/*
 * 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
 *
 *      https://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.tsfile.external.commons.lang3.function;

import java.util.function.Supplier;

/**
 * Helps use {@link Supplier}.
 *
 * @since 3.13.0
 */
public class Suppliers {

  /**
   * Returns the singleton supplier that always returns null.
   *
   * <p>This supplier never throws an exception.
   */
  @SuppressWarnings("rawtypes")
  private static Supplier NUL = () -> null;

  /**
   * Null-safe call to {@link Supplier#get()}.
   *
   * @param <T> the type of results supplied by this supplier.
   * @param supplier the supplier or null.
   * @return Result of {@link Supplier#get()} or null.
   */
  public static <T> T get(final Supplier<T> supplier) {
    return supplier == null ? null : supplier.get();
  }

  /**
   * Gets the singleton supplier that always returns null.
   *
   * <p>This supplier never throws an exception.
   *
   * @param <T> Supplied type.
   * @return The NUL singleton.
   * @since 3.14.0
   */
  @SuppressWarnings("unchecked")
  public static <T> Supplier<T> nul() {
    return NUL;
  }

  /**
   * Make private in 4.0.
   *
   * @deprecated TODO Make private in 4.0.
   */
  @Deprecated
  public Suppliers() {
    // empty
  }
}
