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   /*
    * 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 org.jboss.netty.handler.codec.http;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.handler.codec.compression.JdkZlibEncoder;
  import org.jboss.netty.handler.codec.compression.ZlibEncoder;
  import org.jboss.netty.handler.codec.compression.ZlibWrapper;
  import org.jboss.netty.handler.codec.embedder.EncoderEmbedder;
  import org.jboss.netty.logging.InternalLogger;
  import org.jboss.netty.logging.InternalLoggerFactory;
  import org.jboss.netty.util.internal.DetectionUtil;
  import org.jboss.netty.util.internal.StringUtil;
  import org.jboss.netty.util.internal.SystemPropertyUtil;
  
  /**
   * Compresses an {@link HttpMessage} and an {@link HttpChunk} in {@code gzip} or
   * {@code deflate} encoding while respecting the {@code "Accept-Encoding"} header.
   * If there is no matching encoding, no compression is done.  For more
   * information on how this handler modifies the message, please refer to
   * {@link HttpContentEncoder}.
   */
  public class HttpContentCompressor extends HttpContentEncoder {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(HttpContentCompressor.class);
  
      private static final int DEFAULT_JDK_WINDOW_SIZE = 15;
      private static final int DEFAULT_JDK_MEM_LEVEL = 8;
  
      private static final boolean noJdkZlibEncoder;
  
      static {
          noJdkZlibEncoder = SystemPropertyUtil.getBoolean("io.netty.noJdkZlibEncoder", false);
          if (logger.isDebugEnabled()) {
              logger.debug("-Dio.netty.noJdkZlibEncoder: " + noJdkZlibEncoder);
          }
      }
  
      private final int compressionLevel;
      private final int windowBits;
      private final int memLevel;
  
      /**
       * Creates a new handler with the default compression level (<tt>6</tt>), default window size
       * ({@value #DEFAULT_JDK_WINDOW_SIZE}) and default memory level ({@value #DEFAULT_JDK_MEM_LEVEL}).
       */
      public HttpContentCompressor() {
          this(6);
      }
  
      /**
       * Creates a new handler with the specified compression level, default window size
       * ({@value #DEFAULT_JDK_WINDOW_SIZE}) and default memory level ({@value #DEFAULT_JDK_MEM_LEVEL}).
       *
       * @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}.
       */
      public HttpContentCompressor(int compressionLevel) {
          this(compressionLevel, DEFAULT_JDK_WINDOW_SIZE, DEFAULT_JDK_MEM_LEVEL);
      }
  
      /**
       * Creates a new handler with the specified compression level, window size, and memory level.
       *
       * @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 {@value #DEFAULT_JDK_WINDOW_SIZE}.
       * @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 {@value #DEFAULT_JDK_MEM_LEVEL}.
       */
      public HttpContentCompressor(int compressionLevel, int windowBits, int memLevel) {
          if (compressionLevel < 0 || compressionLevel > 9) {
              throw new IllegalArgumentException(
                      "compressionLevel: " + compressionLevel + " (expected: 0-9)");
          }
         if (windowBits < 9 || windowBits > 15) {
             throw new IllegalArgumentException(
                     "windowBits: " + windowBits + " (expected: 9-15)");
         }
         if (memLevel < 1 || memLevel > 9) {
             throw new IllegalArgumentException(
                     "memLevel: " + memLevel + " (expected: 1-9)");
         }
         this.compressionLevel = compressionLevel;
         this.windowBits = windowBits;
         this.memLevel = memLevel;
     }
 
     @Override
     protected EncoderEmbedder<ChannelBuffer> newContentEncoder(
             HttpMessage msg, String acceptEncoding) throws Exception {
         String contentEncoding = msg.headers().get(HttpHeaders.Names.CONTENT_ENCODING);
         if (contentEncoding != null &&
             !HttpHeaders.Values.IDENTITY.equalsIgnoreCase(contentEncoding)) {
             // Encoded already.
             return null;
         }
 
         ZlibWrapper wrapper = determineWrapper(acceptEncoding);
         if (wrapper == null) {
             return null;
         }
 
         if (DetectionUtil.javaVersion() < 7 || noJdkZlibEncoder ||
             windowBits != DEFAULT_JDK_WINDOW_SIZE || memLevel != DEFAULT_JDK_MEM_LEVEL) {
             return new EncoderEmbedder<ChannelBuffer>(
                     new ZlibEncoder(wrapper, compressionLevel, windowBits, memLevel));
         } else {
             return new EncoderEmbedder<ChannelBuffer>(
                     new JdkZlibEncoder(wrapper, compressionLevel));
         }
     }
 
     @Override
     protected String getTargetContentEncoding(String acceptEncoding) throws Exception {
         ZlibWrapper wrapper = determineWrapper(acceptEncoding);
         if (wrapper == null) {
             return null;
         }
 
         switch (wrapper) {
         case GZIP:
             return "gzip";
         case ZLIB:
             return "deflate";
         default:
             throw new Error();
         }
     }
 
     private static ZlibWrapper determineWrapper(String acceptEncoding) {
         float starQ = -1.0f;
         float gzipQ = -1.0f;
         float deflateQ = -1.0f;
         for (String encoding: StringUtil.split(acceptEncoding, ',')) {
             float q = 1.0f;
             int equalsPos = encoding.indexOf('=');
             if (equalsPos != -1) {
                 try {
                     q = Float.valueOf(encoding.substring(equalsPos + 1));
                 } catch (NumberFormatException e) {
                     // Ignore encoding
                     q = 0.0f;
                 }
             }
             if (encoding.indexOf('*') >= 0) {
                 starQ = q;
             } else if (encoding.contains("gzip") && q > gzipQ) {
                 gzipQ = q;
             } else if (encoding.contains("deflate") && q > deflateQ) {
                 deflateQ = q;
             }
         }
         if (gzipQ > 0.0f || deflateQ > 0.0f) {
             if (gzipQ >= deflateQ) {
                 return ZlibWrapper.GZIP;
             } else {
                 return ZlibWrapper.ZLIB;
             }
         }
         if (starQ > 0.0f) {
             if (gzipQ == -1.0f) {
                 return ZlibWrapper.GZIP;
             }
             if (deflateQ == -1.0f) {
                 return ZlibWrapper.ZLIB;
             }
         }
         return null;
     }
 }