/*
    * ====================================================================
    * 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.IOException;
  import java.time.Instant;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.apache.hc.client5.http.async.methods.SimpleHttpResponse;
  import org.apache.hc.client5.http.cache.HttpCacheEntry;
  import org.apache.hc.client5.http.cache.ResourceIOException;
  import org.apache.hc.core5.http.EntityDetails;
  import org.apache.hc.core5.http.Header;
  import org.apache.hc.core5.http.HttpHeaders;
  import org.apache.hc.core5.http.HttpRequest;
  import org.apache.hc.core5.http.HttpResponse;
  import org.apache.hc.core5.http.HttpStatus;
  import org.apache.hc.core5.http.Method;
  
  public class CachingExecBase {
  
      final AtomicLong cacheHits = new AtomicLong();
      final AtomicLong cacheMisses = new AtomicLong();
      final AtomicLong cacheUpdates = new AtomicLong();
  
      final ResponseCachingPolicy responseCachingPolicy;
      final CacheValidityPolicy validityPolicy;
      final CachedHttpResponseGenerator responseGenerator;
      final CacheableRequestPolicy cacheableRequestPolicy;
      final CachedResponseSuitabilityChecker suitabilityChecker;
      final CacheConfig cacheConfig;
  
      CachingExecBase(
              final CacheValidityPolicy validityPolicy,
              final ResponseCachingPolicy responseCachingPolicy,
              final CachedHttpResponseGenerator responseGenerator,
              final CacheableRequestPolicy cacheableRequestPolicy,
              final CachedResponseSuitabilityChecker suitabilityChecker,
              final CacheConfig config) {
          this.responseCachingPolicy = responseCachingPolicy;
          this.validityPolicy = validityPolicy;
          this.responseGenerator = responseGenerator;
          this.cacheableRequestPolicy = cacheableRequestPolicy;
          this.suitabilityChecker = suitabilityChecker;
          this.cacheConfig = config != null ? config : CacheConfig.DEFAULT;
      }
  
      CachingExecBase(final CacheConfig config) {
          super();
          this.cacheConfig = config != null ? config : CacheConfig.DEFAULT;
          this.validityPolicy = new CacheValidityPolicy(config);
          this.responseGenerator = new CachedHttpResponseGenerator(this.validityPolicy);
          this.cacheableRequestPolicy = new CacheableRequestPolicy();
          this.suitabilityChecker = new CachedResponseSuitabilityChecker(this.validityPolicy, this.cacheConfig);
          this.responseCachingPolicy = new ResponseCachingPolicy(
                  this.cacheConfig.isSharedCache(),
                  this.cacheConfig.isNeverCacheHTTP10ResponsesWithQuery(),
                  this.cacheConfig.isNeverCacheHTTP11ResponsesWithQuery());
      }
  
      /**
       * Reports the number of times that the cache successfully responded
       * to an {@link HttpRequest} without contacting the origin server.
       * @return the number of cache hits
       */
      public long getCacheHits() {
          return cacheHits.get();
      }
  
      /**
       * Reports the number of times that the cache contacted the origin
       * server because it had no appropriate response cached.
       * @return the number of cache misses
       */
      public long getCacheMisses() {
         return cacheMisses.get();
     }
 
     /**
      * Reports the number of times that the cache was able to satisfy
      * a response by revalidating an existing but stale cache entry.
      * @return the number of cache revalidations
      */
     public long getCacheUpdates() {
         return cacheUpdates.get();
     }
 
     SimpleHttpResponse generateCachedResponse(
             final HttpRequest request,
             final HttpCacheEntry entry,
             final Instant now) throws ResourceIOException {
         if (shouldSendNotModifiedResponse(request, entry, now)) {
             return responseGenerator.generateNotModifiedResponse(entry);
         } else {
             return responseGenerator.generateResponse(request, entry);
         }
     }
 
     SimpleHttpResponse generateGatewayTimeout() {
         return SimpleHttpResponse.create(HttpStatus.SC_GATEWAY_TIMEOUT, "Gateway Timeout");
     }
 
     SimpleHttpResponse unvalidatedCacheHit(final HttpRequest request, final HttpCacheEntry entry) throws IOException {
         return responseGenerator.generateResponse(request, entry);
     }
 
     Instant getCurrentDate() {
         return Instant.now();
     }
 
     boolean clientRequestsOurOptions(final HttpRequest request) {
         if (!Method.OPTIONS.isSame(request.getMethod())) {
             return false;
         }
 
         if (!"*".equals(request.getRequestUri())) {
             return false;
         }
 
         final Header h = request.getFirstHeader(HttpHeaders.MAX_FORWARDS);
         return "0".equals(h != null ? h.getValue() : null);
     }
 
     boolean shouldSendNotModifiedResponse(final HttpRequest request, final HttpCacheEntry responseEntry, final Instant now) {
         return suitabilityChecker.isConditional(request)
                 && suitabilityChecker.allConditionalsMatch(request, responseEntry, now);
     }
 
     boolean staleIfErrorAppliesTo(final int statusCode) {
         return statusCode == HttpStatus.SC_INTERNAL_SERVER_ERROR
                 || statusCode == HttpStatus.SC_BAD_GATEWAY
                 || statusCode == HttpStatus.SC_SERVICE_UNAVAILABLE
                 || statusCode == HttpStatus.SC_GATEWAY_TIMEOUT;
     }
 
     /**
      * For 304 Not modified responses, adds a "Last-Modified" header with the
      * value of the "If-Modified-Since" header passed in the request. This
      * header is required to be able to reuse match the cache entry for
      * subsequent requests but as defined in http specifications it is not
      * included in 304 responses by backend servers. This header will not be
      * included in the resulting response.
      */
     void storeRequestIfModifiedSinceFor304Response(final HttpRequest request, final HttpResponse backendResponse) {
         if (backendResponse.getCode() == HttpStatus.SC_NOT_MODIFIED) {
             final Header h = request.getFirstHeader(HttpHeaders.IF_MODIFIED_SINCE);
             if (h != null) {
                 backendResponse.addHeader(HttpHeaders.LAST_MODIFIED, h.getValue());
             }
         }
     }
 
     boolean isResponseTooBig(final EntityDetails entityDetails) {
         if (entityDetails == null) {
             return false;
         }
         final long contentLength = entityDetails.getContentLength();
         if (contentLength == -1) {
             return false;
         }
         final long maxObjectSize = cacheConfig.getMaxObjectSize();
         return contentLength > maxObjectSize;
     }
 
 }