content: /*
   * Copyright (C) 2020 ActiveJ LLC.
   *
   * Licensed 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 io.activej.config.converter;
  
  import io.activej.config.Config;
  import org.jetbrains.annotations.Nullable;
  
  public abstract class ComplexConfigConverter<T> implements ConfigConverter<T> {
  	private final T defaultValue;
  
  	protected ComplexConfigConverter(T defaultValue) {
  		this.defaultValue = defaultValue;
  	}
  
  	@Override
  	public final T get(Config config) {
  		return provide(config, defaultValue);
  	}
  
  	@Override
  	public final @Nullable T get(Config config, @Nullable T defaultValue) {
  		boolean isNull = defaultValue == null;
  		if (isNull) {
  			defaultValue = this.defaultValue;
  		}
  		T result = provide(config, defaultValue);
  		if (isNull && config.isEmpty()) {
  			return null;
  		}
  		return result;
  	}
  
  	protected abstract T provide(Config config, T defaultValue);
  }
  