//
   //  ========================================================================
   //  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.io.IOException;
  import java.util.List;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.eclipse.jetty.util.StringUtil;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  import org.eclipse.jetty.websocket.api.StatusCode;
  import org.eclipse.jetty.websocket.common.CloseInfo;
  import org.eclipse.jetty.websocket.common.ConnectionState;
  
  /**
   * Simple state tracker for Input / Output and {@link ConnectionState}.
   * <p>
   * Use the various known .on*() methods to trigger a state change.
   * <ul>
   * <li>{@link #onOpened()} - connection has been opened</li>
   * </ul>
   */
  public class IOState
  {
      /**
       * The source of a close handshake. (ie: who initiated it).
       */
      private static enum CloseHandshakeSource
      {
          /** No close handshake initiated (yet) */
          NONE,
          /** Local side initiated the close handshake */
          LOCAL,
          /** Remote side initiated the close handshake */
          REMOTE,
          /** An abnormal close situation (disconnect, timeout, etc...) */
          ABNORMAL;
      }
  
      public static interface ConnectionStateListener
      {
          public void onConnectionStateChange(ConnectionState state);
      }
  
      private static final Logger LOG = Log.getLogger(IOState.class);
      private ConnectionState state;
      private final List<ConnectionStateListener> listeners = new CopyOnWriteArrayList<>();
  
      /** 
       * Is input on websocket available (for reading frames).
       * Used to determine close handshake completion, and track half-close states
       */
      private boolean inputAvailable;
      /** 
       * Is output on websocket available (for writing frames).
       * Used to determine close handshake completion, and track half-closed states.
       */
      private boolean outputAvailable;
      /** 
       * Initiator of the close handshake.
       * Used to determine who initiated a close handshake for reply reasons.
       */
      private CloseHandshakeSource closeHandshakeSource;
      /**
       * The close info for the initiator of the close handshake.
       * It is possible in abnormal close scenarios to have a different
       * final close info that is used to notify the WS-Endpoint's onClose()
       * events with.
       */
      private CloseInfo closeInfo;
      /**
       * Atomic reference to the final close info.
       * This can only be set once, and is used for the WS-Endpoint's onClose()
       * event.
       */
      private AtomicReference<CloseInfo> finalClose = new AtomicReference<>();
      /**
       * Tracker for if the close handshake was completed successfully by
       * both sides.  False if close was sudden or abnormal.
       */
     private boolean cleanClose;
 
     /**
      * Create a new IOState, initialized to {@link ConnectionState#CONNECTING}
      */
     public IOState()
     {
         this.state = ConnectionState.CONNECTING;
         this.inputAvailable = false;
         this.outputAvailable = false;
         this.closeHandshakeSource = CloseHandshakeSource.NONE;
         this.closeInfo = null;
         this.cleanClose = false;
     }
 
     public void addListener(ConnectionStateListener listener)
     {
         listeners.add(listener);
     }
 
     public void assertInputOpen() throws IOException
     {
         if (!isInputAvailable())
         {
             throw new IOException("Connection input is closed");
         }
     }
 
     public void assertOutputOpen() throws IOException
     {
         if (!isOutputAvailable())
         {
             throw new IOException("Connection output is closed");
         }
     }
 
     public CloseInfo getCloseInfo()
     {
         CloseInfo ci = finalClose.get();
         if (ci != null)
         {
             return ci;
         }
         return closeInfo;
     }
 
     public ConnectionState getConnectionState()
     {
         return state;
     }
 
     public boolean isClosed()
     {
         synchronized (state)
         {
             return (state == ConnectionState.CLOSED);
         }
     }
 
     public boolean isInputAvailable()
     {
         return inputAvailable;
     }
 
     public boolean isOpen()
     {
         return (getConnectionState() != ConnectionState.CLOSED);
     }
 
     public boolean isOutputAvailable()
     {
         return outputAvailable;
     }
 
     private void notifyStateListeners(ConnectionState state)
     {
         if (LOG.isDebugEnabled())
             LOG.debug("Notify State Listeners: {}",state);
         for (ConnectionStateListener listener : listeners)
         {
             if (LOG.isDebugEnabled())
             {
                 LOG.debug("{}.onConnectionStateChange({})",listener.getClass().getSimpleName(),state.name());
             }
             listener.onConnectionStateChange(state);
         }
     }
 
     /**
      * A websocket connection has been disconnected for abnormal close reasons.
      * <p>
      * This is the low level disconnect of the socket. It could be the result of a normal close operation, from an IO error, or even from a timeout.
      * @param close the close information
      */
     public void onAbnormalClose(CloseInfo close)
     {
         if (LOG.isDebugEnabled())
             LOG.debug("onAbnormalClose({})",close);
         ConnectionState event = null;
         synchronized (this)
         {
             if (this.state == ConnectionState.CLOSED)
             {
                 // already closed
                 return;
             }
 
             if (this.state == ConnectionState.OPEN)
             {
                 this.cleanClose = false;
             }
 
             this.state = ConnectionState.CLOSED;
             finalClose.compareAndSet(null,close);
             this.inputAvailable = false;
             this.outputAvailable = false;
             this.closeHandshakeSource = CloseHandshakeSource.ABNORMAL;
             event = this.state;
         }
         notifyStateListeners(event);
     }
 
     /**
      * A close handshake has been issued from the local endpoint
      * @param close the close information
      */
     public void onCloseLocal(CloseInfo close)
     {
         ConnectionState event = null;
         ConnectionState abnormalEvent = null;
         ConnectionState initialState = this.state;
         if (LOG.isDebugEnabled())
             LOG.debug("onCloseLocal({}) : {}",close,initialState);
         if (initialState == ConnectionState.CLOSED)
         {
             // already closed
             LOG.debug("already closed");
             return;
         }
 
         if (initialState == ConnectionState.CONNECTED)
         {
             // fast close. a local close request from end-user onConnect/onOpen method
             LOG.debug("FastClose in CONNECTED detected");
             // Force the state open (to allow read/write to endpoint)
             onOpened();
             if (LOG.isDebugEnabled())
                 LOG.debug("FastClose continuing with Closure");
         }
 
         synchronized (this)
         {
             closeInfo = close;
             
             // Turn off further output
             outputAvailable = false;
 
             boolean in = inputAvailable;
             boolean out = outputAvailable;
             if (closeHandshakeSource == CloseHandshakeSource.NONE)
             {
                 closeHandshakeSource = CloseHandshakeSource.LOCAL;
             }
             
             LOG.debug("onCloseLocal(), input={}, output={}",in,out);
 
             if (!in && !out)
             {
                 LOG.debug("Close Handshake satisfied, disconnecting");
                 cleanClose = true;
                 this.state = ConnectionState.CLOSED;
                 finalClose.compareAndSet(null,close);
                 event = this.state;
             }
             else if (this.state == ConnectionState.OPEN)
             {
                 // We are now entering CLOSING (or half-closed)
                 this.state = ConnectionState.CLOSING;
                 event = this.state;
                 
                 // if abnormal, we don't expect an answer.
                 if (close.isAbnormal())
                 {
                     abnormalEvent = ConnectionState.CLOSED;
                     finalClose.compareAndSet(null,close);
                     cleanClose = false;
                     outputAvailable = false;
                     inputAvailable = false;
                     closeHandshakeSource = CloseHandshakeSource.ABNORMAL;
                 }
             }
         }
 
         // Only notify on state change events
         if (event != null)
         {
             notifyStateListeners(event);
             
             if(abnormalEvent != null) 
             {
                 notifyStateListeners(abnormalEvent);
             }
         }
     }
 
     /**
      * A close handshake has been received from the remote endpoint
      * @param close the close information
      */
     public void onCloseRemote(CloseInfo close)
     {
         if (LOG.isDebugEnabled())
             LOG.debug("onCloseRemote({})",close);
         ConnectionState event = null;
         synchronized (this)
         {
             if (this.state == ConnectionState.CLOSED)
             {
                 // already closed
                 return;
             }
 
             closeInfo = close;
             
             // turn off further input
             inputAvailable = false;
 
             boolean in = inputAvailable;
             boolean out = outputAvailable;
             if (closeHandshakeSource == CloseHandshakeSource.NONE)
             {
                 closeHandshakeSource = CloseHandshakeSource.REMOTE;
             }
 
             if (LOG.isDebugEnabled())
                 LOG.debug("onCloseRemote(), input={}, output={}",in,out);
 
             if (!in && !out)
             {
                 LOG.debug("Close Handshake satisfied, disconnecting");
                 cleanClose = true;
                 state = ConnectionState.CLOSED;
                 finalClose.compareAndSet(null,close);
                 event = this.state;
             }
             else if (this.state == ConnectionState.OPEN)
             {
                 // We are now entering CLOSING (or half-closed)
                 this.state = ConnectionState.CLOSING;
                 event = this.state;
             }
         }
 
         // Only notify on state change events
         if (event != null)
         {
             notifyStateListeners(event);
         }
     }
 
     /**
      * WebSocket has successfully upgraded, but the end-user onOpen call hasn't run yet.
      * <p>
      * This is an intermediate state between the RFC's {@link ConnectionState#CONNECTING} and {@link ConnectionState#OPEN}
      */
     public void onConnected()
     {
         ConnectionState event = null;
         synchronized (this)
         {
             if (this.state != ConnectionState.CONNECTING)
             {
                 LOG.debug("Unable to set to connected, not in CONNECTING state: {}",this.state);
                 return;
             }
 
             this.state = ConnectionState.CONNECTED;
             inputAvailable = false; // cannot read (yet)
             outputAvailable = true; // write allowed
             event = this.state;
         }
         notifyStateListeners(event);
     }
 
     /**
      * A websocket connection has failed its upgrade handshake, and is now closed.
      */
     public void onFailedUpgrade()
     {
         assert (this.state == ConnectionState.CONNECTING);
         ConnectionState event = null;
         synchronized (this)
         {
             this.state = ConnectionState.CLOSED;
             cleanClose = false;
             inputAvailable = false;
             outputAvailable = false;
             event = this.state;
         }
         notifyStateListeners(event);
     }
 
     /**
      * A websocket connection has finished its upgrade handshake, and is now open.
      */
     public void onOpened()
     {
         if(LOG.isDebugEnabled())
             LOG.debug(" onOpened()");
         
         ConnectionState event = null;
         synchronized (this)
         {
             if (this.state == ConnectionState.OPEN)
             {
                 // already opened
                 return;
             }
 
             if (this.state != ConnectionState.CONNECTED)
             {
                 LOG.debug("Unable to open, not in CONNECTED state: {}",this.state);
                 return;
             }
 
             this.state = ConnectionState.OPEN;
             this.inputAvailable = true;
             this.outputAvailable = true;
             event = this.state;
         }
         notifyStateListeners(event);
     }
 
     /**
      * The local endpoint has reached a read failure.
      * <p>
      * This could be a normal result after a proper close handshake, or even a premature close due to a connection disconnect.
      * @param t the read failure
      */
     public void onReadFailure(Throwable t)
     {
         ConnectionState event = null;
         synchronized (this)
         {
             if (this.state == ConnectionState.CLOSED)
             {
                 // already closed
                 return;
             }
 
          // Build out Close Reason
             String reason = "WebSocket Read Failure";
             if (t instanceof EOFException)
             {
                 reason = "WebSocket Read EOF";
                 Throwable cause = t.getCause();
                 if ((cause != null) && (StringUtil.isNotBlank(cause.getMessage())))
                 {
                     reason = "EOF: " + cause.getMessage();
                 }
             }
             else
             {
                 if (StringUtil.isNotBlank(t.getMessage()))
                 {
                     reason = t.getMessage();
                 }
             }
 
             CloseInfo close = new CloseInfo(StatusCode.ABNORMAL,reason);
 
             finalClose.compareAndSet(null,close);
 
             this.cleanClose = false;
             this.state = ConnectionState.CLOSED;
             this.closeInfo = close;
             this.inputAvailable = false;
             this.outputAvailable = false;
             this.closeHandshakeSource = CloseHandshakeSource.ABNORMAL;
             event = this.state;
         }
         notifyStateListeners(event);
     }
 
     /**
      * The local endpoint has reached a write failure.
      * <p>
      * A low level I/O failure, or even a jetty side EndPoint close (from idle timeout) are a few scenarios
      * @param t the throwable that caused the write failure
      */
     public void onWriteFailure(Throwable t)
     {
         ConnectionState event = null;
         synchronized (this)
         {
             if (this.state == ConnectionState.CLOSED)
             {
                 // already closed
                 return;
             }
 
             // Build out Close Reason
             String reason = "WebSocket Write Failure";
             if (t instanceof EOFException)
             {
                 reason = "WebSocket Write EOF";
                 Throwable cause = t.getCause();
                 if ((cause != null) && (StringUtil.isNotBlank(cause.getMessage())))
                 {
                     reason = "EOF: " + cause.getMessage();
                 }
             }
             else
             {
                 if (StringUtil.isNotBlank(t.getMessage()))
                 {
                     reason = t.getMessage();
                 }
             }
 
             CloseInfo close = new CloseInfo(StatusCode.ABNORMAL,reason);
 
             finalClose.compareAndSet(null,close);
 
             this.cleanClose = false;
             this.state = ConnectionState.CLOSED;
             this.inputAvailable = false;
             this.outputAvailable = false;
             this.closeHandshakeSource = CloseHandshakeSource.ABNORMAL;
             event = this.state;
         }
         notifyStateListeners(event);
     }
 
     public void onDisconnected()
     {
         ConnectionState event = null;
         synchronized (this)
         {
             if (this.state == ConnectionState.CLOSED)
             {
                 // already closed
                 return;
             }
 
             CloseInfo close = new CloseInfo(StatusCode.ABNORMAL,"Disconnected");
 
             this.cleanClose = false;
             this.state = ConnectionState.CLOSED;
             this.closeInfo = close;
             this.inputAvailable = false;
             this.outputAvailable = false;
             this.closeHandshakeSource = CloseHandshakeSource.ABNORMAL;
             event = this.state;
         }
         notifyStateListeners(event);
     }
 
     @Override
     public String toString()
     {
         StringBuilder str = new StringBuilder();
         str.append(this.getClass().getSimpleName());
         str.append("@").append(Integer.toHexString(hashCode()));
         str.append("[").append(state);
         str.append(',');
         if (!inputAvailable)
         {
             str.append('!');
         }
         str.append("in,");
         if (!outputAvailable)
         {
             str.append('!');
         }
         str.append("out");
         if ((state == ConnectionState.CLOSED) || (state == ConnectionState.CLOSING))
         {
             CloseInfo ci = finalClose.get();
             if (ci != null)
             {
                 str.append(",finalClose=").append(ci);
             }
             else
             {
                 str.append(",close=").append(closeInfo);
             }
             str.append(",clean=").append(cleanClose);
             str.append(",closeSource=").append(closeHandshakeSource);
         }
         str.append(']');
         return str.toString();
     }
 
     public boolean wasAbnormalClose()
     {
         return closeHandshakeSource == CloseHandshakeSource.ABNORMAL;
     }
 
     public boolean wasCleanClose()
     {
         return cleanClose;
     }
 
     public boolean wasLocalCloseInitiated()
     {
         return closeHandshakeSource == CloseHandshakeSource.LOCAL;
     }
 
     public boolean wasRemoteCloseInitiated()
     {
         return closeHandshakeSource == CloseHandshakeSource.REMOTE;
     }
 
 }