/*
 * 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.file;

import org.apache.tsfile.external.commons.io.file.Counters.PathCounters;
import org.apache.tsfile.external.commons.io.filefilter.IOFileFilter;
import org.apache.tsfile.external.commons.io.filefilter.SymbolicLinkFileFilter;
import org.apache.tsfile.external.commons.io.filefilter.TrueFileFilter;

import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.Objects;

/**
 * Counts files, directories, and sizes, as a visit proceeds.
 *
 * @since 2.7
 */
public class CountingPathVisitor extends SimplePathVisitor {

  static final String[] EMPTY_STRING_ARRAY = {};

  static IOFileFilter defaultDirFilter() {
    return TrueFileFilter.INSTANCE;
  }

  static IOFileFilter defaultFileFilter() {
    return new SymbolicLinkFileFilter(FileVisitResult.TERMINATE, FileVisitResult.CONTINUE);
  }

  private final PathCounters pathCounters;
  private final PathFilter fileFilter;
  private final PathFilter dirFilter;

  /**
   * Constructs a new instance.
   *
   * @param pathCounter How to count path visits.
   */
  public CountingPathVisitor(final PathCounters pathCounter) {
    this(pathCounter, defaultFileFilter(), defaultDirFilter());
  }

  /**
   * Constructs a new instance.
   *
   * @param pathCounter How to count path visits.
   * @param fileFilter Filters which files to count.
   * @param dirFilter Filters which directories to count.
   * @since 2.9.0
   */
  public CountingPathVisitor(
      final PathCounters pathCounter, final PathFilter fileFilter, final PathFilter dirFilter) {
    this.pathCounters = Objects.requireNonNull(pathCounter, "pathCounter");
    this.fileFilter = Objects.requireNonNull(fileFilter, "fileFilter");
    this.dirFilter = Objects.requireNonNull(dirFilter, "dirFilter");
  }

  @Override
  public boolean equals(final Object obj) {
    if (this == obj) {
      return true;
    }
    if (!(obj instanceof CountingPathVisitor)) {
      return false;
    }
    final CountingPathVisitor other = (CountingPathVisitor) obj;
    return Objects.equals(pathCounters, other.pathCounters);
  }

  /**
   * Gets the visitation counts.
   *
   * @return the visitation counts.
   */
  public PathCounters getPathCounters() {
    return pathCounters;
  }

  @Override
  public int hashCode() {
    return Objects.hash(pathCounters);
  }

  @Override
  public FileVisitResult postVisitDirectory(final Path dir, final IOException exc)
      throws IOException {
    updateDirCounter(dir, exc);
    return FileVisitResult.CONTINUE;
  }

  @Override
  public FileVisitResult preVisitDirectory(final Path dir, final BasicFileAttributes attributes)
      throws IOException {
    final FileVisitResult accept = dirFilter.accept(dir, attributes);
    return accept != FileVisitResult.CONTINUE
        ? FileVisitResult.SKIP_SUBTREE
        : FileVisitResult.CONTINUE;
  }

  @Override
  public String toString() {
    return pathCounters.toString();
  }

  /**
   * Updates the counter for visiting the given directory.
   *
   * @param dir the visited directory.
   * @param exc Encountered exception.
   * @since 2.9.0
   */
  protected void updateDirCounter(final Path dir, final IOException exc) {
    pathCounters.getDirectoryCounter().increment();
  }

  /**
   * Updates the counters for visiting the given file.
   *
   * @param file the visited file.
   * @param attributes the visited file attributes.
   */
  protected void updateFileCounters(final Path file, final BasicFileAttributes attributes) {
    pathCounters.getFileCounter().increment();
    pathCounters.getByteCounter().add(attributes.size());
  }

  @Override
  public FileVisitResult visitFile(final Path file, final BasicFileAttributes attributes)
      throws IOException {
    // Note: A file can be a symbolic link to a directory.
    if (Files.exists(file) && fileFilter.accept(file, attributes) == FileVisitResult.CONTINUE) {
      updateFileCounters(file, attributes);
    }
    return FileVisitResult.CONTINUE;
  }
}
