/*
    * 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 static org.jboss.netty.handler.codec.spdy.SpdyCodecUtil.*;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.Channels;
  import org.jboss.netty.handler.codec.frame.TooLongFrameException;
  import org.jboss.netty.handler.codec.http.DefaultHttpRequest;
  import org.jboss.netty.handler.codec.http.DefaultHttpResponse;
  import org.jboss.netty.handler.codec.http.HttpHeaders;
  import org.jboss.netty.handler.codec.http.HttpMessage;
  import org.jboss.netty.handler.codec.http.HttpMethod;
  import org.jboss.netty.handler.codec.http.HttpRequest;
  import org.jboss.netty.handler.codec.http.HttpResponse;
  import org.jboss.netty.handler.codec.http.HttpResponseStatus;
  import org.jboss.netty.handler.codec.http.HttpVersion;
  import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;
  
  /**
   * Decodes {@link SpdySynStreamFrame}s, {@link SpdySynReplyFrame}s,
   * and {@link SpdyDataFrame}s into {@link HttpRequest}s and {@link HttpResponse}s.
   */
  public class SpdyHttpDecoder extends OneToOneDecoder {
  
      private final int spdyVersion;
      private final int maxContentLength;
      private final Map<Integer, HttpMessage> messageMap = new HashMap<Integer, HttpMessage>();
  
      /**
       * Creates a new instance for the SPDY/2 protocol
       *
       * @param maxContentLength the maximum length of the message content.
       *        If the length of the message content exceeds this value,
       *        a {@link TooLongFrameException} will be raised.
       */
      @Deprecated
      public SpdyHttpDecoder(int maxContentLength) {
          this(2, maxContentLength);
      }
  
      /**
       * Creates a new instance.
       *
       * @param version the protocol version
       * @param maxContentLength the maximum length of the message content.
       *        If the length of the message content exceeds this value,
       *        a {@link TooLongFrameException} will be raised.
       */
      public SpdyHttpDecoder(int version, int maxContentLength) {
          if (version < SPDY_MIN_VERSION || version > SPDY_MAX_VERSION) {
              throw new IllegalArgumentException(
                      "unsupported version: " + version);
          }
          if (maxContentLength <= 0) {
              throw new IllegalArgumentException(
                      "maxContentLength must be a positive integer: " + maxContentLength);
          }
          spdyVersion = version;
          this.maxContentLength = maxContentLength;
      }
  
      @Override
      protected Object decode(ChannelHandlerContext ctx, Channel channel, Object msg)
              throws Exception {
  
          if (msg instanceof SpdySynStreamFrame) {
  
              // HTTP requests/responses are mapped one-to-one to SPDY streams.
              SpdySynStreamFrame spdySynStreamFrame = (SpdySynStreamFrame) msg;
              int streamID = spdySynStreamFrame.getStreamId();
  
              if (isServerId(streamID)) {
                  // SYN_STREAM frames initiated by the server are pushed resources
                  int associatedToStreamID = spdySynStreamFrame.getAssociatedToStreamId();
  
                  // If a client receives a SYN_STREAM with an Associated-To-Stream-ID of 0
                  // it must reply with a RST_STREAM with error code INVALID_STREAM
                  if (associatedToStreamID == 0) {
                     SpdyRstStreamFrame spdyRstStreamFrame =
                         new DefaultSpdyRstStreamFrame(streamID, SpdyStreamStatus.INVALID_STREAM);
                     Channels.write(ctx, Channels.future(channel), spdyRstStreamFrame);
                 }
 
                 String URL = SpdyHeaders.getUrl(spdyVersion, spdySynStreamFrame);
 
                 // If a client receives a SYN_STREAM without a 'url' header
                 // it must reply with a RST_STREAM with error code PROTOCOL_ERROR
                 if (URL == null) {
                     SpdyRstStreamFrame spdyRstStreamFrame =
                         new DefaultSpdyRstStreamFrame(streamID, SpdyStreamStatus.PROTOCOL_ERROR);
                     Channels.write(ctx, Channels.future(channel), spdyRstStreamFrame);
                 }
 
                 try {
                     HttpResponse httpResponse = createHttpResponse(spdyVersion, spdySynStreamFrame);
 
                     // Set the Stream-ID, Associated-To-Stream-ID, Priority, and URL as headers
                     SpdyHttpHeaders.setStreamId(httpResponse, streamID);
                     SpdyHttpHeaders.setAssociatedToStreamId(httpResponse, associatedToStreamID);
                     SpdyHttpHeaders.setPriority(httpResponse, spdySynStreamFrame.getPriority());
                     SpdyHttpHeaders.setUrl(httpResponse, URL);
 
                     if (spdySynStreamFrame.isLast()) {
                         HttpHeaders.setContentLength(httpResponse, 0);
                         return httpResponse;
                     } else {
                         // Response body will follow in a series of Data Frames
                         messageMap.put(streamID, httpResponse);
                     }
                 } catch (Exception e) {
                     SpdyRstStreamFrame spdyRstStreamFrame =
                         new DefaultSpdyRstStreamFrame(streamID, SpdyStreamStatus.PROTOCOL_ERROR);
                     Channels.write(ctx, Channels.future(channel), spdyRstStreamFrame);
                 }
             } else {
                 // SYN_STREAM frames initiated by the client are HTTP requests
                 try {
                     HttpRequest httpRequest = createHttpRequest(spdyVersion, spdySynStreamFrame);
 
                     // Set the Stream-ID as a header
                     SpdyHttpHeaders.setStreamId(httpRequest, streamID);
 
                     if (spdySynStreamFrame.isLast()) {
                         return httpRequest;
                     } else {
                         // Request body will follow in a series of Data Frames
                         messageMap.put(streamID, httpRequest);
                     }
                 } catch (Exception e) {
                     // If a client sends a SYN_STREAM without all of the method, url (host and path),
                     // scheme, and version headers the server must reply with a HTTP 400 BAD REQUEST reply.
                     // Also sends HTTP 400 BAD REQUEST reply if header name/value pairs are invalid
                     SpdySynReplyFrame spdySynReplyFrame = new DefaultSpdySynReplyFrame(streamID);
                     spdySynReplyFrame.setLast(true);
                     SpdyHeaders.setStatus(spdyVersion, spdySynReplyFrame, HttpResponseStatus.BAD_REQUEST);
                     SpdyHeaders.setVersion(spdyVersion, spdySynReplyFrame, HttpVersion.HTTP_1_0);
                     Channels.write(ctx, Channels.future(channel), spdySynReplyFrame);
                 }
             }
 
         } else if (msg instanceof SpdySynReplyFrame) {
 
             SpdySynReplyFrame spdySynReplyFrame = (SpdySynReplyFrame) msg;
             int streamID = spdySynReplyFrame.getStreamId();
 
             try {
                 HttpResponse httpResponse = createHttpResponse(spdyVersion, spdySynReplyFrame);
 
                 // Set the Stream-ID as a header
                 SpdyHttpHeaders.setStreamId(httpResponse, streamID);
 
                 if (spdySynReplyFrame.isLast()) {
                     HttpHeaders.setContentLength(httpResponse, 0);
                     return httpResponse;
                 } else {
                     // Response body will follow in a series of Data Frames
                     messageMap.put(streamID, httpResponse);
                 }
             } catch (Exception e) {
                 // If a client receives a SYN_REPLY without valid status and version headers
                 // the client must reply with a RST_STREAM frame indicating a PROTOCOL_ERROR
                 SpdyRstStreamFrame spdyRstStreamFrame =
                     new DefaultSpdyRstStreamFrame(streamID, SpdyStreamStatus.PROTOCOL_ERROR);
                 Channels.write(ctx, Channels.future(channel), spdyRstStreamFrame);
             }
 
         } else if (msg instanceof SpdyHeadersFrame) {
 
             SpdyHeadersFrame spdyHeadersFrame = (SpdyHeadersFrame) msg;
             Integer streamID = spdyHeadersFrame.getStreamId();
             HttpMessage httpMessage = messageMap.get(streamID);
 
             // If message is not in map discard HEADERS frame.
             // SpdySessionHandler should prevent this from happening.
             if (httpMessage == null) {
                 return null;
             }
 
             for (Map.Entry<String, String> e: spdyHeadersFrame.getHeaders()) {
                 httpMessage.addHeader(e.getKey(), e.getValue());
             }
 
         } else if (msg instanceof SpdyDataFrame) {
 
             SpdyDataFrame spdyDataFrame = (SpdyDataFrame) msg;
             Integer streamID = spdyDataFrame.getStreamId();
             HttpMessage httpMessage = messageMap.get(streamID);
 
             // If message is not in map discard Data Frame.
             // SpdySessionHandler should prevent this from happening.
             if (httpMessage == null) {
                 return null;
             }
 
             ChannelBuffer content = httpMessage.getContent();
             if (content.readableBytes() > maxContentLength - spdyDataFrame.getData().readableBytes()) {
                 messageMap.remove(streamID);
                 throw new TooLongFrameException(
                         "HTTP content length exceeded " + maxContentLength + " bytes.");
             }
 
             if (content == ChannelBuffers.EMPTY_BUFFER) {
                 content = ChannelBuffers.dynamicBuffer(channel.getConfig().getBufferFactory());
                 content.writeBytes(spdyDataFrame.getData());
                 httpMessage.setContent(content);
             } else {
                 content.writeBytes(spdyDataFrame.getData());
             }
 
             if (spdyDataFrame.isLast()) {
                 HttpHeaders.setContentLength(httpMessage, content.readableBytes());
                 messageMap.remove(streamID);
                 return httpMessage;
             }
 
         } else if (msg instanceof SpdyRstStreamFrame) {
 
             SpdyRstStreamFrame spdyRstStreamFrame = (SpdyRstStreamFrame) msg;
             Integer streamID = spdyRstStreamFrame.getStreamId();
             messageMap.remove(streamID);
         }
 
         return null;
     }
 
     private static HttpRequest createHttpRequest(int spdyVersion, SpdyHeaderBlock requestFrame)
             throws Exception {
         // Create the first line of the request from the name/value pairs
         HttpMethod  method      = SpdyHeaders.getMethod(spdyVersion, requestFrame);
         String      url         = SpdyHeaders.getUrl(spdyVersion, requestFrame);
         HttpVersion httpVersion = SpdyHeaders.getVersion(spdyVersion, requestFrame);
         SpdyHeaders.removeMethod(spdyVersion, requestFrame);
         SpdyHeaders.removeUrl(spdyVersion, requestFrame);
         SpdyHeaders.removeVersion(spdyVersion, requestFrame);
 
         HttpRequest httpRequest = new DefaultHttpRequest(httpVersion, method, url);
 
         // Remove the scheme header
         SpdyHeaders.removeScheme(spdyVersion, requestFrame);
 
         if (spdyVersion >= 3) {
             // Replace the SPDY host header with the HTTP host header
             String host = SpdyHeaders.getHost(requestFrame);
             SpdyHeaders.removeHost(requestFrame);
             HttpHeaders.setHost(httpRequest, host);
         }
 
         for (Map.Entry<String, String> e: requestFrame.getHeaders()) {
             httpRequest.addHeader(e.getKey(), e.getValue());
         }
 
         // The Connection and Keep-Alive headers are no longer valid
         HttpHeaders.setKeepAlive(httpRequest, true);
 
         // Transfer-Encoding header is not valid
         httpRequest.removeHeader(HttpHeaders.Names.TRANSFER_ENCODING);
 
         return httpRequest;
     }
 
     private static HttpResponse createHttpResponse(int spdyVersion, SpdyHeaderBlock responseFrame)
             throws Exception {
         // Create the first line of the response from the name/value pairs
         HttpResponseStatus status = SpdyHeaders.getStatus(spdyVersion, responseFrame);
         HttpVersion version = SpdyHeaders.getVersion(spdyVersion, responseFrame);
         SpdyHeaders.removeStatus(spdyVersion, responseFrame);
         SpdyHeaders.removeVersion(spdyVersion, responseFrame);
 
         HttpResponse httpResponse = new DefaultHttpResponse(version, status);
         for (Map.Entry<String, String> e: responseFrame.getHeaders()) {
             httpResponse.addHeader(e.getKey(), e.getValue());
         }
 
         // The Connection and Keep-Alive headers are no longer valid
         HttpHeaders.setKeepAlive(httpResponse, true);
 
         // Transfer-Encoding header is not valid
         httpResponse.removeHeader(HttpHeaders.Names.TRANSFER_ENCODING);
         httpResponse.removeHeader(HttpHeaders.Names.TRAILER);
 
         return httpResponse;
     }
 }