/*******************************************************************************
 * Copyright 2019 Graz University of Technology
 * MOA ZS has been developed in a cooperation between EGIZ
 * and Graz University of Technology.
 * Licensed under the EUPL, Version 1.2 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * https://joinup.ec.europa.eu/news/understanding-eupl-v12
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 *******************************************************************************/
package at.gv.egiz.moazs.util;

import java.util.Optional;

import static java.util.Optional.ofNullable;

/**
 * Helper function for coalescing nullables value without cluttering code with if-else cascades
 * @author les2
 * @source https://stackoverflow.com/questions/2768054/how-to-get-the-first-non-null-value-in-java
 */
public final class NullCoalesce {

    private NullCoalesce(){}

    /**
     * @return the first not-null value
     * @param a
     * @param b
     * @param <T>
     * @return a if a != null, otherwise b.
     */
    public static <T> Optional<T> coalesce(T a, T b) {
        return a != null ? ofNullable(a) : ofNullable(b);
    }

    public static <T> Optional<T> coalesce(T a, T b, T c) {
        return a != null ? ofNullable(a) : coalesce(b,c);
    }

    public static <T> Optional<T> coalesce(T a, T b, T c, T d) {
        return a != null ? ofNullable(a) : coalesce(b,c,d);
    }

}