/**
    * 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.classic.sift;
  
  import ch.qos.logback.classic.spi.ILoggingEvent;
  import ch.qos.logback.core.sift.Discriminator;
  import ch.qos.logback.core.spi.ContextAwareBase;
  
  /**
   * This discriminator returns the value context to which this event is attached
   * to. If the said value is null, then a default value is returned.
   * 
   * <p>
   * Both Key and the DefaultValue are user specified properties.
   * 
   * @author Ceki G&uuml;lc&uuml;
   * 
   */
  public class ContextBasedDiscriminator extends ContextAwareBase implements
      Discriminator<ILoggingEvent> {
  
    private static final String KEY = "contextName";
    private String defaultValue;
    private boolean started = false;
  
    public ContextBasedDiscriminator() {
    }
  
    /**
     * Return the name of the current context name as found in the logging event.
     */
    public String getDiscriminatingValue(ILoggingEvent event) {
      String contextName = event.getLoggerContextVO().getName();
  
      if (contextName == null) {
        return defaultValue;
      } else {
        return contextName;
      }
    }
  
    public boolean isStarted() {
      return started;
    }
  
    public void start() {
      started = true;
    }
  
    public void stop() {
      started = false;
    }
  
    public String getKey() {
      return KEY;
    }
  
    public void setKey(String key) {
      throw new UnsupportedOperationException(
          "Key cannot be set. Using fixed key " + KEY);
    }
  
    /**
     * @see #setDefaultValue(String)
     * @return
     */
    public String getDefaultValue() {
      return defaultValue;
    }
  
    /**
     * The default context name in case the context name is not set for the
     * current logging event.
     * 
     * @param defaultValue
     */
    public void setDefaultValue(String defaultValue) {
      this.defaultValue = defaultValue;
    }
  }