/*
    * ====================================================================
    * 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.async;
  
  import java.io.IOException;
  
  import org.apache.hc.client5.http.HttpRequestRetryStrategy;
  import org.apache.hc.client5.http.async.AsyncExecCallback;
  import org.apache.hc.client5.http.async.AsyncExecChain;
  import org.apache.hc.client5.http.async.AsyncExecChainHandler;
  import org.apache.hc.client5.http.impl.ChainElement;
  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.EntityDetails;
  import org.apache.hc.core5.http.HttpException;
  import org.apache.hc.core5.http.HttpHost;
  import org.apache.hc.core5.http.HttpRequest;
  import org.apache.hc.core5.http.HttpResponse;
  import org.apache.hc.core5.http.nio.AsyncDataConsumer;
  import org.apache.hc.core5.http.nio.AsyncEntityProducer;
  import org.apache.hc.core5.http.nio.entity.DiscardingEntityConsumer;
  import org.apache.hc.core5.http.support.BasicRequestBuilder;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.TimeValue;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Request executor in the asynchronous request execution chain that is
   * responsible for making a decision whether a request that failed due to
   * an I/O exception or received a specific response from the target server should
   * be re-executed.
   * <p>
   * Further responsibilities such as communication with the opposite
   * endpoint is delegated to the next executor in the request execution
   * chain.
   * </p>
   * <p>
   * If this handler is active, pay particular attention to the placement
   * of other handlers within the handler chain relative to the retry handler.
   * Use {@link ChainElement#RETRY} as name when referring to this handler.
   * </p>
   * <p>
   * If a custom handler is placed <b>before</b> the retry handler, the handler will
   * see the initial request and the final outcome after the last retry. Elapsed time
   * will account for any delays imposed by the retry handler.
   * </p>
   *
   * <p>
   * A custom handler which is placed <b>after</b> the retry handler will be invoked for
   * each individual retry. Elapsed time will measure each individual http request,
   * without the delay imposed by the retry handler.
   * </p>
   *
   * @since 5.0
   */
  @Contract(threading = ThreadingBehavior.STATELESS)
  @Internal
  public final class AsyncHttpRequestRetryExec implements AsyncExecChainHandler {
  
      private static final Logger LOG = LoggerFactory.getLogger(AsyncHttpRequestRetryExec.class);
  
      private final HttpRequestRetryStrategy retryStrategy;
  
      public AsyncHttpRequestRetryExec(final HttpRequestRetryStrategy retryStrategy) {
          Args.notNull(retryStrategy, "retryStrategy");
          this.retryStrategy = retryStrategy;
      }
  
      private static class State {
  
          volatile boolean retrying;
          volatile int status;
         volatile TimeValue delay;
 
     }
 
     private void internalExecute(
             final State state,
             final HttpRequest request,
             final AsyncEntityProducer entityProducer,
             final AsyncExecChain.Scope scope,
             final AsyncExecChain chain,
             final AsyncExecCallback asyncExecCallback) throws HttpException, IOException {
 
         final String exchangeId = scope.exchangeId;
 
         chain.proceed(BasicRequestBuilder.copy(request).build(), entityProducer, scope, new AsyncExecCallback() {
 
             @Override
             public AsyncDataConsumer handleResponse(
                     final HttpResponse response,
                     final EntityDetails entityDetails) throws HttpException, IOException {
                 final HttpClientContext clientContext = scope.clientContext;
                 if (entityProducer != null && !entityProducer.isRepeatable()) {
                     if (LOG.isDebugEnabled()) {
                         LOG.debug("{} cannot retry non-repeatable request", exchangeId);
                     }
                     return asyncExecCallback.handleResponse(response, entityDetails);
                 }
                 state.retrying = retryStrategy.retryRequest(response, scope.execCount.get(), clientContext);
                 if (state.retrying) {
                     state.status = response.getCode();
                     state.delay = retryStrategy.getRetryInterval(response, scope.execCount.get(), clientContext);
                     return new DiscardingEntityConsumer<>();
                 }
                 return asyncExecCallback.handleResponse(response, entityDetails);
             }
 
             @Override
             public void handleInformationResponse(final HttpResponse response) throws HttpException, IOException {
                 asyncExecCallback.handleInformationResponse(response);
             }
 
             @Override
             public void completed() {
                 if (state.retrying) {
                     final int execCount = scope.execCount.incrementAndGet();
                     if (entityProducer != null) {
                        entityProducer.releaseResources();
                     }
                     final HttpHost target = scope.route.getTargetHost();
                     final TimeValue delay = TimeValue.isPositive(state.delay) ? state.delay : TimeValue.ZERO_MILLISECONDS;
                     if (LOG.isInfoEnabled()) {
                         LOG.info("{} {} responded with status {}; " +
                                         "request will be automatically re-executed in {} (exec count {})",
                                 exchangeId, target, state.status, delay, execCount);
                     }
                     scope.scheduler.scheduleExecution(
                             request,
                             entityProducer,
                             scope,
                             (r, e, s, c) -> execute(r, e, s, chain, c),
                             asyncExecCallback,
                             delay);
                 } else {
                     asyncExecCallback.completed();
                 }
             }
 
             @Override
             public void failed(final Exception cause) {
                 if (cause instanceof IOException) {
                     final HttpHost target = scope.route.getTargetHost();
                     final HttpClientContext clientContext = scope.clientContext;
                     if (entityProducer != null && !entityProducer.isRepeatable()) {
                         if (LOG.isDebugEnabled()) {
                             LOG.debug("{} cannot retry non-repeatable request", exchangeId);
                         }
                     } else if (retryStrategy.retryRequest(request, (IOException) cause, scope.execCount.get(), clientContext)) {
                         if (LOG.isDebugEnabled()) {
                             LOG.debug("{} {}", exchangeId, cause.getMessage(), cause);
                         }
                         scope.execRuntime.discardEndpoint();
                         if (entityProducer != null) {
                             entityProducer.releaseResources();
                         }
                         state.retrying = true;
                         final int execCount = scope.execCount.incrementAndGet();
                         state.delay = retryStrategy.getRetryInterval(request, (IOException) cause, execCount - 1, clientContext);
                         final TimeValue delay = TimeValue.isPositive(state.delay) ? state.delay : TimeValue.ZERO_MILLISECONDS;
                         if (LOG.isInfoEnabled()) {
                             LOG.info("{} recoverable I/O exception ({}) caught when sending request to {};" +
                                             "request will be automatically re-executed in {} (exec count {})",
                                     exchangeId, cause.getClass().getName(), target, delay, execCount);
                         }
                         scope.scheduler.scheduleExecution(
                                 request,
                                 entityProducer,
                                 scope,
                                 (r, e, s, c) -> execute(r, e, s, chain, c),
                                 asyncExecCallback,
                                 delay);
                         return;
                     }
                 }
                 asyncExecCallback.failed(cause);
             }
 
         });
 
     }
 
     @Override
     public void execute(
             final HttpRequest request,
             final AsyncEntityProducer entityProducer,
             final AsyncExecChain.Scope scope,
             final AsyncExecChain chain,
             final AsyncExecCallback asyncExecCallback) throws HttpException, IOException {
         final State state = new State();
         state.retrying = false;
         internalExecute(state, request, entityProducer, scope, chain, asyncExecCallback);
     }
 
 }