/*
 * 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.tsfile.external.commons.io.filefilter;

import java.io.File;
import java.io.Serializable;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.attribute.BasicFileAttributes;

/**
 * This filter accepts {@link File}s that are files (not directories).
 *
 * <p>For example, here is how to print out a list of the real files within the current directory:
 *
 * <h2>Using Classic IO</h2>
 *
 * <pre>
 * File dir = FileUtils.current();
 * String[] files = dir.list(FileFileFilter.INSTANCE);
 * for (String file : files) {
 *     System.out.println(file);
 * }
 * </pre>
 *
 * <h2>Using NIO</h2>
 *
 * <pre>
 * final Path dir = PathUtils.current();
 * final AccumulatorPathVisitor visitor = AccumulatorPathVisitor.withLongCounters(FileFileFilter.INSTANCE);
 * //
 * // Walk one dir
 * Files.<b>walkFileTree</b>(dir, Collections.emptySet(), 1, visitor);
 * System.out.println(visitor.getPathCounters());
 * System.out.println(visitor.getFileList());
 * //
 * visitor.getPathCounters().reset();
 * //
 * // Walk dir tree
 * Files.<b>walkFileTree</b>(dir, visitor);
 * System.out.println(visitor.getPathCounters());
 * System.out.println(visitor.getDirList());
 * System.out.println(visitor.getFileList());
 * </pre>
 *
 * <h2>Deprecating Serialization</h2>
 *
 * <p><em>Serialization is deprecated and will be removed in 3.0.</em>
 *
 * @since 1.3
 * @see FileFilterUtils#fileFileFilter()
 */
public class FileFileFilter extends AbstractFileFilter implements Serializable {

  /**
   * Singleton instance of file filter.
   *
   * @since 2.9.0
   */
  public static final IOFileFilter INSTANCE = new FileFileFilter();

  /**
   * Singleton instance of file filter.
   *
   * @deprecated Use {@link #INSTANCE}.
   */
  @Deprecated public static final IOFileFilter FILE = INSTANCE;

  private static final long serialVersionUID = 5345244090827540862L;

  /** Restrictive constructor. */
  protected FileFileFilter() {}

  /**
   * Checks to see if the file is a file.
   *
   * @param file the File to check
   * @return true if the file is a file
   */
  @Override
  public boolean accept(final File file) {
    return file.isFile();
  }

  /**
   * Checks to see if the file is a file.
   *
   * @param file the File to check
   * @return true if the file is a file
   * @since 2.9.0
   */
  @Override
  public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
    return toFileVisitResult(Files.isRegularFile(file));
  }
}
