/*
    * 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.logging.log4j.core.util;
  
  import java.io.File;
  import java.util.List;
  
  import org.apache.logging.log4j.core.config.Configuration;
  import org.apache.logging.log4j.core.config.ConfigurationListener;
  import org.apache.logging.log4j.core.config.Reconfigurable;
  
  /**
   * Watcher for configuration files. Causes a reconfiguration when a file changes.
   */
  public abstract class AbstractWatcher implements Watcher {
  
      private final Reconfigurable reconfigurable;
      private final List<ConfigurationListener> configurationListeners;
      private final Log4jThreadFactory threadFactory;
      private final Configuration configuration;
      private Source source;
  
      public AbstractWatcher(final Configuration configuration, final Reconfigurable reconfigurable,
              final List<ConfigurationListener> configurationListeners) {
          this.configuration = configuration;
          this.reconfigurable = reconfigurable;
          this.configurationListeners = configurationListeners;
          this.threadFactory = configurationListeners != null ?
              Log4jThreadFactory.createDaemonThreadFactory("ConfiguratonFileWatcher") : null;
      }
  
      @Override
      public List<ConfigurationListener> getListeners() {
          return configurationListeners;
      }
  
      @Override
      public void modified() {
          for (final ConfigurationListener configurationListener : configurationListeners) {
              final Thread thread = threadFactory.newThread(new ReconfigurationRunnable(configurationListener, reconfigurable));
              thread.start();
          }
      }
  
      public Configuration getConfiguration() {
          return configuration;
      }
  
      public abstract long getLastModified();
  
      public abstract boolean isModified();
  
      @Override
      public void watching(Source source) {
          this.source = source;
      }
  
      @Override
      public Source getSource() {
          return source;
      }
  
      /**
       * Helper class for triggering a reconfiguration in a background thread.
       */
      public static class ReconfigurationRunnable implements Runnable {
  
          private final ConfigurationListener configurationListener;
          private final Reconfigurable reconfigurable;
  
          public ReconfigurationRunnable(final ConfigurationListener configurationListener, final Reconfigurable reconfigurable) {
              this.configurationListener = configurationListener;
              this.reconfigurable = reconfigurable;
          }
  
          @Override
          public void run() {
              configurationListener.onChange(reconfigurable);
          }
      }
  }