/**
 * 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.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.EOFException;
import java.net.Proxy;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import java.net.URL;
import java.net.HttpURLConnection;

/** An HTTP-based {@link Transceiver} implementation. */
public class HttpTransceiver extends Transceiver {
  static final String CONTENT_TYPE = "avro/binary";

  private URL url;
  private Proxy proxy;
  private HttpURLConnection connection;
  private int timeout;

  public HttpTransceiver(URL url) { this.url = url; }

  public HttpTransceiver(URL url, Proxy proxy) {
    this(url);
    this.proxy = proxy;
  }

  /** Set the connect and read timeouts, in milliseconds. */
  public void setTimeout(int timeout) { this.timeout = timeout; }

  public String getRemoteName() { return this.url.toString(); }

  public synchronized List<ByteBuffer> readBuffers() throws IOException {
    InputStream in = connection.getInputStream();
    try {
      return readBuffers(in);
    } finally {
      in.close();
    }
  }

  public synchronized void writeBuffers(List<ByteBuffer> buffers)
    throws IOException {
    if (proxy == null)
      connection = (HttpURLConnection)url.openConnection();
    else
      connection = (HttpURLConnection)url.openConnection(proxy);

    connection.setRequestMethod("POST");
    connection.setRequestProperty("Content-Type", CONTENT_TYPE);
    connection.setRequestProperty("Content-Length",
                                  Integer.toString(getLength(buffers)));
    connection.setDoOutput(true);
    connection.setReadTimeout(timeout);
    connection.setConnectTimeout(timeout);

    OutputStream out = connection.getOutputStream();
    try {
      writeBuffers(buffers, out);
    } finally {
      out.close();
    }
  }

  static int getLength(List<ByteBuffer> buffers) {
    int length = 0;
    for (ByteBuffer buffer : buffers) {
      length += 4;
      length += buffer.remaining();
    }
    length += 4;
    return length;
  }

  static List<ByteBuffer> readBuffers(InputStream in)
    throws IOException {
    List<ByteBuffer> buffers = new ArrayList<ByteBuffer>();
    while (true) {
      int length = (in.read()<<24)+(in.read()<<16)+(in.read()<<8)+in.read();
      if (length == 0) {                       // end of buffers
        return buffers;
      }
      ByteBuffer buffer = ByteBuffer.allocate(length);
      while (buffer.hasRemaining()) {
        int p = buffer.position();
        int i = in.read(buffer.array(), p, buffer.remaining());
        if (i < 0)
          throw new EOFException("Unexpected EOF");
        buffer.position(p+i);
      }
      buffer.flip();
      buffers.add(buffer);
    }
  }

  static void writeBuffers(List<ByteBuffer> buffers, OutputStream out)
    throws IOException {
    for (ByteBuffer buffer : buffers) {
      writeLength(buffer.limit(), out);           // length-prefix
      out.write(buffer.array(), buffer.position(), buffer.remaining());
      buffer.position(buffer.limit());
    }
    writeLength(0, out);                          // null-terminate
  }

  private static void writeLength(int length, OutputStream out)
    throws IOException {
    out.write(0xff & (length >>> 24));
    out.write(0xff & (length >>> 16));
    out.write(0xff & (length >>> 8));
    out.write(0xff & length);
  }
}