001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.juneau.commons.settings;
018
019import static org.apache.juneau.commons.utils.Shorts.*;
020
021import java.util.function.*;
022
023/**
024 * A functional interface for creating read-only {@link PropertySource} instances from a function.
025 */
026@FunctionalInterface
027public interface FunctionalPropertySource extends PropertySource {
028
029   @Override
030   PropertyLookupResult get(String name);
031
032   /**
033    * Creates a functional source from a function that returns a string.
034    *
035    * @param function The function to delegate property lookups to. Must not be <c>null</c>.
036    * @return A new functional property source instance.
037    */
038   static FunctionalPropertySource of(UnaryOperator<String> function) {
039      return name -> {
040         var v = function.apply(name);
041         return v == null ? PropertyLookupResult.missing() : PropertyLookupResult.present(o(v));
042      };
043   }
044}