001/*
002 * Copyright (C) 2022 - 2023, the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *    http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package io.github.ascopes.jct.filemanagers.config;
017
018import io.github.ascopes.jct.filemanagers.JctFileManager;
019import java.util.ArrayDeque;
020import java.util.Deque;
021import java.util.List;
022import org.apiguardian.api.API;
023import org.apiguardian.api.API.Status;
024import org.slf4j.Logger;
025import org.slf4j.LoggerFactory;
026
027/**
028 * A chain of configurers to apply to a file manager.
029 *
030 * <p>While not designed for concurrent use, all operations are shielded by a
031 * mutex to guard against potentially confusing behaviour should this component
032 * be shared across multiple threads.
033 *
034 * @author Ashley Scopes
035 * @since 0.0.1
036 */
037@API(since = "0.0.1", status = Status.STABLE)
038public final class JctFileManagerConfigurerChain {
039
040  private static final Logger LOGGER = LoggerFactory.getLogger(JctFileManagerConfigurerChain.class);
041
042  private final Object lock;
043  private final Deque<JctFileManagerConfigurer> configurers;
044
045  /**
046   * Initialise this chain.
047   */
048  public JctFileManagerConfigurerChain() {
049    lock = new Object();
050    configurers = new ArrayDeque<>(16);
051  }
052
053  /**
054   * Add a configurer to the start of the chain.
055   *
056   * @param configurer the configurer to add.
057   * @return this chain for further calls.
058   */
059  public JctFileManagerConfigurerChain addFirst(JctFileManagerConfigurer configurer) {
060    synchronized (lock) {
061      configurers.addFirst(configurer);
062    }
063    return this;
064  }
065
066  /**
067   * Add a configurer to the end of the chain.
068   *
069   * @param configurer the configurer to add.
070   * @return this chain for further calls.
071   */
072  public JctFileManagerConfigurerChain addLast(JctFileManagerConfigurer configurer) {
073    synchronized (lock) {
074      configurers.addLast(configurer);
075    }
076    return this;
077  }
078
079  /**
080   * Get an immutable copy of the list of configurers.
081   *
082   * @return the list of configurers.
083   */
084  public List<JctFileManagerConfigurer> list() {
085    synchronized (lock) {
086      return List.copyOf(configurers);
087    }
088  }
089
090  /**
091   * Apply each configurer to the given file manager in order.
092   *
093   * @param fileManager the file manager to configure.
094   * @return the configured file manager to use. This may or may not be the same object as the input
095   *     parameter, depending on how the configurers manipulate the input object.
096   */
097  public JctFileManager configure(JctFileManager fileManager) {
098    synchronized (lock) {
099      for (var configurer : configurers) {
100        if (configurer.isEnabled()) {
101          LOGGER.debug("Applying {} to file manager", configurer);
102          fileManager = configurer.configure(fileManager);
103        } else {
104          LOGGER.trace("Skipping {}", configurer);
105        }
106      }
107    }
108
109    return fileManager;
110  }
111}