/*
    * ====================================================================
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.hc.core5.http.nio.entity;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.SeekableByteChannel;
  import java.nio.file.Files;
  import java.nio.file.OpenOption;
  import java.nio.file.Path;
  import java.util.Collections;
  import java.util.Set;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.hc.core5.http.ContentType;
  import org.apache.hc.core5.http.nio.AsyncEntityProducer;
  import org.apache.hc.core5.http.nio.DataStreamChannel;
  import org.apache.hc.core5.io.Closer;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.Asserts;
  
  /**
   * {@link AsyncEntityProducer} implementation that generates a data stream from the content at a {@link Path}.
   *
   * @since 5.2
   */
  public final class PathEntityProducer implements AsyncEntityProducer {
  
      private static final int BUFFER_SIZE = 8192;
      private final Path file;
      private final OpenOption[] openOptions;
      private final ByteBuffer byteBuffer;
      private final long length;
      private final ContentType contentType;
      private final boolean chunked;
      private final AtomicReference<Exception> exception;
      private final AtomicReference<SeekableByteChannel> channelRef;
      private boolean eof;
  
      public PathEntityProducer(final Path file, final ContentType contentType, final boolean chunked,
              final OpenOption... openOptions) throws IOException {
          this(file, BUFFER_SIZE, contentType, chunked, openOptions);
      }
  
      public PathEntityProducer(final Path file, final ContentType contentType, final OpenOption... openOptions)
              throws IOException {
          this(file, contentType, false, openOptions);
      }
  
      public PathEntityProducer(final Path file, final int bufferSize, final ContentType contentType,
              final boolean chunked, final OpenOption... openOptions) throws IOException {
          this.file = Args.notNull(file, "file");
          this.openOptions = openOptions;
          this.length = Files.size(file);
          this.byteBuffer = ByteBuffer.allocate(bufferSize);
          this.contentType = contentType;
          this.chunked = chunked;
          this.channelRef = new AtomicReference<>();
          this.exception = new AtomicReference<>();
      }
  
      public PathEntityProducer(final Path file, final OpenOption... openOptions) throws IOException {
          this(file, ContentType.APPLICATION_OCTET_STREAM, openOptions);
      }
  
      @Override
      public int available() {
          return Integer.MAX_VALUE;
      }
  
      @Override
      public void failed(final Exception cause) {
          if (exception.compareAndSet(null, cause)) {
              releaseResources();
          }
     }
 
     @Override
     public String getContentEncoding() {
         return null;
     }
 
     @Override
     public long getContentLength() {
         return length;
     }
 
     @Override
     public String getContentType() {
         return contentType != null ? contentType.toString() : null;
     }
 
     public Exception getException() {
         return exception.get();
     }
 
     @Override
     public Set<String> getTrailerNames() {
         return Collections.emptySet();
     }
 
     @Override
     public boolean isChunked() {
         return chunked;
     }
 
     @Override
     public boolean isRepeatable() {
         return true;
     }
 
     @Override
     public void produce(final DataStreamChannel dataStreamChannel) throws IOException {
         SeekableByteChannel seekableByteChannel = channelRef.get();
         if (seekableByteChannel == null) {
             seekableByteChannel = Files.newByteChannel(file, openOptions);
             Asserts.check(channelRef.getAndSet(seekableByteChannel) == null, "Illegal producer state");
         }
         if (!eof) {
             final int bytesRead = seekableByteChannel.read(byteBuffer);
             if (bytesRead < 0) {
                 eof = true;
             }
         }
         if (byteBuffer.position() > 0) {
             byteBuffer.flip();
             dataStreamChannel.write(byteBuffer);
             byteBuffer.compact();
         }
         if (eof && byteBuffer.position() == 0) {
             dataStreamChannel.endStream();
             releaseResources();
         }
     }
 
     @Override
     public void releaseResources() {
         eof = false;
         Closer.closeQuietly(channelRef.getAndSet(null));
     }
 
 }