/*
    * 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:
    *
    *   https://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.http;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.embedded.EmbeddedChannel;
  import io.netty.handler.codec.MessageToByteEncoder;
  import io.netty.handler.codec.compression.Brotli;
  import io.netty.handler.codec.compression.BrotliEncoder;
  import io.netty.handler.codec.compression.BrotliOptions;
  import io.netty.handler.codec.compression.CompressionOptions;
  import io.netty.handler.codec.compression.DeflateOptions;
  import io.netty.handler.codec.compression.GzipOptions;
  import io.netty.handler.codec.compression.SnappyFrameEncoder;
  import io.netty.handler.codec.compression.SnappyOptions;
  import io.netty.handler.codec.compression.StandardCompressionOptions;
  import io.netty.handler.codec.compression.ZlibCodecFactory;
  import io.netty.handler.codec.compression.ZlibWrapper;
  import io.netty.handler.codec.compression.Zstd;
  import io.netty.handler.codec.compression.ZstdEncoder;
  import io.netty.handler.codec.compression.ZstdOptions;
  import io.netty.util.internal.ObjectUtil;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import static io.netty.util.internal.ObjectUtil.checkInRange;
  
  /**
   * Compresses an {@link HttpMessage} and an {@link HttpContent} 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 final BrotliOptions brotliOptions;
      private final GzipOptions gzipOptions;
      private final DeflateOptions deflateOptions;
      private final ZstdOptions zstdOptions;
      private final SnappyOptions snappyOptions;
  
      private final int contentSizeThreshold;
      private ChannelHandlerContext ctx;
  
      private static final CompressionOptions[] DEFAULT_COMPRESSION_OPTIONS;
      static {
          List<CompressionOptions> options = new ArrayList<>(5);
          options.add(StandardCompressionOptions.gzip());
          options.add(StandardCompressionOptions.deflate());
          options.add(StandardCompressionOptions.snappy());
          if (Brotli.isAvailable()) {
              options.add(StandardCompressionOptions.brotli());
          }
          if (Zstd.isAvailable()) {
              options.add(StandardCompressionOptions.zstd());
          }
          DEFAULT_COMPRESSION_OPTIONS = options.toArray(new CompressionOptions[0]);
      }
  
      /**
       * Creates a new handler with {@link StandardCompressionOptions#brotli()} (if supported) ,
       * {@link StandardCompressionOptions#zstd()} (if supported), {@link StandardCompressionOptions#snappy()},
       * {@link StandardCompressionOptions#gzip()} and {@link StandardCompressionOptions#deflate()}.
       */
      public HttpContentCompressor() {
          this(0, (CompressionOptions[]) null);
      }
  
      /**
       * Creates a new handler with the specified compression level, default
       * window size (<tt>15</tt>) and default memory level (<tt>8</tt>).
       *
       * @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}.
       */
      @Deprecated
      public HttpContentCompressor(int compressionLevel) {
          this(compressionLevel, 15, 8, 0);
      }
  
     /**
      * 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 {@code 15}.
      * @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 {@code 8}
      */
     @Deprecated
     public HttpContentCompressor(int compressionLevel, int windowBits, int memLevel) {
         this(compressionLevel, windowBits, memLevel, 0);
     }
 
     /**
      * 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 {@code 15}.
      * @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 {@code 8}
      * @param contentSizeThreshold
      *        The response body is compressed when the size of the response
      *        body exceeds the threshold. The value should be a non negative
      *        number. {@code 0} will enable compression for all responses.
      */
     @Deprecated
     public HttpContentCompressor(int compressionLevel, int windowBits, int memLevel, int contentSizeThreshold) {
         this(contentSizeThreshold,
                 defaultCompressionOptions(
                     StandardCompressionOptions.gzip(
                             checkInRange(compressionLevel, 0, 9, "compressionLevel"),
                             checkInRange(windowBits, 9, 15, "windowBits"),
                             checkInRange(memLevel, 1, 9, "memLevel")
                     ),
                     StandardCompressionOptions.deflate(
                             checkInRange(compressionLevel, 0, 9, "compressionLevel"),
                             checkInRange(windowBits, 9, 15, "windowBits"),
                             checkInRange(memLevel, 1, 9, "memLevel")
                     )
                 )
         );
     }
 
     /**
      * Create a new {@link HttpContentCompressor} Instance with specified
      * {@link CompressionOptions}s and contentSizeThreshold set to {@code 0}
      *
      * @param compressionOptions {@link CompressionOptions} or {@code null} if the default
      *        should be used.
      */
     public HttpContentCompressor(CompressionOptions... compressionOptions) {
         this(0, compressionOptions);
     }
 
     /**
      * Create a new {@link HttpContentCompressor} instance with specified
      * {@link CompressionOptions}s
      *
      * @param contentSizeThreshold
      *        The response body is compressed when the size of the response
      *        body exceeds the threshold. The value should be a non negative
      *        number. {@code 0} will enable compression for all responses.
      * @param compressionOptions {@link CompressionOptions} or {@code null}
      *        if the default should be used.
      */
     public HttpContentCompressor(int contentSizeThreshold, CompressionOptions... compressionOptions) {
         this.contentSizeThreshold = ObjectUtil.checkPositiveOrZero(contentSizeThreshold, "contentSizeThreshold");
         BrotliOptions brotliOptions = null;
         GzipOptions gzipOptions = null;
         DeflateOptions deflateOptions = null;
         ZstdOptions zstdOptions = null;
         SnappyOptions snappyOptions = null;
         if (compressionOptions == null || compressionOptions.length == 0) {
             compressionOptions = DEFAULT_COMPRESSION_OPTIONS;
         }
 
         ObjectUtil.deepCheckNotNull("compressionOptions", compressionOptions);
         for (CompressionOptions compressionOption : compressionOptions) {
             // BrotliOptions' class initialization depends on Brotli classes being on the classpath.
             // The Brotli.isAvailable check ensures that BrotliOptions will only get instantiated if Brotli is
             // on the classpath.
             // This results in the static analysis of native-image identifying the instanceof BrotliOptions check
             // and thus BrotliOptions itself as unreachable, enabling native-image to link all classes
             // at build time and not complain about the missing Brotli classes.
             if (Brotli.isAvailable() && compressionOption instanceof BrotliOptions) {
                 brotliOptions = (BrotliOptions) compressionOption;
             } else if (compressionOption instanceof GzipOptions) {
                 gzipOptions = (GzipOptions) compressionOption;
             } else if (compressionOption instanceof DeflateOptions) {
                 deflateOptions = (DeflateOptions) compressionOption;
             } else if (Zstd.isAvailable() && compressionOption instanceof ZstdOptions) {
                 zstdOptions = (ZstdOptions) compressionOption;
             } else if (compressionOption instanceof SnappyOptions) {
                 snappyOptions = (SnappyOptions) compressionOption;
             } else {
                 throw new IllegalArgumentException("Unsupported " + CompressionOptions.class.getSimpleName() +
                         ": " + compressionOption);
             }
         }
 
         this.gzipOptions = gzipOptions;
         this.deflateOptions = deflateOptions;
         this.brotliOptions = brotliOptions;
         this.zstdOptions = zstdOptions;
         this.snappyOptions = snappyOptions;
     }
 
     @Deprecated
     private static CompressionOptions[] defaultCompressionOptions(
             GzipOptions gzipOptions, DeflateOptions deflateOptions) {
         List<CompressionOptions> options = new ArrayList<>(5);
         options.add(gzipOptions);
         options.add(deflateOptions);
         options.add(StandardCompressionOptions.snappy());
 
         if (Brotli.isAvailable()) {
             options.add(StandardCompressionOptions.brotli());
         }
         if (Zstd.isAvailable()) {
             options.add(StandardCompressionOptions.zstd());
         }
         return options.toArray(new CompressionOptions[0]);
     }
 
     @Override
     public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
         this.ctx = ctx;
     }
 
     @Override
     protected Result beginEncode(HttpResponse httpResponse, String acceptEncoding) throws Exception {
         if (this.contentSizeThreshold > 0) {
             if (httpResponse instanceof HttpContent &&
                     ((HttpContent) httpResponse).content().readableBytes() < contentSizeThreshold) {
                 return null;
             }
         }
 
         String contentEncoding = httpResponse.headers().get(HttpHeaderNames.CONTENT_ENCODING);
         if (contentEncoding != null) {
             // Content-Encoding was set, either as something specific or as the IDENTITY encoding
             // Therefore, we should NOT encode here
             return null;
         }
 
         String targetContentEncoding = determineEncoding(acceptEncoding);
         if (targetContentEncoding == null) {
             return null;
         }
 
         Channel channel = ctx.channel();
         return new Result(targetContentEncoding,
                 EmbeddedChannel.builder()
                         .channelId(channel.id())
                         .hasDisconnect(channel.metadata().hasDisconnect())
                         .config(channel.config())
                         .handlers(createEncoderFor(targetContentEncoding))
                         .build());
     }
 
     private MessageToByteEncoder<ByteBuf> createEncoderFor(String targetContentEncoding) {
         switch (targetContentEncoding) {
             case "br":
                 if (brotliOptions == null || !Brotli.isAvailable()) {
                     throw new IllegalStateException("Brotli not configured");
                 }
                 return new BrotliEncoder(brotliOptions.parameters());
             case "zstd":
                 if (zstdOptions == null) {
                     throw new IllegalStateException("Zstd not configured");
                 }
                 return new ZstdEncoder(
                         zstdOptions.compressionLevel(),
                         zstdOptions.blockSize(),
                         zstdOptions.maxEncodeSize()
                 );
             case "snappy":
                 if (snappyOptions == null) {
                     throw new IllegalStateException("Snappy not configured");
                 }
                 return new SnappyFrameEncoder();
             case "gzip":
                 if (gzipOptions == null) {
                     throw new IllegalStateException("Gzip not configured");
                 }
                 return ZlibCodecFactory.newZlibEncoder(
                         ZlibWrapper.GZIP,
                         gzipOptions.compressionLevel(),
                         gzipOptions.windowBits(),
                         gzipOptions.memLevel()
                 );
             case "deflate":
                 if (deflateOptions == null) {
                     throw new IllegalStateException("Deflate not configured");
                 }
                 return ZlibCodecFactory.newZlibEncoder(
                         ZlibWrapper.ZLIB,
                         deflateOptions.compressionLevel(),
                         deflateOptions.windowBits(),
                         deflateOptions.memLevel()
                 );
             default:
                 throw new IllegalStateException("Unknown encoding: " + targetContentEncoding);
         }
     }
 
     @SuppressWarnings("FloatingPointEquality")
     protected String determineEncoding(String acceptEncoding) {
         float starQ = -1.0f;
         float brQ = -1.0f;
         float zstdQ = -1.0f;
         float snappyQ = -1.0f;
         float gzipQ = -1.0f;
         float deflateQ = -1.0f;
 
         int start = 0;
         int length = acceptEncoding.length();
         while (start < length) {
             int comma = acceptEncoding.indexOf(',', start);
             if (comma == -1) {
                 comma = length;
             }
             String encoding = acceptEncoding.substring(start, comma);
             float q = 1.0f;
             int equalsPos = encoding.indexOf('=');
             if (equalsPos != -1) {
                 try {
                     q = Float.parseFloat(encoding.substring(equalsPos + 1));
                 } catch (NumberFormatException e) {
                     // Ignore encoding
                     q = 0.0f;
                 }
             }
             if (encoding.contains("*")) {
                 starQ = q;
             } else if (encoding.contains("br") && q > brQ) {
                 brQ = q;
             } else if (encoding.contains("zstd") && q > zstdQ) {
                 zstdQ = q;
             } else if (encoding.contains("snappy") && q > snappyQ) {
                 snappyQ = q;
             } else if (encoding.contains("gzip") && q > gzipQ) {
                 gzipQ = q;
             } else if (encoding.contains("deflate") && q > deflateQ) {
                 deflateQ = q;
             }
             start = comma + 1;
         }
         if (brQ > 0.0f || zstdQ > 0.0f || snappyQ > 0.0f || gzipQ > 0.0f || deflateQ > 0.0f) {
             if (brQ != -1.0f && brQ >= zstdQ && this.brotliOptions != null) {
                 return "br";
             } else if (zstdQ != -1.0f && zstdQ >= snappyQ && this.zstdOptions != null) {
                 return "zstd";
             } else if (snappyQ != -1.0f && snappyQ >= gzipQ && this.snappyOptions != null) {
                 return "snappy";
             } else if (gzipQ != -1.0f && gzipQ >= deflateQ && this.gzipOptions != null) {
                 return "gzip";
             } else if (deflateQ != -1.0f && this.deflateOptions != null) {
                 return "deflate";
             }
         }
         if (starQ > 0.0f) {
             if (brQ == -1.0f && this.brotliOptions != null) {
                 return "br";
             }
             if (zstdQ == -1.0f && this.zstdOptions != null) {
                 return "zstd";
             }
             if (snappyQ == -1.0f && this.snappyOptions != null) {
                 return "snappy";
             }
             if (gzipQ == -1.0f && this.gzipOptions != null) {
                 return "gzip";
             }
             if (deflateQ == -1.0f && this.deflateOptions != null) {
                 return "deflate";
             }
         }
         return null;
     }
 
     @Deprecated
     @SuppressWarnings("FloatingPointEquality")
     protected ZlibWrapper determineWrapper(String acceptEncoding) {
         float starQ = -1.0f;
         float gzipQ = -1.0f;
         float deflateQ = -1.0f;
         for (String encoding : acceptEncoding.split(",")) {
             float q = 1.0f;
             int equalsPos = encoding.indexOf('=');
             if (equalsPos != -1) {
                 try {
                     q = Float.parseFloat(encoding.substring(equalsPos + 1));
                 } catch (NumberFormatException e) {
                     // Ignore encoding
                     q = 0.0f;
                 }
             }
             if (encoding.contains("*")) {
                 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;
     }
 
 }