/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.core5.http2.impl.nio;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  
  import org.apache.hc.core5.annotation.Internal;
  import org.apache.hc.core5.concurrent.FutureCallback;
  import org.apache.hc.core5.http.ConnectionClosedException;
  import org.apache.hc.core5.http.impl.nio.BufferedData;
  import org.apache.hc.core5.reactor.IOSession;
  import org.apache.hc.core5.reactor.ProtocolIOSession;
  import org.apache.hc.core5.util.Args;
  
  /**
   * I/O event handler for events fired by {@link ProtocolIOSession} that implements
   * server side of the HTTP/2 protocol negotiation handshake.
   *
   * @since 5.1
   */
  @Internal
  public class H2OnlyServerHttpProtocolNegotiator extends ProtocolNegotiatorBase {
  
      final static byte[] PREFACE = ClientHttpProtocolNegotiator.PREFACE;
  
      private final ServerH2StreamMultiplexerFactory http2StreamHandlerFactory;
      private final BufferedData inBuf;
  
      public H2OnlyServerHttpProtocolNegotiator(
              final ProtocolIOSession ioSession,
              final ServerH2StreamMultiplexerFactory http2StreamHandlerFactory) {
          this(ioSession, http2StreamHandlerFactory, null);
      }
  
      public H2OnlyServerHttpProtocolNegotiator(
              final ProtocolIOSession ioSession,
              final ServerH2StreamMultiplexerFactory http2StreamHandlerFactory,
              final FutureCallback<ProtocolIOSession> resultCallback) {
          super(ioSession, resultCallback);
          this.http2StreamHandlerFactory = Args.notNull(http2StreamHandlerFactory, "HTTP/2 stream handler factory");
          this.inBuf = BufferedData.allocate(1024);
      }
  
      @Override
      public void connected(final IOSession session) throws IOException {
      }
  
      @Override
      public void inputReady(final IOSession session, final ByteBuffer src) throws IOException {
          if (src != null) {
              inBuf.put(src);
          }
          boolean endOfStream = false;
          if (inBuf.length() < PREFACE.length) {
              final int bytesRead = inBuf.readFrom(session);
              if (bytesRead == -1) {
                  endOfStream = true;
              }
          }
          final ByteBuffer data = inBuf.data();
          if (data.remaining() >= PREFACE.length) {
              for (int i = 0; i < PREFACE.length; i++) {
                  if (data.get() != PREFACE[i]) {
                      throw new ProtocolNegotiationException("Unexpected HTTP/2 preface");
                  }
              }
              startProtocol(new ServerH2IOEventHandler(http2StreamHandlerFactory.create(ioSession)), data.hasRemaining() ? data : null);
          } else {
              if (endOfStream) {
                  throw new ConnectionClosedException();
              }
          }
      }
 
     @Override
     public void outputReady(final IOSession session) throws IOException {
     }
 
     @Override
     public String toString() {
         return getClass().getName();
     }
 
 }