/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
    *
    * This program and the accompanying materials are dual-licensed under
    * either the terms of the Eclipse Public License v1.0 as published by
    * the Eclipse Foundation
    *
    *   or (per the licensee's choosing)
   *
   * under the terms of the GNU Lesser General Public License version 2.1
   * as published by the Free Software Foundation.
   */
  package ch.qos.logback.core.sift;
  
  import ch.qos.logback.core.Appender;
  import ch.qos.logback.core.Context;
  import ch.qos.logback.core.CoreConstants;
  import ch.qos.logback.core.helpers.NOPAppender;
  import ch.qos.logback.core.joran.spi.JoranException;
  import ch.qos.logback.core.spi.AbstractComponentTracker;
  import ch.qos.logback.core.spi.ContextAwareImpl;
  
  /**
   * Track appenders by key. When an appender is not used for longer than
   * {@link #DEFAULT_TIMEOUT} it is stopped and removed.
   *
   * @author Tommy Becker
   * @author Ceki Gulcu
   * @author David Roussel
   */
  public class AppenderTracker<E> extends AbstractComponentTracker<Appender<E>> {
  
      int nopaWarningCount = 0;
  
      final Context context;
      final AppenderFactory<E> appenderFactory;
      final ContextAwareImpl contextAware;
  
      public AppenderTracker(Context context, AppenderFactory<E> appenderFactory) {
          super();
          this.context = context;
          this.appenderFactory = appenderFactory;
          this.contextAware = new ContextAwareImpl(context, this);
      }
  
      @Override
      protected void processPriorToRemoval(Appender<E> component) {
          component.stop();
      }
  
      @Override
      protected Appender<E> buildComponent(String key) {
          Appender<E> appender = null;
          try {
              appender = appenderFactory.buildAppender(context, key);
          } catch (JoranException je) {
              contextAware.addError("Error while building appender with discriminating value [" + key + "]");
          }
          if (appender == null) {
              appender = buildNOPAppender(key);
          }
  
          return appender;
      }
  
      private NOPAppender<E> buildNOPAppender(String key) {
          if (nopaWarningCount < CoreConstants.MAX_ERROR_COUNT) {
              nopaWarningCount++;
              contextAware.addError("Building NOPAppender for discriminating value [" + key + "]");
          }
          NOPAppender<E> nopa = new NOPAppender<E>();
          nopa.setContext(context);
          nopa.start();
          return nopa;
      }
  
      @Override
      protected boolean isComponentStale(Appender<E> appender) {
          return !appender.isStarted();
      }
  
  }