/*
    * ====================================================================
    * 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.io.Serializable;
  import java.util.Collections;
  import java.util.Date;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.Map;
  
  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.HttpStatus;
  import org.apache.hc.core5.http.MessageHeaders;
  import org.apache.hc.core5.http.ProtocolException;
  import org.apache.hc.core5.http.message.HeaderGroup;
  import org.apache.hc.core5.util.Args;
  
  /**
   * Structure used to store an {@link org.apache.hc.core5.http.HttpResponse} in a cache.
   * Some entries can optionally depend on system resources that may require
   * explicit deallocation. In such a case {@link #getResource()} should return
   * a non null instance of {@link Resource} that must be deallocated by calling
   * {@link Resource#dispose()} method when no longer used.
   *
   * @since 4.1
   */
  @Contract(threading = ThreadingBehavior.IMMUTABLE)
  public class HttpCacheEntry implements MessageHeaders, Serializable {
  
      private static final long serialVersionUID = -6300496422359477413L;
      private static final String REQUEST_METHOD_HEADER_NAME = "Hc-Request-Method";
  
      private final Date requestDate;
      private final Date responseDate;
      private final int status;
      private final HeaderGroup responseHeaders;
      private final Resource resource;
      private final Map<String, String> variantMap;
      private final Date date;
  
      /**
       * Create a new {@link HttpCacheEntry} with variants.
       * @param requestDate
       *          Date/time when the request was made (Used for age
       *            calculations)
       * @param responseDate
       *          Date/time that the response came back (Used for age
       *            calculations)
       * @param status
       *          HTTP status from origin response
       * @param responseHeaders
       *          Header[] from original HTTP Response
       * @param resource representing origin response body
       * @param variantMap 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(
              final Date requestDate,
              final Date responseDate,
              final int status,
              final Header[] responseHeaders,
              final Resource resource,
              final Map<String, String> variantMap) {
          super();
          Args.notNull(requestDate, "Request date");
          Args.notNull(responseDate, "Response date");
          Args.check(status >= HttpStatus.SC_SUCCESS, "Status code");
          Args.notNull(responseHeaders, "Response headers");
         this.requestDate = requestDate;
         this.responseDate = responseDate;
         this.status = status;
         this.responseHeaders = new HeaderGroup();
         this.responseHeaders.setHeaders(responseHeaders);
         this.resource = resource;
         this.variantMap = variantMap != null ? new HashMap<>(variantMap) : null;
         this.date = parseDate();
     }
 
     /**
      * Create a new {@link HttpCacheEntry}.
      *
      * @param requestDate
      *          Date/time when the request was made (Used for age
      *            calculations)
      * @param responseDate
      *          Date/time that the response came back (Used for age
      *            calculations)
      * @param status
      *          HTTP status from origin response
      * @param responseHeaders
      *          Header[] from original HTTP Response
      * @param resource representing origin response body
      */
     public HttpCacheEntry(final Date requestDate, final Date responseDate, final int status,
             final Header[] responseHeaders, final Resource resource) {
         this(requestDate, responseDate, status, responseHeaders, resource, new HashMap<String,String>());
     }
 
     /**
      * Find the "Date" response header and parse it into a java.util.Date
      * @return the Date value of the header or null if the header is not present
      */
     private Date parseDate() {
         return DateUtils.parseDate(this, HttpHeaders.DATE);
     }
 
     /**
      * Returns the status from the origin {@link org.apache.hc.core5.http.HttpResponse}.
      */
     public int getStatus() {
         return this.status;
     }
 
     /**
      * Returns the time the associated origin request was initiated by the
      * caching module.
      * @return {@link Date}
      */
     public Date getRequestDate() {
         return requestDate;
     }
 
     /**
      * Returns the time the origin response was received by the caching module.
      * @return {@link Date}
      */
     public Date getResponseDate() {
         return responseDate;
     }
 
     /**
      * Returns all the headers that were on the origin response.
      */
     @Override
     public Header[] getHeaders() {
         final HeaderGroup filteredHeaders = new HeaderGroup();
         for (final Iterator<Header> iterator = responseHeaders.headerIterator(); iterator.hasNext();) {
             final Header header = iterator.next();
             if (!REQUEST_METHOD_HEADER_NAME.equals(header.getName())) {
                 filteredHeaders.addHeader(header);
             }
         }
         return filteredHeaders.getHeaders();
     }
 
     /**
      * Returns the first header from the origin response with the given
      * name.
      */
     @Override
     public Header getFirstHeader(final String name) {
         if (REQUEST_METHOD_HEADER_NAME.equalsIgnoreCase(name)) {
             return null;
         }
         return responseHeaders.getFirstHeader(name);
     }
 
     /**
      * @since 5.0
      */
     @Override
     public Header getLastHeader(final String name) {
         return responseHeaders.getLastHeader(name);
     }
 
     /**
      * Gets all the headers with the given name that were on the origin
      * response.
      */
     @Override
     public Header[] getHeaders(final String name) {
         if (REQUEST_METHOD_HEADER_NAME.equalsIgnoreCase(name)) {
             return new Header[0];
         }
         return responseHeaders.getHeaders(name);
     }
 
     /**
      * @since 5.0
      */
     @Override
     public boolean containsHeader(final String name) {
         return responseHeaders.containsHeader(name);
     }
 
     /**
      * @since 5.0
      */
     @Override
     public int countHeaders(final String name) {
         return responseHeaders.countHeaders(name);
     }
 
     /**
      * @since 5.0
      */
     @Override
     public Header getHeader(final String name) throws ProtocolException {
         return responseHeaders.getHeader(name);
     }
 
     /**
      * @since 5.0
      */
     @Override
     public Iterator<Header> headerIterator() {
         return responseHeaders.headerIterator();
     }
 
     /**
      * @since 5.0
      */
     @Override
     public Iterator<Header> headerIterator(final String name) {
         return responseHeaders.headerIterator(name);
     }
 
     /**
      * Gets the Date value of the "Date" header or null if the header is missing or cannot be
      * parsed.
      *
      * @since 4.3
      */
     public Date getDate() {
         return date;
     }
 
     /**
      * Returns the {@link Resource} containing the origin response body.
      */
     public Resource getResource() {
         return this.resource;
     }
 
     /**
      * Indicates whether the origin response indicated the associated
      * resource had variants (i.e. that the Vary header was set on the
      * origin response).
      * @return {@code true} if this cached response was a variant
      */
     public boolean hasVariants() {
         return getFirstHeader(HeaderConstants.VARY) != null;
     }
 
     /**
      * Returns an index about where in the cache different variants for
      * a given resource are stored. This maps "variant keys" to "cache keys",
      * where the variant key is derived from the varying request headers,
      * and the cache key is the location in the
      * {@link HttpCacheStorage} where that
      * particular variant is stored. The first variant returned is used as
      * the "parent" entry to hold this index of the other variants.
      */
     public Map<String, String> getVariantMap() {
         return Collections.unmodifiableMap(variantMap);
     }
 
     /**
      * Returns the HTTP request method that was used to create the cached
      * response entry.
      *
      * @since 4.4
      */
     public String getRequestMethod() {
         final Header requestMethodHeader = responseHeaders.getFirstHeader(REQUEST_METHOD_HEADER_NAME);
         if (requestMethodHeader != null) {
             return requestMethodHeader.getValue();
         }
         return HeaderConstants.GET_METHOD;
     }
 
     /**
      * Provides a string representation of this instance suitable for
      * human consumption.
      */
     @Override
     public String toString() {
         return "[request date=" + this.requestDate + "; response date=" + this.responseDate
                 + "; status=" + this.status + "]";
     }
 
 }