/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.log4j.net;
  
  import org.apache.log4j.AppenderSkeleton;
  import org.apache.log4j.helpers.Constants;
  import org.apache.log4j.helpers.LogLog;
  import org.apache.log4j.spi.LoggingEvent;
  import org.apache.log4j.xml.XMLLayout;
  
  import java.io.IOException;
  import java.net.DatagramPacket;
  import java.net.DatagramSocket;
  import java.net.InetAddress;
  import java.net.UnknownHostException;
  
  
  /**
   * Sends log information as a UDP datagrams.
   * <p>
   * <p>The UDPAppender is meant to be used as a diagnostic logging tool
   * so that logging can be monitored by a simple UDP client.
   * <p>
   * <p>Messages are not sent as LoggingEvent objects but as text after
   * applying the designated Layout.
   * <p>
   * <p>The port and remoteHost properties can be set in configuration properties.
   * By setting the remoteHost to a broadcast address any number of clients can
   * listen for log messages.
   * <p>
   * <p>This was inspired and really extended/copied from {@link SocketAppender}.
   * Please see the docs for the proper credit to the authors of that class.
   *
   * @author <a href="mailto:kbrown@versatilesolutions.com">Kevin Brown</a>
   * @author Scott Deboy &lt;sdeboy@apache.org&gt;
   */
  public class UDPAppender extends AppenderSkeleton implements PortBased {
      /**
       * The default port number for the UDP packets, 9991.
       */
      public static final int DEFAULT_PORT = 9991;
  
      /**
       * We remember host name as String in addition to the resolved
       * InetAddress so that it can be returned via getOption().
       */
      String hostname;
      String remoteHost;
      String application;
      String encoding;
      InetAddress address;
      int port = DEFAULT_PORT;
      DatagramSocket outSocket;
  
      /**
       * The MulticastDNS zone advertised by a UDPAppender
       */
      public static final String ZONE = "_log4j_xml_udp_appender.local.";
  
      // if there is something irrecoverably wrong with the settings, there is no
      // point in sending out packeets.
      boolean inError = false;
      private boolean advertiseViaMulticastDNS;
      private ZeroConfSupport zeroConf;
  
      public UDPAppender() {
          super(false);
      }
  
      /**
       * Sends UDP packets to the <code>address</code> and <code>port</code>.
       */
      public UDPAppender(final InetAddress address, final int port) {
          super(false);
          this.address = address;
          this.remoteHost = address.getHostName();
          this.port = port;
          activateOptions();
      }
  
      /**
       * Sends UDP packets to the <code>address</code> and <code>port</code>.
       */
      public UDPAppender(final String host, final int port) {
         super(false);
         this.port = port;
         this.address = getAddressByName(host);
         this.remoteHost = host;
         activateOptions();
     }
 
     /**
      * Open the UDP sender for the <b>RemoteHost</b> and <b>Port</b>.
      */
     public void activateOptions() {
         try {
             hostname = InetAddress.getLocalHost().getHostName();
         } catch (UnknownHostException uhe) {
             try {
                 hostname = InetAddress.getLocalHost().getHostAddress();
             } catch (UnknownHostException uhe2) {
                 hostname = "unknown";
             }
         }
 
         //allow system property of application to be primary
         if (application == null) {
             application = System.getProperty(Constants.APPLICATION_KEY);
         } else {
             if (System.getProperty(Constants.APPLICATION_KEY) != null) {
                 application = application + "-" + System.getProperty(Constants.APPLICATION_KEY);
             }
         }
 
         if (remoteHost != null) {
             address = getAddressByName(remoteHost);
             connect(address, port);
         } else {
             String err = "The RemoteHost property is required for SocketAppender named " + name;
             LogLog.error(err);
             throw new IllegalStateException(err);
         }
 
         if (layout == null) {
             layout = new XMLLayout();
         }
 
         if (advertiseViaMulticastDNS) {
             zeroConf = new ZeroConfSupport(ZONE, port, getName());
             zeroConf.advertise();
         }
 
         super.activateOptions();
     }
 
     /**
      * Close this appender.
      * <p>This will mark the appender as closed and
      * call then {@link #cleanUp} method.
      */
     public synchronized void close() {
         if (closed) {
             return;
         }
 
         if (advertiseViaMulticastDNS) {
             zeroConf.unadvertise();
         }
 
         this.closed = true;
         cleanUp();
     }
 
     /**
      * Close the UDP Socket and release the underlying
      * connector thread if it has been created
      */
     public void cleanUp() {
         if (outSocket != null) {
             try {
                 outSocket.close();
             } catch (Exception e) {
                 LogLog.error("Could not close outSocket.", e);
             }
 
             outSocket = null;
         }
     }
 
     void connect(InetAddress address, int port) {
         if (this.address == null) {
             return;
         }
 
         try {
             // First, close the previous connection if any.
             cleanUp();
             outSocket = new DatagramSocket();
             outSocket.connect(address, port);
         } catch (IOException e) {
             LogLog.error(
                 "Could not open UDP Socket for sending.", e);
             inError = true;
         }
     }
 
     public void append(LoggingEvent event) {
         if (inError) {
             return;
         }
 
         if (event == null) {
             return;
         }
 
         if (address == null) {
             return;
         }
 
         if (outSocket != null) {
             event.setProperty(Constants.HOSTNAME_KEY, hostname);
             if (application != null) {
                 event.setProperty(Constants.APPLICATION_KEY, application);
             }
 
             try {
                 StringBuilder buf = new StringBuilder(layout.format(event));
 
                 byte[] payload;
                 if (encoding == null) {
                     payload = buf.toString().getBytes();
                 } else {
                     payload = buf.toString().getBytes(encoding);
                 }
 
                 DatagramPacket dp =
                     new DatagramPacket(payload, payload.length, address, port);
                 outSocket.send(dp);
             } catch (IOException e) {
                 outSocket = null;
                 LogLog.warn("Detected problem with UDP connection: " + e);
             }
         }
     }
 
     public boolean isActive() {
         return !inError;
     }
 
     InetAddress getAddressByName(String host) {
         try {
             return InetAddress.getByName(host);
         } catch (Exception e) {
             LogLog.error("Could not find address of [" + host + "].", e);
             return null;
         }
     }
 
     /**
      * The UDPAppender uses layouts. Hence, this method returns
      * <code>true</code>.
      */
     public boolean requiresLayout() {
         return true;
     }
 
     /**
      * The <b>RemoteHost</b> option takes a string value which should be
      * the host name or ipaddress to send the UDP packets.
      */
     public void setRemoteHost(String host) {
         remoteHost = host;
     }
 
     /**
      * Returns value of the <b>RemoteHost</b> option.
      */
     public String getRemoteHost() {
         return remoteHost;
     }
 
     /**
      * The <b>App</b> option takes a string value which should be the name of the application getting logged.
      * If property was already set (via system property), don't set here.
      */
     public void setApplication(String app) {
         this.application = app;
     }
 
     /**
      * Returns value of the <b>App</b> option.
      */
     public String getApplication() {
         return application;
     }
 
     /**
      * The <b>Encoding</b> option specifies how the bytes are encoded.  If this option is not specified,
      * the System encoding is used.
      */
     public void setEncoding(String encoding) {
         this.encoding = encoding;
     }
 
     /**
      * Returns value of the <b>Encoding</b> option.
      */
     public String getEncoding() {
         return encoding;
     }
 
     /**
      * The <b>Port</b> option takes a positive integer representing
      * the port where UDP packets will be sent.
      */
     public void setPort(int port) {
         this.port = port;
     }
 
     /**
      * Returns value of the <b>Port</b> option.
      */
     public int getPort() {
         return port;
     }
 
     public void setAdvertiseViaMulticastDNS(boolean advertiseViaMulticastDNS) {
         this.advertiseViaMulticastDNS = advertiseViaMulticastDNS;
     }
 
     public boolean isAdvertiseViaMulticastDNS() {
         return advertiseViaMulticastDNS;
     }
 }