/*
    * 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.uring;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.Channel;
  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.EventLoop;
  import io.netty.channel.socket.DuplexChannel;
  import io.netty.channel.unix.IovArray;
  import io.netty.channel.unix.Limits;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.net.SocketAddress;
  import java.io.IOException;
  
  import static io.netty.channel.unix.Errors.ioResult;
  
  abstract class AbstractIoUringStreamChannel extends AbstractIoUringChannel implements DuplexChannel {
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(AbstractIoUringStreamChannel.class);
      private static final ChannelMetadata METADATA = new ChannelMetadata(false, 16);
  
      // Store the opCode so we know if we used WRITE or WRITEV.
      private byte writeOpCode;
  
      // Keep track of the ids used for write and read so we can cancel these when needed.
      private long writeId;
      private long readId;
  
      AbstractIoUringStreamChannel(Channel parent, LinuxSocket socket, boolean active) {
          // Use a blocking fd, we can make use of fastpoll.
          super(parent, LinuxSocket.makeBlocking(socket), active);
      }
  
      AbstractIoUringStreamChannel(Channel parent, LinuxSocket socket, SocketAddress remote) {
          // Use a blocking fd, we can make use of fastpoll.
          super(parent, LinuxSocket.makeBlocking(socket), remote);
      }
  
      @Override
      public ChannelMetadata metadata() {
          return METADATA;
      }
  
      @Override
      protected final AbstractUringUnsafe newUnsafe() {
          return new IoUringStreamUnsafe();
      }
  
      @Override
      public final ChannelFuture shutdown() {
          return shutdown(newPromise());
      }
  
      @Override
      public final 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;
      }
  
      @Override
      protected final void doShutdownOutput() throws Exception {
          socket.shutdown(false, true);
      }
  
      private void shutdownInput0(final ChannelPromise promise) {
          try {
              socket.shutdown(true, false);
              promise.setSuccess();
          } catch (Throwable cause) {
             promise.setFailure(cause);
         }
     }
 
     @Override
     public final boolean isOutputShutdown() {
         return socket.isOutputShutdown();
     }
 
     @Override
     public final boolean isInputShutdown() {
         return socket.isInputShutdown();
     }
 
     @Override
     public final boolean isShutdown() {
         return socket.isShutdown();
     }
 
     @Override
     public final ChannelFuture shutdownOutput() {
         return shutdownOutput(newPromise());
     }
 
     @Override
     public final 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 final ChannelFuture shutdownInput() {
         return shutdownInput(newPromise());
     }
 
     @Override
     public final 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 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.info("Exception suppressed because a previous exception occurred.",
                              shutdownInputCause);
             }
             promise.setFailure(shutdownOutputCause);
         } else if (shutdownInputCause != null) {
             promise.setFailure(shutdownInputCause);
         } else {
             promise.setSuccess();
         }
     }
 
     @Override
     protected final void doRegister(ChannelPromise promise) {
         super.doRegister(promise);
         promise.addListener(f -> {
             if (f.isSuccess()) {
                 if (active) {
                     // Register for POLLRDHUP if this channel is already considered active.
                     schedulePollRdHup();
                 }
             }
         });
     }
 
     private final class IoUringStreamUnsafe extends AbstractUringUnsafe {
 
         private ByteBuf readBuffer;
         private IovArray iovArray;
 
         @Override
         protected int scheduleWriteMultiple(ChannelOutboundBuffer in) {
             assert iovArray == null;
             assert writeId == 0;
             int numElements = Math.min(in.size(), Limits.IOV_MAX);
             ByteBuf iovArrayBuffer = alloc().directBuffer(numElements * IovArray.IOV_SIZE);
             iovArray = new IovArray(iovArrayBuffer);
             try {
                 int offset = iovArray.count();
                 in.forEachFlushedMessage(iovArray);
 
                 int fd = fd().intValue();
                 IoUringIoRegistration registration = registration();
                 IoUringIoOps ops = IoUringIoOps.newWritev(fd, 0, 0, iovArray.memoryAddress(offset),
                         iovArray.count() - offset, nextOpsId());
                 byte opCode = ops.opcode();
                 writeId = registration.submit(ops);
                 writeOpCode = opCode;
             } catch (Exception e) {
                 iovArray.release();
                 iovArray = null;
 
                 // This should never happen, anyway fallback to single write.
                 scheduleWriteSingle(in.current());
             }
             return 1;
         }
 
         @Override
         protected int scheduleWriteSingle(Object msg) {
             assert iovArray == null;
             assert writeId == 0;
             ByteBuf buf = (ByteBuf) msg;
 
             int fd = fd().intValue();
             IoUringIoRegistration registration = registration();
             IoUringIoOps ops = IoUringIoOps.newWrite(fd, 0, 0,
                     buf.memoryAddress() + buf.readerIndex(), buf.readableBytes(), nextOpsId());
             byte opCode = ops.opcode();
             writeId = registration.submit(ops);
             writeOpCode = opCode;
             return 1;
         }
 
         @Override
         protected int scheduleRead0(boolean first) {
             assert readBuffer == null;
             assert readId == 0;
 
             final IoUringRecvByteAllocatorHandle allocHandle = recvBufAllocHandle();
             ByteBuf byteBuf = allocHandle.allocate(alloc());
             allocHandle.attemptedBytesRead(byteBuf.writableBytes());
 
             readBuffer = byteBuf;
 
             int fd = fd().intValue();
             IoUringIoRegistration registration = registration();
             // Depending on if this is the first read or not we will use Native.MSG_DONTWAIT.
             // The idea is that if the socket is blocking we can do the first read in a blocking fashion
             // and so not need to also register POLLIN. As we can not 100 % sure if reads after the first will
             // be possible directly we schedule these with Native.MSG_DONTWAIT. This allows us to still be
             // able to signal the fireChannelReadComplete() in a timely manner and be consistent with other
             // transports.
             IoUringIoOps ops = IoUringIoOps.newRecv(fd, 0, first ? 0 : Native.MSG_DONTWAIT,
                     byteBuf.memoryAddress() + byteBuf.writerIndex(), byteBuf.writableBytes(), nextOpsId());
             readId = registration.submit(ops);
             return 1;
         }
 
         @Override
         protected void readComplete0(int res, int flags, int data, int outstanding) {
             assert readId != 0;
             readId = 0;
             boolean close = false;
 
             final IoUringRecvByteAllocatorHandle allocHandle = recvBufAllocHandle();
             final ChannelPipeline pipeline = pipeline();
             ByteBuf byteBuf = this.readBuffer;
             this.readBuffer = null;
             assert byteBuf != null;
 
             try {
                 if (res < 0) {
                     if (res == Native.ERRNO_ECANCELED_NEGATIVE) {
                         byteBuf.release();
                         return;
                     }
                     // If res is negative we should pass it to ioResult(...) which will either throw
                     // or convert it to 0 if we could not read because the socket was not readable.
                     allocHandle.lastBytesRead(ioResult("io_uring read", res));
                 } else if (res > 0) {
                     byteBuf.writerIndex(byteBuf.writerIndex() + res);
                     allocHandle.lastBytesRead(res);
                 } else {
                     // EOF which we signal with -1.
                     allocHandle.lastBytesRead(-1);
                 }
                 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.
                         shutdownInput(false);
                     }
                     allocHandle.readComplete();
                     pipeline.fireChannelReadComplete();
                     return;
                 }
 
                 allocHandle.incMessagesRead(1);
                 pipeline.fireChannelRead(byteBuf);
                 byteBuf = null;
                 if (allocHandle.continueReading() &&
                         // If IORING_CQE_F_SOCK_NONEMPTY is supported we should check for it first before
                         // trying to schedule a read. If it's supported and not part of the flags we know for sure
                         // that the next read (which would be using Native.MSG_DONTWAIT) will complete without
                         // be able to read any data. This is useless work and we can skip it.
                         (!IoUring.isIOUringCqeFSockNonEmptySupported() ||
                         (flags & Native.IORING_CQE_F_SOCK_NONEMPTY) != 0)) {
                     // Let's schedule another read.
                     scheduleRead(false);
                 } else {
                     // We did not fill the whole ByteBuf so we should break the "read loop" and try again later.
                     allocHandle.readComplete();
                     pipeline.fireChannelReadComplete();
                 }
             } catch (Throwable t) {
                 handleReadException(pipeline, byteBuf, t, close, allocHandle);
             }
         }
 
         private void handleReadException(ChannelPipeline pipeline, ByteBuf byteBuf,
                                          Throwable cause, boolean close,
                                          IoUringRecvByteAllocatorHandle allocHandle) {
             if (byteBuf != null) {
                 if (byteBuf.isReadable()) {
                     pipeline.fireChannelRead(byteBuf);
                 } else {
                     byteBuf.release();
                 }
             }
             allocHandle.readComplete();
             pipeline.fireChannelReadComplete();
             pipeline.fireExceptionCaught(cause);
             if (close || cause instanceof IOException) {
                 shutdownInput(false);
             }
         }
 
         @Override
         boolean writeComplete0(int res, int flags, int data, int outstanding) {
             assert writeId != 0;
             writeId = 0;
             writeOpCode = 0;
             IovArray iovArray = this.iovArray;
             if (iovArray != null) {
                 this.iovArray = null;
                 iovArray.release();
             }
             if (res >= 0) {
                 unsafe().outboundBuffer().removeBytes(res);
             } else if (res == Native.ERRNO_ECANCELED_NEGATIVE) {
                 return true;
             } else {
                 try {
                     if (ioResult("io_uring write", res) == 0) {
                         return false;
                     }
                 } catch (Throwable cause) {
                     handleWriteError(cause);
                 }
             }
             return true;
         }
     }
 
     @Override
     protected final void cancelOutstandingReads(IoUringIoRegistration registration, int numOutstandingReads) {
         if (readId != 0) {
             // Let's try to cancel outstanding reads as these might be submitted and waiting for data (via fastpoll).
             assert numOutstandingReads == 1;
             int fd = fd().intValue();
             IoUringIoOps ops = IoUringIoOps.newAsyncCancel(fd, 0, readId, Native.IORING_OP_RECV);
             registration.submit(ops);
         } else {
             assert numOutstandingReads == 0;
         }
     }
 
     @Override
     protected final void cancelOutstandingWrites(IoUringIoRegistration registration, int numOutstandingWrites) {
         if (writeId != 0) {
             // Let's try to cancel outstanding writes as these might be submitted and waiting to finish writing
             // (via fastpoll).
             assert numOutstandingWrites == 1;
             assert writeOpCode != 0;
             int fd = fd().intValue();
             registration.submit(IoUringIoOps.newAsyncCancel(fd, 0, writeId, writeOpCode));
         } else {
             assert numOutstandingWrites == 0;
         }
     }
 }