/*
    * ====================================================================
    * 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.core5.http.impl.io;
  
  import java.io.IOException;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.apache.hc.core5.annotation.Contract;
  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.ConnectionReuseStrategy;
  import org.apache.hc.core5.http.ContentType;
  import org.apache.hc.core5.http.HeaderElements;
  import org.apache.hc.core5.http.HttpException;
  import org.apache.hc.core5.http.HttpHeaders;
  import org.apache.hc.core5.http.HttpRequestMapper;
  import org.apache.hc.core5.http.HttpResponseFactory;
  import org.apache.hc.core5.http.HttpStatus;
  import org.apache.hc.core5.http.HttpVersion;
  import org.apache.hc.core5.http.ProtocolVersion;
  import org.apache.hc.core5.http.UnsupportedHttpVersionException;
  import org.apache.hc.core5.http.impl.DefaultConnectionReuseStrategy;
  import org.apache.hc.core5.http.impl.Http1StreamListener;
  import org.apache.hc.core5.http.impl.ServerSupport;
  import org.apache.hc.core5.http.io.HttpRequestHandler;
  import org.apache.hc.core5.http.io.HttpServerConnection;
  import org.apache.hc.core5.http.io.HttpServerRequestHandler;
  import org.apache.hc.core5.http.io.entity.EntityUtils;
  import org.apache.hc.core5.http.io.entity.StringEntity;
  import org.apache.hc.core5.http.io.support.BasicHttpServerExpectationDecorator;
  import org.apache.hc.core5.http.io.support.BasicHttpServerRequestHandler;
  import org.apache.hc.core5.http.message.BasicClassicHttpResponse;
  import org.apache.hc.core5.http.message.MessageSupport;
  import org.apache.hc.core5.http.protocol.HttpContext;
  import org.apache.hc.core5.http.protocol.HttpCoreContext;
  import org.apache.hc.core5.http.protocol.HttpProcessor;
  import org.apache.hc.core5.util.Args;
  
  /**
   * {@code HttpService} is a server side HTTP protocol handler based on
   * the classic (blocking) I/O model.
   * <p>
   * {@code HttpService} relies on {@link HttpProcessor} to generate mandatory
   * protocol headers for all outgoing messages and apply common, cross-cutting
   * message transformations to all incoming and outgoing messages, whereas
   * individual {@link HttpRequestHandler}s are expected to implement
   * application specific content generation and processing.
   * <p>
   * {@code HttpService} uses {@link HttpRequestMapper} to map
   * matching request handler for a particular request URI of an incoming HTTP
   * request.
   *
   * @since 4.0
   */
  @Contract(threading = ThreadingBehavior.IMMUTABLE_CONDITIONAL)
  public class HttpService {
  
      private final HttpProcessor processor;
      private final HttpServerRequestHandler requestHandler;
      private final ConnectionReuseStrategy connReuseStrategy;
      private final Http1StreamListener streamListener;
  
      /**
       * Create a new HTTP service.
       *
       * @param processor the processor to use on requests and responses
       * @param handlerMapper  the handler mapper
       * @param responseFactory  the response factory. If {@code null}
       *   {@link DefaultClassicHttpResponseFactory#INSTANCE} will be used.
       * @param connReuseStrategy the connection reuse strategy. If {@code null}
       *   {@link DefaultConnectionReuseStrategy#INSTANCE} will be used.
       * @param streamListener message stream listener.
       */
     public HttpService(
             final HttpProcessor processor,
             final HttpRequestMapper<HttpRequestHandler> handlerMapper,
             final ConnectionReuseStrategy connReuseStrategy,
             final HttpResponseFactory<ClassicHttpResponse> responseFactory,
             final Http1StreamListener streamListener) {
         this(processor,
                 new BasicHttpServerExpectationDecorator(new BasicHttpServerRequestHandler(handlerMapper, responseFactory)),
                 connReuseStrategy,
                 streamListener);
     }
 
     /**
      * Create a new HTTP service.
      *
      * @param processor the processor to use on requests and responses
      * @param handlerMapper  the handler mapper
      * @param connReuseStrategy the connection reuse strategy. If {@code null}
      *   {@link DefaultConnectionReuseStrategy#INSTANCE} will be used.
      * @param responseFactory  the response factory. If {@code null}
      *   {@link DefaultClassicHttpResponseFactory#INSTANCE} will be used.
      */
     public HttpService(
             final HttpProcessor processor,
             final HttpRequestMapper<HttpRequestHandler> handlerMapper,
             final ConnectionReuseStrategy connReuseStrategy,
             final HttpResponseFactory<ClassicHttpResponse> responseFactory) {
         this(processor, handlerMapper, connReuseStrategy, responseFactory, null);
     }
 
     /**
      * Create a new HTTP service.
      *
      * @param processor the processor to use on requests and responses
      * @param requestHandler  the request handler.
      * @param connReuseStrategy the connection reuse strategy. If {@code null}
      *   {@link DefaultConnectionReuseStrategy#INSTANCE} will be used.
      * @param streamListener message stream listener.
      */
     public HttpService(
             final HttpProcessor processor,
             final HttpServerRequestHandler requestHandler,
             final ConnectionReuseStrategy connReuseStrategy,
             final Http1StreamListener streamListener) {
         super();
         this.processor =  Args.notNull(processor, "HTTP processor");
         this.requestHandler =  Args.notNull(requestHandler, "Request handler");
         this.connReuseStrategy = connReuseStrategy != null ? connReuseStrategy : DefaultConnectionReuseStrategy.INSTANCE;
         this.streamListener = streamListener;
     }
 
     /**
      * Create a new HTTP service.
      *
      * @param processor the processor to use on requests and responses
      * @param requestHandler  the request handler.
      */
     public HttpService(
             final HttpProcessor processor, final HttpServerRequestHandler requestHandler) {
         this(processor, requestHandler, null, null);
     }
 
     /**
      * Handles receives one HTTP request over the given connection within the
      * given execution context and sends a response back to the client.
      *
      * @param conn the active connection to the client
      * @param context the actual execution context.
      * @throws IOException in case of an I/O error.
      * @throws HttpException in case of HTTP protocol violation or a processing
      *   problem.
      */
     public void handleRequest(
             final HttpServerConnection conn,
             final HttpContext context) throws IOException, HttpException {
 
         final AtomicBoolean responseSubmitted = new AtomicBoolean(false);
         try {
             final ClassicHttpRequest request = conn.receiveRequestHeader();
             if (streamListener != null) {
                 streamListener.onRequestHead(conn, request);
             }
             conn.receiveRequestEntity(request);
             final ProtocolVersion transportVersion = request.getVersion();
             context.setProtocolVersion(transportVersion != null ? transportVersion : HttpVersion.HTTP_1_1);
             context.setAttribute(HttpCoreContext.SSL_SESSION, conn.getSSLSession());
             context.setAttribute(HttpCoreContext.CONNECTION_ENDPOINT, conn.getEndpointDetails());
             context.setAttribute(HttpCoreContext.HTTP_REQUEST, request);
             this.processor.process(request, request.getEntity(), context);
 
             this.requestHandler.handle(request, new HttpServerRequestHandler.ResponseTrigger() {
 
                 @Override
                 public void sendInformation(final ClassicHttpResponse response) throws HttpException, IOException {
                     if (responseSubmitted.get()) {
                         throw new HttpException("Response already submitted");
                     }
                     if (response.getCode() >= HttpStatus.SC_SUCCESS) {
                         throw new HttpException("Invalid intermediate response");
                     }
                     if (streamListener != null) {
                         streamListener.onResponseHead(conn, response);
                     }
                     conn.sendResponseHeader(response);
                     conn.flush();
                 }
 
                 @Override
                 public void submitResponse(final ClassicHttpResponse response) throws HttpException, IOException {
                     try {
                         final ProtocolVersion transportVersion = response.getVersion();
                         if (transportVersion != null && transportVersion.greaterEquals(HttpVersion.HTTP_2)) {
                             throw new UnsupportedHttpVersionException(transportVersion);
                         }
                         ServerSupport.validateResponse(response, response.getEntity());
                         context.setProtocolVersion(transportVersion != null ? transportVersion : HttpVersion.HTTP_1_1);
                         context.setAttribute(HttpCoreContext.HTTP_RESPONSE, response);
                         processor.process(response, response.getEntity(), context);
 
                         responseSubmitted.set(true);
                         conn.sendResponseHeader(response);
                         if (streamListener != null) {
                             streamListener.onResponseHead(conn, response);
                         }
                         if (MessageSupport.canResponseHaveBody(request.getMethod(), response)) {
                             conn.sendResponseEntity(response);
                         }
                         // Make sure the request content is fully consumed
                         EntityUtils.consume(request.getEntity());
                         final boolean keepAlive = connReuseStrategy.keepAlive(request, response, context);
                         if (streamListener != null) {
                             streamListener.onExchangeComplete(conn, keepAlive);
                         }
                         if (!keepAlive) {
                             conn.close();
                         }
                         conn.flush();
                     } finally {
                         response.close();
                     }
                 }
 
             }, context);
 
         } catch (final HttpException ex) {
             if (responseSubmitted.get()) {
                 throw ex;
             }
             try (final ClassicHttpResponse errorResponse = new BasicClassicHttpResponse(HttpStatus.SC_INTERNAL_SERVER_ERROR)) {
                 handleException(ex, errorResponse);
                 errorResponse.setHeader(HttpHeaders.CONNECTION, HeaderElements.CLOSE);
                 context.setAttribute(HttpCoreContext.HTTP_RESPONSE, errorResponse);
                 this.processor.process(errorResponse, errorResponse.getEntity(), context);
 
                 conn.sendResponseHeader(errorResponse);
                 if (streamListener != null) {
                     streamListener.onResponseHead(conn, errorResponse);
                 }
                 conn.sendResponseEntity(errorResponse);
                 conn.close();
             }
         }
     }
 
     /**
      * Handles the given exception and generates an HTTP response to be sent
      * back to the client to inform about the exceptional condition encountered
      * in the course of the request processing.
      *
      * @param ex the exception.
      * @param response the HTTP response.
      */
     protected void handleException(final HttpException ex, final ClassicHttpResponse response) {
         response.setCode(toStatusCode(ex));
         response.setEntity(new StringEntity(ServerSupport.toErrorMessage(ex), ContentType.TEXT_PLAIN));
     }
 
     protected int toStatusCode(final Exception ex) {
         return ServerSupport.toStatusCode(ex);
     }
 
 }