/*
    * Copyright 2013 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.handler.codec.http.websocketx;
  
  
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelOutboundHandler;
  import io.netty.channel.ChannelPromise;
  import io.netty.handler.codec.MessageToMessageDecoder;
  import io.netty.util.ReferenceCountUtil;
  import io.netty.util.concurrent.Future;
  import io.netty.util.concurrent.PromiseNotifier;
  
  import java.net.SocketAddress;
  import java.nio.channels.ClosedChannelException;
  import java.util.List;
  import java.util.concurrent.TimeUnit;
  
  abstract class WebSocketProtocolHandler extends MessageToMessageDecoder<WebSocketFrame>
          implements ChannelOutboundHandler {
  
      private final boolean dropPongFrames;
      private final WebSocketCloseStatus closeStatus;
      private final long forceCloseTimeoutMillis;
      private ChannelPromise closeSent;
      private Future<?> forceCloseTimeoutTask;
  
      /**
       * Creates a new {@link WebSocketProtocolHandler} that will <i>drop</i> {@link PongWebSocketFrame}s.
       */
      WebSocketProtocolHandler() {
          this(true);
      }
  
      /**
       * Creates a new {@link WebSocketProtocolHandler}, given a parameter that determines whether or not to drop {@link
       * PongWebSocketFrame}s.
       *
       * @param dropPongFrames
       *            {@code true} if {@link PongWebSocketFrame}s should be dropped
       */
      WebSocketProtocolHandler(boolean dropPongFrames) {
          this(dropPongFrames, null, WebSocketServerProtocolConfig.DEFAULT_FORCE_CLOSE_TIMEOUT_MILLIS);
      }
  
      WebSocketProtocolHandler(boolean dropPongFrames,
                               WebSocketCloseStatus closeStatus,
                               long forceCloseTimeoutMillis) {
          super(WebSocketFrame.class);
          this.dropPongFrames = dropPongFrames;
          this.closeStatus = closeStatus;
          this.forceCloseTimeoutMillis = forceCloseTimeoutMillis;
      }
  
      @Override
      protected void decode(ChannelHandlerContext ctx, WebSocketFrame frame, List<Object> out) throws Exception {
          if (frame instanceof PingWebSocketFrame) {
              frame.content().retain();
              ctx.writeAndFlush(new PongWebSocketFrame(frame.content()));
              readIfNeeded(ctx);
              return;
          }
          if (frame instanceof PongWebSocketFrame && dropPongFrames) {
              readIfNeeded(ctx);
              return;
          }
  
          out.add(frame.retain());
      }
  
      private static void readIfNeeded(ChannelHandlerContext ctx) {
          if (!ctx.channel().config().isAutoRead()) {
              ctx.read();
          }
      }
  
      @Override
      public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
          if (closeStatus == null || !ctx.channel().isActive()) {
              ctx.close(promise);
          } else {
              if (closeSent == null) {
                  write(ctx, new CloseWebSocketFrame(closeStatus, ctx.alloc()), ctx.newPromise());
              }
              flush(ctx);
             closeSent.addListener(future -> ctx.close(promise));
         }
     }
 
     @Override
     public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
         if (closeSent != null) {
             ReferenceCountUtil.release(msg);
             promise.setFailure(new ClosedChannelException());
         } else if (msg instanceof CloseWebSocketFrame) {
             closeSent(promise.unvoid());
             ctx.write(msg).addListener(new PromiseNotifier<Void, ChannelFuture>(false, closeSent));
         } else {
             ctx.write(msg, promise);
         }
     }
 
     @Override
     public void flush(ChannelHandlerContext ctx) throws Exception {
         ctx.flush();
         // Give the flush a chance to complete synchronously before arming the deadline, so a write that
         // finishes immediately (e.g. EmbeddedChannel, or a fast socket) never races the force-close timer.
         if (closeSent != null) {
             applyCloseSentTimeout(ctx);
         }
     }
 
     /**
      * Records the {@link ChannelPromise} used to write the outgoing close frame. Every code path that initiates
      * the close handshake must call this, and must subsequently give
      * {@link #applyCloseSentTimeout(ChannelHandlerContext)} a chance to run (directly, or indirectly via
      * {@link #flush(ChannelHandlerContext)}) so the channel is guaranteed to close even if the outbound write
      * never completes (e.g. the peer stops reading and the socket send buffer fills up).
      */
     void closeSent(ChannelPromise promise) {
         if (closeSent != null) {
             // Already sending (or already sent) a close frame, e.g. a peer that sends more than one CLOSE
             // frame. Keep the original promise (and the deadline already armed for it) authoritative, and
             // just cascade its outcome onto the new one instead of losing track of the original.
             closeSent.addListener(new PromiseNotifier<Void, ChannelFuture>(false, promise));
             return;
         }
         closeSent = promise;
     }
 
     void applyCloseSentTimeout(ChannelHandlerContext ctx) {
         if (forceCloseTimeoutTask != null || closeSent.isDone() || forceCloseTimeoutMillis < 0) {
             return;
         }
 
         final Future<?> timeoutTask = ctx.executor().schedule(new Runnable() {
             @Override
             public void run() {
                 if (!closeSent.isDone()) {
                     closeSent.tryFailure(buildHandshakeException("send close frame timed out"));
                     // Do not rely on some other listener eventually closing the channel once closeSent
                     // completes (e.g. write(CloseWebSocketFrame) without a subsequent close() call attaches
                     // none): close it here so the deadline is enforced unconditionally.
                     ctx.close();
                 }
             }
         }, forceCloseTimeoutMillis, TimeUnit.MILLISECONDS);
         forceCloseTimeoutTask = timeoutTask;
 
         closeSent.addListener(future -> timeoutTask.cancel(false));
     }
 
     /**
      * Returns a {@link WebSocketHandshakeException} that depends on which client or server pipeline
      * this handler belongs. Should be overridden in implementation otherwise a default exception is used.
      */
     protected WebSocketHandshakeException buildHandshakeException(String message) {
         return new WebSocketHandshakeException(message);
     }
 
     @Override
     public void bind(ChannelHandlerContext ctx, SocketAddress localAddress,
                      ChannelPromise promise) throws Exception {
         ctx.bind(localAddress, promise);
     }
 
     @Override
     public void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress,
                         SocketAddress localAddress, ChannelPromise promise) throws Exception {
         ctx.connect(remoteAddress, localAddress, promise);
     }
 
     @Override
     public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise)
             throws Exception {
         ctx.disconnect(promise);
     }
 
     @Override
     public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
         ctx.deregister(promise);
     }
 
     @Override
     public void read(ChannelHandlerContext ctx) throws Exception {
         ctx.read();
     }
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
         ctx.fireExceptionCaught(cause);
         ctx.close();
     }
 }