// Licensed under Apache License version 2.0
   package javax.jmdns.impl.tasks.resolver;
   
   import java.io.IOException;
   import java.util.Timer;
   import java.util.logging.Level;
   import java.util.logging.Logger;
   
   import javax.jmdns.impl.DNSOutgoing;
  import javax.jmdns.impl.JmDNSImpl;
  import javax.jmdns.impl.constants.DNSConstants;
  import javax.jmdns.impl.tasks.DNSTask;
  
  /**
   * This is the root class for all resolver tasks.
   * 
   * @author Pierre Frisch
   */
  public abstract class DNSResolverTask extends DNSTask {
      private static Logger logger = Logger.getLogger(DNSResolverTask.class.getName());
  
      /**
       * Counts the number of queries being sent.
       */
      protected int         _count = 0;
  
      /**
       * @param jmDNSImpl
       */
      public DNSResolverTask(JmDNSImpl jmDNSImpl) {
          super(jmDNSImpl);
      }
  
      /*
       * (non-Javadoc)
       * @see java.lang.Object#toString()
       */
      @Override
      public String toString() {
          return super.toString() + " count: " + _count;
      }
  
      /*
       * (non-Javadoc)
       * @see javax.jmdns.impl.tasks.DNSTask#start(java.util.Timer)
       */
      @Override
      public void start(Timer timer) {
          if (!this.getDns().isCanceling() && !this.getDns().isCanceled()) {
              timer.schedule(this, DNSConstants.QUERY_WAIT_INTERVAL, DNSConstants.QUERY_WAIT_INTERVAL);
          }
      }
  
      /*
       * (non-Javadoc)
       * @see java.util.TimerTask#run()
       */
      @Override
      public void run() {
          try {
              if (this.getDns().isCanceling() || this.getDns().isCanceled()) {
                  this.cancel();
              } else {
                  if (_count++ < 3) {
                      if (logger.isLoggable(Level.FINER)) {
                          logger.finer(this.getName() + ".run() JmDNS " + this.description());
                      }
                      DNSOutgoing out = new DNSOutgoing(DNSConstants.FLAGS_QR_QUERY);
                      out = this.addQuestions(out);
                      if (this.getDns().isAnnounced()) {
                          out = this.addAnswers(out);
                      }
                      if (!out.isEmpty()) {
                          this.getDns().send(out);
                      }
                  } else {
                      // After three queries, we can quit.
                      this.cancel();
                  }
              }
          } catch (Throwable e) {
              logger.log(Level.WARNING, this.getName() + ".run() exception ", e);
              this.getDns().recover();
          }
      }
  
      /**
       * Overridden by subclasses to add questions to the message.<br/>
       * <b>Note:</b> Because of message size limitation the returned message may be different than the message parameter.
       * 
       * @param out
       *            outgoing message
       * @return the outgoing message.
       * @exception IOException
       */
      protected abstract DNSOutgoing addQuestions(DNSOutgoing out) throws IOException;
  
      /**
       * Overridden by subclasses to add questions to the message.<br/>
      * <b>Note:</b> Because of message size limitation the returned message may be different than the message parameter.
      * 
      * @param out
      *            outgoing message
      * @return the outgoing message.
      * @exception IOException
      */
     protected abstract DNSOutgoing addAnswers(DNSOutgoing out) throws IOException;
 
     /**
      * Returns a description of the resolver for debugging
      * 
      * @return resolver description
      */
     protected abstract String description();
 
 }