//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.websocket.common.io;
  
  import java.io.EOFException;
  import java.nio.ByteBuffer;
  import java.util.ArrayDeque;
  import java.util.ArrayList;
  import java.util.Deque;
  import java.util.List;
  import java.util.Objects;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.eclipse.jetty.io.ByteBufferPool;
  import org.eclipse.jetty.io.EndPoint;
  import org.eclipse.jetty.util.BufferUtil;
  import org.eclipse.jetty.util.IteratingCallback;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  import org.eclipse.jetty.websocket.api.BatchMode;
  import org.eclipse.jetty.websocket.api.WriteCallback;
  import org.eclipse.jetty.websocket.api.extensions.Frame;
  import org.eclipse.jetty.websocket.common.Generator;
  import org.eclipse.jetty.websocket.common.OpCode;
  import org.eclipse.jetty.websocket.common.frames.BinaryFrame;
  
  /**
   * Interface for working with bytes destined for {@link EndPoint#write(org.eclipse.jetty.util.Callback, ByteBuffer...)}
   */
  public class FrameFlusher
  {
      private class Flusher extends IteratingCallback
      {
          private final List<FrameEntry> entries;
          private final List<ByteBuffer> buffers;
          private ByteBuffer aggregate;
          private BatchMode batchMode;
  
          public Flusher(int maxGather)
          {
              entries = new ArrayList<>(maxGather);
              buffers = new ArrayList<>((maxGather * 2) + 1);
          }
  
          private Action batch()
          {
              if (aggregate == null)
              {
                  aggregate = bufferPool.acquire(bufferSize,true);
                  if (LOG.isDebugEnabled())
                  {
                      LOG.debug("{} acquired aggregate buffer {}",FrameFlusher.this,aggregate);
                  }
              }
  
              // Do not allocate the iterator here.
              for (int i = 0; i < entries.size(); ++i)
              {
                  FrameEntry entry = entries.get(i);
  
                  entry.generateHeaderBytes(aggregate);
  
                  ByteBuffer payload = entry.frame.getPayload();
                  if (BufferUtil.hasContent(payload))
                  {
                      BufferUtil.append(aggregate,payload);
                  }
              }
              if (LOG.isDebugEnabled())
              {
                  LOG.debug("{} aggregated {} frames: {}",FrameFlusher.this,entries.size(),entries);
              }
              succeeded();
              return Action.SCHEDULED;
          }
  
          @Override
          protected void onCompleteSuccess()
          {
              // This IteratingCallback never completes.
          }
  
          @Override
         public void onCompleteFailure(Throwable x)
         {
             for (FrameEntry entry : entries)
             {
                 notifyCallbackFailure(entry.callback,x);
                 entry.release();
             }
             entries.clear();
             failure = x;
             onFailure(x);
         }
 
         private Action flush()
         {
             if (!BufferUtil.isEmpty(aggregate))
             {
                 buffers.add(aggregate);
                 if (LOG.isDebugEnabled())
                 {
                     LOG.debug("{} flushing aggregate {}",FrameFlusher.this,aggregate);
                 }
             }
 
             // Do not allocate the iterator here.
             for (int i = 0; i < entries.size(); ++i)
             {
                 FrameEntry entry = entries.get(i);
                 // Skip the "synthetic" frame used for flushing.
                 if (entry.frame == FLUSH_FRAME)
                 {
                     continue;
                 }
                 buffers.add(entry.generateHeaderBytes());
                 ByteBuffer payload = entry.frame.getPayload();
                 if (BufferUtil.hasContent(payload))
                 {
                     buffers.add(payload);
                 }
             }
 
             if (LOG.isDebugEnabled())
             {
                 LOG.debug("{} flushing {} frames: {}",FrameFlusher.this,entries.size(),entries);
             }
 
             if (buffers.isEmpty())
             {
                 releaseAggregate();
                 // We may have the FLUSH_FRAME to notify.
                 succeedEntries();
                 return Action.IDLE;
             }
 
             endpoint.write(this,buffers.toArray(new ByteBuffer[buffers.size()]));
             buffers.clear();
             return Action.SCHEDULED;
         }
 
         @Override
         protected Action process() throws Exception
         {
             int space = aggregate == null?bufferSize:BufferUtil.space(aggregate);
             BatchMode currentBatchMode = BatchMode.AUTO;
             synchronized (lock)
             {
                 while ((entries.size() <= maxGather) && !queue.isEmpty())
                 {
                     FrameEntry entry = queue.poll();
                     currentBatchMode = BatchMode.max(currentBatchMode,entry.batchMode);
 
                     // Force flush if we need to.
                     if (entry.frame == FLUSH_FRAME)
                     {
                         currentBatchMode = BatchMode.OFF;
                     }
 
                     int payloadLength = BufferUtil.length(entry.frame.getPayload());
                     int approxFrameLength = Generator.MAX_HEADER_LENGTH + payloadLength;
 
                     // If it is a "big" frame, avoid copying into the aggregate buffer.
                     if (approxFrameLength > (bufferSize >> 2))
                     {
                         currentBatchMode = BatchMode.OFF;
                     }
 
                     // If the aggregate buffer overflows, do not batch.
                     space -= approxFrameLength;
                     if (space <= 0)
                     {
                         currentBatchMode = BatchMode.OFF;
                     }
 
                     entries.add(entry);
                 }
             }
 
             if (LOG.isDebugEnabled())
             {
                 LOG.debug("{} processing {} entries: {}",FrameFlusher.this,entries.size(),entries);
             }
 
             if (entries.isEmpty())
             {
                 if (batchMode != BatchMode.AUTO)
                 {
                     // Nothing more to do, release the aggregate buffer if we need to.
                     // Releasing it here rather than in succeeded() allows for its reuse.
                     releaseAggregate();
                     return Action.IDLE;
                 }
 
                 LOG.debug("{} auto flushing",FrameFlusher.this);
                 return flush();
             }
 
             batchMode = currentBatchMode;
 
             return currentBatchMode == BatchMode.OFF?flush():batch();
         }
 
         private void releaseAggregate()
         {
             if ((aggregate != null) && BufferUtil.isEmpty(aggregate))
             {
                 bufferPool.release(aggregate);
                 aggregate = null;
             }
         }
 
         @Override
         public void succeeded()
         {
             succeedEntries();
             super.succeeded();
         }
 
         private void succeedEntries()
         {
             // Do not allocate the iterator here.
             for (int i = 0; i < entries.size(); ++i)
             {
                 FrameEntry entry = entries.get(i);
                 notifyCallbackSuccess(entry.callback);
                 entry.release();
             }
             entries.clear();
         }
     }
 
     private class FrameEntry
     {
         private final Frame frame;
         private final WriteCallback callback;
         private final BatchMode batchMode;
         private ByteBuffer headerBuffer;
 
         private FrameEntry(Frame frame, WriteCallback callback, BatchMode batchMode)
         {
             this.frame = Objects.requireNonNull(frame);
             this.callback = callback;
             this.batchMode = batchMode;
         }
 
         private ByteBuffer generateHeaderBytes()
         {
             return headerBuffer = generator.generateHeaderBytes(frame);
         }
 
         private void generateHeaderBytes(ByteBuffer buffer)
         {
             generator.generateHeaderBytes(frame,buffer);
         }
 
         private void release()
         {
             if (headerBuffer != null)
             {
                 generator.getBufferPool().release(headerBuffer);
                 headerBuffer = null;
             }
         }
 
         @Override
         public String toString()
         {
             return String.format("%s[%s,%s,%s,%s]",getClass().getSimpleName(),frame,callback,batchMode,failure);
         }
     }
 
     public static final BinaryFrame FLUSH_FRAME = new BinaryFrame();
     private static final Logger LOG = Log.getLogger(FrameFlusher.class);
     private final ByteBufferPool bufferPool;
     private final EndPoint endpoint;
     private final int bufferSize;
     private final Generator generator;
     private final int maxGather;
     private final Object lock = new Object();
     private final Deque<FrameEntry> queue = new ArrayDeque<>();
     private final Flusher flusher;
     private final AtomicBoolean closed = new AtomicBoolean();
     private volatile Throwable failure;
 
     public FrameFlusher(ByteBufferPool bufferPool, Generator generator, EndPoint endpoint, int bufferSize, int maxGather)
     {
         this.bufferPool = bufferPool;
         this.endpoint = endpoint;
         this.bufferSize = bufferSize;
         this.generator = Objects.requireNonNull(generator);
         this.maxGather = maxGather;
         this.flusher = new Flusher(maxGather);
     }
 
     public void close()
     {
         if (closed.compareAndSet(false,true))
         {
             LOG.debug("{} closing {}",this);
             EOFException eof = new EOFException("Connection has been closed locally");
             flusher.failed(eof);
 
             // Fail also queued entries.
             List<FrameEntry> entries = new ArrayList<>();
             synchronized (lock)
             {
                 entries.addAll(queue);
                 queue.clear();
             }
             // Notify outside sync block.
             for (FrameEntry entry : entries)
             {
                 notifyCallbackFailure(entry.callback,eof);
             }
         }
     }
 
     public void enqueue(Frame frame, WriteCallback callback, BatchMode batchMode)
     {
         if (closed.get())
         {
             notifyCallbackFailure(callback,new EOFException("Connection has been closed locally"));
             return;
         }
         if (flusher.isFailed())
         {
             notifyCallbackFailure(callback,failure);
             return;
         }
 
         FrameEntry entry = new FrameEntry(frame,callback,batchMode);
 
         synchronized (lock)
         {
             switch (frame.getOpCode())
             {
                 case OpCode.PING:
                 {
                     // Prepend PINGs so they are processed first.
                     queue.offerFirst(entry);
                     break;
                 }
                 case OpCode.CLOSE:
                 {
                     // There may be a chance that other frames are
                     // added after this close frame, but we will
                     // fail them later to keep it simple here.
                     closed.set(true);
                     queue.offer(entry);
                     break;
                 }
                 default:
                 {
                     queue.offer(entry);
                     break;
                 }
             }
         }
 
         if (LOG.isDebugEnabled())
         {
             LOG.debug("{} queued {}",this,entry);
         }
 
         flusher.iterate();
     }
 
     protected void notifyCallbackFailure(WriteCallback callback, Throwable failure)
     {
         try
         {
             if (callback != null)
             {
                 callback.writeFailed(failure);
             }
         }
         catch (Throwable x)
         {
             if (LOG.isDebugEnabled())
                 LOG.debug("Exception while notifying failure of callback " + callback,x);
         }
     }
 
     protected void notifyCallbackSuccess(WriteCallback callback)
     {
         try
         {
             if (callback != null)
             {
                 callback.writeSuccess();
             }
         }
         catch (Throwable x)
         {
             if (LOG.isDebugEnabled())
                 LOG.debug("Exception while notifying success of callback " + callback,x);
         }
     }
 
     protected void onFailure(Throwable x)
     {
         LOG.warn(x);
     }
 
     @Override
     public String toString()
     {
         ByteBuffer aggregate = flusher.aggregate;
         return String.format("%s[queueSize=%d,aggregateSize=%d,failure=%s]",getClass().getSimpleName(),queue.size(),aggregate == null?0:aggregate.position(),
                 failure);
     }
 }