/*
    * Copyright 2015 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.channel.epoll;
  
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelConfig;
  import io.netty.channel.ChannelMetadata;
  import io.netty.channel.ChannelOutboundBuffer;
  import io.netty.channel.ChannelPipeline;
  import io.netty.channel.ChannelPromise;
  import io.netty.channel.ServerChannel;
  
  import java.net.InetSocketAddress;
  import java.net.SocketAddress;
  
  public abstract class AbstractEpollServerChannel extends AbstractEpollChannel implements ServerChannel {
      private static final ChannelMetadata METADATA = new ChannelMetadata(false, 16);
  
      protected AbstractEpollServerChannel(int fd) {
          this(new LinuxSocket(fd), false);
      }
  
      protected AbstractEpollServerChannel(LinuxSocket fd) {
          this(fd, isSoErrorZero(fd));
      }
  
      protected AbstractEpollServerChannel(LinuxSocket fd, boolean active) {
          super(null, fd, active, EpollIoOps.valueOf(0));
      }
  
      @Override
      public ChannelMetadata metadata() {
          return METADATA;
      }
  
      @Override
      protected InetSocketAddress remoteAddress0() {
          return null;
      }
  
      @Override
      protected AbstractEpollUnsafe newUnsafe() {
          return new EpollServerSocketUnsafe();
      }
  
      @Override
      protected void doWrite(ChannelOutboundBuffer in) throws Exception {
          throw new UnsupportedOperationException();
      }
  
      @Override
      protected Object filterOutboundMessage(Object msg) throws Exception {
          throw new UnsupportedOperationException();
      }
  
      protected abstract Channel newChildChannel(int fd, byte[] remote, int offset, int len) throws Exception;
  
      final class EpollServerSocketUnsafe extends AbstractEpollUnsafe {
          // Will hold the remote address after accept(...) was successful.
          // We need 24 bytes for the address as maximum + 1 byte for storing the length.
          // So use 26 bytes as it's a power of two.
          private final byte[] acceptedAddress = new byte[26];
  
          @Override
          public void connect(SocketAddress socketAddress, SocketAddress socketAddress2, ChannelPromise channelPromise) {
              // Connect not supported by ServerChannel implementations
              channelPromise.setFailure(new UnsupportedOperationException());
          }
  
          @Override
          void epollInReady() {
              assert eventLoop().inEventLoop();
              final ChannelConfig config = config();
              if (shouldBreakEpollInReady(config)) {
                  clearEpollIn0();
                  return;
              }
              final EpollRecvByteAllocatorHandle allocHandle = recvBufAllocHandle();
              final ChannelPipeline pipeline = pipeline();
              allocHandle.reset(config);
              allocHandle.attemptedBytesRead(1);
  
              Throwable exception = null;
              try {
                  try {
                      do {
                         // lastBytesRead represents the fd. We use lastBytesRead because it must be set so that the
                         // EpollRecvByteAllocatorHandle knows if it should try to read again or not when autoRead is
                         // enabled.
                         allocHandle.lastBytesRead(socket.accept(acceptedAddress));
                         if (allocHandle.lastBytesRead() == -1) {
                             // this means everything was handled for now
                             break;
                         }
                         allocHandle.incMessagesRead(1);
 
                         readPending = false;
                         pipeline.fireChannelRead(newChildChannel(allocHandle.lastBytesRead(), acceptedAddress, 1,
                                                                  acceptedAddress[0]));
                     } while (allocHandle.continueReading());
                 } catch (Throwable t) {
                     exception = t;
                 }
                 allocHandle.readComplete();
                 pipeline.fireChannelReadComplete();
 
                 if (exception != null) {
                     pipeline.fireExceptionCaught(exception);
                 }
             } finally {
                 if (shouldStopReading(config)) {
                     clearEpollIn();
                 }
             }
         }
     }
 
     @Override
     protected boolean doConnect(SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
         throw new UnsupportedOperationException();
     }
 }