/*
 * 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.
 */
package org.apache.juneau.http.header;

import java.time.*;
import java.util.function.*;

import org.apache.juneau.http.annotation.*;

/**
 * Represents a parsed <l>Last-Modified</l> HTTP response header.
 *
 * <p>
 * The last modified date for the requested object (in "HTTP-date" format as defined by RFC 7231).
 *
 * <h5 class='figure'>Example</h5>
 * <p class='bcode'>
 *    Last-Modified: Tue, 15 Nov 1994 12:45:26 GMT
 * </p>
 *
 * <h5 class='topic'>RFC2616 Specification</h5>
 *
 * The Last-Modified entity-header field indicates the date and time at which the origin server believes the variant was
 * last modified.
 *
 * <p class='bcode'>
 *    Last-Modified  = "Last-Modified" ":" HTTP-date
 * </p>
 *
 * <p>
 * An example of its use is...
 * <p class='bcode'>
 *    Last-Modified: Tue, 15 Nov 1994 12:45:26 GMT
 * </p>
 *
 * <p>
 * The exact meaning of this header field depends on the implementation of the origin server and the nature of the
 * original resource.
 * For files, it may be just the file system last-modified time.
 * For entities with dynamically included parts, it may be the most recent of the set of last-modify times for its
 * component parts.
 * For database gateways, it may be the last-update time stamp of the record.
 * For virtual objects, it may be the last time the internal state changed.
 *
 * <p>
 * An origin server MUST NOT send a Last-Modified date which is later than the server's time of message origination.
 * In such cases, where the resource's last modification would indicate some time in the future, the server MUST replace
 * that date with the message origination date.
 *
 * <p>
 * An origin server SHOULD obtain the Last-Modified value of the entity as close as possible to the time that it
 * generates the Date value of its response.
 * This allows a recipient to make an accurate assessment of the entity's modification time, especially if the entity
 * changes near the time that the response is generated.
 *
 * <p>
 * HTTP/1.1 servers SHOULD send Last-Modified whenever feasible.
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/JuneauRestCommonBasics">juneau-rest-common Basics</a>
 *    <li class='extlink'><a class="doclink" href="https://www.w3.org/Protocols/rfc2616/rfc2616.html">Hypertext Transfer Protocol -- HTTP/1.1</a>
 * </ul>
 *
 * @serial exclude
 */
@Header("Last-Modified")
public class LastModified extends BasicDateHeader {

   //-----------------------------------------------------------------------------------------------------------------
   // Static
   //-----------------------------------------------------------------------------------------------------------------

   private static final long serialVersionUID = 1L;
   private static final String NAME = "Last-Modified";

   /**
    * Static creator.
    *
    * @param value
    *    The header value.
    *    <br>Must be an RFC-1123 formated string (e.g. <js>"Sat, 29 Oct 1994 19:43:31 GMT"</js>).
    *    <br>Can be <jk>null</jk>.
    * @return A new header bean, or <jk>null</jk> if the name is <jk>null</jk> or empty or the value is <jk>null</jk>.
    */
   public static LastModified of(String value) {
      return value == null ? null : new LastModified(value);
   }

   /**
    * Static creator.
    *
    * @param value
    *    The header value.
    *    <br>Can be <jk>null</jk>.
    * @return A new header bean, or <jk>null</jk> if the name is <jk>null</jk> or empty or the value is <jk>null</jk>.
    */
   public static LastModified of(ZonedDateTime value) {
      return value == null ? null : new LastModified(value);
   }

   /**
    * Static creator with delayed value.
    *
    * <p>
    * Header value is re-evaluated on each call to {@link #getValue()}.
    *
    * @param value
    *    The supplier of the header value.
    *    <br>Can be <jk>null</jk>.
    * @return A new header bean, or <jk>null</jk> if the name is <jk>null</jk> or empty or the value is <jk>null</jk>.
    */
   public static LastModified of(Supplier<ZonedDateTime> value) {
      return value == null ? null : new LastModified(value);
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Instance
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * Constructor.
    *
    * @param value
    *    The header value.
    *    <br>Must be an RFC-1123 formated string (e.g. <js>"Sat, 29 Oct 1994 19:43:31 GMT"</js>).
    *    <br>Can be <jk>null</jk>.
    */
   public LastModified(String value) {
      super(NAME, value);
   }

   /**
    * Constructor.
    *
    * @param value
    *    The header value.
    *    <br>Can be <jk>null</jk>.
    */
   public LastModified(ZonedDateTime value) {
      super(NAME, value);
   }

   /**
    * Constructor with delayed value.
    *
    * <p>
    * Header value is re-evaluated on each call to {@link #getValue()}.
    *
    * @param value
    *    The supplier of the header value.
    *    <br>Can be <jk>null</jk>.
    */
   public LastModified(Supplier<ZonedDateTime> value) {
      super(NAME, value);
   }
}