/*
 * 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.tuple;

import java.util.Map;
import java.util.Objects;

/////////////////////////////////////////////////////////////////////////////////////////////////
// IoTDB
/////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * An immutable pair consisting of two {@link Object} elements.
 *
 * <p>Although the implementation is immutable, there is no restriction on the objects that may be
 * stored. If mutable objects are stored in the pair, then the pair itself effectively becomes
 * mutable.
 *
 * <p>#ThreadSafe# if both paired objects are thread-safe
 *
 * @param <L> the left element type
 * @param <R> the right element type
 * @since 3.0
 */
public class ImmutablePair<L, R> extends Pair<L, R> {

  /**
   * An empty array.
   *
   * <p>Consider using {@link #emptyArray()} to avoid generics warnings.
   *
   * @since 3.10
   */
  public static final ImmutablePair<?, ?>[] EMPTY_ARRAY = {};

  /** An immutable pair of nulls. */
  // This is not defined with generics to avoid warnings in call sites.
  @SuppressWarnings("rawtypes")
  private static final ImmutablePair NULL = new ImmutablePair<>(null, null);

  /** 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> ImmutablePair<L, R>[] emptyArray() {
    return (ImmutablePair<L, R>[]) EMPTY_ARRAY;
  }

  /**
   * Creates an immutable pair of two objects inferring the generic types.
   *
   * <p>This factory allows the pair to be created using inference to obtain the generic types.
   *
   * @param <L> the left element type
   * @param <R> the right element type
   * @param left the left element, may be null
   * @return a pair formed from the two parameters, not null
   * @since 3.11
   */
  public static <L, R> Pair<L, R> left(final L left) {
    return of(left, null);
  }

  /**
   * Returns an immutable pair of nulls.
   *
   * @param <L> the left element of this pair. Value is {@code null}.
   * @param <R> the right element of this pair. Value is {@code null}.
   * @return an immutable pair of nulls.
   * @since 3.6
   */
  @SuppressWarnings("unchecked")
  public static <L, R> ImmutablePair<L, R> nullPair() {
    return NULL;
  }

  /**
   * Creates an immutable pair of two objects inferring the generic types.
   *
   * <p>This factory allows the pair to be created using inference to obtain 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 pair formed from the two parameters, not null
   */
  public static <L, R> ImmutablePair<L, R> of(final L left, final R right) {
    return left != null || right != null ? new ImmutablePair<>(left, right) : nullPair();
  }

  /**
   * Creates an immutable pair from a map entry.
   *
   * <p>This factory allows the pair to be created using inference to obtain the generic types.
   *
   * @param <L> the left element type
   * @param <R> the right element type
   * @param pair the existing map entry.
   * @return a pair formed from the map entry
   * @since 3.10
   */
  public static <L, R> ImmutablePair<L, R> of(final Map.Entry<L, R> pair) {
    return pair != null ? new ImmutablePair<>(pair.getKey(), pair.getValue()) : nullPair();
  }

  /**
   * Creates an immutable pair of two non-null objects inferring the generic types.
   *
   * <p>This factory allows the pair to be created using inference to obtain 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 pair formed from the two parameters, not null
   * @throws NullPointerException if any input is null
   * @since 3.13.0
   */
  public static <L, R> ImmutablePair<L, R> ofNonNull(final L left, final R right) {
    return of(Objects.requireNonNull(left, "left"), Objects.requireNonNull(right, "right"));
  }

  /**
   * Creates an immutable pair of two objects inferring the generic types.
   *
   * <p>This factory allows the pair to be created using inference to obtain the generic types.
   *
   * @param <L> the left element type
   * @param <R> the right element type
   * @param right the right element, may be null
   * @return a pair formed from the two parameters, not null
   * @since 3.11
   */
  public static <L, R> Pair<L, R> right(final R right) {
    return of(null, right);
  }

  /** Left object */
  public final L left;

  /** Right object */
  public final R right;

  /**
   * Create a new pair instance.
   *
   * @param left the left value, may be null
   * @param right the right value, may be null
   */
  public ImmutablePair(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;
  }

  /**
   * Throws {@link UnsupportedOperationException}.
   *
   * <p>This pair is immutable, so this operation is not supported.
   *
   * @param value the value to set
   * @return never
   * @throws UnsupportedOperationException as this operation is not supported
   */
  @Override
  public R setValue(final R value) {
    throw new UnsupportedOperationException();
  }
}
