/*
    * 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.
   */
  package org.apache.commons.compress.compressors.snappy;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  
  import org.apache.commons.codec.digest.PureJavaCrc32C;
  import org.apache.commons.compress.compressors.CompressorOutputStream;
  import org.apache.commons.compress.compressors.lz77support.Parameters;
  import org.apache.commons.compress.utils.ByteUtils;
  
  /**
   * CompressorOutputStream for the framing Snappy format.
   *
   * <p>
   * Based on the "spec" in the version "Last revised: 2013-10-25"
   * </p>
   *
   * @see <a href="https://github.com/google/snappy/blob/master/framing_format.txt">Snappy framing format description</a>
   * @since 1.14
   * @NotThreadSafe
   */
  public class FramedSnappyCompressorOutputStream extends CompressorOutputStream<OutputStream> {
      // see spec:
      // > However, we place an additional restriction that the uncompressed data
      // > in a chunk must be no longer than 65,536 bytes. This allows consumers to
      // > easily use small fixed-size buffers.
      private static final int MAX_COMPRESSED_BUFFER_SIZE = 1 << 16;
  
      static long mask(long x) {
          // ugly, maybe we should just have used ints and deal with the
          // overflow
          x = x >> 15 | x << 17;
          x += FramedSnappyCompressorInputStream.MASK_OFFSET;
          x &= 0xffffFFFFL;
          return x;
      }
  
      private final Parameters params;
      private final PureJavaCrc32C checksum = new PureJavaCrc32C();
      // used in one-arg write method
      private final byte[] oneByte = new byte[1];
      private final byte[] buffer = new byte[MAX_COMPRESSED_BUFFER_SIZE];
  
      private int currentIndex;
  
      private final ByteUtils.ByteConsumer consumer;
  
      /**
       * Constructs a new output stream that compresses snappy-framed-compressed data to the specified output stream.
       *
       * @param out the OutputStream to which to write the compressed data
       * @throws IOException if writing the signature fails
       */
      public FramedSnappyCompressorOutputStream(final OutputStream out) throws IOException {
          this(out, SnappyCompressorOutputStream.createParameterBuilder(SnappyCompressorInputStream.DEFAULT_BLOCK_SIZE).build());
      }
  
      /**
       * Constructs a new output stream that compresses snappy-framed-compressed data to the specified output stream.
       *
       * @param out    the OutputStream to which to write the compressed data
       * @param params parameters used to fine-tune compression, in particular to balance compression ratio vs compression speed.
       * @throws IOException if writing the signature fails
       */
      public FramedSnappyCompressorOutputStream(final OutputStream out, final Parameters params) throws IOException {
          super(out);
          this.params = params;
          consumer = new ByteUtils.OutputStreamByteConsumer(out);
          out.write(FramedSnappyCompressorInputStream.SZ_SIGNATURE);
      }
  
      @Override
      public void close() throws IOException {
          try {
              finish();
          } finally {
              out.close();
          }
      }
  
     /**
      * Compresses all remaining data and writes it to the stream, doesn't close the underlying stream.
      *
      * @throws IOException if an error occurs
      */
     public void finish() throws IOException {
         flushBuffer();
     }
 
     private void flushBuffer() throws IOException {
         if (currentIndex == 0) {
             return;
         }
         out.write(FramedSnappyCompressorInputStream.COMPRESSED_CHUNK_TYPE);
         final ByteArrayOutputStream baos = new ByteArrayOutputStream();
         try (OutputStream o = new SnappyCompressorOutputStream(baos, currentIndex, params)) {
             o.write(buffer, 0, currentIndex);
         }
         final byte[] b = baos.toByteArray();
         writeLittleEndian(3, b.length + 4L /* CRC */);
         writeCrc();
         out.write(b);
         currentIndex = 0;
     }
 
     @Override
     public void write(final byte[] data, int off, int len) throws IOException {
         int blockDataRemaining = buffer.length - currentIndex;
         while (len > 0) {
             final int copyLen = Math.min(len, blockDataRemaining);
             System.arraycopy(data, off, buffer, currentIndex, copyLen);
             off += copyLen;
             blockDataRemaining -= copyLen;
             len -= copyLen;
             currentIndex += copyLen;
             if (blockDataRemaining == 0) {
                 flushBuffer();
                 blockDataRemaining = buffer.length;
             }
         }
     }
 
     @Override
     public void write(final int b) throws IOException {
         oneByte[0] = (byte) (b & 0xff);
         write(oneByte);
     }
 
     private void writeCrc() throws IOException {
         checksum.update(buffer, 0, currentIndex);
         writeLittleEndian(4, mask(checksum.getValue()));
         checksum.reset();
     }
 
     private void writeLittleEndian(final int numBytes, final long num) throws IOException {
         ByteUtils.toLittleEndian(consumer, num, numBytes);
     }
 }