/*
    * ====================================================================
    * 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.cache;
  
  import java.net.URI;
  import java.time.Instant;
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.Locale;
  import java.util.Set;
  
  import org.apache.hc.client5.http.impl.cache.CacheKeyGenerator;
  import org.apache.hc.client5.http.utils.DateUtils;
  import org.apache.hc.core5.annotation.Contract;
  import org.apache.hc.core5.annotation.ThreadingBehavior;
  import org.apache.hc.core5.http.Header;
  import org.apache.hc.core5.http.HttpHeaders;
  import org.apache.hc.core5.http.HttpHost;
  import org.apache.hc.core5.http.HttpMessage;
  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.message.BasicHeader;
  import org.apache.hc.core5.http.message.HeaderGroup;
  import org.apache.hc.core5.http.message.MessageSupport;
  import org.apache.hc.core5.util.Args;
  
  /**
   * {@link HttpCacheEntry} factory.
   *
   * @since 5.4
   */
  @Contract(threading = ThreadingBehavior.IMMUTABLE)
  public class HttpCacheEntryFactory {
  
      /**
       * Default instance of {@link HttpCacheEntryFactory}.
       */
      public static final HttpCacheEntryFactory INSTANCE = new HttpCacheEntryFactory();
  
      private static HeaderGroup headers(final Iterator<Header> it) {
          final HeaderGroup headerGroup = new HeaderGroup();
          while (it.hasNext()) {
              headerGroup.addHeader(it.next());
          }
          return headerGroup;
      }
  
      HeaderGroup mergeHeaders(final HttpCacheEntry entry, final HttpResponse response) {
          final HeaderGroup headerGroup = new HeaderGroup();
          for (final Iterator<Header> it = entry.headerIterator(); it.hasNext(); ) {
              final Header entryHeader = it.next();
              final String headerName = entryHeader.getName();
              if (!response.containsHeader(headerName)) {
                  headerGroup.addHeader(entryHeader);
              }
          }
          final Set<String> responseHopByHop = MessageSupport.hopByHopConnectionSpecific(response);
          for (final Iterator<Header> it = response.headerIterator(); it.hasNext(); ) {
              final Header responseHeader = it.next();
              final String headerName = responseHeader.getName();
              if (!responseHopByHop.contains(headerName.toLowerCase(Locale.ROOT))) {
                  headerGroup.addHeader(responseHeader);
              }
          }
          return headerGroup;
      }
  
      /**
       * This method should be provided by the core
       */
      static HeaderGroup filterHopByHopHeaders(final HttpMessage message) {
          final Set<String> hopByHop = MessageSupport.hopByHopConnectionSpecific(message);
          final HeaderGroup headerGroup = new HeaderGroup();
         for (final Iterator<Header> it = message.headerIterator(); it.hasNext(); ) {
             final Header header = it.next();
             if (!hopByHop.contains(header.getName())) {
                 headerGroup.addHeader(header);
             }
         }
         return headerGroup;
     }
 
     static void ensureDate(final HeaderGroup headers, final Instant instant) {
         if (!headers.containsHeader(HttpHeaders.DATE)) {
             headers.addHeader(new BasicHeader(HttpHeaders.DATE, DateUtils.formatStandardDate(instant)));
         }
     }
 
     /**
      * Creates a new root {@link HttpCacheEntry} (parent of multiple variants).
      *
      * @param latestVariant    The most recently created variant entry
      * @param variants         describing cache entries that are variants of this parent entry; this
      *                         maps a "variant key" (derived from the varying request headers) to a
      *                         "cache key" (where in the cache storage the particular variant is
      *                         located)
      */
     public HttpCacheEntry createRoot(final HttpCacheEntry latestVariant,
                                      final Collection<String> variants) {
         Args.notNull(latestVariant, "Request");
         Args.notNull(variants, "Variants");
         return new HttpCacheEntry(
                 latestVariant.getRequestInstant(),
                 latestVariant.getResponseInstant(),
                 latestVariant.getRequestMethod(),
                 latestVariant.getRequestURI(),
                 headers(latestVariant.requestHeaderIterator()),
                 latestVariant.getStatus(),
                 headers(latestVariant.headerIterator()),
                 null,
                 variants);
     }
 
     /**
      * Create a new {@link HttpCacheEntry} with the given {@link Resource}.
      *
      * @param requestInstant   Date/time when the request was made (Used for age calculations)
      * @param responseInstant  Date/time that the response came back (Used for age calculations)
      * @param host             Target host
      * @param request          Original client request (a deep copy of this object is made)
      * @param response         Origin response (a deep copy of this object is made)
      * @param resource         Resource representing origin response body
      */
     public HttpCacheEntry create(final Instant requestInstant,
                                  final Instant responseInstant,
                                  final HttpHost host,
                                  final HttpRequest request,
                                  final HttpResponse response,
                                  final Resource resource) {
         Args.notNull(requestInstant, "Request instant");
         Args.notNull(responseInstant, "Response instant");
         Args.notNull(host, "Host");
         Args.notNull(request, "Request");
         Args.notNull(response, "Origin response");
         final String s = CacheKeyGenerator.getRequestUri(host, request);
         final URI uri = CacheKeyGenerator.normalize(s);
         final HeaderGroup requestHeaders = filterHopByHopHeaders(request);
         // Strip AUTHORIZATION from request headers
         requestHeaders.removeHeaders(HttpHeaders.AUTHORIZATION);
         final HeaderGroup responseHeaders = filterHopByHopHeaders(response);
         ensureDate(responseHeaders, responseInstant);
         return new HttpCacheEntry(
                 requestInstant,
                 responseInstant,
                 request.getMethod(),
                 uri.toASCIIString(),
                 requestHeaders,
                 response.getCode(),
                 responseHeaders,
                 resource,
                 null);
     }
 
     /**
      * Creates updated entry with the new information from the response. Should only be used for
      * 304 responses.
      *
      * @param requestInstant   Date/time when the request was made (Used for age calculations)
      * @param responseInstant  Date/time that the response came back (Used for age calculations)
      * @param host             Target host
      * @param request          Original client request (a deep copy of this object is made)
      * @param response         Origin response (a deep copy of this object is made)
      * @param entry            Existing cache entry.
      */
     public HttpCacheEntry createUpdated(
             final Instant requestInstant,
             final Instant responseInstant,
             final HttpHost host,
             final HttpRequest request,
             final HttpResponse response,
             final HttpCacheEntry entry) {
         Args.notNull(requestInstant, "Request instant");
         Args.notNull(responseInstant, "Response instant");
         Args.notNull(response, "Origin response");
         Args.check(response.getCode() == HttpStatus.SC_NOT_MODIFIED,
                 "Response must have 304 status code");
         Args.notNull(entry, "Cache entry");
         if (HttpCacheEntry.isNewer(entry, response)) {
             return entry;
         }
         final String s = CacheKeyGenerator.getRequestUri(host, request);
         final URI uri = CacheKeyGenerator.normalize(s);
         final HeaderGroup requestHeaders = filterHopByHopHeaders(request);
         // Strip AUTHORIZATION from request headers
         requestHeaders.removeHeaders(HttpHeaders.AUTHORIZATION);
         final HeaderGroup mergedHeaders = mergeHeaders(entry, response);
         return new HttpCacheEntry(
                 requestInstant,
                 responseInstant,
                 request.getMethod(),
                 uri.toASCIIString(),
                 requestHeaders,
                 entry.getStatus(),
                 mergedHeaders,
                 entry.getResource(),
                 null);
     }
 
     /**
      * Creates a copy of the given {@link HttpCacheEntry}. Please note the underlying
      * {@link Resource} is copied by reference.
      */
     public HttpCacheEntry copy(final HttpCacheEntry entry) {
         if (entry == null) {
             return null;
         }
         return new HttpCacheEntry(
                 entry.getRequestInstant(),
                 entry.getResponseInstant(),
                 entry.getRequestMethod(),
                 entry.getRequestURI(),
                 headers(entry.requestHeaderIterator()),
                 entry.getStatus(),
                 headers(entry.headerIterator()),
                 entry.getResource(),
                 entry.hasVariants() ? new HashSet<>(entry.getVariants()) : null);
     }
 
 }