/*
    * Copyright 2013 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 org.jboss.netty.handler.codec.spdy;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  
  import java.util.zip.Deflater;
  
  import static org.jboss.netty.handler.codec.spdy.SpdyCodecUtil.*;
  
  class SpdyHeaderBlockZlibEncoder extends SpdyHeaderBlockRawEncoder {
  
      private final Deflater compressor;
  
      private boolean finished;
  
      SpdyHeaderBlockZlibEncoder(SpdyVersion spdyVersion, int compressionLevel) {
          super(spdyVersion);
          if (compressionLevel < 0 || compressionLevel > 9) {
              throw new IllegalArgumentException(
                      "compressionLevel: " + compressionLevel + " (expected: 0-9)");
          }
          compressor = new Deflater(compressionLevel);
          compressor.setDictionary(SPDY_DICT);
      }
  
      private int setInput(ChannelBuffer decompressed) {
          int len = decompressed.readableBytes();
  
          if (decompressed.hasArray()) {
              compressor.setInput(decompressed.array(), decompressed.arrayOffset() + decompressed.readerIndex(), len);
          } else {
              byte[] in = new byte[len];
              decompressed.getBytes(decompressed.readerIndex(), in);
              compressor.setInput(in, 0, in.length);
          }
  
          return len;
      }
  
      private void encode(ChannelBuffer compressed) {
          while (compressInto(compressed)) {
              // Although unlikely, it's possible that the compressed size is larger than the decompressed size
              compressed.ensureWritableBytes(compressed.capacity() << 1);
          }
      }
  
      private boolean compressInto(ChannelBuffer compressed) {
          byte[] out = compressed.array();
          int off = compressed.arrayOffset() + compressed.writerIndex();
          int toWrite = compressed.writableBytes();
          int numBytes = compressor.deflate(out, off, toWrite, Deflater.SYNC_FLUSH);
          compressed.writerIndex(compressed.writerIndex() + numBytes);
          return numBytes == toWrite;
      }
  
      @Override
      public synchronized ChannelBuffer encode(SpdyHeadersFrame frame) throws Exception {
          if (frame == null) {
              throw new IllegalArgumentException("frame");
          }
  
          if (finished) {
              return ChannelBuffers.EMPTY_BUFFER;
          }
  
          ChannelBuffer decompressed = super.encode(frame);
          if (decompressed.readableBytes() == 0) {
              return ChannelBuffers.EMPTY_BUFFER;
          }
  
          ChannelBuffer compressed = ChannelBuffers.dynamicBuffer(decompressed.readableBytes());
          int len = setInput(decompressed);
          encode(compressed);
          decompressed.skipBytes(len);
  
          return compressed;
      }
  
      @Override
      public synchronized void end() {
          if (finished) {
              return;
          }
          finished = true;
         compressor.end();
         super.end();
     }
 }