/*
    * 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.netty.handler.codec.http.websocketx.extensions.compression;
  
  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionData;
  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionDecoder;
  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionEncoder;
  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionFilterProvider;
  import io.netty.handler.codec.http.websocketx.extensions.WebSocketServerExtension;
  import io.netty.handler.codec.http.websocketx.extensions.WebSocketServerExtensionHandshaker;
  
  import java.util.Collections;
  
  import static io.netty.util.internal.ObjectUtil.*;
  
  /**
   * <a href="https://tools.ietf.org/id/draft-tyoshino-hybi-websocket-perframe-deflate-06.txt">perframe-deflate</a>
   * handshake implementation.
   */
  public final class DeflateFrameServerExtensionHandshaker implements WebSocketServerExtensionHandshaker {
  
      static final String X_WEBKIT_DEFLATE_FRAME_EXTENSION = "x-webkit-deflate-frame";
      static final String DEFLATE_FRAME_EXTENSION = "deflate-frame";
  
      private final int compressionLevel;
      private final WebSocketExtensionFilterProvider extensionFilterProvider;
  
      /**
       * Constructor with default configuration.
       */
      public DeflateFrameServerExtensionHandshaker() {
          this(6);
      }
  
      /**
       * Constructor with custom configuration.
       *
       * @param compressionLevel
       *            Compression level between 0 and 9 (default is 6).
       */
      public DeflateFrameServerExtensionHandshaker(int compressionLevel) {
          this(compressionLevel, WebSocketExtensionFilterProvider.DEFAULT);
      }
  
      /**
       * Constructor with custom configuration.
       *
       * @param compressionLevel
       *            Compression level between 0 and 9 (default is 6).
       * @param extensionFilterProvider
       *            provides server extension filters for per frame deflate encoder and decoder.
       */
      public DeflateFrameServerExtensionHandshaker(int compressionLevel,
              WebSocketExtensionFilterProvider extensionFilterProvider) {
          if (compressionLevel < 0 || compressionLevel > 9) {
              throw new IllegalArgumentException(
                      "compressionLevel: " + compressionLevel + " (expected: 0-9)");
          }
          this.compressionLevel = compressionLevel;
          this.extensionFilterProvider = checkNotNull(extensionFilterProvider, "extensionFilterProvider");
      }
  
      @Override
      public WebSocketServerExtension handshakeExtension(WebSocketExtensionData extensionData) {
          if (!X_WEBKIT_DEFLATE_FRAME_EXTENSION.equals(extensionData.name()) &&
              !DEFLATE_FRAME_EXTENSION.equals(extensionData.name())) {
              return null;
          }
  
          if (extensionData.parameters().isEmpty()) {
              return new DeflateFrameServerExtension(compressionLevel, extensionData.name(), extensionFilterProvider);
          } else {
              return null;
          }
      }
  
      private static class DeflateFrameServerExtension implements WebSocketServerExtension {
  
          private final String extensionName;
          private final int compressionLevel;
          private final WebSocketExtensionFilterProvider extensionFilterProvider;
  
          DeflateFrameServerExtension(int compressionLevel, String extensionName,
                  WebSocketExtensionFilterProvider extensionFilterProvider) {
              this.extensionName = extensionName;
              this.compressionLevel = compressionLevel;
             this.extensionFilterProvider = extensionFilterProvider;
         }
 
         @Override
         public int rsv() {
             return RSV1;
         }
 
         @Override
         public WebSocketExtensionEncoder newExtensionEncoder() {
             return new PerFrameDeflateEncoder(compressionLevel, 15, false,
                                               extensionFilterProvider.encoderFilter());
         }
 
         @Override
         public WebSocketExtensionDecoder newExtensionDecoder() {
             return new PerFrameDeflateDecoder(false, extensionFilterProvider.decoderFilter());
         }
 
         @Override
         public WebSocketExtensionData newReponseData() {
             return new WebSocketExtensionData(extensionName, Collections.<String, String>emptyMap());
         }
     }
 
 }