/*
    * ====================================================================
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.client5.http.impl.classic;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.Locale;
  
  import org.apache.hc.client5.http.classic.ExecChain;
  import org.apache.hc.client5.http.classic.ExecChainHandler;
  import org.apache.hc.client5.http.config.RequestConfig;
  import org.apache.hc.client5.http.entity.DecompressingEntity;
  import org.apache.hc.client5.http.entity.DeflateInputStreamFactory;
  import org.apache.hc.client5.http.entity.GZIPInputStreamFactory;
  import org.apache.hc.client5.http.entity.InputStreamFactory;
  import org.apache.hc.client5.http.protocol.HttpClientContext;
  import org.apache.hc.core5.annotation.Contract;
  import org.apache.hc.core5.annotation.Internal;
  import org.apache.hc.core5.annotation.ThreadingBehavior;
  import org.apache.hc.core5.http.ClassicHttpRequest;
  import org.apache.hc.core5.http.ClassicHttpResponse;
  import org.apache.hc.core5.http.Header;
  import org.apache.hc.core5.http.HeaderElement;
  import org.apache.hc.core5.http.HttpEntity;
  import org.apache.hc.core5.http.HttpException;
  import org.apache.hc.core5.http.HttpHeaders;
  import org.apache.hc.core5.http.config.Lookup;
  import org.apache.hc.core5.http.config.RegistryBuilder;
  import org.apache.hc.core5.http.message.BasicHeaderValueParser;
  import org.apache.hc.core5.http.message.MessageSupport;
  import org.apache.hc.core5.http.message.ParserCursor;
  import org.apache.hc.core5.util.Args;
  
  /**
   * Request execution handler in the classic request execution chain
   * that is responsible for automatic response content decompression.
   * <p>
   * Further responsibilities such as communication with the opposite
   * endpoint is delegated to the next executor in the request execution
   * chain.
   * </p>
   *
   * @since 5.0
   */
  @Contract(threading = ThreadingBehavior.STATELESS)
  @Internal
  public final class ContentCompressionExec implements ExecChainHandler {
  
      private final Header acceptEncoding;
      private final Lookup<InputStreamFactory> decoderRegistry;
      private final boolean ignoreUnknown;
  
      /**
       * An empty immutable {@code String} array.
       */
      private static final String[] EMPTY_STRING_ARRAY = new String[0];
  
      public ContentCompressionExec(
              final List<String> acceptEncoding,
              final Lookup<InputStreamFactory> decoderRegistry,
              final boolean ignoreUnknown) {
          this.acceptEncoding = MessageSupport.format(HttpHeaders.ACCEPT_ENCODING,
              acceptEncoding != null ? acceptEncoding.toArray(
                      EMPTY_STRING_ARRAY) : new String[] {"gzip", "x-gzip", "deflate"});
  
          this.decoderRegistry = decoderRegistry != null ? decoderRegistry :
                  RegistryBuilder.<InputStreamFactory>create()
                          .register("gzip", GZIPInputStreamFactory.getInstance())
                          .register("x-gzip", GZIPInputStreamFactory.getInstance())
                          .register("deflate", DeflateInputStreamFactory.getInstance())
                          .build();
          this.ignoreUnknown = ignoreUnknown;
      }
  
     public ContentCompressionExec(final boolean ignoreUnknown) {
         this(null, null, ignoreUnknown);
     }
 
     /**
      * Handles {@code gzip} and {@code deflate} compressed entities by using the following
      * decoders:
      * <ul>
      * <li>gzip - see {@link java.util.zip.GZIPInputStream}</li>
      * <li>deflate - see {@link org.apache.hc.client5.http.entity.DeflateInputStream}</li>
      * </ul>
      */
     public ContentCompressionExec() {
         this(null, null, true);
     }
 
 
     @Override
     public ClassicHttpResponse execute(
             final ClassicHttpRequest request,
             final ExecChain.Scope scope,
             final ExecChain chain) throws IOException, HttpException {
         Args.notNull(request, "HTTP request");
         Args.notNull(scope, "Scope");
 
         final HttpClientContext clientContext = scope.clientContext;
         final RequestConfig requestConfig = clientContext.getRequestConfig();
 
         /* Signal support for Accept-Encoding transfer encodings. */
         if (!request.containsHeader(HttpHeaders.ACCEPT_ENCODING) && requestConfig.isContentCompressionEnabled()) {
             request.addHeader(acceptEncoding);
         }
 
         final ClassicHttpResponse response = chain.proceed(request, scope);
 
         final HttpEntity entity = response.getEntity();
         // entity can be null in case of 304 Not Modified, 204 No Content or similar
         // check for zero length entity.
         if (requestConfig.isContentCompressionEnabled() && entity != null && entity.getContentLength() != 0) {
             final String contentEncoding = entity.getContentEncoding();
             if (contentEncoding != null) {
                 final ParserCursor cursor = new ParserCursor(0, contentEncoding.length());
                 final HeaderElement[] codecs = BasicHeaderValueParser.INSTANCE.parseElements(contentEncoding, cursor);
                 for (final HeaderElement codec : codecs) {
                     final String codecname = codec.getName().toLowerCase(Locale.ROOT);
                     final InputStreamFactory decoderFactory = decoderRegistry.lookup(codecname);
                     if (decoderFactory != null) {
                         response.setEntity(new DecompressingEntity(response.getEntity(), decoderFactory));
                         response.removeHeaders(HttpHeaders.CONTENT_LENGTH);
                         response.removeHeaders(HttpHeaders.CONTENT_ENCODING);
                         response.removeHeaders(HttpHeaders.CONTENT_MD5);
                     } else {
                         if (!"identity".equals(codecname) && !ignoreUnknown) {
                             throw new HttpException("Unsupported Content-Encoding: " + codec.getName());
                         }
                     }
                 }
             }
         }
         return response;
     }
 
 }