/*
 * 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.util.function.*;

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


/**
 * Represents a parsed <l>Accept-Charset</l> HTTP request header.
 *
 * <p>
 * Character sets that are acceptable.
 *
 * <h5 class='figure'>Example</h5>
 * <p class='bcode'>
 *    Accept-Charset: utf-8
 * </p>
 *
 * <h5 class='topic'>RFC2616 Specification</h5>
 *
 * The Accept-Charset request-header field can be used to indicate what character sets are acceptable for the response.
 *
 * <p>
 * This field allows clients capable of understanding more comprehensive or special- purpose character sets to signal
 * that capability to a server which is capable of representing documents in those character sets.
 * <p class='bcode'>
 *    Accept-Charset = "Accept-Charset" ":"
 *                     1#( ( charset | "*" )[ ";" "q" "=" qvalue ] )
 * </p>
 *
 * <p>
 * Character set values are described in section 3.4. Each charset MAY be given an associated quality value which
 * represents the user's preference for that charset.
 * The default value is q=1.
 * An example is...
 * <p class='bcode'>
 *    Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
 * </p>
 *
 * <p>
 * The special value "*", if present in the Accept-Charset field, matches every character set (including ISO-8859-1)
 * which is not mentioned elsewhere in the Accept-Charset field.
 *
 * <p>
 * If no "*" is present in an Accept-Charset field, then all character sets not explicitly mentioned get a quality
 * value of 0, except for ISO-8859-1, which gets a quality value of 1 if not explicitly mentioned.
 *
 * <p>
 * If no Accept-Charset header is present, the default is that any character set is acceptable.
 *
 * <p>
 * If an Accept-Charset header is present, and if the server cannot send a response which is acceptable according to
 * the Accept-Charset header, then the server SHOULD send an error response with the 406 (not acceptable) status code,
 * though the sending of an unacceptable response is also allowed.
 *
 * <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("Accept-Charset")
public class AcceptCharset extends BasicStringRangesHeader {

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

   private static final long serialVersionUID = 1L;
   private static final String NAME = "Accept-Charset";

   private static final Cache<String,AcceptCharset> CACHE = Cache.of(String.class, AcceptCharset.class).build();

   /**
    * Static creator.
    *
    * @param value
    *    The header value.
    *    <br>Must be parsable by {@link StringRanges#of(String)}.
    *    <br>Can be <jk>null</jk>.
    * @return A new header bean, or <jk>null</jk> if the value is <jk>null</jk>.
    */
   public static AcceptCharset of(String value) {
      return value == null ? null : CACHE.get(value, ()->new AcceptCharset(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 value is <jk>null</jk>.
    */
   public static AcceptCharset of(StringRanges value) {
      return value == null ? null : new AcceptCharset(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 value is <jk>null</jk>.
    */
   public static AcceptCharset of(Supplier<StringRanges> value) {
      return value == null ? null : new AcceptCharset(value);
   }

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

   /**
    * Constructor.
    *
    * @param value
    *    The header value.
    *    <br>Must be parsable by {@link StringRanges#of(String)}.
    *    <br>Can be <jk>null</jk>.
    */
   public AcceptCharset(String value) {
      super(NAME, value);
   }

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