/*
    * 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.compressors.lz4;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  
  import org.apache.commons.compress.compressors.CompressorOutputStream;
  import org.apache.commons.compress.utils.ByteUtils;
  
  /**
   * CompressorOutputStream for the LZ4 frame format.
   *
   * <p>
   * Based on the "spec" in the version "1.5.1 (31/03/2015)"
   * </p>
   *
   * @see <a href="https://lz4.github.io/lz4/lz4_Frame_format.html">LZ4 Frame Format Description</a>
   * @since 1.14
   * @NotThreadSafe
   */
  public class FramedLZ4CompressorOutputStream extends CompressorOutputStream<OutputStream> {
  
      /**
       * Enumerates the block sizes supported by the format.
       */
      public enum BlockSize {
  
          /** Block size of 64K. */
          K64(64 * 1024, 4),
  
          /** Block size of 256K. */
          K256(256 * 1024, 5),
  
          /** Block size of 1M. */
          M1(1024 * 1024, 6),
  
          /** Block size of 4M. */
          M4(4096 * 1024, 7);
  
          private final int size;
          private final int index;
  
          BlockSize(final int size, final int index) {
              this.size = size;
              this.index = index;
          }
  
          int getIndex() {
              return index;
          }
  
          int getSize() {
              return size;
          }
      }
  
      /**
       * Parameters of the LZ4 frame format.
       */
      public static class Parameters {
  
          /**
           * The default parameters of 4M block size, enabled content checksum, disabled block checksums and independent blocks.
           *
           * <p>
           * This matches the defaults of the lz4 command line utility.
           * </p>
           */
          public static final Parameters DEFAULT = new Parameters(BlockSize.M4, true, false, false);
          private final BlockSize blockSize;
          private final boolean withContentChecksum;
          private final boolean withBlockChecksum;
          private final boolean withBlockDependency;
  
          private final org.apache.commons.compress.compressors.lz77support.Parameters lz77params;
  
          /**
           * Sets up custom a custom block size for the LZ4 stream but otherwise uses the defaults of enabled content checksum, disabled block checksums and
           * independent blocks.
           *
           * @param blockSize the size of a single block.
          */
         public Parameters(final BlockSize blockSize) {
             this(blockSize, true, false, false);
         }
 
         /**
          * Sets up custom parameters for the LZ4 stream.
          *
          * @param blockSize           the size of a single block.
          * @param withContentChecksum whether to write a content checksum
          * @param withBlockChecksum   whether to write a block checksum. Note that block checksums are not supported by the lz4 command line utility
          * @param withBlockDependency whether a block may depend on the content of a previous block. Enabling this may improve compression ratio but makes it
          *                            impossible to decompress the output in parallel.
          */
         public Parameters(final BlockSize blockSize, final boolean withContentChecksum, final boolean withBlockChecksum, final boolean withBlockDependency) {
             this(blockSize, withContentChecksum, withBlockChecksum, withBlockDependency, BlockLZ4CompressorOutputStream.createParameterBuilder().build());
         }
 
         /**
          * Sets up custom parameters for the LZ4 stream.
          *
          * @param blockSize           the size of a single block.
          * @param withContentChecksum whether to write a content checksum
          * @param withBlockChecksum   whether to write a block checksum. Note that block checksums are not supported by the lz4 command line utility
          * @param withBlockDependency whether a block may depend on the content of a previous block. Enabling this may improve compression ratio but makes it
          *                            impossible to decompress the output in parallel.
          * @param lz77params          parameters used to fine-tune compression, in particular to balance compression ratio vs compression speed.
          */
         public Parameters(final BlockSize blockSize, final boolean withContentChecksum, final boolean withBlockChecksum, final boolean withBlockDependency,
                 final org.apache.commons.compress.compressors.lz77support.Parameters lz77params) {
             this.blockSize = blockSize;
             this.withContentChecksum = withContentChecksum;
             this.withBlockChecksum = withBlockChecksum;
             this.withBlockDependency = withBlockDependency;
             this.lz77params = lz77params;
         }
 
         /**
          * Sets up custom a custom block size for the LZ4 stream but otherwise uses the defaults of enabled content checksum, disabled block checksums and
          * independent blocks.
          *
          * @param blockSize  the size of a single block.
          * @param lz77params parameters used to fine-tune compression, in particular to balance compression ratio vs compression speed.
          */
         public Parameters(final BlockSize blockSize, final org.apache.commons.compress.compressors.lz77support.Parameters lz77params) {
             this(blockSize, true, false, false, lz77params);
         }
 
         @Override
         public String toString() {
             return "LZ4 Parameters with BlockSize " + blockSize + ", withContentChecksum " + withContentChecksum + ", withBlockChecksum " + withBlockChecksum
                     + ", withBlockDependency " + withBlockDependency;
         }
     }
 
     private static final byte[] END_MARK = new byte[4];
     // used in one-arg write method
     private final byte[] oneByte = new byte[1];
     private final byte[] blockData;
     private final Parameters params;
 
     // used for frame header checksum and content checksum, if requested
     private final org.apache.commons.codec.digest.XXHash32 contentHash = new org.apache.commons.codec.digest.XXHash32();
     // used for block checksum, if requested
     private final org.apache.commons.codec.digest.XXHash32 blockHash;
 
     // only created if the config requires block dependency
     private final byte[] blockDependencyBuffer;
 
     private int collectedBlockDependencyBytes;
     private int currentIndex;
 
     /**
      * Constructs a new output stream that compresses data using the LZ4 frame format using the default block size of 4MB.
      *
      * @param out the OutputStream to which to write the compressed data
      * @throws IOException if writing the signature fails
      */
     public FramedLZ4CompressorOutputStream(final OutputStream out) throws IOException {
         this(out, Parameters.DEFAULT);
     }
 
     /**
      * Constructs a new output stream that compresses data using the LZ4 frame format using the given block size.
      *
      * @param out    the OutputStream to which to write the compressed data
      * @param params the parameters to use
      * @throws IOException if writing the signature fails
      */
     public FramedLZ4CompressorOutputStream(final OutputStream out, final Parameters params) throws IOException {
         super(out);
         this.params = params;
         blockData = new byte[params.blockSize.getSize()];
         blockHash = params.withBlockChecksum ? new org.apache.commons.codec.digest.XXHash32() : null;
         out.write(FramedLZ4CompressorInputStream.LZ4_SIGNATURE);
         writeFrameDescriptor();
         blockDependencyBuffer = params.withBlockDependency ? new byte[BlockLZ4CompressorInputStream.WINDOW_SIZE] : null;
     }
 
     private void appendToBlockDependencyBuffer(final byte[] b, final int off, int len) {
         len = Math.min(len, blockDependencyBuffer.length);
         if (len > 0) {
             final int keep = blockDependencyBuffer.length - len;
             if (keep > 0) {
                 // move last keep bytes towards the start of the buffer
                 System.arraycopy(blockDependencyBuffer, len, blockDependencyBuffer, 0, keep);
             }
             // append new data
             System.arraycopy(b, off, blockDependencyBuffer, keep, len);
             collectedBlockDependencyBytes = Math.min(collectedBlockDependencyBytes + len, blockDependencyBuffer.length);
         }
     }
 
     @Override
     public void close() throws IOException {
         try {
             finish();
         } finally {
             super.close();
         }
     }
 
     /**
      * Compresses all blockDataRemaining data and writes it to the stream, doesn't close the underlying stream.
      *
      * @throws IOException if an error occurs
      */
     @Override
     public void finish() throws IOException {
         if (!isFinished()) {
             flushBlock();
             writeTrailer();
             super.finish();
         }
     }
 
     private void flushBlock() throws IOException {
         if (currentIndex == 0) {
             return;
         }
         final boolean withBlockDependency = params.withBlockDependency;
         final ByteArrayOutputStream baos = new ByteArrayOutputStream();
         try (BlockLZ4CompressorOutputStream o = new BlockLZ4CompressorOutputStream(baos, params.lz77params)) {
             if (withBlockDependency) {
                 o.prefill(blockDependencyBuffer, blockDependencyBuffer.length - collectedBlockDependencyBytes, collectedBlockDependencyBytes);
             }
             o.write(blockData, 0, currentIndex);
         }
         if (withBlockDependency) {
             appendToBlockDependencyBuffer(blockData, 0, currentIndex);
         }
         final byte[] b = baos.toByteArray();
         if (b.length > currentIndex) { // compression increased size, maybe beyond blocksize
             ByteUtils.toLittleEndian(out, currentIndex | FramedLZ4CompressorInputStream.UNCOMPRESSED_FLAG_MASK, 4);
             out.write(blockData, 0, currentIndex);
             if (params.withBlockChecksum) {
                 blockHash.update(blockData, 0, currentIndex);
             }
         } else {
             ByteUtils.toLittleEndian(out, b.length, 4);
             out.write(b);
             if (params.withBlockChecksum) {
                 blockHash.update(b, 0, b.length);
             }
         }
         if (params.withBlockChecksum) {
             ByteUtils.toLittleEndian(out, blockHash.getValue(), 4);
             blockHash.reset();
         }
         currentIndex = 0;
     }
 
     @Override
     public void write(final byte[] data, int off, int len) throws IOException {
         if (params.withContentChecksum) {
             contentHash.update(data, off, len);
         }
         int blockDataRemaining = blockData.length - currentIndex;
         while (len > 0) {
             final int copyLen = Math.min(len, blockDataRemaining);
             System.arraycopy(data, off, blockData, currentIndex, copyLen);
             off += copyLen;
             blockDataRemaining -= copyLen;
             len -= copyLen;
             currentIndex += copyLen;
             if (blockDataRemaining == 0) {
                 flushBlock();
                 blockDataRemaining = blockData.length;
             }
         }
     }
 
     @Override
     public void write(final int b) throws IOException {
         oneByte[0] = (byte) (b & 0xff);
         write(oneByte);
     }
 
     private void writeFrameDescriptor() throws IOException {
         int flags = FramedLZ4CompressorInputStream.SUPPORTED_VERSION;
         if (!params.withBlockDependency) {
             flags |= FramedLZ4CompressorInputStream.BLOCK_INDEPENDENCE_MASK;
         }
         if (params.withContentChecksum) {
             flags |= FramedLZ4CompressorInputStream.CONTENT_CHECKSUM_MASK;
         }
         if (params.withBlockChecksum) {
             flags |= FramedLZ4CompressorInputStream.BLOCK_CHECKSUM_MASK;
         }
         out.write(flags);
         contentHash.update(flags);
         final int bd = params.blockSize.getIndex() << 4 & FramedLZ4CompressorInputStream.BLOCK_MAX_SIZE_MASK;
         out.write(bd);
         contentHash.update(bd);
         out.write((int) (contentHash.getValue() >> 8 & 0xff));
         contentHash.reset();
     }
 
     private void writeTrailer() throws IOException {
         out.write(END_MARK);
         if (params.withContentChecksum) {
             ByteUtils.toLittleEndian(out, contentHash.getValue(), 4);
         }
     }
 
 }