/*
    * 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.netty.handler.codec.compression;
  
  import com.jcraft.jzlib.Deflater;
  import com.jcraft.jzlib.JZlib;
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelPromise;
  import io.netty.util.concurrent.EventExecutor;
  import io.netty.util.concurrent.PromiseNotifier;
  import io.netty.util.internal.EmptyArrays;
  import io.netty.util.internal.ObjectUtil;
  
  import java.util.concurrent.TimeUnit;
  
  /**
   * Compresses a {@link ByteBuf} using the deflate algorithm.
   */
  public class JZlibEncoder extends ZlibEncoder {
  
      private final int wrapperOverhead;
      private final Deflater z = new Deflater();
      private volatile boolean finished;
      private volatile ChannelHandlerContext ctx;
  
      private static final int THREAD_POOL_DELAY_SECONDS = 10;
  
      /**
       * Creates a new zlib encoder with the default compression level ({@code 6}),
       * default window bits ({@code 15}), default memory level ({@code 8}),
       * and the default wrapper ({@link ZlibWrapper#ZLIB}).
       *
       * @throws CompressionException if failed to initialize zlib
       */
      public JZlibEncoder() {
          this(6);
      }
  
      /**
       * Creates a new zlib encoder with the specified {@code compressionLevel},
       * default window bits ({@code 15}), default memory level ({@code 8}),
       * and the default wrapper ({@link ZlibWrapper#ZLIB}).
       *
       * @param compressionLevel
       *        {@code 1} yields the fastest compression and {@code 9} yields the
       *        best compression.  {@code 0} means no compression.  The default
       *        compression level is {@code 6}.
       *
       * @throws CompressionException if failed to initialize zlib
       */
      public JZlibEncoder(int compressionLevel) {
          this(ZlibWrapper.ZLIB, compressionLevel);
      }
  
      /**
       * Creates a new zlib encoder with the default compression level ({@code 6}),
       * default window bits ({@code 15}), default memory level ({@code 8}),
       * and the specified wrapper.
       *
       * @throws CompressionException if failed to initialize zlib
       */
      public JZlibEncoder(ZlibWrapper wrapper) {
          this(wrapper, 6);
      }
  
      /**
       * Creates a new zlib encoder with the specified {@code compressionLevel},
       * default window bits ({@code 15}), default memory level ({@code 8}),
       * and the specified wrapper.
       *
       * @param compressionLevel
       *        {@code 1} yields the fastest compression and {@code 9} yields the
       *        best compression.  {@code 0} means no compression.  The default
       *        compression level is {@code 6}.
       *
       * @throws CompressionException if failed to initialize zlib
       */
      public JZlibEncoder(ZlibWrapper wrapper, int compressionLevel) {
          this(wrapper, compressionLevel, 15, 8);
      }
  
      /**
      * Creates a new zlib encoder with the specified {@code compressionLevel},
      * the specified {@code windowBits}, the specified {@code memLevel}, and
      * the specified wrapper.
      *
      * @param compressionLevel
      *        {@code 1} yields the fastest compression and {@code 9} yields the
      *        best compression.  {@code 0} means no compression.  The default
      *        compression level is {@code 6}.
      * @param windowBits
      *        The base two logarithm of the size of the history buffer.  The
      *        value should be in the range {@code 9} to {@code 15} inclusive.
      *        Larger values result in better compression at the expense of
      *        memory usage.  The default value is {@code 15}.
      * @param memLevel
      *        How much memory should be allocated for the internal compression
      *        state.  {@code 1} uses minimum memory and {@code 9} uses maximum
      *        memory.  Larger values result in better and faster compression
      *        at the expense of memory usage.  The default value is {@code 8}
      *
      * @throws CompressionException if failed to initialize zlib
      */
     public JZlibEncoder(ZlibWrapper wrapper, int compressionLevel, int windowBits, int memLevel) {
         ObjectUtil.checkInRange(compressionLevel, 0, 9, "compressionLevel");
         ObjectUtil.checkInRange(windowBits, 9, 15, "windowBits");
         ObjectUtil.checkInRange(memLevel, 1, 9, "memLevel");
         ObjectUtil.checkNotNull(wrapper, "wrapper");
 
         if (wrapper == ZlibWrapper.ZLIB_OR_NONE) {
             throw new IllegalArgumentException(
                     "wrapper '" + ZlibWrapper.ZLIB_OR_NONE + "' is not " +
                     "allowed for compression.");
         }
 
         int resultCode = z.init(
                 compressionLevel, windowBits, memLevel,
                 ZlibUtil.convertWrapperType(wrapper));
         if (resultCode != JZlib.Z_OK) {
             ZlibUtil.fail(z, "initialization failure", resultCode);
         }
 
         wrapperOverhead = ZlibUtil.wrapperOverhead(wrapper);
     }
 
     /**
      * Creates a new zlib encoder with the default compression level ({@code 6}),
      * default window bits ({@code 15}), default memory level ({@code 8}),
      * and the specified preset dictionary.  The wrapper is always
      * {@link ZlibWrapper#ZLIB} because it is the only format that supports
      * the preset dictionary.
      *
      * @param dictionary  the preset dictionary
      *
      * @throws CompressionException if failed to initialize zlib
      */
     public JZlibEncoder(byte[] dictionary) {
         this(6, dictionary);
     }
 
     /**
      * Creates a new zlib encoder with the specified {@code compressionLevel},
      * default window bits ({@code 15}), default memory level ({@code 8}),
      * and the specified preset dictionary.  The wrapper is always
      * {@link ZlibWrapper#ZLIB} because it is the only format that supports
      * the preset dictionary.
      *
      * @param compressionLevel
      *        {@code 1} yields the fastest compression and {@code 9} yields the
      *        best compression.  {@code 0} means no compression.  The default
      *        compression level is {@code 6}.
      * @param dictionary  the preset dictionary
      *
      * @throws CompressionException if failed to initialize zlib
      */
     public JZlibEncoder(int compressionLevel, byte[] dictionary) {
         this(compressionLevel, 15, 8, dictionary);
     }
 
     /**
      * Creates a new zlib encoder with the specified {@code compressionLevel},
      * the specified {@code windowBits}, the specified {@code memLevel},
      * and the specified preset dictionary.  The wrapper is always
      * {@link ZlibWrapper#ZLIB} because it is the only format that supports
      * the preset dictionary.
      *
      * @param compressionLevel
      *        {@code 1} yields the fastest compression and {@code 9} yields the
      *        best compression.  {@code 0} means no compression.  The default
      *        compression level is {@code 6}.
      * @param windowBits
      *        The base two logarithm of the size of the history buffer.  The
      *        value should be in the range {@code 9} to {@code 15} inclusive.
      *        Larger values result in better compression at the expense of
      *        memory usage.  The default value is {@code 15}.
      * @param memLevel
      *        How much memory should be allocated for the internal compression
      *        state.  {@code 1} uses minimum memory and {@code 9} uses maximum
      *        memory.  Larger values result in better and faster compression
      *        at the expense of memory usage.  The default value is {@code 8}
      * @param dictionary  the preset dictionary
      *
      * @throws CompressionException if failed to initialize zlib
      */
     public JZlibEncoder(int compressionLevel, int windowBits, int memLevel, byte[] dictionary) {
         ObjectUtil.checkInRange(compressionLevel, 0, 9, "compressionLevel");
         ObjectUtil.checkInRange(windowBits, 9, 15, "windowBits");
         ObjectUtil.checkInRange(memLevel, 1, 9, "memLevel");
         ObjectUtil.checkNotNull(dictionary, "dictionary");
 
         int resultCode;
         resultCode = z.deflateInit(
                 compressionLevel, windowBits, memLevel,
                 JZlib.W_ZLIB); // Default: ZLIB format
         if (resultCode != JZlib.Z_OK) {
             ZlibUtil.fail(z, "initialization failure", resultCode);
         } else {
             resultCode = z.deflateSetDictionary(dictionary, dictionary.length);
             if (resultCode != JZlib.Z_OK) {
                 ZlibUtil.fail(z, "failed to set the dictionary", resultCode);
             }
         }
 
         wrapperOverhead = ZlibUtil.wrapperOverhead(ZlibWrapper.ZLIB);
     }
 
     @Override
     public ChannelFuture close() {
         return close(ctx().channel().newPromise());
     }
 
     @Override
     public ChannelFuture close(final ChannelPromise promise) {
         ChannelHandlerContext ctx = ctx();
         EventExecutor executor = ctx.executor();
         if (executor.inEventLoop()) {
             return finishEncode(ctx, promise);
         } else {
             final ChannelPromise p = ctx.newPromise();
             executor.execute(new Runnable() {
                 @Override
                 public void run() {
                     ChannelFuture f = finishEncode(ctx(), p);
                     PromiseNotifier.cascade(f, promise);
                 }
             });
             return p;
         }
     }
 
     private ChannelHandlerContext ctx() {
         ChannelHandlerContext ctx = this.ctx;
         if (ctx == null) {
             throw new IllegalStateException("not added to a pipeline");
         }
         return ctx;
     }
 
     @Override
     public boolean isClosed() {
         return finished;
     }
 
     @Override
     protected void encode(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception {
         if (finished) {
             out.writeBytes(in);
             return;
         }
 
         int inputLength = in.readableBytes();
         if (inputLength == 0) {
             return;
         }
 
         try {
             // Configure input.
             boolean inHasArray = in.hasArray();
             z.avail_in = inputLength;
             if (inHasArray) {
                 z.next_in = in.array();
                 z.next_in_index = in.arrayOffset() + in.readerIndex();
             } else {
                 byte[] array = new byte[inputLength];
                 in.getBytes(in.readerIndex(), array);
                 z.next_in = array;
                 z.next_in_index = 0;
             }
             int oldNextInIndex = z.next_in_index;
 
             // Configure output.
             int maxOutputLength = (int) Math.ceil(inputLength * 1.001) + 12 + wrapperOverhead;
             out.ensureWritable(maxOutputLength);
             z.avail_out = maxOutputLength;
             z.next_out = out.array();
             z.next_out_index = out.arrayOffset() + out.writerIndex();
             int oldNextOutIndex = z.next_out_index;
 
             // Note that Z_PARTIAL_FLUSH has been deprecated.
             int resultCode;
             try {
                 resultCode = z.deflate(JZlib.Z_SYNC_FLUSH);
             } finally {
                 in.skipBytes(z.next_in_index - oldNextInIndex);
             }
 
             if (resultCode != JZlib.Z_OK) {
                 ZlibUtil.fail(z, "compression failure", resultCode);
             }
 
             int outputLength = z.next_out_index - oldNextOutIndex;
             if (outputLength > 0) {
                 out.writerIndex(out.writerIndex() + outputLength);
             }
         } finally {
             // Deference the external references explicitly to tell the VM that
             // the allocated byte arrays are temporary so that the call stack
             // can be utilized.
             // I'm not sure if the modern VMs do this optimization though.
             z.next_in = null;
             z.next_out = null;
         }
     }
 
     @Override
     public void close(
             final ChannelHandlerContext ctx,
             final ChannelPromise promise) {
         ChannelFuture f = finishEncode(ctx, ctx.newPromise());
         f.addListener(new ChannelFutureListener() {
             @Override
             public void operationComplete(ChannelFuture f) throws Exception {
                 ctx.close(promise);
             }
         });
 
         if (!f.isDone()) {
             // Ensure the channel is closed even if the write operation completes in time.
             ctx.executor().schedule(new Runnable() {
                 @Override
                 public void run() {
                     ctx.close(promise);
                 }
             }, THREAD_POOL_DELAY_SECONDS, TimeUnit.SECONDS);
         }
     }
 
     private ChannelFuture finishEncode(ChannelHandlerContext ctx, ChannelPromise promise) {
         if (finished) {
             promise.setSuccess();
             return promise;
         }
         finished = true;
 
         ByteBuf footer;
         try {
             // Configure input.
             z.next_in = EmptyArrays.EMPTY_BYTES;
             z.next_in_index = 0;
             z.avail_in = 0;
 
             // Configure output.
             byte[] out = new byte[32]; // room for ADLER32 + ZLIB / CRC32 + GZIP header
             z.next_out = out;
             z.next_out_index = 0;
             z.avail_out = out.length;
 
             // Write the ADLER32 checksum (stream footer).
             int resultCode = z.deflate(JZlib.Z_FINISH);
             if (resultCode != JZlib.Z_OK && resultCode != JZlib.Z_STREAM_END) {
                 promise.setFailure(ZlibUtil.deflaterException(z, "compression failure", resultCode));
                 return promise;
             } else if (z.next_out_index != 0) { // lgtm[java/constant-comparison]
                 // Suppressed a warning above to be on the safe side
                 // even if z.next_out_index seems to be always 0 here
                 footer = Unpooled.wrappedBuffer(out, 0, z.next_out_index);
             } else {
                 footer = Unpooled.EMPTY_BUFFER;
             }
         } finally {
             z.deflateEnd();
 
             // Deference the external references explicitly to tell the VM that
             // the allocated byte arrays are temporary so that the call stack
             // can be utilized.
             // I'm not sure if the modern VMs do this optimization though.
             z.next_in = null;
             z.next_out = null;
         }
         return ctx.writeAndFlush(footer, promise);
     }
 
     @Override
     public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
         this.ctx = ctx;
     }
 }