/*
 * 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 static java.time.format.DateTimeFormatter.*;
import static java.time.temporal.ChronoUnit.*;
import static org.apache.juneau.commons.utils.Shorts.*;

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


/**
 * Represents an HTTP <c>If-Range</c> header.
 *
 * <p>
 * If the entity is unchanged, send me the part(s) that I am missing; otherwise, send me the entire new entity.
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/NextGenRestClient">Next-Generation REST Client</a>
 * </ul>
 *
 * @since 9.2.1
 */
@SuppressWarnings({
   "java:S2160" // equals() on HttpHeaderBean uses name + getValue()
})
public class IfRange extends HttpHeaderBean {

   /** The header name */
   public static final String NAME = "If-Range";

   private static boolean isEtag(String s) {
      return s != null && (s.startsWith("\"") || s.startsWith("W/"));
   }

   private final EntityTag etagValue;
   private final ZonedDateTime zonedValue;
   private final Supplier<?> supplier;

   /**
    * Constructor with an entity-tag value.
    *
    * @param value The entity tag. May be <jk>null</jk>.
    */
   public IfRange(EntityTag value) {
      super(NAME, (String)null);
      this.etagValue = value;
      this.zonedValue = null;
      this.supplier = null;
   }

   /**
    * Constructor with a wire string (HTTP-date or entity-tag).
    *
    * @param value The header value. May be <jk>null</jk>.
    */
   public IfRange(String value) {
      super(NAME, (String)null);
      if (value != null && isEtag(value)) {
         this.etagValue = EntityTag.of(value);
         this.zonedValue = null;
      } else {
         this.etagValue = null;
         this.zonedValue = ie(value) ? null : parseHttpDate(value);
      }
      this.supplier = null;
   }

   /**
    * Constructor with a lazy supplier of {@link EntityTag} or {@link ZonedDateTime}.
    *
    * @param valueSupplier Supplier for the value. Must not be <jk>null</jk>.
    */
   public IfRange(Supplier<?> valueSupplier) {
      super(NAME, (String)null);
      this.etagValue = null;
      this.zonedValue = null;
      this.supplier = valueSupplier;
   }

   /**
    * Constructor with an HTTP-date.
    *
    * @param value The date/time. May be <jk>null</jk>.
    */
   public IfRange(ZonedDateTime value) {
      super(NAME, (String)null);
      this.etagValue = null;
      this.zonedValue = value;
      this.supplier = null;
   }

   /**
    * @return This header as an {@link EntityTag}.
    */
   public Optional<EntityTag> asEntityTag() {
      if (nn(supplier)) {
         var o = supplier.get();
         return o(o instanceof EntityTag o2 ? o2 : null);
      }
      return o(etagValue);
   }

   /**
    * @return This header as a {@link ZonedDateTime} when the value is an HTTP-date.
    */
   public Optional<ZonedDateTime> asZonedDateTime() {
      if (nn(supplier)) {
         var o = supplier.get();
         return o(o instanceof ZonedDateTime o2 ? o2 : null);
      }
      return o(zonedValue);
   }

   @Override /* HttpHeader */
   public String getValue() {
      if (nn(supplier)) {
         var o = supplier.get();
         if (o == null)
            return null;
         if (o instanceof EntityTag o2)
            return o2.toString();
         if (o instanceof ZonedDateTime o2)
            return RFC_1123_DATE_TIME.format(o2);
         throw rex("Invalid object type returned by supplier: %s", cn(o));
      }
      if (nn(etagValue))
         return s(etagValue);
      if (nn(zonedValue))
         return RFC_1123_DATE_TIME.format(zonedValue);
      return null;
   }

   /**
    * Static factory with an entity-tag.
    *
    * @param value The tag. May be <jk>null</jk>, in which case <jk>null</jk> is returned.
    * @return A new instance, or <jk>null</jk> if <c>value</c> is <jk>null</jk>.
    */
   public static IfRange of(EntityTag value) {
      return value == null ? null : new IfRange(value);
   }

   /**
    * Static factory with a wire string.
    *
    * @param value The value. May be <jk>null</jk>, in which case <jk>null</jk> is returned.
    * @return A new instance, or <jk>null</jk> if <c>value</c> is <jk>null</jk>.
    */
   public static IfRange of(String value) {
      return value == null ? null : new IfRange(value);
   }

   /**
    * Static factory with a lazy supplier.
    *
    * @param valueSupplier Supplier of {@link EntityTag} or {@link ZonedDateTime}. Must not be <jk>null</jk>.
    * @return A new instance. Never <jk>null</jk>.
    */
   public static IfRange of(Supplier<?> valueSupplier) {
      return new IfRange(valueSupplier);
   }

   /**
    * Static factory with an HTTP-date.
    *
    * @param value The date/time. May be <jk>null</jk>, in which case <jk>null</jk> is returned.
    * @return A new instance, or <jk>null</jk> if <c>value</c> is <jk>null</jk>.
    */
   public static IfRange of(ZonedDateTime value) {
      return value == null ? null : new IfRange(value);
   }

   private static ZonedDateTime parseHttpDate(String value) {
      return ZonedDateTime.from(RFC_1123_DATE_TIME.parse(value)).truncatedTo(SECONDS);
   }
}