/*
    * 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
    *
   *   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 org.apache.commons.compress.utils;
  
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.nio.channels.ClosedChannelException;
  import java.nio.channels.WritableByteChannel;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.apache.commons.io.IOUtils;
  
  /**
   * This class supports writing to an OutputStream or WritableByteChannel in fixed length blocks.
   * <p>
   * It can be be used to support output to devices such as tape drives that require output in this format. If the final block does not have enough content to
   * fill an entire block, the output will be padded to a full block size.
   * </p>
   *
   * <p>
   * This class can be used to support TAR,PAX, and CPIO blocked output to character special devices. It is not recommended that this class be used unless writing
   * to such devices, as the padding serves no useful purpose in such cases.
   * </p>
   *
   * <p>
   * This class should normally wrap a FileOutputStream or associated WritableByteChannel directly. If there is an intervening filter that modified the output,
   * such as a CompressorOutputStream, or performs its own buffering, such as BufferedOutputStream, output to the device may no longer be of the specified size.
   * </p>
   *
   * <p>
   * Any content written to this stream should be self-delimiting and should tolerate any padding added to fill the last block.
   * </p>
   *
   * @since 1.15
   */
  public class FixedLengthBlockOutputStream extends OutputStream implements WritableByteChannel {
  
      /**
       * Helper class to provide channel wrapper for arbitrary output stream that doesn't alter the size of writes. We can't use Channels.newChannel, because for
       * non FileOutputStreams, it breaks up writes into 8KB max chunks. Since the purpose of this class is to always write complete blocks, we need to write a
       * simple class to take care of it.
       */
      private static final class BufferAtATimeOutputChannel implements WritableByteChannel {
  
          private final OutputStream out;
          private final AtomicBoolean closed = new AtomicBoolean();
  
          private BufferAtATimeOutputChannel(final OutputStream out) {
              this.out = out;
          }
  
          @Override
          public void close() throws IOException {
              if (closed.compareAndSet(false, true)) {
                  out.close();
              }
          }
  
          @Override
          public boolean isOpen() {
              return !closed.get();
          }
  
          @Override
          public int write(final ByteBuffer buffer) throws IOException {
              if (!isOpen()) {
                  throw new ClosedChannelException();
              }
              if (!buffer.hasArray()) {
                  throw new IOException("Direct buffer somehow written to BufferAtATimeOutputChannel");
              }
  
              try {
                  final int pos = buffer.position();
                  final int len = buffer.limit() - pos;
                  out.write(buffer.array(), buffer.arrayOffset() + pos, len);
                  buffer.position(buffer.limit());
                  return len;
              } catch (final IOException e) {
                  IOUtils.closeQuietly(this);
                 throw e;
             }
         }
 
     }
 
     private final WritableByteChannel out;
     private final int blockSize;
     private final ByteBuffer buffer;
 
     private final AtomicBoolean closed = new AtomicBoolean();
 
     /**
      * Constructs a fixed length block output stream with given destination stream and block size.
      *
      * @param os        The stream to wrap.
      * @param blockSize The block size to use.
      */
     public FixedLengthBlockOutputStream(final OutputStream os, final int blockSize) {
         if (os instanceof FileOutputStream) {
             final FileOutputStream fileOutputStream = (FileOutputStream) os;
             out = fileOutputStream.getChannel();
             buffer = ByteBuffer.allocateDirect(blockSize);
         } else {
             out = new BufferAtATimeOutputChannel(os);
             buffer = ByteBuffer.allocate(blockSize);
         }
         this.blockSize = blockSize;
     }
 
     /**
      * Constructs a fixed length block output stream with given destination writable byte channel and block size.
      *
      * @param out       The writable byte channel to wrap.
      * @param blockSize The block size to use.
      */
     public FixedLengthBlockOutputStream(final WritableByteChannel out, final int blockSize) {
         this.out = out;
         this.blockSize = blockSize;
         this.buffer = ByteBuffer.allocateDirect(blockSize);
     }
 
     @Override
     public void close() throws IOException {
         if (closed.compareAndSet(false, true)) {
             try {
                 flushBlock();
             } finally {
                 out.close();
             }
         }
     }
 
     /**
      * Potentially pads and then writes the current block to the underlying stream.
      *
      * @throws IOException if writing fails
      */
     public void flushBlock() throws IOException {
         if (buffer.position() != 0) {
             padBlock();
             writeBlock();
         }
     }
 
     @Override
     public boolean isOpen() {
         if (!out.isOpen()) {
             closed.set(true);
         }
         return !closed.get();
     }
 
     private void maybeFlush() throws IOException {
         if (!buffer.hasRemaining()) {
             writeBlock();
         }
     }
 
     private void padBlock() {
         buffer.order(ByteOrder.nativeOrder());
         int bytesToWrite = buffer.remaining();
         if (bytesToWrite > 8) {
             final int align = buffer.position() & 7;
             if (align != 0) {
                 final int limit = 8 - align;
                 for (int i = 0; i < limit; i++) {
                     buffer.put((byte) 0);
                 }
                 bytesToWrite -= limit;
             }
 
             while (bytesToWrite >= 8) {
                 buffer.putLong(0L);
                 bytesToWrite -= 8;
             }
         }
         while (buffer.hasRemaining()) {
             buffer.put((byte) 0);
         }
     }
 
     @Override
     public void write(final byte[] b, final int offset, final int length) throws IOException {
         if (!isOpen()) {
             throw new ClosedChannelException();
         }
         int off = offset;
         int len = length;
         while (len > 0) {
             final int n = Math.min(len, buffer.remaining());
             buffer.put(b, off, n);
             maybeFlush();
             len -= n;
             off += n;
         }
     }
 
     @Override
     public int write(final ByteBuffer src) throws IOException {
         if (!isOpen()) {
             throw new ClosedChannelException();
         }
         final int srcRemaining = src.remaining();
         if (srcRemaining >= buffer.remaining()) {
             int srcLeft = srcRemaining;
             final int savedLimit = src.limit();
             // If we're not at the start of buffer, we have some bytes already buffered
             // fill up the reset of buffer and write the block.
             if (buffer.position() != 0) {
                 final int n = buffer.remaining();
                 src.limit(src.position() + n);
                 buffer.put(src);
                 writeBlock();
                 srcLeft -= n;
             }
             // whilst we have enough bytes in src for complete blocks,
             // write them directly from src without copying them to buffer
             while (srcLeft >= blockSize) {
                 src.limit(src.position() + blockSize);
                 out.write(src);
                 srcLeft -= blockSize;
             }
             // copy any remaining bytes into buffer
             src.limit(savedLimit);
         }
         // if we don't have enough bytes in src to fill up a block we must buffer
         buffer.put(src);
         return srcRemaining;
     }
 
     @Override
     public void write(final int b) throws IOException {
         if (!isOpen()) {
             throw new ClosedChannelException();
         }
         buffer.put((byte) b);
         maybeFlush();
     }
 
     private void writeBlock() throws IOException {
         buffer.flip();
         final int i = out.write(buffer);
         final boolean hasRemaining = buffer.hasRemaining();
         if (i != blockSize || hasRemaining) {
             throw new IOException(String.format("Failed to write %,d bytes atomically. Only wrote  %,d", blockSize, i));
         }
         buffer.clear();
     }
 
 }