//
   //  ========================================================================
   //  Copyright (c) 1995-2014 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.server;
  
  import java.io.IOException;
  import java.util.Objects;
  import javax.servlet.ReadListener;
  import javax.servlet.ServletInputStream;
  
  import org.eclipse.jetty.io.EofException;
  import org.eclipse.jetty.io.RuntimeIOException;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  /**
   * {@link HttpInput} provides an implementation of {@link ServletInputStream} for {@link HttpChannel}.
   * <p/>
   * Content may arrive in patterns such as [content(), content(), messageComplete()] so that this class
   * maintains two states: the content state that tells whether there is content to consume and the EOF
   * state that tells whether an EOF has arrived.
   * Only once the content has been consumed the content state is moved to the EOF state.
   */
  public abstract class HttpInput<T> extends ServletInputStream implements Runnable
  {
      private final static Logger LOG = Log.getLogger(HttpInput.class);
  
      private final byte[] _oneByteBuffer = new byte[1];
      private final Object _lock;
      private HttpChannelState _channelState;
      private ReadListener _listener;
      private Throwable _onError;
      private boolean _notReady;
      private State _contentState = STREAM;
      private State _eofState;
      private long _contentRead;
  
      protected HttpInput()
      {
          this(null);
      }
  
      protected HttpInput(Object lock)
      {
          _lock = lock == null ? this : lock;
      }
  
      public void init(HttpChannelState state)
      {
          synchronized (lock())
          {
              _channelState = state;
          }
      }
  
      public final Object lock()
      {
          return _lock;
      }
  
      public void recycle()
      {
          synchronized (lock())
          {
              _listener = null;
              _onError = null;
              _notReady = false;
              _contentState = STREAM;
              _eofState = null;
              _contentRead = 0;
          }
      }
  
      @Override
      public int available()
      {
          try
          {
              synchronized (lock())
              {
                  T item = getNextContent();
                  return item == null ? 0 : remaining(item);
              }
          }
         catch (IOException e)
         {
             throw new RuntimeIOException(e);
         }
     }
 
     @Override
     public int read() throws IOException
     {
         int read = read(_oneByteBuffer, 0, 1);
         return read < 0 ? -1 : _oneByteBuffer[0] & 0xFF;
     }
 
     @Override
     public int read(byte[] b, int off, int len) throws IOException
     {
         synchronized (lock())
         {
             T item = getNextContent();
             if (item == null)
             {
                 _contentState.waitForContent(this);
                 item = getNextContent();
                 if (item == null)
                     return _contentState.noContent();
             }
             int l = get(item, b, off, len);
             _contentRead += l;
             return l;
         }
     }
 
     /**
      * A convenience method to call nextContent and to check the return value, which if null then the
      * a check is made for EOF and the state changed accordingly.
      *
      * @return Content or null if none available.
      * @throws IOException
      * @see #nextContent()
      */
     protected T getNextContent() throws IOException
     {
         T content = nextContent();
         if (content == null)
         {
             synchronized (lock())
             {
                 if (_eofState != null)
                 {
                     if (LOG.isDebugEnabled())
                         LOG.debug("{} eof {}", this, _eofState);
                     _contentState = _eofState;
                 }
             }
         }
         return content;
     }
 
     /**
      * Access the next content to be consumed from.   Returning the next item does not consume it
      * and it may be returned multiple times until it is consumed.
      * <p/>
      * Calls to {@link #get(Object, byte[], int, int)}
      * or {@link #consume(Object, int)} are required to consume data from the content.
      *
      * @return the content or null if none available.
      * @throws IOException if retrieving the content fails
      */
     protected abstract T nextContent() throws IOException;
 
     /**
      * @param item the content
      * @return how many bytes remain in the given content
      */
     protected abstract int remaining(T item);
 
     /**
      * Copies the given content into the given byte buffer.
      *
      * @param item   the content to copy from
      * @param buffer the buffer to copy into
      * @param offset the buffer offset to start copying from
      * @param length the space available in the buffer
      * @return the number of bytes actually copied
      */
     protected abstract int get(T item, byte[] buffer, int offset, int length);
 
     /**
      * Consumes the given content.
      *
      * @param item   the content to consume
      * @param length the number of bytes to consume
      */
     protected abstract void consume(T item, int length);
 
     /**
      * Blocks until some content or some end-of-file event arrives.
      *
      * @throws IOException if the wait is interrupted
      */
     protected abstract void blockForContent() throws IOException;
 
     /**
      * Adds some content to this input stream.
      *
      * @param item the content to add
      */
     public abstract void content(T item);
 
     protected boolean onAsyncRead()
     {
         synchronized (lock())
         {
             if (_listener == null)
                 return false;
         }
         _channelState.onReadPossible();
         return true;
     }
 
     public long getContentRead()
     {
         synchronized (lock())
         {
             return _contentRead;
         }
     }
 
     /**
      * This method should be called to signal that an EOF has been
      * detected before all the expected content arrived.
      * <p/>
      * Typically this will result in an EOFException being thrown
      * from a subsequent read rather than a -1 return.
      */
     public void earlyEOF()
     {
         synchronized (lock())
         {
             if (!isEOF())
             {
                 if (LOG.isDebugEnabled())
                     LOG.debug("{} early EOF", this);
                 _eofState = EARLY_EOF;
                 if (_listener == null)
                     return;
             }
         }
         _channelState.onReadPossible();
     }
 
 
     public boolean isEarlyEOF()
     {
         synchronized (lock())
         {
             return _contentState==EARLY_EOF;
         }
     }
     
     /**
      * This method should be called to signal that all the expected
      * content arrived.
      */
     public void messageComplete()
     {
         synchronized (lock())
         {
             if (!isEOF())
             {
                 if (LOG.isDebugEnabled())
                     LOG.debug("{} EOF", this);
                 _eofState = EOF;
                 if (_listener == null)
                     return;
             }
         }
         _channelState.onReadPossible();
     }
 
     public boolean consumeAll()
     {
         synchronized (lock())
         {
             // Don't bother reading if we already know there was an error.
             if (_onError != null)
                 return false;
 
             try
             {
                 while (!isFinished())
                 {
                     T item = getNextContent();
                     if (item == null)
                         _contentState.waitForContent(this);
                     else
                         consume(item, remaining(item));
                 }
                 return true;
             }
             catch (IOException e)
             {
                 LOG.debug(e);
                 return false;
             }
         }
     }
 
     public boolean isAsync()
     {
         synchronized (lock())
         {
             return _contentState==ASYNC;
         }
     }
     
     /**
      * @return whether an EOF has been detected, even though there may be content to consume.
      */
     public boolean isEOF()
     {
         synchronized (lock())
         {
             return _eofState != null && _eofState.isEOF();
         }
     }
 
     @Override
     public boolean isFinished()
     {
         synchronized (lock())
         {
             return _contentState.isEOF();
         }
     }
     
 
     @Override
     public boolean isReady()
     {
         boolean finished;
         synchronized (lock())
         {
             if (_contentState.isEOF())
                 return true;
             if (_listener == null )
                 return true;
             if (available() > 0)
                 return true;
             if (_notReady)
                 return false;
             _notReady = true;
             finished = isFinished();
         }
         if (finished)
             _channelState.onReadPossible();
         else
             unready();
         return false;
     }
 
     protected void unready()
     {
     }
 
     @Override
     public void setReadListener(ReadListener readListener)
     {
         readListener = Objects.requireNonNull(readListener);
         synchronized (lock())
         {
             if (_contentState != STREAM)
                 throw new IllegalStateException("state=" + _contentState);
             _contentState = ASYNC;
             _listener = readListener;
             _notReady = true;
         }
         _channelState.onReadPossible();
     }
 
     public void failed(Throwable x)
     {
         synchronized (lock())
         {
             if (_onError != null)
                 LOG.warn(x);
             else
                 _onError = x;
         }
     }
 
     @Override
     public void run()
     {
         final Throwable error;
         final ReadListener listener;
         boolean available = false;
         final boolean eof;
 
         synchronized (lock())
         {
             if (!_notReady || _listener == null)
                 return;
 
             error = _onError;
             listener = _listener;
 
             try
             {
                 T item = getNextContent();
                 available = item != null && remaining(item) > 0;
             }
             catch (Exception e)
             {
                 failed(e);
             }
 
             eof = !available && isFinished();
             _notReady = !available && !eof;
         }
 
         try
         {
             if (error != null)
                 listener.onError(error);
             else if (available)
                 listener.onDataAvailable();
             else if (eof)
                 listener.onAllDataRead();
             else
                 unready();
         }
         catch (Throwable e)
         {
             LOG.warn(e.toString());
             LOG.debug(e);
             listener.onError(e);
         }
     }
 
     protected static abstract class State
     {
         public void waitForContent(HttpInput<?> in) throws IOException
         {
         }
 
         public int noContent() throws IOException
         {
             return -1;
         }
 
         public boolean isEOF()
         {
             return false;
         }
     }
 
     protected static final State STREAM = new State()
     {
         @Override
         public void waitForContent(HttpInput<?> input) throws IOException
         {
             input.blockForContent();
         }
 
         @Override
         public String toString()
         {
             return "STREAM";
         }
     };
 
     protected static final State ASYNC = new State()
     {
         @Override
         public int noContent() throws IOException
         {
             return 0;
         }
 
         @Override
         public String toString()
         {
             return "ASYNC";
         }
     };
 
     protected static final State EARLY_EOF = new State()
     {
         @Override
         public int noContent() throws IOException
         {
             throw new EofException("Early EOF");
         }
 
         @Override
         public boolean isEOF()
         {
             return true;
         }
 
         @Override
         public String toString()
         {
             return "EARLY_EOF";
         }
     };
 
     protected static final State EOF = new State()
     {
         @Override
         public boolean isEOF()
         {
             return true;
         }
 
         @Override
         public String toString()
         {
             return "EOF";
         }
     };
 }