/*
    * 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.ChannelPipeline;
  import io.netty.channel.CombinedChannelDuplexHandler;
  import io.netty.handler.codec.PrematureChannelClosureException;
  
  import java.util.ArrayDeque;
  import java.util.List;
  import java.util.Queue;
  import java.util.concurrent.atomic.AtomicLong;
  
  import static io.netty.handler.codec.http.HttpObjectDecoder.DEFAULT_ALLOW_DUPLICATE_CONTENT_LENGTHS;
  import static io.netty.handler.codec.http.HttpObjectDecoder.DEFAULT_ALLOW_PARTIAL_CHUNKS;
  import static io.netty.handler.codec.http.HttpObjectDecoder.DEFAULT_MAX_CHUNK_SIZE;
  import static io.netty.handler.codec.http.HttpObjectDecoder.DEFAULT_MAX_HEADER_SIZE;
  import static io.netty.handler.codec.http.HttpObjectDecoder.DEFAULT_MAX_INITIAL_LINE_LENGTH;
  import static io.netty.handler.codec.http.HttpObjectDecoder.DEFAULT_VALIDATE_HEADERS;
  
  /**
   * A combination of {@link HttpRequestEncoder} and {@link HttpResponseDecoder}
   * which enables easier client side HTTP implementation. {@link HttpClientCodec}
   * provides additional state management for <tt>HEAD</tt> and <tt>CONNECT</tt>
   * requests, which {@link HttpResponseDecoder} lacks.  Please refer to
   * {@link HttpResponseDecoder} to learn what additional state management needs
   * to be done for <tt>HEAD</tt> and <tt>CONNECT</tt> and why
   * {@link HttpResponseDecoder} can not handle it by itself.
   * <p>
   * If the {@link Channel} is closed and there are missing responses,
   * a {@link PrematureChannelClosureException} is thrown.
   *
   * <h3>Header Validation</h3>
   *
   * It is recommended to always enable header validation.
   * <p>
   * Without header validation, your system can become vulnerable to
   * <a href="https://cwe.mitre.org/data/definitions/113.html">
   *     CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')
   * </a>.
   * <p>
   * This recommendation stands even when both peers in the HTTP exchange are trusted,
   * as it helps with defence-in-depth.
   *
   * @see HttpServerCodec
   */
  public final class HttpClientCodec extends CombinedChannelDuplexHandler<HttpResponseDecoder, HttpRequestEncoder>
          implements HttpClientUpgradeHandler.SourceCodec {
      public static final boolean DEFAULT_FAIL_ON_MISSING_RESPONSE = false;
      public static final boolean DEFAULT_PARSE_HTTP_AFTER_CONNECT_REQUEST = false;
  
      /** A queue that is used for correlating a request and a response. */
      private final Queue<HttpMethod> queue = new ArrayDeque<HttpMethod>();
      private final boolean parseHttpAfterConnectRequest;
  
      /** If true, decoding stops (i.e. pass-through) */
      private boolean done;
  
      private final AtomicLong requestResponseCounter = new AtomicLong();
      private final boolean failOnMissingResponse;
  
      /**
       * Creates a new instance with the default decoder options
       * ({@code maxInitialLineLength (4096)}, {@code maxHeaderSize (8192)}, and
       * {@code maxChunkSize (8192)}).
       */
      public HttpClientCodec() {
          this(new HttpDecoderConfig(),
                  DEFAULT_PARSE_HTTP_AFTER_CONNECT_REQUEST,
                  DEFAULT_FAIL_ON_MISSING_RESPONSE);
      }
  
      /**
       * Creates a new instance with the specified decoder options.
       */
      public HttpClientCodec(int maxInitialLineLength, int maxHeaderSize, int maxChunkSize) {
          this(new HttpDecoderConfig()
                          .setMaxInitialLineLength(maxInitialLineLength)
                          .setMaxHeaderSize(maxHeaderSize)
                          .setMaxChunkSize(maxChunkSize),
                  DEFAULT_PARSE_HTTP_AFTER_CONNECT_REQUEST,
                  DEFAULT_FAIL_ON_MISSING_RESPONSE);
      }
 
     /**
      * Creates a new instance with the specified decoder options.
      */
     public HttpClientCodec(
             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean failOnMissingResponse) {
         this(new HttpDecoderConfig()
                         .setMaxInitialLineLength(maxInitialLineLength)
                         .setMaxHeaderSize(maxHeaderSize)
                         .setMaxChunkSize(maxChunkSize),
                 DEFAULT_PARSE_HTTP_AFTER_CONNECT_REQUEST,
                 failOnMissingResponse);
     }
 
     /**
      * Creates a new instance with the specified decoder options.
      *
      * @deprecated Prefer the {@link #HttpClientCodec(int, int, int, boolean)} constructor,
      * to always enable header validation.
      */
     @Deprecated
     public HttpClientCodec(
             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean failOnMissingResponse,
             boolean validateHeaders) {
         this(new HttpDecoderConfig()
                         .setMaxInitialLineLength(maxInitialLineLength)
                         .setMaxHeaderSize(maxHeaderSize)
                         .setMaxChunkSize(maxChunkSize)
                         .setValidateHeaders(validateHeaders),
                 DEFAULT_PARSE_HTTP_AFTER_CONNECT_REQUEST,
                 failOnMissingResponse);
     }
 
     /**
      * Creates a new instance with the specified decoder options.
      *
      * @deprecated Prefer the {@link #HttpClientCodec(HttpDecoderConfig, boolean, boolean)} constructor,
      * to always enable header validation.
      */
     @Deprecated
     public HttpClientCodec(
             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean failOnMissingResponse,
             boolean validateHeaders, boolean parseHttpAfterConnectRequest) {
         this(new HttpDecoderConfig()
                         .setMaxInitialLineLength(maxInitialLineLength)
                         .setMaxHeaderSize(maxHeaderSize)
                         .setMaxChunkSize(maxChunkSize)
                         .setValidateHeaders(validateHeaders),
                 parseHttpAfterConnectRequest,
                 failOnMissingResponse);
     }
 
     /**
      * Creates a new instance with the specified decoder options.
      *
      * @deprecated Prefer the {@link #HttpClientCodec(HttpDecoderConfig, boolean, boolean)} constructor,
      * to always enable header validation.
      */
     @Deprecated
     public HttpClientCodec(
             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean failOnMissingResponse,
             boolean validateHeaders, int initialBufferSize) {
         this(new HttpDecoderConfig()
                         .setMaxInitialLineLength(maxInitialLineLength)
                         .setMaxHeaderSize(maxHeaderSize)
                         .setMaxChunkSize(maxChunkSize)
                         .setValidateHeaders(validateHeaders)
                         .setInitialBufferSize(initialBufferSize),
                 DEFAULT_PARSE_HTTP_AFTER_CONNECT_REQUEST,
                 failOnMissingResponse);
     }
 
     /**
      * Creates a new instance with the specified decoder options.
      *
      * @deprecated Prefer the {@link #HttpClientCodec(HttpDecoderConfig, boolean, boolean)} constructor,
      * to always enable header validation.
      */
     @Deprecated
     public HttpClientCodec(
             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean failOnMissingResponse,
             boolean validateHeaders, int initialBufferSize, boolean parseHttpAfterConnectRequest) {
         this(new HttpDecoderConfig()
                         .setMaxInitialLineLength(maxInitialLineLength)
                         .setMaxHeaderSize(maxHeaderSize)
                         .setMaxChunkSize(maxChunkSize)
                         .setValidateHeaders(validateHeaders)
                         .setInitialBufferSize(initialBufferSize),
                 parseHttpAfterConnectRequest,
                 failOnMissingResponse);
     }
     /**
      * Creates a new instance with the specified decoder options.
      *
      * @deprecated Prefer the {@link #HttpClientCodec(HttpDecoderConfig, boolean, boolean)} constructor,
      * to always enable header validation.
      */
     @Deprecated
     public HttpClientCodec(
             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean failOnMissingResponse,
             boolean validateHeaders, int initialBufferSize, boolean parseHttpAfterConnectRequest,
             boolean allowDuplicateContentLengths) {
         this(new HttpDecoderConfig()
                         .setMaxInitialLineLength(maxInitialLineLength)
                         .setMaxHeaderSize(maxHeaderSize)
                         .setMaxChunkSize(maxChunkSize)
                         .setValidateHeaders(validateHeaders)
                         .setInitialBufferSize(initialBufferSize)
                         .setAllowDuplicateContentLengths(allowDuplicateContentLengths),
                 parseHttpAfterConnectRequest,
                 failOnMissingResponse);
     }
 
     /**
      * Creates a new instance with the specified decoder options.
      *
      * @deprecated Prefer the {@link #HttpClientCodec(HttpDecoderConfig, boolean, boolean)}
      * constructor, to always enable header validation.
      */
     @Deprecated
     public HttpClientCodec(
             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean failOnMissingResponse,
             boolean validateHeaders, int initialBufferSize, boolean parseHttpAfterConnectRequest,
             boolean allowDuplicateContentLengths, boolean allowPartialChunks) {
         this(new HttpDecoderConfig()
                 .setMaxInitialLineLength(maxInitialLineLength)
                 .setMaxHeaderSize(maxHeaderSize)
                 .setMaxChunkSize(maxChunkSize)
                 .setValidateHeaders(validateHeaders)
                 .setInitialBufferSize(initialBufferSize)
                 .setAllowDuplicateContentLengths(allowDuplicateContentLengths)
                 .setAllowPartialChunks(allowPartialChunks),
                 parseHttpAfterConnectRequest,
                 failOnMissingResponse);
     }
 
     /**
      * Creates a new instance with the specified decoder options.
      */
     public HttpClientCodec(
             HttpDecoderConfig config, boolean parseHttpAfterConnectRequest, boolean failOnMissingResponse) {
         init(new Decoder(config), new Encoder());
         this.parseHttpAfterConnectRequest = parseHttpAfterConnectRequest;
         this.failOnMissingResponse = failOnMissingResponse;
     }
 
     /**
      * Prepares to upgrade to another protocol from HTTP. Disables the {@link Encoder}.
      */
     @Override
     public void prepareUpgradeFrom(ChannelHandlerContext ctx) {
         ((Encoder) outboundHandler()).upgraded = true;
     }
 
     /**
      * Upgrades to another protocol from HTTP. Removes the {@link Decoder} and {@link Encoder} from
      * the pipeline.
      */
     @Override
     public void upgradeFrom(ChannelHandlerContext ctx) {
         final ChannelPipeline p = ctx.pipeline();
         p.remove(this);
     }
 
     public void setSingleDecode(boolean singleDecode) {
         inboundHandler().setSingleDecode(singleDecode);
     }
 
     public boolean isSingleDecode() {
         return inboundHandler().isSingleDecode();
     }
 
     private final class Encoder extends HttpRequestEncoder {
 
         boolean upgraded;
 
         @Override
         protected void encode(
                 ChannelHandlerContext ctx, Object msg, List<Object> out) throws Exception {
 
             if (upgraded) {
                 // HttpObjectEncoder overrides .write and does not release msg, so we don't need to retain it here
                 out.add(msg);
                 return;
             }
 
             if (msg instanceof HttpRequest) {
                 queue.offer(((HttpRequest) msg).method());
             }
 
             super.encode(ctx, msg, out);
 
             if (failOnMissingResponse && !done) {
                 // check if the request is chunked if so do not increment
                 if (msg instanceof LastHttpContent) {
                     // increment as its the last chunk
                     requestResponseCounter.incrementAndGet();
                 }
             }
         }
     }
 
     private final class Decoder extends HttpResponseDecoder {
         Decoder(HttpDecoderConfig config) {
             super(config);
         }
 
         @Override
         protected void decode(
                 ChannelHandlerContext ctx, ByteBuf buffer, List<Object> out) throws Exception {
             if (done) {
                 int readable = actualReadableBytes();
                 if (readable == 0) {
                     // if non is readable just return null
                     // https://github.com/netty/netty/issues/1159
                     return;
                 }
                 out.add(buffer.readBytes(readable));
             } else {
                 int oldSize = out.size();
                 super.decode(ctx, buffer, out);
                 if (failOnMissingResponse) {
                     int size = out.size();
                     for (int i = oldSize; i < size; i++) {
                         decrement(out.get(i));
                     }
                 }
             }
         }
 
         private void decrement(Object msg) {
             if (msg == null) {
                 return;
             }
 
             // check if it's an Header and its transfer encoding is not chunked.
             if (msg instanceof LastHttpContent) {
                 requestResponseCounter.decrementAndGet();
             }
         }
 
         @Override
         protected boolean isContentAlwaysEmpty(HttpMessage msg) {
             // Get the method of the HTTP request that corresponds to the
             // current response.
             //
             // Even if we do not use the method to compare we still need to poll it to ensure we keep
             // request / response pairs in sync.
             HttpMethod method = queue.poll();
 
             final HttpResponseStatus status = ((HttpResponse) msg).status();
             final HttpStatusClass statusClass = status.codeClass();
             final int statusCode = status.code();
             if (statusClass == HttpStatusClass.INFORMATIONAL) {
                 // An informational response should be excluded from paired comparison.
                 // Just delegate to super method which has all the needed handling.
                 return super.isContentAlwaysEmpty(msg);
             }
 
             // If the remote peer did for example send multiple responses for one request (which is not allowed per
             // spec but may still be possible) method will be null so guard against it.
             if (method != null) {
                 char firstChar = method.name().charAt(0);
                 switch (firstChar) {
                     case 'H':
                         // According to 4.3, RFC2616:
                         // All responses to the HEAD request method MUST NOT include a
                         // message-body, even though the presence of entity-header fields
                         // might lead one to believe they do.
                         if (HttpMethod.HEAD.equals(method)) {
                             return true;
 
                             // The following code was inserted to work around the servers
                             // that behave incorrectly.  It has been commented out
                             // because it does not work with well behaving servers.
                             // Please note, even if the 'Transfer-Encoding: chunked'
                             // header exists in the HEAD response, the response should
                             // have absolutely no content.
                             //
                             //// Interesting edge case:
                             //// Some poorly implemented servers will send a zero-byte
                             //// chunk if Transfer-Encoding of the response is 'chunked'.
                             ////
                             //// return !msg.isChunked();
                         }
                         break;
                     case 'C':
                         // Successful CONNECT request results in a response with empty body.
                         if (statusCode == 200) {
                             if (HttpMethod.CONNECT.equals(method)) {
                                 // Proxy connection established - Parse HTTP only if configured by
                                 // parseHttpAfterConnectRequest, else pass through.
                                 if (!parseHttpAfterConnectRequest) {
                                     done = true;
                                     queue.clear();
                                 }
                                 return true;
                             }
                         }
                         break;
                     default:
                         break;
                 }
             }
             return super.isContentAlwaysEmpty(msg);
         }
 
         @Override
         public void channelInactive(ChannelHandlerContext ctx)
                 throws Exception {
             super.channelInactive(ctx);
 
             if (failOnMissingResponse) {
                 long missingResponses = requestResponseCounter.get();
                 if (missingResponses > 0) {
                     ctx.fireExceptionCaught(new PrematureChannelClosureException(
                             "channel gone inactive with " + missingResponses +
                             " missing response(s)"));
                 }
             }
         }
     }
 }