/*
    * Copyright 2012 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:
    *
    *   http://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 org.jboss.netty.handler.codec.spdy;
  
  import javax.net.ssl.SSLEngine;
  
  import org.jboss.netty.channel.ChannelEvent;
  import org.jboss.netty.channel.ChannelHandler;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.ChannelPipeline;
  import org.jboss.netty.channel.ChannelUpstreamHandler;
  import org.jboss.netty.handler.codec.http.HttpChunkAggregator;
  import org.jboss.netty.handler.codec.http.HttpRequest;
  import org.jboss.netty.handler.codec.http.HttpRequestDecoder;
  import org.jboss.netty.handler.codec.http.HttpResponseEncoder;
  import org.jboss.netty.handler.ssl.SslHandler;
  
  /**
   * {@link ChannelUpstreamHandler} which is responsible to setup the {@link ChannelPipeline} either for
   * HTTP or SPDY. This offers an easy way for users to support both at the same time while not care to
   * much about the low-level details.
   *
   */
  public abstract class SpdyOrHttpChooser implements ChannelUpstreamHandler {
  
      public enum SelectedProtocol {
          SpdyVersion3_1,
          HttpVersion1_1,
          HttpVersion1_0,
          None
      }
  
      private final int maxSpdyContentLength;
      private final int maxHttpContentLength;
  
      protected SpdyOrHttpChooser(int maxSpdyContentLength, int maxHttpContentLength) {
          this.maxSpdyContentLength = maxSpdyContentLength;
          this.maxHttpContentLength = maxHttpContentLength;
      }
  
      /**
       * Return the {@link SelectedProtocol} for the {@link SSLEngine}. If its not known yet implementations
       * MUST return {@link SelectedProtocol#None}.
       *
       */
      protected abstract SelectedProtocol getProtocol(SSLEngine engine);
  
      public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
          // Get the SslHandler from the ChannelPipeline so we can obtain the SslEngine from it.
          SslHandler handler = ctx.getPipeline().get(SslHandler.class);
          if (handler == null) {
              // SslHandler is needed by SPDY by design.
              throw new IllegalStateException("SslHandler is needed for SPDY");
          }
  
          ChannelPipeline pipeline = ctx.getPipeline();
          SelectedProtocol protocol = getProtocol(handler.getEngine());
          switch (protocol) {
          case None:
              // Not done with choosing the protocol, so just return here for now,
              return;
          case SpdyVersion3_1:
              addSpdyHandlers(ctx, SpdyVersion.SPDY_3_1);
              break;
          case HttpVersion1_0:
          case HttpVersion1_1:
              addHttpHandlers(ctx);
              break;
          default:
              throw new IllegalStateException("Unknown SelectedProtocol");
          }
          // When we reached here we can remove this handler as its now clear what protocol we want to use
          // from this point on.
          pipeline.remove(this);
          ctx.sendUpstream(e);
      }
  
      /**
       * Add all {@link ChannelHandler}'s that are needed for SPDY with the given version.
       */
      protected void addSpdyHandlers(ChannelHandlerContext ctx, SpdyVersion version) {
          ChannelPipeline pipeline = ctx.getPipeline();
          pipeline.addLast("spdyFrameCodec", new SpdyFrameCodec(version));
          pipeline.addLast("spdySessionHandler", new SpdySessionHandler(version, true));
          pipeline.addLast("spdyHttpEncoder", new SpdyHttpEncoder(version));
          pipeline.addLast("spdyHttpDecoder", new SpdyHttpDecoder(version, maxSpdyContentLength));
         pipeline.addLast("spdyStreamIdHandler", new SpdyHttpResponseStreamIdHandler());
         pipeline.addLast("httpRequestHandler", createHttpRequestHandlerForSpdy());
     }
 
     /**
      * Add all {@link ChannelHandler}'s that are needed for HTTP.
      */
     protected void addHttpHandlers(ChannelHandlerContext ctx) {
         ChannelPipeline pipeline = ctx.getPipeline();
         pipeline.addLast("httpRequestDecoder", new HttpRequestDecoder());
         pipeline.addLast("httpResponseEncoder", new HttpResponseEncoder());
         pipeline.addLast("httpChunkAggregator", new HttpChunkAggregator(maxHttpContentLength));
         pipeline.addLast("httpRequestHandler", createHttpRequestHandlerForHttp());
     }
 
     /**
      * Create the {@link ChannelUpstreamHandler} that is responsible for handling the {@link HttpRequest}'s
      * when the {@link SelectedProtocol} was {@link SelectedProtocol#HttpVersion1_0} or
      * {@link SelectedProtocol#HttpVersion1_1}
      */
     protected abstract ChannelUpstreamHandler createHttpRequestHandlerForHttp();
 
     /**
      * Create the {@link ChannelUpstreamHandler} that is responsible for handling the {@link HttpRequest}'s
      * when the {@link SelectedProtocol} was {@link SelectedProtocol#SpdyVersion3_1}.
      *
      * By default this method will just delecate to {@link #createHttpRequestHandlerForHttp()}, but
      * sub-classes may override this to change the behaviour.
      */
     protected ChannelUpstreamHandler createHttpRequestHandlerForSpdy() {
         return createHttpRequestHandlerForHttp();
     }
 }