/*
    * Copyright 2014 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.handler.stream.ChunkedInput;
  
  /**
   * A {@link ChunkedInput} that fetches data chunk by chunk for use with HTTP chunked transfers.
   * <p>
   * Each chunk from the input data will be wrapped within a {@link HttpContent}. At the end of the input data,
   * {@link LastHttpContent} will be written.
   * <p>
   * Ensure that your HTTP response header contains {@code Transfer-Encoding: chunked}.
   * <p>
   * <pre>
   * public void messageReceived(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
   *     HttpResponse response = new DefaultHttpResponse(HTTP_1_1, OK);
   *     response.headers().set(TRANSFER_ENCODING, CHUNKED);
   *     ctx.write(response);
   *
   *     HttpContentChunkedInput httpChunkWriter = new HttpChunkedInput(
   *         new ChunkedFile(&quot;/tmp/myfile.txt&quot;));
   *     ChannelFuture sendFileFuture = ctx.write(httpChunkWriter);
   * }
   * </pre>
   */
  public class HttpChunkedInput implements ChunkedInput<HttpContent> {
  
      private final ChunkedInput<ByteBuf> input;
      private final LastHttpContent lastHttpContent;
      private boolean sentLastChunk;
  
      /**
       * Creates a new instance using the specified input.
       * @param input {@link ChunkedInput} containing data to write
       */
      public HttpChunkedInput(ChunkedInput<ByteBuf> input) {
          this.input = input;
          lastHttpContent = LastHttpContent.EMPTY_LAST_CONTENT;
      }
  
      /**
       * Creates a new instance using the specified input. {@code lastHttpContent} will be written as the terminating
       * chunk.
       * @param input {@link ChunkedInput} containing data to write
       * @param lastHttpContent {@link LastHttpContent} that will be written as the terminating chunk. Use this for
       *            training headers.
       */
      public HttpChunkedInput(ChunkedInput<ByteBuf> input, LastHttpContent lastHttpContent) {
          this.input = input;
          this.lastHttpContent = lastHttpContent;
      }
  
      @Override
      public boolean isEndOfInput() throws Exception {
          if (input.isEndOfInput()) {
              // Only end of input after last HTTP chunk has been sent
              return sentLastChunk;
          } else {
              return false;
          }
      }
  
      @Override
      public void close() throws Exception {
          input.close();
      }
  
      @Override
      public HttpContent readChunk(ChannelHandlerContext ctx) throws Exception {
          if (input.isEndOfInput()) {
              if (sentLastChunk) {
                  return null;
              } else {
                  // Send last chunk for this input
                  sentLastChunk = true;
                  return lastHttpContent;
              }
          } else {
              ByteBuf buf = input.readChunk(ctx);
              if (buf == null) {
                  return null;
              }
              return new DefaultHttpContent(buf);
         }
     }
 }