/*
    * Copyright 2024 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.socket.nio;
  
  import io.netty.channel.ChannelConfig;
  import io.netty.channel.ChannelException;
  import io.netty.channel.ChannelMetadata;
  import io.netty.channel.ChannelOption;
  import io.netty.channel.ChannelOutboundBuffer;
  import io.netty.channel.DefaultChannelConfig;
  import io.netty.channel.ServerChannelRecvByteBufAllocator;
  import io.netty.channel.nio.AbstractNioMessageChannel;
  import io.netty.util.NetUtil;
  import io.netty.util.internal.PlatformDependent;
  import io.netty.util.internal.SocketUtils;
  import io.netty.util.internal.SuppressJava6Requirement;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.io.IOException;
  import java.lang.reflect.Method;
  
  import java.net.SocketAddress;
  import java.nio.channels.SelectionKey;
  import java.nio.channels.ServerSocketChannel;
  import java.nio.channels.SocketChannel;
  import java.nio.channels.spi.SelectorProvider;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  
  import static io.netty.channel.ChannelOption.SO_BACKLOG;
  import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
  
  
  /**
   * A {@link io.netty.channel.ServerChannel} implementation which uses
   * NIO selector based implementation to support UNIX Domain Sockets. This is only supported when using Java 16+.
   */
  public final class NioServerDomainSocketChannel extends AbstractNioMessageChannel
          implements io.netty.channel.ServerChannel {
      private static final Method OPEN_SERVER_SOCKET_CHANNEL_WITH_FAMILY =
              SelectorProviderUtil.findOpenMethod("openServerSocketChannel");
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(NioServerDomainSocketChannel.class);
      private static final ChannelMetadata METADATA = new ChannelMetadata(false, 16);
      private static final SelectorProvider DEFAULT_SELECTOR_PROVIDER = SelectorProvider.provider();
      private final NioDomainServerSocketChannelConfig config;
      private volatile boolean bound;
  
      // Package-private for testing.
      static ServerSocketChannel newChannel(SelectorProvider provider) {
          if (PlatformDependent.javaVersion() < 16) {
              throw new UnsupportedOperationException("Only supported with Java 16+");
          }
          try {
              ServerSocketChannel channel =
                      SelectorProviderUtil.newDomainSocketChannel(OPEN_SERVER_SOCKET_CHANNEL_WITH_FAMILY, provider);
              if (channel == null) {
                  throw new ChannelException("Failed to open a socket.");
              }
              return channel;
          } catch (IOException e) {
              throw new ChannelException("Failed to open a socket.", e);
          }
      }
  
      @Override
      protected ServerSocketChannel javaChannel() {
          return (ServerSocketChannel) super.javaChannel();
      }
  
      /**
       * Create a new instance
       */
      public NioServerDomainSocketChannel() {
          this(DEFAULT_SELECTOR_PROVIDER);
      }
  
      /**
       * Create a new instance using the given {@link SelectorProvider}.
       */
      public NioServerDomainSocketChannel(SelectorProvider provider) {
          this(newChannel(provider));
      }
  
     /**
      * Create a new instance using the given {@link ServerSocketChannel}.
      */
     @SuppressJava6Requirement(reason = "Usage guarded by java version check")
     public NioServerDomainSocketChannel(ServerSocketChannel channel) {
         super(null, channel, SelectionKey.OP_ACCEPT);
         if (PlatformDependent.javaVersion() < 16) {
             throw new UnsupportedOperationException("Only supported with Java 16+");
         }
         config = new NioDomainServerSocketChannelConfig(this);
         try {
             // Check if we already have a local address bound.
             bound = channel.getLocalAddress() != null;
         } catch (IOException e) {
             throw new ChannelException(e);
         }
     }
 
     @Override
     public ChannelConfig config() {
         return config;
     }
 
     @Override
     public ChannelMetadata metadata() {
         return METADATA;
     }
 
     @Override
     public boolean isActive() {
         // As java.nio.ServerSocketChannel.isBound() will continue to return true even after the channel was closed
         // we will also need to check if it is open.
         return isOpen() && bound;
     }
 
     @SuppressJava6Requirement(reason = "Usage guarded by java version check")
     @Override
     protected void doBind(SocketAddress localAddress) throws Exception {
         javaChannel().bind(localAddress, config.getBacklog());
         bound = true;
     }
 
     @Override
     protected void doDisconnect() throws Exception {
         throw new UnsupportedOperationException();
     }
 
     @Override
     protected int doReadMessages(List<Object> buf) throws Exception {
         SocketChannel ch = SocketUtils.accept(javaChannel());
         try {
             if (ch != null) {
                 buf.add(new NioDomainSocketChannel(this, ch));
                 return 1;
             }
         } catch (Throwable t) {
             logger.warn("Failed to create a new channel from an accepted socket.", t);
 
             try {
                 ch.close();
             } catch (Throwable t2) {
                 logger.warn("Failed to close a socket.", t2);
             }
         }
 
         return 0;
     }
 
     @Override
     protected boolean doWriteMessage(Object msg, ChannelOutboundBuffer in) throws Exception {
         throw new UnsupportedOperationException();
     }
 
     @Override
     protected void doClose() throws Exception {
         // Obtain the localAddress before we close the channel so it will not return null if we did not retrieve
         // it before.
         SocketAddress local = localAddress();
         try {
             super.doClose();
         } finally {
             javaChannel().close();
             if (local != null) {
                 NioDomainSocketUtil.deleteSocketFile(local);
             }
         }
     }
 
     @SuppressJava6Requirement(reason = "Usage guarded by java version check")
     @Override
     protected SocketAddress localAddress0() {
         // do not use unsafe which uses native transport (epoll or kqueue)
         // do not use javaChannel().socket() which is not nio
         try {
             return javaChannel().getLocalAddress();
         } catch (Exception ignore) {
             // ignore
         }
         return null;
     }
 
     @Override
     protected SocketAddress remoteAddress0() {
         return null;
     }
 
     private final class NioDomainServerSocketChannelConfig extends DefaultChannelConfig {
 
         private volatile int backlog = NetUtil.SOMAXCONN;
 
         private NioDomainServerSocketChannelConfig(NioServerDomainSocketChannel channel) {
             super(channel, new ServerChannelRecvByteBufAllocator());
         }
 
         @Override
         protected void autoReadCleared() {
             clearReadPending();
         }
 
         @Override
         public Map<ChannelOption<?>, Object> getOptions() {
             List<ChannelOption<?>> options = new ArrayList<ChannelOption<?>>();
             options.add(SO_BACKLOG);
             for (ChannelOption<?> opt : NioChannelOption.getOptions(jdkChannel())) {
                 options.add(opt);
             }
             return getOptions(super.getOptions(), options.toArray(new ChannelOption[0]));
         }
 
         @SuppressWarnings("unchecked")
         @Override
         public <T> T getOption(ChannelOption<T> option) {
             if (option == SO_BACKLOG) {
                 return (T) Integer.valueOf(getBacklog());
             }
             if (option instanceof NioChannelOption) {
                 return NioChannelOption.getOption(jdkChannel(), (NioChannelOption<T>) option);
             }
 
             return super.getOption(option);
         }
 
         @Override
         public <T> boolean setOption(ChannelOption<T> option, T value) {
             if (option == SO_BACKLOG) {
                 validate(option, value);
                 setBacklog((Integer) value);
             } else if (option instanceof NioChannelOption) {
                 return NioChannelOption.setOption(jdkChannel(), (NioChannelOption<T>) option, value);
             } else {
                 return super.setOption(option, value);
             }
 
             return true;
         }
 
         private int getBacklog() {
             return backlog;
         }
 
         private NioDomainServerSocketChannelConfig setBacklog(int backlog) {
             checkPositiveOrZero(backlog, "backlog");
             this.backlog = backlog;
             return this;
         }
 
         private ServerSocketChannel jdkChannel() {
             return ((NioServerDomainSocketChannel) channel).javaChannel();
         }
     }
 
     // Override just to to be able to call directly via unit tests.
     @Override
     protected boolean closeOnReadError(Throwable cause) {
         return super.closeOnReadError(cause);
     }
 
     @Override
     protected boolean doConnect(
             SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
         throw new UnsupportedOperationException();
     }
 
     @Override
     protected void doFinishConnect() throws Exception {
         throw new UnsupportedOperationException();
     }
 }