/*
    * 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.logging.log4j.core.net;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.net.DatagramPacket;
  import java.net.DatagramSocket;
  import java.net.InetAddress;
  import java.net.SocketException;
  import java.net.UnknownHostException;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.appender.AppenderLoggingException;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * OutputStream for UDP connections.
   */
  public class DatagramOutputStream extends OutputStream {
  
      /**
       * Allow subclasses access to the status logger without creating another instance.
       */
      protected static final Logger LOGGER = StatusLogger.getLogger();
  
      private static final int SHIFT_1 = 8;
      private static final int SHIFT_2 = 16;
      private static final int SHIFT_3 = 24;
  
      private DatagramSocket ds;
      private final InetAddress address;
      private final int port;
  
      private byte[] data;
  
      private final byte[] header;
      private final byte[] footer;
  
      /**
       * The Constructor.
       * @param host The host to connect to.
       * @param port The port on the host.
       */
      public DatagramOutputStream(final String host, final int port, final byte[] header, final byte[] footer) {
          this.port = port;
          this.header = header;
          this.footer = footer;
          try {
              address = InetAddress.getByName(host);
          } catch (final UnknownHostException ex) {
              final String msg = "Could not find host " + host;
              LOGGER.error(msg, ex);
              throw new AppenderLoggingException(msg, ex);
          }
  
          try {
              ds = new DatagramSocket();
          } catch (final SocketException ex) {
              final String msg = "Could not instantiate DatagramSocket to " + host;
              LOGGER.error(msg, ex);
              throw new AppenderLoggingException(msg, ex);
          }
      }
  
      @Override
      public synchronized void write(final byte[] bytes, final int offset, final int length) throws IOException {
          copy(bytes, offset, length);
      }
  
      @Override
      public synchronized void write(final int i) throws IOException {
          copy(new byte[] {(byte) (i >>> SHIFT_3), (byte) (i >>> SHIFT_2), (byte) (i >>> SHIFT_1), (byte) i}, 0, 4);
      }
  
      @Override
      public synchronized void write(final byte[] bytes) throws IOException {
          copy(bytes, 0, bytes.length);
      }
  
      @Override
      public synchronized void flush() throws IOException {
          try {
              if (this.data != null && this.ds != null && this.address != null) {
                  if (footer != null) {
                     copy(footer, 0, footer.length);
                 }
                 final DatagramPacket packet = new DatagramPacket(data, data.length, address, port);
                 ds.send(packet);
             }
         } finally {
             data = null;
             if (header != null) {
                 copy(header, 0, header.length);
             }
         }
     }
 
     @Override
     public synchronized void close() throws IOException {
         if (ds != null) {
             if (data != null) {
                 flush();
             }
             ds.close();
             ds = null;
         }
     }
 
     private void copy(final byte[] bytes, final int offset, final int length) {
         final int index = data == null ? 0 : data.length;
         final byte[] copy = new byte[length + index];
         if (data != null) {
             System.arraycopy(data, 0, copy, 0, data.length);
         }
         System.arraycopy(bytes, offset, copy, index, length);
         data = copy;
     }
 }