/*
    * 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:
    *
    *   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 io.netty.handler.codec.compression;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelPromise;
  import io.netty.channel.ChannelPromiseNotifier;
  import io.netty.util.concurrent.EventExecutor;
  
  import java.util.concurrent.TimeUnit;
  import java.util.zip.CRC32;
  import java.util.zip.Deflater;
  
  /**
   * Compresses a {@link ByteBuf} using the deflate algorithm.
   */
  public class JdkZlibEncoder extends ZlibEncoder {
  
      private final ZlibWrapper wrapper;
      private final Deflater deflater;
      private volatile boolean finished;
      private volatile ChannelHandlerContext ctx;
  
      /*
       * GZIP support
       */
      private final CRC32 crc = new CRC32();
      private static final byte[] gzipHeader = {0x1f, (byte) 0x8b, Deflater.DEFLATED, 0, 0, 0, 0, 0, 0, 0};
      private boolean writeHeader = true;
  
      /**
       * Creates a new zlib encoder with the default compression level ({@code 6})
       * and the default wrapper ({@link ZlibWrapper#ZLIB}).
       *
       * @throws CompressionException if failed to initialize zlib
       */
      public JdkZlibEncoder() {
          this(6);
      }
  
      /**
       * Creates a new zlib encoder with the specified {@code compressionLevel}
       * 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 JdkZlibEncoder(int compressionLevel) {
          this(ZlibWrapper.ZLIB, compressionLevel);
      }
  
      /**
       * Creates a new zlib encoder with the default compression level ({@code 6})
       * and the specified wrapper.
       *
       * @throws CompressionException if failed to initialize zlib
       */
      public JdkZlibEncoder(ZlibWrapper wrapper) {
          this(wrapper, 6);
      }
  
      /**
       * Creates a new zlib encoder with the specified {@code compressionLevel}
       * 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 JdkZlibEncoder(ZlibWrapper wrapper, int compressionLevel) {
          if (compressionLevel < 0 || compressionLevel > 9) {
              throw new IllegalArgumentException(
                      "compressionLevel: " + compressionLevel + " (expected: 0-9)");
          }
          if (wrapper == null) {
              throw new NullPointerException("wrapper");
         }
         if (wrapper == ZlibWrapper.ZLIB_OR_NONE) {
             throw new IllegalArgumentException(
                     "wrapper '" + ZlibWrapper.ZLIB_OR_NONE + "' is not " +
                     "allowed for compression.");
         }
 
         this.wrapper = wrapper;
         deflater = new Deflater(compressionLevel, wrapper != ZlibWrapper.ZLIB);
     }
 
     /**
      * Creates a new zlib encoder with the default compression level ({@code 6})
      * 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 JdkZlibEncoder(byte[] dictionary) {
         this(6, dictionary);
     }
 
     /**
      * Creates a new zlib encoder with the specified {@code compressionLevel}
      * 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 JdkZlibEncoder(int compressionLevel, byte[] dictionary) {
         if (compressionLevel < 0 || compressionLevel > 9) {
             throw new IllegalArgumentException(
                     "compressionLevel: " + compressionLevel + " (expected: 0-9)");
         }
         if (dictionary == null) {
             throw new NullPointerException("dictionary");
         }
 
         wrapper = ZlibWrapper.ZLIB;
         deflater = new Deflater(compressionLevel);
         deflater.setDictionary(dictionary);
     }
 
     @Override
     public ChannelFuture close() {
         return close(ctx().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);
                     f.addListener(new ChannelPromiseNotifier(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 uncompressed, ByteBuf out) throws Exception {
         if (finished) {
             out.writeBytes(uncompressed);
             return;
         }
 
         int len = uncompressed.readableBytes();
         if (len == 0) {
             return;
         }
 
         int offset;
         byte[] inAry;
         if (uncompressed.hasArray()) {
             // if it is backed by an array we not need to to do a copy at all
             inAry = uncompressed.array();
             offset = uncompressed.arrayOffset() + uncompressed.readerIndex();
             // skip all bytes as we will consume all of them
             uncompressed.skipBytes(len);
         } else {
             inAry = new byte[len];
             uncompressed.readBytes(inAry);
             offset = 0;
         }
 
         if (writeHeader) {
             writeHeader = false;
             if (wrapper == ZlibWrapper.GZIP) {
                 out.writeBytes(gzipHeader);
             }
         }
 
         if (wrapper == ZlibWrapper.GZIP) {
             crc.update(inAry, offset, len);
         }
 
         deflater.setInput(inAry, offset, len);
         while (!deflater.needsInput()) {
             deflate(out);
         }
     }
 
     @Override
     protected final ByteBuf allocateBuffer(ChannelHandlerContext ctx, ByteBuf msg,
                                            boolean preferDirect) throws Exception {
         int sizeEstimate = (int) Math.ceil(msg.readableBytes() * 1.001) + 12;
         if (writeHeader) {
             switch (wrapper) {
                 case GZIP:
                     sizeEstimate += gzipHeader.length;
                     break;
                 case ZLIB:
                     sizeEstimate += 2; // first two magic bytes
                     break;
                 default:
                     // no op
             }
         }
         return ctx.alloc().heapBuffer(sizeEstimate);
     }
 
     @Override
     public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
         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);
                 }
             }, 10, TimeUnit.SECONDS); // FIXME: Magic number
         }
     }
 
     private ChannelFuture finishEncode(final ChannelHandlerContext ctx, ChannelPromise promise) {
         if (finished) {
             promise.setSuccess();
             return promise;
         }
 
         finished = true;
         ByteBuf footer = ctx.alloc().heapBuffer();
         if (writeHeader && wrapper == ZlibWrapper.GZIP) {
             // Write the GZIP header first if not written yet. (i.e. user wrote nothing.)
             writeHeader = false;
             footer.writeBytes(gzipHeader);
         }
 
         deflater.finish();
 
         while (!deflater.finished()) {
             deflate(footer);
             if (!footer.isWritable()) {
                 // no more space so write it to the channel and continue
                 ctx.write(footer);
                 footer = ctx.alloc().heapBuffer();
             }
         }
         if (wrapper == ZlibWrapper.GZIP) {
             int crcValue = (int) crc.getValue();
             int uncBytes = deflater.getTotalIn();
             footer.writeByte(crcValue);
             footer.writeByte(crcValue >>> 8);
             footer.writeByte(crcValue >>> 16);
             footer.writeByte(crcValue >>> 24);
             footer.writeByte(uncBytes);
             footer.writeByte(uncBytes >>> 8);
             footer.writeByte(uncBytes >>> 16);
             footer.writeByte(uncBytes >>> 24);
         }
         deflater.end();
         return ctx.writeAndFlush(footer, promise);
     }
 
     private void deflate(ByteBuf out) {
         int numBytes;
         do {
             int writerIndex = out.writerIndex();
             numBytes = deflater.deflate(
                     out.array(), out.arrayOffset() + writerIndex, out.writableBytes(), Deflater.SYNC_FLUSH);
             out.writerIndex(writerIndex + numBytes);
         } while (numBytes > 0);
     }
 
     @Override
     public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
         this.ctx = ctx;
     }
 }