/*
    * Copyright 2009 Red Hat, Inc.
    *
    * Red Hat 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.http;
  
  import static org.jboss.netty.buffer.ChannelBuffers.*;
  import static org.jboss.netty.handler.codec.http.HttpCodecUtil.*;
  
  import java.io.UnsupportedEncodingException;
  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.handler.codec.oneone.OneToOneEncoder;
  import org.jboss.netty.util.CharsetUtil;
  
  /**
   * Encodes an {@link HttpMessage} or an {@link HttpChunk} into
   * a {@link ChannelBuffer}.
   *
   * <h3>Extensibility</h3>
   *
   * Please note that this encoder is designed to be extended to implement
   * a protocol derived from HTTP, such as
   * <a href="http://en.wikipedia.org/wiki/Real_Time_Streaming_Protocol">RTSP</a> and
   * <a href="http://en.wikipedia.org/wiki/Internet_Content_Adaptation_Protocol">ICAP</a>.
   * To implement the encoder of such a derived protocol, extend this class and
   * implement all abstract methods properly.
   *
   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
   * @author Andy Taylor (andy.taylor@jboss.org)
   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
   * @version $Rev: 2121 $, $Date: 2010-02-02 09:38:07 +0900 (Tue, 02 Feb 2010) $
   *
   * @apiviz.landmark
   */
  public abstract class HttpMessageEncoder extends OneToOneEncoder {
  
      private static final ChannelBuffer LAST_CHUNK =
          copiedBuffer("0\r\n\r\n", CharsetUtil.US_ASCII);
  
      private volatile boolean chunked;
  
      /**
       * Creates a new instance.
       */
      protected HttpMessageEncoder() {
          super();
      }
  
      @Override
      protected Object encode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
          if (msg instanceof HttpMessage) {
              HttpMessage m = (HttpMessage) msg;
              boolean chunked = this.chunked = HttpCodecUtil.isTransferEncodingChunked(m);
              ChannelBuffer header = ChannelBuffers.dynamicBuffer(
                      channel.getConfig().getBufferFactory());
              encodeInitialLine(header, m);
              encodeHeaders(header, m);
              header.writeByte(CR);
              header.writeByte(LF);
  
              ChannelBuffer content = m.getContent();
              if (!content.readable()) {
                  return header; // no content
              } else if (chunked) {
                  throw new IllegalArgumentException(
                          "HttpMessage.content must be empty " +
                          "if Transfer-Encoding is chunked.");
              } else {
                  return wrappedBuffer(header, content);
              }
          }
  
          if (msg instanceof HttpChunk) {
              HttpChunk chunk = (HttpChunk) msg;
              if (chunked) {
                  if (chunk.isLast()) {
                      chunked = false;
                      if (chunk instanceof HttpChunkTrailer) {
                          ChannelBuffer trailer = ChannelBuffers.dynamicBuffer(
                                  channel.getConfig().getBufferFactory());
                          trailer.writeByte((byte) '0');
                          trailer.writeByte(CR);
                          trailer.writeByte(LF);
                         encodeTrailingHeaders(trailer, (HttpChunkTrailer) chunk);
                         trailer.writeByte(CR);
                         trailer.writeByte(LF);
                         return trailer;
                     } else {
                         return LAST_CHUNK.duplicate();
                     }
                 } else {
                     ChannelBuffer content = chunk.getContent();
                     int contentLength = content.readableBytes();
 
                     return wrappedBuffer(
                             copiedBuffer(
                                     Integer.toHexString(contentLength),
                                     CharsetUtil.US_ASCII),
                             wrappedBuffer(CRLF),
                             content.slice(content.readerIndex(), contentLength),
                             wrappedBuffer(CRLF));
                 }
             } else {
                 if (chunk.isLast()) {
                     return null;
                 } else {
                     return chunk.getContent();
                 }
             }
 
         }
 
         // Unknown message type.
         return msg;
     }
 
     private void encodeHeaders(ChannelBuffer buf, HttpMessage message) {
         try {
             for (Map.Entry<String, String> h: message.getHeaders()) {
                 encodeHeader(buf, h.getKey(), h.getValue());
             }
         } catch (UnsupportedEncodingException e) {
             throw (Error) new Error().initCause(e);
         }
     }
 
     private void encodeTrailingHeaders(ChannelBuffer buf, HttpChunkTrailer trailer) {
         try {
             for (Map.Entry<String, String> h: trailer.getHeaders()) {
                 encodeHeader(buf, h.getKey(), h.getValue());
             }
         } catch (UnsupportedEncodingException e) {
             throw (Error) new Error().initCause(e);
         }
     }
 
     private void encodeHeader(ChannelBuffer buf, String header, String value)
             throws UnsupportedEncodingException {
         buf.writeBytes(header.getBytes("ASCII"));
         buf.writeByte(COLON);
         buf.writeByte(SP);
         buf.writeBytes(value.getBytes("ASCII"));
         buf.writeByte(CR);
         buf.writeByte(LF);
     }
 
     protected abstract void encodeInitialLine(ChannelBuffer buf, HttpMessage message) throws Exception;
 }