/*
    * Copyright 2014 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 java.util.zip.DataFormatException;
  import java.util.zip.Inflater;
  
  import static io.netty.handler.codec.spdy.SpdyCodecUtil.*;
  
  final class SpdyHeaderBlockZlibDecoder extends SpdyHeaderBlockRawDecoder {
  
      private static final int DEFAULT_BUFFER_CAPACITY = 4096;
      private static final SpdyProtocolException INVALID_HEADER_BLOCK =
              new SpdyProtocolException("Invalid Header Block");
  
      private final Inflater decompressor = new Inflater();
  
      private ByteBuf decompressed;
  
      SpdyHeaderBlockZlibDecoder(SpdyVersion spdyVersion, int maxHeaderSize) {
          super(spdyVersion, maxHeaderSize);
      }
  
      @Override
      void decode(ByteBufAllocator alloc, ByteBuf headerBlock, SpdyHeadersFrame frame) throws Exception {
          int len = setInput(headerBlock);
  
          int numBytes;
          do {
              numBytes = decompress(alloc, frame);
          } while (numBytes > 0);
  
          // z_stream has an internal 64-bit hold buffer
          // it is always capable of consuming the entire input
          if (decompressor.getRemaining() != 0) {
              // we reached the end of the deflate stream
              throw INVALID_HEADER_BLOCK;
          }
  
          headerBlock.skipBytes(len);
      }
  
      private int setInput(ByteBuf compressed) {
          int len = compressed.readableBytes();
  
          if (compressed.hasArray()) {
              decompressor.setInput(compressed.array(), compressed.arrayOffset() + compressed.readerIndex(), len);
          } else {
              byte[] in = new byte[len];
              compressed.getBytes(compressed.readerIndex(), in);
              decompressor.setInput(in, 0, in.length);
          }
  
          return len;
      }
  
      private int decompress(ByteBufAllocator alloc, SpdyHeadersFrame frame) throws Exception {
          ensureBuffer(alloc);
          byte[] out = decompressed.array();
          int off = decompressed.arrayOffset() + decompressed.writerIndex();
          try {
              int numBytes = decompressor.inflate(out, off, decompressed.writableBytes());
              if (numBytes == 0 && decompressor.needsDictionary()) {
                  try {
                      decompressor.setDictionary(SPDY_DICT);
                  } catch (IllegalArgumentException ignored) {
                      throw INVALID_HEADER_BLOCK;
                  }
                  numBytes = decompressor.inflate(out, off, decompressed.writableBytes());
              }
              if (frame != null) {
                  decompressed.writerIndex(decompressed.writerIndex() + numBytes);
                  decodeHeaderBlock(decompressed, frame);
                  decompressed.discardReadBytes();
              }
  
              return numBytes;
          } catch (DataFormatException e) {
              throw new SpdyProtocolException("Received invalid header block", e);
          }
      }
  
      private void ensureBuffer(ByteBufAllocator alloc) {
         if (decompressed == null) {
             decompressed = alloc.heapBuffer(DEFAULT_BUFFER_CAPACITY);
         }
         decompressed.ensureWritable(1);
     }
 
     @Override
     void endHeaderBlock(SpdyHeadersFrame frame) throws Exception {
         super.endHeaderBlock(frame);
         releaseBuffer();
     }
 
     @Override
     public void end() {
         super.end();
         releaseBuffer();
         decompressor.end();
     }
 
     private void releaseBuffer() {
         if (decompressed != null) {
             decompressed.release();
             decompressed = null;
         }
     }
 }