/*
    * 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 io.netty.handler.codec.http;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.CombinedChannelDuplexHandler;
  
  import java.util.ArrayDeque;
  import java.util.List;
  import java.util.Queue;
  
  /**
   * A combination of {@link HttpRequestDecoder} and {@link HttpResponseEncoder}
   * which enables easier server side HTTP implementation.
   *
   * @see HttpClientCodec
   */
  public final class HttpServerCodec extends CombinedChannelDuplexHandler<HttpRequestDecoder, HttpResponseEncoder>
          implements HttpServerUpgradeHandler.SourceCodec {
  
      /** A queue that is used for correlating a request and a response. */
      private final Queue<HttpMethod> queue = new ArrayDeque<HttpMethod>();
  
      /**
       * Creates a new instance with the default decoder options
       * ({@code maxInitialLineLength (4096}}, {@code maxHeaderSize (8192)}, and
       * {@code maxChunkSize (8192)}).
       */
      public HttpServerCodec() {
          this(4096, 8192, 8192);
      }
  
      /**
       * Creates a new instance with the specified decoder options.
       */
      public HttpServerCodec(int maxInitialLineLength, int maxHeaderSize, int maxChunkSize) {
          init(new HttpServerRequestDecoder(maxInitialLineLength, maxHeaderSize, maxChunkSize),
                  new HttpServerResponseEncoder());
      }
  
      /**
       * Creates a new instance with the specified decoder options.
       */
      public HttpServerCodec(int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean validateHeaders) {
          init(new HttpServerRequestDecoder(maxInitialLineLength, maxHeaderSize, maxChunkSize, validateHeaders),
                  new HttpServerResponseEncoder());
      }
  
      /**
       * Creates a new instance with the specified decoder options.
       */
      public HttpServerCodec(int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean validateHeaders,
                             int initialBufferSize) {
          init(
            new HttpServerRequestDecoder(maxInitialLineLength, maxHeaderSize, maxChunkSize,
                    validateHeaders, initialBufferSize),
            new HttpServerResponseEncoder());
      }
  
      /**
       * Upgrades to another protocol from HTTP. Removes the {@link HttpRequestDecoder} and
       * {@link HttpResponseEncoder} from the pipeline.
       */
      @Override
      public void upgradeFrom(ChannelHandlerContext ctx) {
          ctx.pipeline().remove(this);
      }
  
      private final class HttpServerRequestDecoder extends HttpRequestDecoder {
          public HttpServerRequestDecoder(int maxInitialLineLength, int maxHeaderSize, int maxChunkSize) {
              super(maxInitialLineLength, maxHeaderSize, maxChunkSize);
          }
  
          public HttpServerRequestDecoder(int maxInitialLineLength, int maxHeaderSize, int maxChunkSize,
                                          boolean validateHeaders) {
              super(maxInitialLineLength, maxHeaderSize, maxChunkSize, validateHeaders);
          }
  
          public HttpServerRequestDecoder(int maxInitialLineLength, int maxHeaderSize, int maxChunkSize,
                                          boolean validateHeaders, int initialBufferSize) {
              super(maxInitialLineLength, maxHeaderSize, maxChunkSize, validateHeaders, initialBufferSize);
          }
  
          @Override
          protected void decode(ChannelHandlerContext ctx, ByteBuf buffer, List<Object> out) throws Exception {
             int oldSize = out.size();
             super.decode(ctx, buffer, out);
             int size = out.size();
             for (int i = oldSize; i < size; i++) {
                 Object obj = out.get(i);
                 if (obj instanceof HttpRequest) {
                     queue.add(((HttpRequest) obj).method());
                 }
             }
         }
     }
 
     private final class HttpServerResponseEncoder extends HttpResponseEncoder {
 
         private HttpMethod method;
 
         @Override
         protected void sanitizeHeadersBeforeEncode(HttpResponse msg, boolean isAlwaysEmpty) {
             if (!isAlwaysEmpty && method == HttpMethod.CONNECT && msg.status().codeClass() == HttpStatusClass.SUCCESS) {
                 // Stripping Transfer-Encoding:
                 // See https://tools.ietf.org/html/rfc7230#section-3.3.1
                 msg.headers().remove(HttpHeaderNames.TRANSFER_ENCODING);
                 return;
             }
 
             super.sanitizeHeadersBeforeEncode(msg, isAlwaysEmpty);
         }
 
         @Override
         protected boolean isContentAlwaysEmpty(@SuppressWarnings("unused") HttpResponse msg) {
             method = queue.poll();
             return HttpMethod.HEAD.equals(method) || super.isContentAlwaysEmpty(msg);
         }
     }
 }