/*
 * 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.*;
import java.util.function.*;

import org.apache.http.*;
import org.apache.juneau.assertions.*;
import org.apache.juneau.common.utils.*;

/**
 * Category of headers that consist of a single string value.
 *
 * <p>
 * <h5 class='figure'>Example</h5>
 * <p class='bcode'>
 *    Host: www.myhost.com:8080
 * </p>
 *
 * <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
 */
public class BasicStringHeader extends BasicHeader {

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

   private static final long serialVersionUID = 1L;

   /**
    * Static creator.
    *
    * @param name The header name.
    * @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>.
    * @throws IllegalArgumentException If name is <jk>null</jk> or empty.
    */
   public static BasicStringHeader of(String name, String value) {
      return value == null ? null : new BasicStringHeader(name, value);
   }

   /**
    * Static creator with delayed value.
    *
    * <p>
    * Header value is re-evaluated on each call to {@link #getValue()}.
    *
    * @param name The header name.
    * @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>.
    * @throws IllegalArgumentException If name is <jk>null</jk> or empty.
    */
   public static BasicStringHeader of(String name, Supplier<String> value) {
      return value == null ? null : new BasicStringHeader(name, value);
   }

   /**
    * Creates a {@link Header} from a name/value pair string (e.g. <js>"Foo: bar"</js>)
    *
    * @param pair The pair string.
    * @return A new header bean.
    */
   public static BasicStringHeader ofPair(String pair) {
      if (pair == null)
         return null;
      int i = pair.indexOf(':');
      if (i == -1)
         i = pair.indexOf('=');
      if (i == -1)
         return of(pair, "");
      return of(pair.substring(0,i).trim(), pair.substring(i+1).trim());
   }

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

   private final String value;
   private final Supplier<String> supplier;

   /**
    * Constructor.
    *
    * @param name The header name.
    * @param value
    *    The header value.
    *    <br>Can be <jk>null</jk>.
    * @throws IllegalArgumentException If name is <jk>null</jk> or empty.
    */
   public BasicStringHeader(String name, String value) {
      super(name, value);
      this.value = value;
      this.supplier = null;
   }

   /**
    * Constructor with delayed value.
    *
    * <p>
    * Header value is re-evaluated on each call to {@link #getValue()}.
    *
    * @param name The header name.
    * @param value
    *    The supplier of the header value.
    *    <br>Can be <jk>null</jk>.
    * @throws IllegalArgumentException If name is <jk>null</jk> or empty.
    */
   public BasicStringHeader(String name, Supplier<String> value) {
      super(name, null);
      this.value = null;
      this.supplier = value;
   }

   @Override /* Header */
   public String getValue() {
      return Utils.s(value());
   }

   @Override /* BasicHeader */
   public Optional<String> asString() {
      return Utils.opt(value());
   }

   /**
    * Provides the ability to perform fluent-style assertions on this header.
    *
    * <h5 class='section'>Examples:</h5>
    * <p class='bjava'>
    *    <jc>// Validates the content type header is provided.</jc>
    *    <jv>client</jv>
    *       .get(<jsf>URL</jsf>)
    *       .run()
    *       .getHeader(<js>"Content-Type"</js>).assertString().exists();
    * </p>
    *
    * @return A new fluent assertion object.
    * @throws AssertionError If assertion failed.
    */
   public FluentStringAssertion<BasicStringHeader> assertString() {
      return new FluentStringAssertion<>(value(), this);
   }


   /**
    * Return the value if present, otherwise return <c>other</c>.
    *
    * <p>
    * This is a shortened form for calling <c>asString().orElse(<jv>other</jv>)</c>.
    *
    * @param other The value to be returned if there is no value present, can be <jk>null</jk>.
    * @return The value, if present, otherwise <c>other</c>.
    */
   @Override
   public String orElse(String other) {
      String x = value();
      return x != null ? x : other;
   }

   private String value() {
      if (supplier != null)
         return supplier.get();
      return value;
   }
}