/*
    * 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 io.netty.handler.codec.spdy;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufAllocator;
  import io.netty.buffer.Unpooled;
  
  import java.util.zip.Deflater;
  
  import static io.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(ByteBuf 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 ByteBuf encode(ByteBufAllocator alloc, int len) {
          ByteBuf compressed = alloc.heapBuffer(len);
          boolean release = true;
          try {
              while (compressInto(compressed)) {
                  // Although unlikely, it's possible that the compressed size is larger than the decompressed size
                  compressed.ensureWritable(compressed.capacity() << 1);
              }
              release = false;
              return compressed;
          } finally {
              if (release) {
                  compressed.release();
              }
          }
      }
  
      private boolean compressInto(ByteBuf 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 ByteBuf encode(ByteBufAllocator alloc, SpdyHeadersFrame frame) throws Exception {
          if (frame == null) {
              throw new IllegalArgumentException("frame");
          }
  
          if (finished) {
              return Unpooled.EMPTY_BUFFER;
          }
  
          ByteBuf decompressed = super.encode(alloc, frame);
          try {
              if (!decompressed.isReadable()) {
                  return Unpooled.EMPTY_BUFFER;
              }
  
              int len = setInput(decompressed);
              return encode(alloc, len);
         } finally {
             decompressed.release();
         }
     }
 
     @Override
     public void end() {
         if (finished) {
             return;
         }
         finished = true;
         compressor.end();
         super.end();
     }
 }