/*
    * ====================================================================
    * 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.cache;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.Set;
  import java.util.concurrent.Future;
  import java.util.concurrent.RejectedExecutionException;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.ScheduledFuture;
  import java.util.concurrent.ScheduledThreadPoolExecutor;
  
  import org.apache.hc.client5.http.cache.HeaderConstants;
  import org.apache.hc.client5.http.schedule.ConcurrentCountMap;
  import org.apache.hc.client5.http.schedule.SchedulingStrategy;
  import org.apache.hc.core5.http.Header;
  import org.apache.hc.core5.http.HttpResponse;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.TimeValue;
  import org.apache.hc.core5.util.Timeout;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Abstract cache re-validation class.
   */
  class CacheRevalidatorBase implements Closeable {
  
      interface ScheduledExecutor {
  
          Future<?> schedule(Runnable command, TimeValue timeValue) throws RejectedExecutionException;
  
          void shutdown();
  
          void awaitTermination(final Timeout timeout) throws InterruptedException;
  
      }
  
      public static ScheduledExecutor wrap(final ScheduledExecutorService executorService) {
  
          return new ScheduledExecutor() {
  
              @Override
              public ScheduledFuture<?> schedule(final Runnable command, final TimeValue timeValue) throws RejectedExecutionException {
                  Args.notNull(command, "Runnable");
                  Args.notNull(timeValue, "Time value");
                  return executorService.schedule(command, timeValue.getDuration(), timeValue.getTimeUnit());
              }
  
              @Override
              public void shutdown() {
                  executorService.shutdown();
              }
  
              @Override
              public void awaitTermination(final Timeout timeout) throws InterruptedException {
                  Args.notNull(timeout, "Timeout");
                  executorService.awaitTermination(timeout.getDuration(), timeout.getTimeUnit());
              }
  
          };
  
      }
  
      private final ScheduledExecutor scheduledExecutor;
      private final SchedulingStrategy schedulingStrategy;
      private final Set<String> pendingRequest;
      private final ConcurrentCountMap<String> failureCache;
  
      private static final Logger LOG = LoggerFactory.getLogger(CacheRevalidatorBase.class);
  
      /**
      * Create CacheValidator which will make ache revalidation requests
      * using the supplied {@link SchedulingStrategy} and {@link ScheduledExecutor}.
      */
     public CacheRevalidatorBase(
             final ScheduledExecutor scheduledExecutor,
             final SchedulingStrategy schedulingStrategy) {
         this.scheduledExecutor = scheduledExecutor;
         this.schedulingStrategy = schedulingStrategy;
         this.pendingRequest = new HashSet<>();
         this.failureCache = new ConcurrentCountMap<>();
     }
 
     /**
      * Create CacheValidator which will make ache revalidation requests
      * using the supplied {@link SchedulingStrategy} and {@link ScheduledThreadPoolExecutor}.
      */
     public CacheRevalidatorBase(
             final ScheduledThreadPoolExecutor scheduledThreadPoolExecutor,
             final SchedulingStrategy schedulingStrategy) {
         this(wrap(scheduledThreadPoolExecutor), schedulingStrategy);
     }
 
     /**
      * Schedules an asynchronous re-validation
      */
     void scheduleRevalidation(final String cacheKey, final Runnable command) {
         synchronized (pendingRequest) {
             if (!pendingRequest.contains(cacheKey)) {
                 final int consecutiveFailedAttempts = failureCache.getCount(cacheKey);
                 final TimeValue executionTime = schedulingStrategy.schedule(consecutiveFailedAttempts);
                 try {
                     scheduledExecutor.schedule(command, executionTime);
                     pendingRequest.add(cacheKey);
                 } catch (final RejectedExecutionException ex) {
                     LOG.debug("Revalidation of cache entry with key {} could not be scheduled", cacheKey, ex);
                 }
             }
         }
     }
 
     @Override
     public void close() throws IOException {
         scheduledExecutor.shutdown();
     }
 
     public void awaitTermination(final Timeout timeout) throws InterruptedException {
         Args.notNull(timeout, "Timeout");
         scheduledExecutor.awaitTermination(timeout);
     }
 
     void jobSuccessful(final String identifier) {
         failureCache.resetCount(identifier);
         synchronized (pendingRequest) {
             pendingRequest.remove(identifier);
         }
     }
 
     void jobFailed(final String identifier) {
         failureCache.increaseCount(identifier);
         synchronized (pendingRequest) {
             pendingRequest.remove(identifier);
         }
     }
 
     Set<String> getScheduledIdentifiers() {
         synchronized (pendingRequest) {
             return new HashSet<>(pendingRequest);
         }
     }
 
     /**
      * Determines if the given response is generated from a stale cache entry.
      * @param httpResponse the response to be checked
      * @return whether the response is stale or not
      */
     boolean isStale(final HttpResponse httpResponse) {
         for (final Iterator<Header> it = httpResponse.headerIterator(HeaderConstants.WARNING); it.hasNext(); ) {
             /*
              * warn-codes
              * 110 = Response is stale
              * 111 = Revalidation failed
              */
             final Header warning = it.next();
             final String warningValue = warning.getValue();
             if (warningValue.startsWith("110") || warningValue.startsWith("111")) {
                 return true;
             }
         }
         return false;
     }
 
 }