package javax.jmdns;
   
   import java.net.InetAddress;
   import java.net.NetworkInterface;
   import java.util.concurrent.atomic.AtomicReference;
   
   import javax.jmdns.impl.NetworkTopologyDiscoveryImpl;
   
   /**
   * This class is used to resolve the list of Internet address to use when attaching JmDNS to the network.
   * <p>
   * To create you own filtering class for Internet Addresses you will need to implement the class and the factory delegate. These must be called before any other call to JmDNS.
   *
   * <pre>
   * public static class MyNetworkTopologyDiscovery implements NetworkTopologyDiscovery {
   *
   *     &#064;Override
   *     public InetAddress[] getInetAddresses() {
   *         // TODO Auto-generated method stub
   *         return null;
   *     }
   *
   *     &#064;Override
   *     public boolean useInetAddress(NetworkInterface networkInterface, InetAddress interfaceAddress) {
   *         // TODO Auto-generated method stub
   *         return false;
   *     }
   *
   * }
   *
   * public static class MyClass implements NetworkTopologyDiscovery.Factory.ClassDelegate {
   *     public MyClass() {
   *         super();
   *         NetworkTopologyDiscovery.Factory.setClassDelegate(this);
   *
   *         // Access JmDNS or JmmDNS
   *     }
   *
   *     &#064;Override
   *     public NetworkTopologyDiscovery newNetworkTopologyDiscovery() {
   *         return new MyNetworkTopologyDiscovery();
   *     }
   *
   * }
   * </pre>
   *
   * </p>
   *
   * @author Pierre Frisch
   */
  public interface NetworkTopologyDiscovery {
  
      /**
       * NetworkTopologyDiscovery.Factory enable the creation of new instance of NetworkTopologyDiscovery.
       */
      public static final class Factory {
          private static volatile NetworkTopologyDiscovery _instance;
  
          /**
           * This interface defines a delegate to the NetworkTopologyDiscovery.Factory class to enable subclassing.
           */
          public static interface ClassDelegate {
  
              /**
               * Allows the delegate the opportunity to construct and return a different NetworkTopologyDiscovery.
               *
               * @return Should return a new NetworkTopologyDiscovery Object.
               * @see #classDelegate()
               * @see #setClassDelegate(ClassDelegate anObject)
               */
              public NetworkTopologyDiscovery newNetworkTopologyDiscovery();
          }
  
          private static final AtomicReference<Factory.ClassDelegate> _databaseClassDelegate = new AtomicReference<Factory.ClassDelegate>();
  
          private Factory() {
              super();
          }
  
          /**
           * Assigns <code>delegate</code> as NetworkTopologyDiscovery's class delegate. The class delegate is optional.
           *
           * @param delegate
           *            The object to set as NetworkTopologyDiscovery's class delegate.
           * @see #classDelegate()
           * @see JmmDNS.Factory.ClassDelegate
           */
          public static void setClassDelegate(Factory.ClassDelegate delegate) {
              _databaseClassDelegate.set(delegate);
          }
  
          /**
           * Returns NetworkTopologyDiscovery's class delegate.
           *
           * @return NetworkTopologyDiscovery's class delegate.
           * @see #setClassDelegate(ClassDelegate anObject)
           * @see JmmDNS.Factory.ClassDelegate
           */
          public static Factory.ClassDelegate classDelegate() {
             return _databaseClassDelegate.get();
         }
 
         /**
          * Returns a new instance of NetworkTopologyDiscovery using the class delegate if it exists.
          *
          * @return new instance of NetworkTopologyDiscovery
          */
         protected static NetworkTopologyDiscovery newNetworkTopologyDiscovery() {
             NetworkTopologyDiscovery instance = null;
             Factory.ClassDelegate delegate = _databaseClassDelegate.get();
             if (delegate != null) {
                 instance = delegate.newNetworkTopologyDiscovery();
             }
             return (instance != null ? instance : new NetworkTopologyDiscoveryImpl());
         }
 
         /**
          * Return the instance of the Multihommed Multicast DNS.
          *
          * @return the JmmDNS
          */
         public static NetworkTopologyDiscovery getInstance() {
             if (_instance == null) {
                 synchronized (NetworkTopologyDiscovery.Factory.class) {
                     if (_instance == null) {
                         _instance = NetworkTopologyDiscovery.Factory.newNetworkTopologyDiscovery();
                     }
                 }
             }
             return _instance;
         }
     }
 
     /**
      * Get all local Internet Addresses for the machine.
      *
      * @return Set of InetAddress
      */
     public abstract InetAddress[] getInetAddresses();
 
     /**
      * Check if a given InetAddress should be used for mDNS
      *
      * @param networkInterface
      * @param interfaceAddress
      * @return <code>true</code> is the address is to be used, <code>false</code> otherwise.
      */
     public boolean useInetAddress(NetworkInterface networkInterface, InetAddress interfaceAddress);
 
     /**
      * Locks the given InetAddress if the device requires it.
      *
      * @param interfaceAddress
      */
     public void lockInetAddress(InetAddress interfaceAddress);
 
     /**
      * Locks the given InetAddress if the device requires it.
      *
      * @param interfaceAddress
      */
     public void unlockInetAddress(InetAddress interfaceAddress);
 
 }