/*
    * 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:
    *
    * 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.netty5.handler.codec.http2;
  
  import io.netty5.buffer.api.Buffer;
  import io.netty5.channel.ChannelHandlerContext;
  import io.netty5.channel.embedded.EmbeddedChannel;
  import io.netty5.handler.codec.ByteToMessageDecoder;
  import io.netty5.handler.codec.compression.Brotli;
  import io.netty5.handler.codec.compression.BrotliCompressor;
  import io.netty5.handler.codec.compression.BrotliOptions;
  import io.netty5.handler.codec.compression.CompressionOptions;
  import io.netty5.handler.codec.compression.Compressor;
  import io.netty5.handler.codec.compression.DeflateOptions;
  import io.netty5.handler.codec.compression.GzipOptions;
  import io.netty5.handler.codec.compression.StandardCompressionOptions;
  import io.netty5.handler.codec.compression.ZlibCompressor;
  import io.netty5.handler.codec.compression.ZlibWrapper;
  import io.netty5.handler.codec.compression.ZstdCompressor;
  import io.netty5.handler.codec.compression.ZstdOptions;
  import io.netty5.util.concurrent.Future;
  import io.netty5.util.concurrent.Promise;
  import io.netty5.util.concurrent.PromiseCombiner;
  import io.netty5.util.internal.ObjectUtil;
  import io.netty5.util.internal.UnstableApi;
  
  import static io.netty5.handler.codec.http.HttpHeaderNames.CONTENT_ENCODING;
  import static io.netty5.handler.codec.http.HttpHeaderNames.CONTENT_LENGTH;
  import static io.netty5.handler.codec.http.HttpHeaderValues.BR;
  import static io.netty5.handler.codec.http.HttpHeaderValues.DEFLATE;
  import static io.netty5.handler.codec.http.HttpHeaderValues.GZIP;
  import static io.netty5.handler.codec.http.HttpHeaderValues.IDENTITY;
  import static io.netty5.handler.codec.http.HttpHeaderValues.X_DEFLATE;
  import static io.netty5.handler.codec.http.HttpHeaderValues.X_GZIP;
  import static io.netty5.handler.codec.http.HttpHeaderValues.ZSTD;
  import static java.util.Objects.requireNonNull;
  
  /**
   * A decorating HTTP2 encoder that will compress data frames according to the {@code content-encoding} header for each
   * stream. The compression provided by this class will be applied to the data for the entire stream.
   */
  @UnstableApi
  public class CompressorHttp2ConnectionEncoder extends DecoratingHttp2ConnectionEncoder {
      private int compressionLevel;
      private int windowBits;
      private int memLevel;
      private final Http2Connection.PropertyKey propertyKey;
  
      private final boolean supportsCompressionOptions;
  
      private BrotliOptions brotliOptions;
      private GzipOptions gzipCompressionOptions;
      private DeflateOptions deflateOptions;
      private ZstdOptions zstdOptions;
  
      /**
       * Create a new {@link CompressorHttp2ConnectionEncoder} instance
       * with default implementation of {@link StandardCompressionOptions}
       */
      public CompressorHttp2ConnectionEncoder(Http2ConnectionEncoder delegate) {
          this(delegate, defaultCompressionOptions());
      }
  
      /**
       * Create a new {@link CompressorHttp2ConnectionEncoder} instance
       */
      @Deprecated
      public CompressorHttp2ConnectionEncoder(Http2ConnectionEncoder delegate, int compressionLevel, int windowBits,
                                              int memLevel) {
          super(delegate);
          this.compressionLevel = ObjectUtil.checkInRange(compressionLevel, 0, 9, "compressionLevel");
          this.windowBits = ObjectUtil.checkInRange(windowBits, 9, 15, "windowBits");
          this.memLevel = ObjectUtil.checkInRange(memLevel, 1, 9, "memLevel");
  
          propertyKey = connection().newKey();
          connection().addListener(new Http2ConnectionAdapter() {
              @Override
              public void onStreamRemoved(Http2Stream stream) {
                  final Compressor compressor = stream.getProperty(propertyKey);
                  if (compressor != null) {
                      cleanup(stream, compressor);
                  }
              }
          });
  
          supportsCompressionOptions = false;
      }
 
     /**
      * Create a new {@link CompressorHttp2ConnectionEncoder} with
      * specified {@link StandardCompressionOptions}
      */
     public CompressorHttp2ConnectionEncoder(Http2ConnectionEncoder delegate,
                                             CompressionOptions... compressionOptionsArgs) {
         super(delegate);
         requireNonNull(compressionOptionsArgs, "CompressionOptions");
         ObjectUtil.deepCheckNotNull("CompressionOptions", compressionOptionsArgs);
 
         for (CompressionOptions compressionOptions : compressionOptionsArgs) {
             // 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() && compressionOptions instanceof BrotliOptions) {
                 brotliOptions = (BrotliOptions) compressionOptions;
             } else if (compressionOptions instanceof GzipOptions) {
                 gzipCompressionOptions = (GzipOptions) compressionOptions;
             } else if (compressionOptions instanceof DeflateOptions) {
                 deflateOptions = (DeflateOptions) compressionOptions;
             } else if (compressionOptions instanceof ZstdOptions) {
                 zstdOptions = (ZstdOptions) compressionOptions;
             } else {
                 throw new IllegalArgumentException("Unsupported " + CompressionOptions.class.getSimpleName() +
                         ": " + compressionOptions);
             }
         }
 
         supportsCompressionOptions = true;
 
         propertyKey = connection().newKey();
         connection().addListener(new Http2ConnectionAdapter() {
             @Override
             public void onStreamRemoved(Http2Stream stream) {
                 final Compressor compressor = stream.getProperty(propertyKey);
                 if (compressor != null) {
                     cleanup(stream, compressor);
                 }
             }
         });
     }
 
     private static CompressionOptions[] defaultCompressionOptions() {
         if (Brotli.isAvailable()) {
             return new CompressionOptions[] {
                     StandardCompressionOptions.brotli(),
                     StandardCompressionOptions.gzip(),
                     StandardCompressionOptions.deflate() };
         }
         return new CompressionOptions[] { StandardCompressionOptions.gzip(), StandardCompressionOptions.deflate() };
     }
 
     @Override
     public Future<Void> writeData(final ChannelHandlerContext ctx, final int streamId, Buffer data, int padding,
                                   final boolean endOfStream) {
         final Http2Stream stream = connection().stream(streamId);
         final Compressor compressor = stream == null ? null : (Compressor) stream.getProperty(propertyKey);
         if (compressor == null) {
             // The compressor may be null if no compatible encoding type was found in this stream's headers
             return super.writeData(ctx, streamId, data, padding, endOfStream);
         }
 
         try {
             Buffer buf = compressor.compress(data, ctx.bufferAllocator());
             if (buf.readableBytes() == 0) {
                 buf.close();
                 if (endOfStream) {
                     buf = compressor.finish(ctx.bufferAllocator());
                     return super.writeData(ctx, streamId, buf, padding,
                             true);
                 }
                 // END_STREAM is not set and the assumption is data is still forthcoming.
                 return ctx.newSucceededFuture();
             }
 
             Future<Void> future = super.writeData(ctx, streamId, buf, padding, false);
             if (endOfStream) {
                 Promise<Void> promise = ctx.newPromise();
                 PromiseCombiner combiner = new PromiseCombiner(ctx.executor());
                 combiner.add(future);
 
                 buf = compressor.finish(ctx.bufferAllocator());
 
                 // Padding is only communicated once on the first iteration
                 future = super.writeData(ctx, streamId, buf, 0, true);
                 combiner.add(future);
                 combiner.finish(promise);
                 return promise.asFuture();
             }
             return future;
 
         } catch (Throwable cause) {
             return ctx.newFailedFuture(cause);
         } finally {
             if (endOfStream) {
                 cleanup(stream, compressor);
             }
         }
     }
 
     @Override
     public Future<Void> writeHeaders(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int padding,
             boolean endStream) {
         try {
             // Determine if compression is required and sanitize the headers.
             Compressor compressor = newCompressor(ctx, headers, endStream);
 
             // Write the headers and create the stream object.
             Future<Void> future = super.writeHeaders(ctx, streamId, headers, padding, endStream);
 
             // After the stream object has been created, then attach the compressor as a property for data compression.
             bindCompressorToStream(compressor, streamId);
 
             return future;
         } catch (Throwable e) {
             return ctx.newFailedFuture(e);
         }
     }
 
     @Override
     public Future<Void> writeHeaders(final ChannelHandlerContext ctx, final int streamId, final Http2Headers headers,
             final int streamDependency, final short weight, final boolean exclusive, final int padding,
             final boolean endOfStream) {
         try {
             // Determine if compression is required and sanitize the headers.
             Compressor compressor = newCompressor(ctx, headers, endOfStream);
 
             // Write the headers and create the stream object.
             Future<Void> future = super.writeHeaders(ctx, streamId, headers, streamDependency, weight, exclusive,
                                                       padding, endOfStream);
 
             // After the stream object has been created, then attach the compressor as a property for data compression.
             bindCompressorToStream(compressor, streamId);
 
             return future;
         } catch (Throwable e) {
             return ctx.newFailedFuture(e);
         }
     }
 
     /**
      * Returns a new {@link Compressor} that encodes the HTTP2 message content encoded in the specified
      * {@code contentEncoding}.
      *
      * @param ctx the context.
      * @param contentEncoding the value of the {@code content-encoding} header
      * @return a new {@link ByteToMessageDecoder} if the specified encoding is supported.
      * Otherwise {@code null}.
      * Alternatively, you can throw a {@link Http2Exception} to block unknown encoding.
      * @throws Http2Exception If the specified encoding is not supported and warrants an exception
      */
     protected Compressor newContentCompressor(ChannelHandlerContext ctx, CharSequence contentEncoding)
             throws Http2Exception {
         if (GZIP.contentEqualsIgnoreCase(contentEncoding) || X_GZIP.contentEqualsIgnoreCase(contentEncoding)) {
             return newCompressionChannel(ctx, ZlibWrapper.GZIP);
         }
         if (DEFLATE.contentEqualsIgnoreCase(contentEncoding) || X_DEFLATE.contentEqualsIgnoreCase(contentEncoding)) {
             return newCompressionChannel(ctx, ZlibWrapper.ZLIB);
         }
         if (Brotli.isAvailable() && brotliOptions != null && BR.contentEqualsIgnoreCase(contentEncoding)) {
             return BrotliCompressor.newFactory(brotliOptions.parameters()).get();
         }
         if (zstdOptions != null && ZSTD.contentEqualsIgnoreCase(contentEncoding)) {
             return ZstdCompressor.newFactory(zstdOptions.compressionLevel(),
                     zstdOptions.blockSize(), zstdOptions.maxEncodeSize()).get();
         }
         // 'identity' or unsupported
         return null;
     }
 
     /**
      * Returns the expected content encoding of the decoded content. Returning {@code contentEncoding} is the default
      * behavior, which is the case for most compressors.
      *
      * @param contentEncoding the value of the {@code content-encoding} header
      * @return the expected content encoding of the new content.
      * @throws Http2Exception if the {@code contentEncoding} is not supported and warrants an exception
      */
     protected CharSequence getTargetContentEncoding(CharSequence contentEncoding) throws Http2Exception {
         return contentEncoding;
     }
 
     /**
      * Generate a new instance of an {@link Compressor} capable of compressing data
      * @param ctx the context.
      * @param wrapper Defines what type of encoder should be used
      */
     private Compressor newCompressionChannel(final ChannelHandlerContext ctx, ZlibWrapper wrapper) {
         if (supportsCompressionOptions) {
             if (wrapper == ZlibWrapper.GZIP && gzipCompressionOptions != null) {
                 return ZlibCompressor.newFactory(wrapper, gzipCompressionOptions.compressionLevel()).get();
             } else if (wrapper == ZlibWrapper.ZLIB && deflateOptions != null) {
                 return ZlibCompressor.newFactory(wrapper, deflateOptions.compressionLevel()).get();
             } else {
                 throw new IllegalArgumentException("Unsupported ZlibWrapper: " + wrapper);
             }
         }
         return ZlibCompressor.newFactory(wrapper, compressionLevel).get();
     }
 
     /**
      * Checks if a new compressor object is needed for the stream identified by {@code streamId}. This method will
      * modify the {@code content-encoding} header contained in {@code headers}.
      *
      * @param ctx the context.
      * @param headers Object representing headers which are to be written
      * @param endOfStream Indicates if the stream has ended
      * @return The channel used to compress data.
      * @throws Http2Exception if any problems occur during initialization.
      */
     private Compressor newCompressor(ChannelHandlerContext ctx, Http2Headers headers, boolean endOfStream)
             throws Http2Exception {
         if (endOfStream) {
             return null;
         }
 
         CharSequence encoding = headers.get(CONTENT_ENCODING);
         if (encoding == null) {
             encoding = IDENTITY;
         }
         final Compressor compressor = newContentCompressor(ctx, encoding);
         if (compressor != null) {
             CharSequence targetContentEncoding = getTargetContentEncoding(encoding);
             if (IDENTITY.contentEqualsIgnoreCase(targetContentEncoding)) {
                 headers.remove(CONTENT_ENCODING);
             } else {
                 headers.set(CONTENT_ENCODING, targetContentEncoding);
             }
 
             // The content length will be for the decompressed data. Since we will compress the data
             // this content-length will not be correct. Instead of queuing messages or delaying sending
             // header frames...just remove the content-length header
             headers.remove(CONTENT_LENGTH);
         }
 
         return compressor;
     }
 
     /**
      * Called after the super class has written the headers and created any associated stream objects.
      * @param compressor The compressor associated with the stream identified by {@code streamId}.
      * @param streamId The stream id for which the headers were written.
      */
     private void bindCompressorToStream(Compressor compressor, int streamId) {
         if (compressor != null) {
             Http2Stream stream = connection().stream(streamId);
             if (stream != null) {
                 stream.setProperty(propertyKey, compressor);
             }
         }
     }
 
     /**
      * Release remaining content from {@link EmbeddedChannel} and remove the compressor from the {@link Http2Stream}.
      *
      * @param stream The stream for which {@code compressor} is the compressor for
      * @param compressor The compressor for {@code stream}
      */
     void cleanup(Http2Stream stream, Compressor compressor) {
         compressor.close();
         stream.removeProperty(propertyKey);
     }
 }