/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2011, 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.AppenderBase;
  import ch.qos.logback.core.CoreConstants;
  import ch.qos.logback.core.helpers.NOPAppender;
  import ch.qos.logback.core.joran.spi.JoranException;
  
  /**
   * This appender serves as the base class for actual SiftingAppenders
   * implemented by the logback-classic and logback-access modules. In a nutshell,
   * a SiftingAppender contains other appenders which it can build dynamically
   * depending on discriminating values supplied by event currently being
   * processed. The built appender is specified as part of a configuration file.
   * 
   * @author Ceki Gulcu
   */
  public abstract class SiftingAppenderBase<E> extends
      AppenderBase<E> {
  
    protected AppenderTracker<E> appenderTracker = new AppenderTrackerImpl<E>();
    AppenderFactoryBase<E> appenderFactory;
  
    Discriminator<E> discriminator;
  
    public void setAppenderFactory(AppenderFactoryBase<E> appenderFactory) {
      this.appenderFactory = appenderFactory;
    }
  
    @Override
    public void start() {
      int errors = 0;
      if (discriminator == null) {
        addError("Missing discriminator. Aborting");
        errors++;
      }
      if (!discriminator.isStarted()) {
        addError("Discriminator has not started successfully. Aborting");
        errors++;
      }
      if (errors == 0) {
        super.start();
      }
    }
  
    @Override
    public void stop() {
      for (Appender<E> appender : appenderTracker.valueList()) {
        appender.stop();
      }
    }
  
    abstract protected long getTimestamp(E event);
  
    @Override
    protected void append(E event) {
      if (!isStarted()) {
        return;
      }
  
      String discriminatingValue = discriminator.getDiscriminatingValue(event);
      long timestamp = getTimestamp(event);
      
      Appender<E> appender = appenderTracker.get(discriminatingValue, timestamp);
      if (appender == null) {
        try {
          appender = appenderFactory.buildAppender(context, discriminatingValue);
          if (appender == null) {
            appender = buildNOPAppender(discriminatingValue);
          }
          appenderTracker.put(discriminatingValue, appender, timestamp);
  
        } catch (JoranException e) {
          addError("Failed to build appender for [" + discriminatingValue + "]",
              e);
          return;
        }
      }
      appenderTracker.stopStaleAppenders(timestamp);
      
      appender.doAppend(event);
    }
  
    public Discriminator<E> getDiscriminator() {
      return discriminator;
    }
 
   public void setDiscriminator(Discriminator<E> discriminator) {
     this.discriminator = discriminator;
   }
   
   
   int nopaWarningCount = 0;
   
   NOPAppender<E> buildNOPAppender(String discriminatingValue) {
     if(nopaWarningCount < CoreConstants.MAX_ERROR_COUNT) {
       nopaWarningCount++;
       addError("Failed to build an appender for discriminating value ["+discriminatingValue+"]");
     }
     NOPAppender<E> nopa = new NOPAppender<E>();
     nopa.setContext(context);
     nopa.start();
     return nopa;
   }
 
   // sometime one needs to close a nested appender immediately
   // for example when executing a command which has its own nested appender
   // and the command also cleans up after itself. However, an open file appender
   // will prevent the folder from being deleted
   // see http://www.qos.ch/pipermail/logback-user/2010-March/001487.html
   /**
    * @since 0.9.19
    */
   public AppenderTracker getAppenderTracker() {
     return appenderTracker;
   }
 
   public String getDiscriminatorKey() {
     if (discriminator != null) {
       return discriminator.getKey();
     } else {
       return null;
     }
   }
 }