/*
    * 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.stream;
  
  import static org.jboss.netty.buffer.ChannelBuffers.*;
  
  import java.nio.ByteBuffer;
  import java.nio.channels.ReadableByteChannel;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  
  /**
   * A {@link ChunkedInput} that fetches data from a {@link ReadableByteChannel}
   * chunk by chunk.  Please note that the {@link ReadableByteChannel} must
   * operate in blocking mode.  Non-blocking mode channels are not supported.
   */
  public class ChunkedNioStream implements ChunkedInput {
  
      private final ReadableByteChannel in;
  
      private final int chunkSize;
      private long offset;
  
      /**
       * Associated ByteBuffer
       */
      private final ByteBuffer byteBuffer;
  
      /**
       * Creates a new instance that fetches data from the specified channel.
       */
      public ChunkedNioStream(ReadableByteChannel in) {
          this(in, ChunkedStream.DEFAULT_CHUNK_SIZE);
      }
  
      /**
       * Creates a new instance that fetches data from the specified channel.
       *
       * @param chunkSize the number of bytes to fetch on each
       *                  {@link #nextChunk()} call
       */
      public ChunkedNioStream(ReadableByteChannel in, int chunkSize) {
          if (in == null) {
              throw new NullPointerException("in");
          }
          if (chunkSize <= 0) {
              throw new IllegalArgumentException("chunkSize: " + chunkSize +
                      " (expected: a positive integer)");
          }
          this.in = in;
          offset = 0;
          this.chunkSize = chunkSize;
          byteBuffer = ByteBuffer.allocate(chunkSize);
      }
  
      /**
       * Returns the number of transferred bytes.
       */
      public long getTransferredBytes() {
          return offset;
      }
  
      public boolean hasNextChunk() throws Exception {
          if (byteBuffer.position() > 0) {
              // A previous read was not over, so there is a next chunk in the buffer at least
              return true;
          }
          if (in.isOpen()) {
              // Try to read a new part, and keep this part (no rewind)
              int b = in.read(byteBuffer);
              if (b < 0) {
                  return false;
              } else {
                  offset += b;
                  return true;
              }
          }
          return false;
      }
  
      public boolean isEndOfInput() throws Exception {
          return !hasNextChunk();
      }
  
      public void close() throws Exception {
          in.close();
     }
 
     public Object nextChunk() throws Exception {
         if (!hasNextChunk()) {
             return null;
         }
         // buffer cannot be not be empty from there
         int readBytes = byteBuffer.position();
         for (;;) {
             int localReadBytes = in.read(byteBuffer);
             if (localReadBytes < 0) {
                 break;
             }
             readBytes += localReadBytes;
             offset += localReadBytes;
 
             if (readBytes == chunkSize) {
                 break;
             }
         }
         byteBuffer.flip();
         // copy since buffer is keeped for next usage
         ChannelBuffer buffer = copiedBuffer(byteBuffer);
         byteBuffer.clear();
         return buffer;
     }
 }