/*
    * 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:
    *
    *   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.spdy;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.MessageToMessageDecoder;
  import io.netty.handler.codec.TooLongFrameException;
  import io.netty.handler.codec.http.DefaultFullHttpRequest;
  import io.netty.handler.codec.http.DefaultFullHttpResponse;
  import io.netty.handler.codec.http.FullHttpMessage;
  import io.netty.handler.codec.http.FullHttpRequest;
  import io.netty.handler.codec.http.FullHttpResponse;
  import io.netty.handler.codec.http.HttpHeaders;
  import io.netty.handler.codec.http.HttpMethod;
  import io.netty.handler.codec.http.HttpResponseStatus;
  import io.netty.handler.codec.http.HttpVersion;
  
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  /**
   * Decodes {@link SpdySynStreamFrame}s, {@link SpdySynReplyFrame}s,
   * and {@link SpdyDataFrame}s into {@link FullHttpRequest}s and {@link FullHttpResponse}s.
   */
  public class SpdyHttpDecoder extends MessageToMessageDecoder<SpdyFrame> {
  
      private final boolean validateHeaders;
      private final int spdyVersion;
      private final int maxContentLength;
      private final Map<Integer, FullHttpMessage> messageMap;
  
      /**
       * 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(SpdyVersion version, int maxContentLength) {
          this(version, maxContentLength, new HashMap<Integer, FullHttpMessage>(), true);
      }
  
      /**
       * 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.
       * @param validateHeaders {@code true} if http headers should be validated
       */
      public SpdyHttpDecoder(SpdyVersion version, int maxContentLength, boolean validateHeaders) {
          this(version, maxContentLength, new HashMap<Integer, FullHttpMessage>(), validateHeaders);
      }
  
      /**
       * Creates a new instance with the specified parameters.
       *
       * @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.
       * @param messageMap the {@link Map} used to hold partially received messages.
       */
      protected SpdyHttpDecoder(SpdyVersion version, int maxContentLength, Map<Integer, FullHttpMessage> messageMap) {
          this(version, maxContentLength, messageMap, true);
      }
  
      /**
       * Creates a new instance with the specified parameters.
       *
       * @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.
       * @param messageMap the {@link Map} used to hold partially received messages.
       * @param validateHeaders {@code true} if http headers should be validated
       */
      protected SpdyHttpDecoder(SpdyVersion version, int maxContentLength, Map<Integer,
              FullHttpMessage> messageMap, boolean validateHeaders) {
          if (version == null) {
              throw new NullPointerException("version");
          }
         if (maxContentLength <= 0) {
             throw new IllegalArgumentException(
                     "maxContentLength must be a positive integer: " + maxContentLength);
         }
         spdyVersion = version.getVersion();
         this.maxContentLength = maxContentLength;
         this.messageMap = messageMap;
         this.validateHeaders = validateHeaders;
     }
 
     protected FullHttpMessage putMessage(int streamId, FullHttpMessage message) {
         return messageMap.put(streamId, message);
     }
 
     protected FullHttpMessage getMessage(int streamId) {
         return messageMap.get(streamId);
     }
 
     protected FullHttpMessage removeMessage(int streamId) {
         return messageMap.remove(streamId);
     }
 
     @Override
     protected void decode(ChannelHandlerContext ctx, SpdyFrame msg, List<Object> out)
             throws Exception {
         if (msg instanceof SpdySynStreamFrame) {
 
             // HTTP requests/responses are mapped one-to-one to SPDY streams.
             SpdySynStreamFrame spdySynStreamFrame = (SpdySynStreamFrame) msg;
             int streamId = spdySynStreamFrame.streamId();
 
             if (SpdyCodecUtil.isServerId(streamId)) {
                 // SYN_STREAM frames initiated by the server are pushed resources
                 int associatedToStreamId = spdySynStreamFrame.associatedStreamId();
 
                 // 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);
                     ctx.writeAndFlush(spdyRstStreamFrame);
                     return;
                 }
 
                 // If a client receives a SYN_STREAM with isLast set,
                 // reply with a RST_STREAM with error code PROTOCOL_ERROR
                 // (we only support pushed resources divided into two header blocks).
                 if (spdySynStreamFrame.isLast()) {
                     SpdyRstStreamFrame spdyRstStreamFrame =
                         new DefaultSpdyRstStreamFrame(streamId, SpdyStreamStatus.PROTOCOL_ERROR);
                     ctx.writeAndFlush(spdyRstStreamFrame);
                     return;
                 }
 
                 // If a client receives a response with a truncated header block,
                 // reply with a RST_STREAM with error code INTERNAL_ERROR.
                 if (spdySynStreamFrame.isTruncated()) {
                     SpdyRstStreamFrame spdyRstStreamFrame =
                     new DefaultSpdyRstStreamFrame(streamId, SpdyStreamStatus.INTERNAL_ERROR);
                     ctx.writeAndFlush(spdyRstStreamFrame);
                     return;
                 }
 
                 try {
                     FullHttpRequest httpRequestWithEntity = createHttpRequest(spdyVersion, spdySynStreamFrame);
 
                     // Set the Stream-ID, Associated-To-Stream-ID, and Priority as headers
                     SpdyHttpHeaders.setStreamId(httpRequestWithEntity, streamId);
                     SpdyHttpHeaders.setAssociatedToStreamId(httpRequestWithEntity, associatedToStreamId);
                     SpdyHttpHeaders.setPriority(httpRequestWithEntity, spdySynStreamFrame.priority());
 
                     out.add(httpRequestWithEntity);
 
                 } catch (Exception e) {
                     SpdyRstStreamFrame spdyRstStreamFrame =
                         new DefaultSpdyRstStreamFrame(streamId, SpdyStreamStatus.PROTOCOL_ERROR);
                     ctx.writeAndFlush(spdyRstStreamFrame);
                 }
             } else {
                 // SYN_STREAM frames initiated by the client are HTTP requests
 
                 // If a client sends a request with a truncated header block, the server must
                 // reply with a HTTP 431 REQUEST HEADER FIELDS TOO LARGE reply.
                 if (spdySynStreamFrame.isTruncated()) {
                     SpdySynReplyFrame spdySynReplyFrame = new DefaultSpdySynReplyFrame(streamId);
                     spdySynReplyFrame.setLast(true);
                     SpdyHeaders.setStatus(spdyVersion,
                             spdySynReplyFrame,
                             HttpResponseStatus.REQUEST_HEADER_FIELDS_TOO_LARGE);
                     SpdyHeaders.setVersion(spdyVersion, spdySynReplyFrame, HttpVersion.HTTP_1_0);
                     ctx.writeAndFlush(spdySynReplyFrame);
                     return;
                 }
 
                 try {
                     FullHttpRequest httpRequestWithEntity = createHttpRequest(spdyVersion, spdySynStreamFrame);
 
                     // Set the Stream-ID as a header
                     SpdyHttpHeaders.setStreamId(httpRequestWithEntity, streamId);
 
                     if (spdySynStreamFrame.isLast()) {
                         out.add(httpRequestWithEntity);
                     } else {
                         // Request body will follow in a series of Data Frames
                         putMessage(streamId, httpRequestWithEntity);
                     }
                 } catch (Exception e) {
                     // If a client sends a SYN_STREAM without all of the getMethod, 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);
                     ctx.writeAndFlush(spdySynReplyFrame);
                 }
             }
 
         } else if (msg instanceof SpdySynReplyFrame) {
 
             SpdySynReplyFrame spdySynReplyFrame = (SpdySynReplyFrame) msg;
             int streamId = spdySynReplyFrame.streamId();
 
             // If a client receives a SYN_REPLY with a truncated header block,
             // reply with a RST_STREAM frame with error code INTERNAL_ERROR.
             if (spdySynReplyFrame.isTruncated()) {
                 SpdyRstStreamFrame spdyRstStreamFrame =
                         new DefaultSpdyRstStreamFrame(streamId, SpdyStreamStatus.INTERNAL_ERROR);
                 ctx.writeAndFlush(spdyRstStreamFrame);
                 return;
             }
 
             try {
                 FullHttpResponse httpResponseWithEntity =
                         createHttpResponse(ctx, spdyVersion, spdySynReplyFrame, validateHeaders);
 
                 // Set the Stream-ID as a header
                 SpdyHttpHeaders.setStreamId(httpResponseWithEntity, streamId);
 
                 if (spdySynReplyFrame.isLast()) {
                     HttpHeaders.setContentLength(httpResponseWithEntity, 0);
                     out.add(httpResponseWithEntity);
                 } else {
                     // Response body will follow in a series of Data Frames
                     putMessage(streamId, httpResponseWithEntity);
                 }
             } catch (Exception e) {
                 // If a client receives a SYN_REPLY without valid getStatus and version headers
                 // the client must reply with a RST_STREAM frame indicating a PROTOCOL_ERROR
                 SpdyRstStreamFrame spdyRstStreamFrame =
                     new DefaultSpdyRstStreamFrame(streamId, SpdyStreamStatus.PROTOCOL_ERROR);
                 ctx.writeAndFlush(spdyRstStreamFrame);
             }
 
         } else if (msg instanceof SpdyHeadersFrame) {
 
             SpdyHeadersFrame spdyHeadersFrame = (SpdyHeadersFrame) msg;
             int streamId = spdyHeadersFrame.streamId();
             FullHttpMessage fullHttpMessage = getMessage(streamId);
 
             if (fullHttpMessage == null) {
                 // HEADERS frames may initiate a pushed response
                 if (SpdyCodecUtil.isServerId(streamId)) {
 
                     // If a client receives a HEADERS with a truncated header block,
                     // reply with a RST_STREAM frame with error code INTERNAL_ERROR.
                     if (spdyHeadersFrame.isTruncated()) {
                         SpdyRstStreamFrame spdyRstStreamFrame =
                             new DefaultSpdyRstStreamFrame(streamId, SpdyStreamStatus.INTERNAL_ERROR);
                         ctx.writeAndFlush(spdyRstStreamFrame);
                         return;
                     }
 
                     try {
                         fullHttpMessage = createHttpResponse(ctx, spdyVersion, spdyHeadersFrame, validateHeaders);
 
                         // Set the Stream-ID as a header
                         SpdyHttpHeaders.setStreamId(fullHttpMessage, streamId);
 
                         if (spdyHeadersFrame.isLast()) {
                             HttpHeaders.setContentLength(fullHttpMessage, 0);
                             out.add(fullHttpMessage);
                         } else {
                             // Response body will follow in a series of Data Frames
                             putMessage(streamId, fullHttpMessage);
                         }
                     } catch (Exception e) {
                         // If a client receives a SYN_REPLY without valid getStatus and version headers
                         // the client must reply with a RST_STREAM frame indicating a PROTOCOL_ERROR
                         SpdyRstStreamFrame spdyRstStreamFrame =
                             new DefaultSpdyRstStreamFrame(streamId, SpdyStreamStatus.PROTOCOL_ERROR);
                         ctx.writeAndFlush(spdyRstStreamFrame);
                     }
                 }
                 return;
             }
 
             // Ignore trailers in a truncated HEADERS frame.
             if (!spdyHeadersFrame.isTruncated()) {
                 for (Map.Entry<String, String> e: spdyHeadersFrame.headers()) {
                     fullHttpMessage.headers().add(e.getKey(), e.getValue());
                 }
             }
 
             if (spdyHeadersFrame.isLast()) {
                 HttpHeaders.setContentLength(fullHttpMessage, fullHttpMessage.content().readableBytes());
                 removeMessage(streamId);
                 out.add(fullHttpMessage);
             }
 
         } else if (msg instanceof SpdyDataFrame) {
 
             SpdyDataFrame spdyDataFrame = (SpdyDataFrame) msg;
             int streamId = spdyDataFrame.streamId();
             FullHttpMessage fullHttpMessage = getMessage(streamId);
 
             // If message is not in map discard Data Frame.
             if (fullHttpMessage == null) {
                 return;
             }
 
             ByteBuf content = fullHttpMessage.content();
             if (content.readableBytes() > maxContentLength - spdyDataFrame.content().readableBytes()) {
                 removeMessage(streamId);
                 throw new TooLongFrameException(
                         "HTTP content length exceeded " + maxContentLength + " bytes.");
             }
 
             ByteBuf spdyDataFrameData = spdyDataFrame.content();
             int spdyDataFrameDataLen = spdyDataFrameData.readableBytes();
             content.writeBytes(spdyDataFrameData, spdyDataFrameData.readerIndex(), spdyDataFrameDataLen);
 
             if (spdyDataFrame.isLast()) {
                 HttpHeaders.setContentLength(fullHttpMessage, content.readableBytes());
                 removeMessage(streamId);
                 out.add(fullHttpMessage);
             }
 
         } else if (msg instanceof SpdyRstStreamFrame) {
 
             SpdyRstStreamFrame spdyRstStreamFrame = (SpdyRstStreamFrame) msg;
             int streamId = spdyRstStreamFrame.streamId();
             removeMessage(streamId);
         }
     }
 
     private static FullHttpRequest createHttpRequest(int spdyVersion, SpdyHeadersFrame requestFrame)
             throws Exception {
         // Create the first line of the request from the name/value pairs
         SpdyHeaders headers     = requestFrame.headers();
         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);
 
         FullHttpRequest req = new DefaultFullHttpRequest(httpVersion, method, url);
 
         // Remove the scheme header
         SpdyHeaders.removeScheme(spdyVersion, requestFrame);
 
         // Replace the SPDY host header with the HTTP host header
         String host = headers.get(SpdyHeaders.HttpNames.HOST);
         headers.remove(SpdyHeaders.HttpNames.HOST);
         req.headers().set(HttpHeaders.Names.HOST, host);
 
         for (Map.Entry<String, String> e: requestFrame.headers()) {
             req.headers().add(e.getKey(), e.getValue());
         }
 
         // The Connection and Keep-Alive headers are no longer valid
         HttpHeaders.setKeepAlive(req, true);
 
         // Transfer-Encoding header is not valid
         req.headers().remove(HttpHeaders.Names.TRANSFER_ENCODING);
 
         return req;
     }
 
     private static FullHttpResponse createHttpResponse(ChannelHandlerContext ctx, int spdyVersion,
                                                        SpdyHeadersFrame responseFrame,
                                                        boolean validateHeaders) 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);
 
         FullHttpResponse res = new DefaultFullHttpResponse(version, status, ctx.alloc().buffer(), validateHeaders);
         for (Map.Entry<String, String> e: responseFrame.headers()) {
             res.headers().add(e.getKey(), e.getValue());
         }
 
         // The Connection and Keep-Alive headers are no longer valid
         HttpHeaders.setKeepAlive(res, true);
 
         // Transfer-Encoding header is not valid
         res.headers().remove(HttpHeaders.Names.TRANSFER_ENCODING);
         res.headers().remove(HttpHeaders.Names.TRAILER);
 
         return res;
     }
 }