/*
    * 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:
    *
    *   https://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.netty5.handler.stream;
  
  import io.netty5.buffer.api.Buffer;
  import io.netty5.buffer.api.BufferAllocator;
  
  import java.nio.ByteBuffer;
  import java.nio.channels.ReadableByteChannel;
  
  import static io.netty5.util.internal.ObjectUtil.checkPositive;
  import static java.util.Objects.requireNonNull;
  
  /**
   * 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<Buffer> {
  
      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 #readChunk(BufferAllocator)} call
       */
      public ChunkedNioStream(ReadableByteChannel in, int chunkSize) {
          this.in = requireNonNull(in, "in");
          this.chunkSize = checkPositive(chunkSize, "chunkSize");
          byteBuffer = ByteBuffer.allocate(chunkSize);
      }
  
      /**
       * Returns the number of transferred bytes.
       */
      public long transferredBytes() {
          return offset;
      }
  
      @Override
      public boolean isEndOfInput() throws Exception {
          if (byteBuffer.position() > 0) {
              // A previous read was not over, so there is a next chunk in the buffer at least
              return false;
          }
          if (in.isOpen()) {
              // Try to read a new part, and keep this part (no rewind)
              int b = in.read(byteBuffer);
              if (b < 0) {
                  return true;
              } else {
                  offset += b;
                  return false;
              }
          }
          return true;
      }
  
      @Override
      public void close() throws Exception {
          in.close();
      }
  
      @Override
      public Buffer readChunk(BufferAllocator allocator) throws Exception {
          if (isEndOfInput()) {
              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();
         boolean release = true;
         Buffer buffer = allocator.allocate(byteBuffer.remaining());
         try {
             buffer.writeBytes(byteBuffer);
             byteBuffer.clear();
             release = false;
             return buffer;
         } finally {
             if (release) {
                 buffer.close();
             }
         }
     }
 
     @Override
     public long length() {
         return -1;
     }
 
     @Override
     public long progress() {
         return offset;
     }
 }