/*
    * ====================================================================
    * 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.http.impl;
  
  import java.io.IOException;
  import java.net.SocketTimeoutException;
  
  import org.apache.http.HttpClientConnection;
  import org.apache.http.HttpConnectionMetrics;
  import org.apache.http.HttpEntity;
  import org.apache.http.HttpEntityEnclosingRequest;
  import org.apache.http.HttpException;
  import org.apache.http.HttpRequest;
  import org.apache.http.HttpResponse;
  import org.apache.http.HttpResponseFactory;
  import org.apache.http.annotation.NotThreadSafe;
  import org.apache.http.entity.ContentLengthStrategy;
  import org.apache.http.impl.entity.EntityDeserializer;
  import org.apache.http.impl.entity.EntitySerializer;
  import org.apache.http.impl.entity.LaxContentLengthStrategy;
  import org.apache.http.impl.entity.StrictContentLengthStrategy;
  import org.apache.http.impl.io.DefaultHttpResponseParser;
  import org.apache.http.impl.io.HttpRequestWriter;
  import org.apache.http.io.EofSensor;
  import org.apache.http.io.HttpMessageParser;
  import org.apache.http.io.HttpMessageWriter;
  import org.apache.http.io.HttpTransportMetrics;
  import org.apache.http.io.SessionInputBuffer;
  import org.apache.http.io.SessionOutputBuffer;
  import org.apache.http.message.LineFormatter;
  import org.apache.http.message.LineParser;
  import org.apache.http.params.HttpParams;
  
  /**
   * Abstract client-side HTTP connection capable of transmitting and receiving
   * data using arbitrary {@link SessionInputBuffer} and
   * {@link SessionOutputBuffer} implementations.
   * <p>
   * The following parameters can be used to customize the behavior of this
   * class:
   * <ul>
   *  <li>{@link org.apache.http.params.CoreProtocolPNames#STRICT_TRANSFER_ENCODING}</li>
   *  <li>{@link org.apache.http.params.CoreConnectionPNames#MAX_HEADER_COUNT}</li>
   *  <li>{@link org.apache.http.params.CoreConnectionPNames#MAX_LINE_LENGTH}</li>
   * </ul>
   *
   * @since 4.0
   */
  @NotThreadSafe
  public abstract class AbstractHttpClientConnection implements HttpClientConnection {
  
      private final EntitySerializer entityserializer;
      private final EntityDeserializer entitydeserializer;
  
      private SessionInputBuffer inbuffer = null;
      private SessionOutputBuffer outbuffer = null;
      private EofSensor eofSensor = null;
      private HttpMessageParser<HttpResponse> responseParser = null;
      private HttpMessageWriter<HttpRequest> requestWriter = null;
      private HttpConnectionMetricsImpl metrics = null;
  
      /**
       * Creates an instance of this class.
       * <p>
       * This constructor will invoke {@link #createEntityDeserializer()}
       * and {@link #createEntitySerializer()} methods in order to initialize
       * HTTP entity serializer and deserializer implementations for this
       * connection.
       */
      public AbstractHttpClientConnection() {
          super();
          this.entityserializer = createEntitySerializer();
          this.entitydeserializer = createEntityDeserializer();
      }
 
     /**
      * Asserts if the connection is open.
      *
      * @throws IllegalStateException if the connection is not open.
      */
     protected abstract void assertOpen() throws IllegalStateException;
 
     /**
      * Creates an instance of {@link EntityDeserializer} with the
      * {@link LaxContentLengthStrategy} implementation to be used for
      * de-serializing entities received over this connection.
      * <p>
      * This method can be overridden in a super class in order to create
      * instances of {@link EntityDeserializer} using a custom
      * {@link ContentLengthStrategy}.
      *
      * @return HTTP entity deserializer
      */
     protected EntityDeserializer createEntityDeserializer() {
         return new EntityDeserializer(new LaxContentLengthStrategy());
     }
 
     /**
      * Creates an instance of {@link EntitySerializer} with the
      * {@link StrictContentLengthStrategy} implementation to be used for
      * serializing HTTP entities sent over this connection.
      * <p>
      * This method can be overridden in a super class in order to create
      * instances of {@link EntitySerializer} using a custom
      * {@link ContentLengthStrategy}.
      *
      * @return HTTP entity serialzier.
      */
     protected EntitySerializer createEntitySerializer() {
         return new EntitySerializer(new StrictContentLengthStrategy());
     }
 
     /**
      * Creates an instance of {@link DefaultHttpResponseFactory} to be used
      * for creating {@link HttpResponse} objects received by over this
      * connection.
      * <p>
      * This method can be overridden in a super class in order to provide
      * a different implementation of the {@link HttpResponseFactory} interface.
      *
      * @return HTTP response factory.
      */
     protected HttpResponseFactory createHttpResponseFactory() {
         return new DefaultHttpResponseFactory();
     }
 
     /**
      * Creates an instance of {@link HttpMessageParser} to be used for parsing
      * HTTP responses received over this connection.
      * <p>
      * This method can be overridden in a super class in order to provide
      * a different implementation of the {@link HttpMessageParser} interface or
      * to pass a different implementation of the {@link LineParser} to the
      * the {@link DefaultHttpResponseParser} constructor.
      *
      * @param buffer the session input buffer.
      * @param responseFactory the HTTP response factory.
      * @param params HTTP parameters.
      * @return HTTP message parser.
      */
     protected HttpMessageParser<HttpResponse> createResponseParser(
             final SessionInputBuffer buffer,
             final HttpResponseFactory responseFactory,
             final HttpParams params) {
         return new DefaultHttpResponseParser(buffer, null, responseFactory, params);
     }
 
     /**
      * Creates an instance of {@link HttpMessageWriter} to be used for
      * writing out HTTP requests sent over this connection.
      * <p>
      * This method can be overridden in a super class in order to provide
      * a different implementation of the {@link HttpMessageWriter} interface or
      * to pass a different implementation of {@link LineFormatter} to the
      * the default implementation {@link HttpRequestWriter}.
      *
      * @param buffer the session output buffer
      * @param params HTTP parameters
      * @return HTTP message writer
      */
     protected HttpMessageWriter<HttpRequest> createRequestWriter(
             final SessionOutputBuffer buffer,
             final HttpParams params) {
         return new HttpRequestWriter(buffer, null, params);
     }
 
     /**
      * @since 4.1
      */
     protected HttpConnectionMetricsImpl createConnectionMetrics(
             final HttpTransportMetrics inTransportMetric,
             final HttpTransportMetrics outTransportMetric) {
         return new HttpConnectionMetricsImpl(inTransportMetric, outTransportMetric);
     }
 
     /**
      * Initializes this connection object with {@link SessionInputBuffer} and
      * {@link SessionOutputBuffer} instances to be used for sending and
      * receiving data. These session buffers can be bound to any arbitrary
      * physical output medium.
      * <p>
      * This method will invoke {@link #createHttpResponseFactory()},
      * {@link #createRequestWriter(SessionOutputBuffer, HttpParams)}
      * and {@link #createResponseParser(SessionInputBuffer, HttpResponseFactory, HttpParams)}
      * methods to initialize HTTP request writer and response parser for this
      * connection.
      *
      * @param inbuffer the session input buffer.
      * @param outbuffer the session output buffer.
      * @param params HTTP parameters.
      */
     protected void init(
             final SessionInputBuffer inbuffer,
             final SessionOutputBuffer outbuffer,
             final HttpParams params) {
         if (inbuffer == null) {
             throw new IllegalArgumentException("Input session buffer may not be null");
         }
         if (outbuffer == null) {
             throw new IllegalArgumentException("Output session buffer may not be null");
         }
         this.inbuffer = inbuffer;
         this.outbuffer = outbuffer;
         if (inbuffer instanceof EofSensor) {
             this.eofSensor = (EofSensor) inbuffer;
         }
         this.responseParser = createResponseParser(
                 inbuffer,
                 createHttpResponseFactory(),
                 params);
         this.requestWriter = createRequestWriter(
                 outbuffer, params);
         this.metrics = createConnectionMetrics(
                 inbuffer.getMetrics(),
                 outbuffer.getMetrics());
     }
 
     public boolean isResponseAvailable(int timeout) throws IOException {
         assertOpen();
         try {
             return this.inbuffer.isDataAvailable(timeout);
         } catch (SocketTimeoutException ex) {
             return false;
         }
     }
 
     public void sendRequestHeader(final HttpRequest request)
             throws HttpException, IOException {
         if (request == null) {
             throw new IllegalArgumentException("HTTP request may not be null");
         }
         assertOpen();
         this.requestWriter.write(request);
         this.metrics.incrementRequestCount();
     }
 
     public void sendRequestEntity(final HttpEntityEnclosingRequest request)
             throws HttpException, IOException {
         if (request == null) {
             throw new IllegalArgumentException("HTTP request may not be null");
         }
         assertOpen();
         if (request.getEntity() == null) {
             return;
         }
         this.entityserializer.serialize(
                 this.outbuffer,
                 request,
                 request.getEntity());
     }
 
     protected void doFlush() throws IOException {
         this.outbuffer.flush();
     }
 
     public void flush() throws IOException {
         assertOpen();
         doFlush();
     }
 
     public HttpResponse receiveResponseHeader()
             throws HttpException, IOException {
         assertOpen();
         HttpResponse response = this.responseParser.parse();
         if (response.getStatusLine().getStatusCode() >= 200) {
             this.metrics.incrementResponseCount();
         }
         return response;
     }
 
     public void receiveResponseEntity(final HttpResponse response)
             throws HttpException, IOException {
         if (response == null) {
             throw new IllegalArgumentException("HTTP response may not be null");
         }
         assertOpen();
         HttpEntity entity = this.entitydeserializer.deserialize(this.inbuffer, response);
         response.setEntity(entity);
     }
 
     protected boolean isEof() {
         return this.eofSensor != null && this.eofSensor.isEof();
     }
 
     public boolean isStale() {
         if (!isOpen()) {
             return true;
         }
         if (isEof()) {
             return true;
         }
         try {
             this.inbuffer.isDataAvailable(1);
             return isEof();
         } catch (SocketTimeoutException ex) {
             return false;
         } catch (IOException ex) {
             return true;
         }
     }
 
     public HttpConnectionMetrics getMetrics() {
         return this.metrics;
     }
 
 }