories treated as zero</li>

  *   <li>Children - contents of a directory (see {@link File#listFiles(java.io.FileFilter)})</li>

  * </ul>

  * <p>

  * <h3>Custom Implementations</h3>

  * If the state of additional {@link File} attributes is required then create a custom

  * {@link FileEntry} with properties for those attributes. Override the

  * {@link #newChildInstance(File)} to return a new instance of the appropriate type.

  * You may also want to override the {@link #refresh(File)} method.

  * @see FileAlterationObserver

  * @since 2.0

  */

 public class FileEntry implements Serializable {

     static final FileEntry[] EMPTY_ENTRIES = new FileEntry[0];

     private final FileEntry parent;

     private FileEntry[] children;

     private final File file;

     private String name;

     private boolean exists;

     private boolean directory;

     private long lastModified;

     private long length;

     /**

      * Construct a new monitor for a specified {@link File}.

      *

      * @param file The file being monitored

      */

     public FileEntry(final File file) {

         this((FileEntry)null, file);

     }

     /**

      * Construct a new monitor for a specified {@link File}.

      *

      * @param parent The parent

      * @param file The file being monitored

      */

     public FileEntry(final FileEntry parent, final File file) {

         if (file == null) {

             throw new IllegalArgumentException("File is missing");

         }

         this.file = file;

         this.parent = parent;

         this.name = file.getName();

     }

     /**

      * Refresh the attributes from the {@link File}, indicating

      * whether the file has changed.

      * <p>

      * This implementation refreshes the <code>name</code>, <code>exists</code>,

      * <code>directory</code>, <code>lastModified</code> and <code>length</code>

      * properties.

      * <p>

      * The <code>exists</code>, <code>directory</code>, <code>lastModified</code>

      * and <code>length</code> properties are compared for changes

      *

      * @param file the file instance to compare to

      * @return {@code true} if the file has changed, otherwise {@code false}

      */

     public boolean refresh(final File file) {

         // cache original values

         final boolean origExists       = exists;

         final long    origLastModified = lastModified;

         final boolean origDirectory    = directory;

         final long    origLength       = length;

         // refresh the values

         name         = file.getName();

         exists       = file.exists();

         directory    = exists ? file.isDirectory() : false;

         lastModified = exists ? file.lastModified() : 0;

         length       = exists && !directory ? file.length() : 0;

         // Return if there are changes

         return exists != origExists ||

                 lastModified != origLastModified ||

                 directory != origDirectory ||

                 length != origLength;

     }

     /**

      * Create a new child instance.

      * <p>

      * Custom implementations should override this method to return

      * a new instance of the appropriate type.

      *

      * @param file The child file

      * @return a new child instance

      */

     public FileEntry newChildInstance(final File file) {

         return new FileEntry(this, file);

     }

     /**

      * Return the parent entry.

      *

      * @return the parent entry

      */

     public FileEntry getParent() {

         return parent;

     }

     /**

      * Return the level

      *

      * @return the level

      */

     public int getLevel() {

         return parent == null ? 0 : parent.getLevel() + 1;

     }

     /**

      * Return the directory's files.

      *

      * @return This directory's files or an empty

      * array if the file is not a directory or the

      * directory is empty

      */

     public FileEntry[] getChildren() {

         return children != null ? children : EMPTY_ENTRIES;

     }

     /**

      * Set the directory's files.

      *

      * @param children This directory's files, may be null

      */

     public void setChildren(final FileEntry[] children) {

         this.children = children;

     }

     /**

      * Return the file being monitored.

      *

      * @return the file being monitored

      */

     public File getFile() {

         return file;

     }

     /**

      * Return the file name.

      *

      * @return the file name

      */

     public String getName() {

         return name;

     }

     /**

      * Set the file name.

      *

      * @param name the file name

      */

     public void setName(final String name) {

         this.name = name;

     }

     /**

      * Return the last modified time from the last time it

      * was checked.

      *

      * @return the last modified time

      */

     public long getLastModified() {

         return lastModified;

     }

     /**

      * Return the last modified time from the last time it

      * was checked.

      *

      * @param lastModified The last modified time

      */

     public void setLastModified(final long lastModified) {

         this.lastModified = lastModified;

     }

     /**

      * Return the length.

      *

      * @return the length

      */

     public long getLength() {

         return length;

     }

     /**

      * Set the length.

      *

      * @param length the length

      */

     public void setLength(final long length) {

         this.length = length;

     }

     /**

      * Indicate whether the file existed the last time it

      * was checked.

      *

      * @return whether the file existed

      */

     public boolean isExists() {

         return exists;

     }

     /**

      * Set whether the file existed the last time it

      * was checked.

      *

      * @param exists whether the file exists or not

      */

     public void setExists(final boolean exists) {

         this.exists = exists;

     }

     /**

      * Indicate whether the file is a directory or not.

      *

      * @return whether the file is a directory or not

      */

     public boolean isDirectory() {

         return directory;

     }

     /**

      * Set whether the file is a directory or not.

      *

      * @param directory whether the file is a directory or not

      */

     public void setDirectory(final boolean directory) {

         this.directory = directory;

     }

 }