/**
 * 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.avro.ipc;

import java.util.List;
import java.util.ArrayList;
import java.io.IOException;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/** A datagram-based {@link Transceiver} implementation. This uses a simple,
 * non-standard wire protocol and is not intended for production services. */
public class DatagramTransceiver extends Transceiver {
  private static final Logger LOG
    = LoggerFactory.getLogger(DatagramTransceiver.class);

  private static final int MAX_SIZE = 16 * 1024;

  private DatagramChannel channel;
  private SocketAddress remote;
  private ByteBuffer buffer = ByteBuffer.allocate(MAX_SIZE);

  public String getRemoteName() { return remote.toString(); }

  public DatagramTransceiver(SocketAddress remote) throws IOException {
    this(DatagramChannel.open());
    this.remote = remote;
  }

  public DatagramTransceiver(DatagramChannel channel) {
    this.channel = channel;
  }

  public synchronized List<ByteBuffer> readBuffers() throws IOException {
    buffer.clear();
    remote = channel.receive(buffer);
    LOG.info("received from "+remote);
    buffer.flip();
    List<ByteBuffer> buffers = new ArrayList<ByteBuffer>();
    while (true) {
      int length = buffer.getInt();
      if (length == 0) {                          // end of buffers
        return buffers;
      }
      ByteBuffer chunk = buffer.slice();          // use data without copying
      chunk.limit(length);
      buffer.position(buffer.position()+length);
      buffers.add(chunk);
    }
  }

  public synchronized void writeBuffers(List<ByteBuffer> buffers)
    throws IOException {
    buffer.clear();
    for (ByteBuffer b : buffers) {
      buffer.putInt(b.remaining());
      buffer.put(b);                              // copy data.  sigh.
    }
    buffer.putInt(0);
    buffer.flip();
    channel.send(buffer, remote);
    LOG.info("sent to "+remote);
  }

}