/*
    * ====================================================================
    * 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 org.apache.hc.client5.http.HttpRoute;
  import org.apache.hc.client5.http.classic.BackoffManager;
  import org.apache.hc.client5.http.classic.ConnectionBackoffStrategy;
  import org.apache.hc.client5.http.classic.ExecChain;
  import org.apache.hc.client5.http.classic.ExecChainHandler;
  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.HttpException;
  import org.apache.hc.core5.util.Args;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Request execution handler in the classic request execution chain
   * that is responsible for execution of an {@link ConnectionBackoffStrategy}.
   * <p>
   * Further responsibilities such as communication with the opposite
   * endpoint is delegated to the next executor in the request execution
   * chain.
   * </p>
   *
   * @since 4.3
   */
  @Contract(threading = ThreadingBehavior.STATELESS)
  public final class BackoffStrategyExec implements ExecChainHandler {
  
      private static final Logger LOG = LoggerFactory.getLogger(BackoffStrategyExec.class);
  
      private final ConnectionBackoffStrategy connectionBackoffStrategy;
      private final BackoffManager backoffManager;
  
      /**
       * Constructs a {@code BackoffStrategyExec} with the specified
       * {@link ConnectionBackoffStrategy} and {@link BackoffManager}.
       *
       * @param connectionBackoffStrategy the strategy to determine whether
       *                                  to backoff based on the response or exception
       * @param backoffManager            the manager responsible for applying backoff
       *                                  and probing actions to the HTTP routes
       */
      public BackoffStrategyExec(
              final ConnectionBackoffStrategy connectionBackoffStrategy,
              final BackoffManager backoffManager) {
          super();
          Args.notNull(connectionBackoffStrategy, "Connection backoff strategy");
          Args.notNull(backoffManager, "Backoff manager");
          this.connectionBackoffStrategy = connectionBackoffStrategy;
          this.backoffManager = backoffManager;
      }
  
      @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 HttpRoute route = scope.route;
  
          final ClassicHttpResponse response;
          try {
              response = chain.proceed(request, scope);
          } catch (final IOException | HttpException ex) {
              if (this.connectionBackoffStrategy.shouldBackoff(ex)) {
                  if (LOG.isDebugEnabled()) {
                      LOG.debug("Backing off route {} due to exception: {}", route, ex.getMessage());
                 }
                 this.backoffManager.backOff(route);
             }
             throw ex;
         }
         if (this.connectionBackoffStrategy.shouldBackoff(response)) {
             if (LOG.isDebugEnabled()) {
                 LOG.debug("Backing off route {} due to response status: {}", route, response.getCode());
             }
             this.backoffManager.backOff(route);
         } else {
             if (LOG.isDebugEnabled()) {
                 LOG.debug("Probing route: {}", route);
             }
             this.backoffManager.probe(route);
         }
         return response;
     }
 
 }