/*
    * 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.commons.lang3.tuple;
  
  import java.util.Map;
  import java.util.Objects;
  
  /**
   * A mutable pair consisting of two {@link Object} elements.
   *
   * <p>
   * Not #ThreadSafe#
   * </p>
   *
   * @param <L> The left element type.
   * @param <R> The right element type.
   * @since 3.0
   */
  public class MutablePair<L, R> extends Pair<L, R> {
  
      /**
       * An empty array.
       * <p>
       * Consider using {@link #emptyArray()} to avoid generics warnings.
       * </p>
       *
       * @since 3.10
       */
      public static final MutablePair<?, ?>[] EMPTY_ARRAY = {};
  
      /** Serialization version */
      private static final long serialVersionUID = 4954918890077093841L;
  
      /**
       * Returns the empty array singleton that can be assigned without compiler warning.
       *
       * @param <L> The left element type.
       * @param <R> The right element type.
       * @return The empty array singleton that can be assigned without compiler warning.
       * @since 3.10
       */
      @SuppressWarnings("unchecked")
      public static <L, R> MutablePair<L, R>[] emptyArray() {
          return (MutablePair<L, R>[]) EMPTY_ARRAY;
      }
  
      /**
       * Creates a mutable pair of two objects inferring the generic types.
       *
       * @param <L> The left element type.
       * @param <R> The right element type.
       * @param left  The left element, may be null.
       * @param right  The right element, may be null.
       * @return A mutable pair formed from the two parameters, not null.
       */
      public static <L, R> MutablePair<L, R> of(final L left, final R right) {
          return new MutablePair<>(left, right);
      }
  
      /**
       * Creates a mutable pair from a map entry.
       *
       * @param <L> The left element type.
       * @param <R> The right element type.
       * @param pair The existing map entry.
       * @return A mutable pair formed from the map entry.
       */
      public static <L, R> MutablePair<L, R> of(final Map.Entry<L, R> pair) {
          final L left;
          final R right;
          if (pair != null) {
              left = pair.getKey();
              right = pair.getValue();
          } else {
              left = null;
              right = null;
          }
          return new MutablePair<>(left, right);
      }
  
      /**
       * Creates a mutable pair of two non-null objects inferring the generic types.
       *
       * @param <L> The left element type.
       * @param <R> The right element type.
      * @param left  The left element, may not be null.
      * @param right  The right element, may not be null.
      * @return A mutable pair formed from the two parameters, not null.
      * @throws NullPointerException Thrown if any input is null.
      * @since 3.13.0
      */
     public static <L, R> MutablePair<L, R> ofNonNull(final L left, final R right) {
         return of(Objects.requireNonNull(left, "left"), Objects.requireNonNull(right, "right"));
     }
 
     /**
      * Creates a mutable pair from a map entry.
      *
      * @param <L> The left element type
      * @param <R> The right element type
      * @param pair The existing map entry.
      * @return A mutable pair formed from the map entry
      * @throws NullPointerException Thrown if the pair is null.
      * @since 3.20
      */
     public static <L, R> MutablePair<L, R> ofNonNull(final Map.Entry<L, R> pair) {
         return of(Objects.requireNonNull(pair, "pair"));
     }
 
     /** Left object. */
     public L left;
 
     /** Right object. */
     public R right;
 
     /**
      * Create a new pair instance of two nulls.
      */
     public MutablePair() {
     }
 
     /**
      * Create a new pair instance.
      *
      * @param left  The left value, may be null.
      * @param right  The right value, may be null.
      */
     public MutablePair(final L left, final R right) {
         this.left = left;
         this.right = right;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public L getLeft() {
         return left;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public R getRight() {
         return right;
     }
 
     /**
      * Sets the left element of the pair.
      *
      * @param left  The new value of the left element, may be null.
      */
     public void setLeft(final L left) {
         this.left = left;
     }
 
     /**
      * Sets the right element of the pair.
      *
      * @param right  The new value of the right element, may be null.
      */
     public void setRight(final R right) {
         this.right = right;
     }
 
     /**
      * Sets the {@code Map.Entry} value.
      * This sets the right element of the pair.
      *
      * @param value  The right value to set, not null.
      * @return The old value for the right element.
      */
     @Override
     public R setValue(final R value) {
         final R result = getRight();
         setRight(value);
         return result;
     }
 
 }