/*
    * Copyright 2016 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.kqueue;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufAllocator;
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelConfig;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelMetadata;
  import io.netty.channel.ChannelOutboundBuffer;
  import io.netty.channel.ChannelPipeline;
  import io.netty.channel.ChannelPromise;
  import io.netty.channel.DefaultFileRegion;
  import io.netty.channel.EventLoop;
  import io.netty.channel.FileRegion;
  import io.netty.channel.internal.ChannelUtils;
  import io.netty.channel.socket.DuplexChannel;
  import io.netty.channel.unix.IovArray;
  import io.netty.channel.unix.SocketWritableByteChannel;
  import io.netty.channel.unix.UnixChannelUtil;
  import io.netty.util.internal.StringUtil;
  import io.netty.util.internal.UnstableApi;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.io.IOException;
  import java.net.SocketAddress;
  import java.nio.ByteBuffer;
  import java.nio.channels.WritableByteChannel;
  import java.util.concurrent.Executor;
  
  import static io.netty.channel.internal.ChannelUtils.MAX_BYTES_PER_GATHERING_WRITE_ATTEMPTED_LOW_THRESHOLD;
  import static io.netty.channel.internal.ChannelUtils.WRITE_STATUS_SNDBUF_FULL;
  
  public abstract class AbstractKQueueStreamChannel extends AbstractKQueueChannel implements DuplexChannel {
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(AbstractKQueueStreamChannel.class);
      private static final ChannelMetadata METADATA = new ChannelMetadata(false, 16);
      private static final String EXPECTED_TYPES =
              " (expected: " + StringUtil.simpleClassName(ByteBuf.class) + ", " +
                      StringUtil.simpleClassName(DefaultFileRegion.class) + ')';
      private WritableByteChannel byteChannel;
      private final Runnable flushTask = new Runnable() {
          @Override
          public void run() {
              // Calling flush0 directly to ensure we not try to flush messages that were added via write(...) in the
              // meantime.
              ((AbstractKQueueUnsafe) unsafe()).flush0();
          }
      };
  
      AbstractKQueueStreamChannel(Channel parent, BsdSocket fd, boolean active) {
          super(parent, fd, active);
      }
  
      AbstractKQueueStreamChannel(Channel parent, BsdSocket fd, SocketAddress remote) {
          super(parent, fd, remote);
      }
  
      AbstractKQueueStreamChannel(BsdSocket fd) {
          this(null, fd, isSoErrorZero(fd));
      }
  
      @Override
      protected AbstractKQueueUnsafe newUnsafe() {
          return new KQueueStreamUnsafe();
      }
  
      @Override
      public ChannelMetadata metadata() {
          return METADATA;
      }
  
      /**
       * Write bytes form the given {@link ByteBuf} to the underlying {@link java.nio.channels.Channel}.
       * @param in the collection which contains objects to write.
       * @param buf the {@link ByteBuf} from which the bytes should be written
       * @return The value that should be decremented from the write quantum which starts at
       * {@link ChannelConfig#getWriteSpinCount()}. The typical use cases are as follows:
       * <ul>
       *     <li>0 - if no write was attempted. This is appropriate if an empty {@link ByteBuf} (or other empty content)
       *     is encountered</li>
       *     <li>1 - if a single call to write data was made to the OS</li>
       *     <li>{@link ChannelUtils#WRITE_STATUS_SNDBUF_FULL} - if an attempt to write data was made to the OS, but no
       *     data was accepted</li>
      * </ul>
      */
     private int writeBytes(ChannelOutboundBuffer in, ByteBuf buf) throws Exception {
         int readableBytes = buf.readableBytes();
         if (readableBytes == 0) {
             in.remove();
             return 0;
         }
 
         if (buf.hasMemoryAddress() || buf.nioBufferCount() == 1) {
             return doWriteBytes(in, buf);
         } else {
             ByteBuffer[] nioBuffers = buf.nioBuffers();
             return writeBytesMultiple(in, nioBuffers, nioBuffers.length, readableBytes,
                     config().getMaxBytesPerGatheringWrite());
         }
     }
 
     private void adjustMaxBytesPerGatheringWrite(long attempted, long written, long oldMaxBytesPerGatheringWrite) {
         // By default we track the SO_SNDBUF when ever it is explicitly set. However some OSes may dynamically change
         // SO_SNDBUF (and other characteristics that determine how much data can be written at once) so we should try
         // make a best effort to adjust as OS behavior changes.
         if (attempted == written) {
             if (attempted << 1 > oldMaxBytesPerGatheringWrite) {
                 config().setMaxBytesPerGatheringWrite(attempted << 1);
             }
         } else if (attempted > MAX_BYTES_PER_GATHERING_WRITE_ATTEMPTED_LOW_THRESHOLD && written < attempted >>> 1) {
             config().setMaxBytesPerGatheringWrite(attempted >>> 1);
         }
     }
 
     /**
      * Write multiple bytes via {@link IovArray}.
      * @param in the collection which contains objects to write.
      * @param array The array which contains the content to write.
      * @return The value that should be decremented from the write quantum which starts at
      * {@link ChannelConfig#getWriteSpinCount()}. The typical use cases are as follows:
      * <ul>
      *     <li>0 - if no write was attempted. This is appropriate if an empty {@link ByteBuf} (or other empty content)
      *     is encountered</li>
      *     <li>1 - if a single call to write data was made to the OS</li>
      *     <li>{@link ChannelUtils#WRITE_STATUS_SNDBUF_FULL} - if an attempt to write data was made to the OS, but
      *     no data was accepted</li>
      * </ul>
      * @throws IOException If an I/O exception occurs during write.
      */
     private int writeBytesMultiple(ChannelOutboundBuffer in, IovArray array) throws IOException {
         final long expectedWrittenBytes = array.size();
         assert expectedWrittenBytes != 0;
         final int cnt = array.count();
         assert cnt != 0;
 
         final long localWrittenBytes = socket.writevAddresses(array.memoryAddress(0), cnt);
         if (localWrittenBytes > 0) {
             adjustMaxBytesPerGatheringWrite(expectedWrittenBytes, localWrittenBytes, array.maxBytes());
             in.removeBytes(localWrittenBytes);
             return 1;
         }
         return WRITE_STATUS_SNDBUF_FULL;
     }
 
     /**
      * Write multiple bytes via {@link ByteBuffer} array.
      * @param in the collection which contains objects to write.
      * @param nioBuffers The buffers to write.
      * @param nioBufferCnt The number of buffers to write.
      * @param expectedWrittenBytes The number of bytes we expect to write.
      * @param maxBytesPerGatheringWrite The maximum number of bytes we should attempt to write.
      * @return The value that should be decremented from the write quantum which starts at
      * {@link ChannelConfig#getWriteSpinCount()}. The typical use cases are as follows:
      * <ul>
      *     <li>0 - if no write was attempted. This is appropriate if an empty {@link ByteBuf} (or other empty content)
      *     is encountered</li>
      *     <li>1 - if a single call to write data was made to the OS</li>
      *     <li>{@link ChannelUtils#WRITE_STATUS_SNDBUF_FULL} - if an attempt to write data was made to the OS, but
      *     no data was accepted</li>
      * </ul>
      * @throws IOException If an I/O exception occurs during write.
      */
     private int writeBytesMultiple(
             ChannelOutboundBuffer in, ByteBuffer[] nioBuffers, int nioBufferCnt, long expectedWrittenBytes,
             long maxBytesPerGatheringWrite) throws IOException {
         assert expectedWrittenBytes != 0;
         if (expectedWrittenBytes > maxBytesPerGatheringWrite) {
             expectedWrittenBytes = maxBytesPerGatheringWrite;
         }
 
         final long localWrittenBytes = socket.writev(nioBuffers, 0, nioBufferCnt, expectedWrittenBytes);
         if (localWrittenBytes > 0) {
             adjustMaxBytesPerGatheringWrite(expectedWrittenBytes, localWrittenBytes, maxBytesPerGatheringWrite);
             in.removeBytes(localWrittenBytes);
             return 1;
         }
         return WRITE_STATUS_SNDBUF_FULL;
     }
 
     /**
      * Write a {@link DefaultFileRegion}
      * @param in the collection which contains objects to write.
      * @param region the {@link DefaultFileRegion} from which the bytes should be written
      * @return The value that should be decremented from the write quantum which starts at
      * {@link ChannelConfig#getWriteSpinCount()}. The typical use cases are as follows:
      * <ul>
      *     <li>0 - if no write was attempted. This is appropriate if an empty {@link ByteBuf} (or other empty content)
      *     is encountered</li>
      *     <li>1 - if a single call to write data was made to the OS</li>
      *     <li>{@link ChannelUtils#WRITE_STATUS_SNDBUF_FULL} - if an attempt to write data was made to the OS, but
      *     no data was accepted</li>
      * </ul>
      */
     private int writeDefaultFileRegion(ChannelOutboundBuffer in, DefaultFileRegion region) throws Exception {
         final long regionCount = region.count();
         final long offset = region.transferred();
 
         if (offset >= regionCount) {
             in.remove();
             return 0;
         }
 
         final long flushedAmount = socket.sendFile(region, region.position(), offset, regionCount - offset);
         if (flushedAmount > 0) {
             in.progress(flushedAmount);
             if (region.transferred() >= regionCount) {
                 in.remove();
             }
             return 1;
         } else if (flushedAmount == 0) {
             validateFileRegion(region, offset);
         }
         return WRITE_STATUS_SNDBUF_FULL;
     }
 
     /**
      * Write a {@link FileRegion}
      * @param in the collection which contains objects to write.
      * @param region the {@link FileRegion} from which the bytes should be written
      * @return The value that should be decremented from the write quantum which starts at
      * {@link ChannelConfig#getWriteSpinCount()}. The typical use cases are as follows:
      * <ul>
      *     <li>0 - if no write was attempted. This is appropriate if an empty {@link ByteBuf} (or other empty content)
      *     is encountered</li>
      *     <li>1 - if a single call to write data was made to the OS</li>
      *     <li>{@link ChannelUtils#WRITE_STATUS_SNDBUF_FULL} - if an attempt to write data was made to the OS, but no
      *     data was accepted</li>
      * </ul>
      */
     private int writeFileRegion(ChannelOutboundBuffer in, FileRegion region) throws Exception {
         if (region.transferred() >= region.count()) {
             in.remove();
             return 0;
         }
 
         if (byteChannel == null) {
             byteChannel = new KQueueSocketWritableByteChannel();
         }
         final long flushedAmount = region.transferTo(byteChannel, region.transferred());
         if (flushedAmount > 0) {
             in.progress(flushedAmount);
             if (region.transferred() >= region.count()) {
                 in.remove();
             }
             return 1;
         }
         return WRITE_STATUS_SNDBUF_FULL;
     }
 
     @Override
     protected void doWrite(ChannelOutboundBuffer in) throws Exception {
         int writeSpinCount = config().getWriteSpinCount();
         do {
             final int msgCount = in.size();
             // Do gathering write if the outbound buffer entries start with more than one ByteBuf.
             if (msgCount > 1 && in.current() instanceof ByteBuf) {
                 writeSpinCount -= doWriteMultiple(in);
             } else if (msgCount == 0) {
                 // Wrote all messages.
                 writeFilter(false);
                 // Return here so we don't set the WRITE flag.
                 return;
             } else { // msgCount == 1
                 writeSpinCount -= doWriteSingle(in);
             }
 
             // We do not break the loop here even if the outbound buffer was flushed completely,
             // because a user might have triggered another write and flush when we notify his or her
             // listeners.
         } while (writeSpinCount > 0);
 
         if (writeSpinCount == 0) {
             // It is possible that we have set the write filter, woken up by KQUEUE because the socket is writable, and
             // then use our write quantum. In this case we no longer want to set the write filter because the socket is
             // still writable (as far as we know). We will find out next time we attempt to write if the socket is
             // writable and set the write filter if necessary.
             writeFilter(false);
 
             // We used our writeSpin quantum, and should try to write again later.
             eventLoop().execute(flushTask);
         } else {
             // Underlying descriptor can not accept all data currently, so set the WRITE flag to be woken up
             // when it can accept more data.
             writeFilter(true);
         }
     }
 
     /**
      * Attempt to write a single object.
      * @param in the collection which contains objects to write.
      * @return The value that should be decremented from the write quantum which starts at
      * {@link ChannelConfig#getWriteSpinCount()}. The typical use cases are as follows:
      * <ul>
      *     <li>0 - if no write was attempted. This is appropriate if an empty {@link ByteBuf} (or other empty content)
      *     is encountered</li>
      *     <li>1 - if a single call to write data was made to the OS</li>
      *     <li>{@link ChannelUtils#WRITE_STATUS_SNDBUF_FULL} - if an attempt to write data was made to the OS, but no
      *     data was accepted</li>
      * </ul>
      * @throws Exception If an I/O error occurs.
      */
     protected int doWriteSingle(ChannelOutboundBuffer in) throws Exception {
         // The outbound buffer contains only one message or it contains a file region.
         Object msg = in.current();
         if (msg instanceof ByteBuf) {
             return writeBytes(in, (ByteBuf) msg);
         } else if (msg instanceof DefaultFileRegion) {
             return writeDefaultFileRegion(in, (DefaultFileRegion) msg);
         } else if (msg instanceof FileRegion) {
             return writeFileRegion(in, (FileRegion) msg);
         } else {
             // Should never reach here.
             throw new Error();
         }
     }
 
     /**
      * Attempt to write multiple {@link ByteBuf} objects.
      * @param in the collection which contains objects to write.
      * @return The value that should be decremented from the write quantum which starts at
      * {@link ChannelConfig#getWriteSpinCount()}. The typical use cases are as follows:
      * <ul>
      *     <li>0 - if no write was attempted. This is appropriate if an empty {@link ByteBuf} (or other empty content)
      *     is encountered</li>
      *     <li>1 - if a single call to write data was made to the OS</li>
      *     <li>{@link ChannelUtils#WRITE_STATUS_SNDBUF_FULL} - if an attempt to write data was made to the OS, but no
      *     data was accepted</li>
      * </ul>
      * @throws Exception If an I/O error occurs.
      */
     private int doWriteMultiple(ChannelOutboundBuffer in) throws Exception {
         final long maxBytesPerGatheringWrite = config().getMaxBytesPerGatheringWrite();
         IovArray array = registration().ioHandler().cleanArray();
         array.maxBytes(maxBytesPerGatheringWrite);
         in.forEachFlushedMessage(array);
 
         if (array.count() >= 1) {
             // TODO: Handle the case where cnt == 1 specially.
             return writeBytesMultiple(in, array);
         }
         // cnt == 0, which means the outbound buffer contained empty buffers only.
         in.removeBytes(0);
         return 0;
     }
 
     @Override
     protected Object filterOutboundMessage(Object msg) {
         if (msg instanceof ByteBuf) {
             ByteBuf buf = (ByteBuf) msg;
             return UnixChannelUtil.isBufferCopyNeededForWrite(buf)? newDirectBuffer(buf) : buf;
         }
 
         if (msg instanceof FileRegion) {
             return msg;
         }
 
         throw new UnsupportedOperationException(
                 "unsupported message type: " + StringUtil.simpleClassName(msg) + EXPECTED_TYPES);
     }
 
     @UnstableApi
     @Override
     protected final void doShutdownOutput() throws Exception {
         socket.shutdown(false, true);
     }
 
     @Override
     public boolean isOutputShutdown() {
         return socket.isOutputShutdown();
     }
 
     @Override
     public boolean isInputShutdown() {
         return socket.isInputShutdown();
     }
 
     @Override
     public boolean isShutdown() {
         return socket.isShutdown();
     }
 
     @Override
     public ChannelFuture shutdownOutput() {
         return shutdownOutput(newPromise());
     }
 
     @Override
     public ChannelFuture shutdownOutput(final ChannelPromise promise) {
         EventLoop loop = eventLoop();
         if (loop.inEventLoop()) {
             ((AbstractUnsafe) unsafe()).shutdownOutput(promise);
         } else {
             loop.execute(new Runnable() {
                 @Override
                 public void run() {
                     ((AbstractUnsafe) unsafe()).shutdownOutput(promise);
                 }
             });
         }
         return promise;
     }
 
     @Override
     public ChannelFuture shutdownInput() {
         return shutdownInput(newPromise());
     }
 
     @Override
     public ChannelFuture shutdownInput(final ChannelPromise promise) {
         EventLoop loop = eventLoop();
         if (loop.inEventLoop()) {
             shutdownInput0(promise);
         } else {
             loop.execute(new Runnable() {
                 @Override
                 public void run() {
                     shutdownInput0(promise);
                 }
             });
         }
         return promise;
     }
 
     private void shutdownInput0(ChannelPromise promise) {
         try {
             socket.shutdown(true, false);
         } catch (Throwable cause) {
             promise.setFailure(cause);
             return;
         }
         promise.setSuccess();
     }
 
     @Override
     public ChannelFuture shutdown() {
         return shutdown(newPromise());
     }
 
     @Override
     public ChannelFuture shutdown(final ChannelPromise promise) {
         ChannelFuture shutdownOutputFuture = shutdownOutput();
         if (shutdownOutputFuture.isDone()) {
             shutdownOutputDone(shutdownOutputFuture, promise);
         } else {
             shutdownOutputFuture.addListener(new ChannelFutureListener() {
                 @Override
                 public void operationComplete(final ChannelFuture shutdownOutputFuture) throws Exception {
                     shutdownOutputDone(shutdownOutputFuture, promise);
                 }
             });
         }
         return promise;
     }
 
     private void shutdownOutputDone(final ChannelFuture shutdownOutputFuture, final ChannelPromise promise) {
         ChannelFuture shutdownInputFuture = shutdownInput();
         if (shutdownInputFuture.isDone()) {
             shutdownDone(shutdownOutputFuture, shutdownInputFuture, promise);
         } else {
             shutdownInputFuture.addListener(new ChannelFutureListener() {
                 @Override
                 public void operationComplete(ChannelFuture shutdownInputFuture) throws Exception {
                     shutdownDone(shutdownOutputFuture, shutdownInputFuture, promise);
                 }
             });
         }
     }
 
     private static void shutdownDone(ChannelFuture shutdownOutputFuture,
                                      ChannelFuture shutdownInputFuture,
                                      ChannelPromise promise) {
         Throwable shutdownOutputCause = shutdownOutputFuture.cause();
         Throwable shutdownInputCause = shutdownInputFuture.cause();
         if (shutdownOutputCause != null) {
             if (shutdownInputCause != null) {
                 logger.debug("Exception suppressed because a previous exception occurred.",
                         shutdownInputCause);
             }
             promise.setFailure(shutdownOutputCause);
         } else if (shutdownInputCause != null) {
             promise.setFailure(shutdownInputCause);
         } else {
             promise.setSuccess();
         }
     }
 
     class KQueueStreamUnsafe extends AbstractKQueueUnsafe {
         // Overridden here just to be able to access this method from AbstractKQueueStreamChannel
         @Override
         protected Executor prepareToClose() {
             return super.prepareToClose();
         }
 
         @Override
         void readReady(final KQueueRecvByteAllocatorHandle allocHandle) {
             final ChannelConfig config = config();
             if (shouldBreakReadReady(config)) {
                 clearReadFilter0();
                 return;
             }
             final ChannelPipeline pipeline = pipeline();
             final ByteBufAllocator allocator = config.getAllocator();
             allocHandle.reset(config);
             readReadyBefore();
 
             ByteBuf byteBuf = null;
             boolean close = false;
             try {
                 do {
                     // we use a direct buffer here as the native implementations only be able
                     // to handle direct buffers.
                     byteBuf = allocHandle.allocate(allocator);
                     allocHandle.lastBytesRead(doReadBytes(byteBuf));
                     if (allocHandle.lastBytesRead() <= 0) {
                         // nothing was read, release the buffer.
                         byteBuf.release();
                         byteBuf = null;
                         close = allocHandle.lastBytesRead() < 0;
                         if (close) {
                             // There is nothing left to read as we received an EOF.
                             readPending = false;
                         }
                         break;
                     }
                     allocHandle.incMessagesRead(1);
                     readPending = false;
                     pipeline.fireChannelRead(byteBuf);
                     byteBuf = null;
 
                     if (shouldBreakReadReady(config)) {
                         // We need to do this for two reasons:
                         //
                         // - If the input was shutdown in between (which may be the case when the user did it in the
                         //   fireChannelRead(...) method we should not try to read again to not produce any
                         //   miss-leading exceptions.
                         //
                         // - If the user closes the channel we need to ensure we not try to read from it again as
                         //   the filedescriptor may be re-used already by the OS if the system is handling a lot of
                         //   concurrent connections and so needs a lot of filedescriptors. If not do this we risk
                         //   reading data from a filedescriptor that belongs to another socket then the socket that
                         //   was "wrapped" by this Channel implementation.
                         break;
                     }
                 } while (allocHandle.continueReading());
 
                 allocHandle.readComplete();
                 pipeline.fireChannelReadComplete();
 
                 if (close) {
                     shutdownInput(false);
                 }
             } catch (Throwable t) {
                 handleReadException(pipeline, byteBuf, t, close, allocHandle);
             } finally {
                 readReadyFinally(config);
             }
         }
 
         private void handleReadException(ChannelPipeline pipeline, ByteBuf byteBuf, Throwable cause, boolean close,
                                          KQueueRecvByteAllocatorHandle allocHandle) {
             if (byteBuf != null) {
                 if (byteBuf.isReadable()) {
                     readPending = false;
                     pipeline.fireChannelRead(byteBuf);
                 } else {
                     byteBuf.release();
                 }
             }
             if (!failConnectPromise(cause)) {
                 allocHandle.readComplete();
                 pipeline.fireChannelReadComplete();
                 pipeline.fireExceptionCaught(cause);
 
                 // If oom will close the read event, release connection.
                 // See https://github.com/netty/netty/issues/10434
                 if (close || cause instanceof OutOfMemoryError || cause instanceof IOException) {
                     shutdownInput(false);
                 }
             }
         }
     }
 
     private final class KQueueSocketWritableByteChannel extends SocketWritableByteChannel {
         KQueueSocketWritableByteChannel() {
             super(socket);
         }
 
         @Override
         protected ByteBufAllocator alloc() {
             return AbstractKQueueStreamChannel.this.alloc();
         }
     }
 }