/*
 * 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 org.apache.tsfile.external.commons.lang3.function.FailableBiConsumer;
import org.apache.tsfile.external.commons.lang3.function.FailableBiFunction;

import java.io.Serializable;
import java.util.Map;
import java.util.Objects;

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

/**
 * A pair consisting of two elements.
 *
 * <p>This class is an abstract implementation defining the basic API. It refers to the elements as
 * 'left' and 'right'. It also implements the {@code Map.Entry} interface where the key is 'left'
 * and the value is 'right'.
 *
 * <p>Subclass implementations may be mutable or immutable. However, there is no restriction on the
 * type of the stored objects that may be stored. If mutable objects are stored in the pair, then
 * the pair itself effectively becomes mutable.
 *
 * @param <L> the left element type.
 * @param <R> the right element type.
 * @since 3.0
 */
public abstract class Pair<L, R> implements Map.Entry<L, R>, Comparable<Pair<L, R>>, Serializable {

  /** Serialization version */
  private static final long serialVersionUID = 4954918890077093841L;

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

  /**
   * 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> Pair<L, R>[] emptyArray() {
    return (Pair<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.
   * @param right the right element, may be null.
   * @return a pair formed from the two parameters, not null.
   */
  public static <L, R> Pair<L, R> of(final L left, final R right) {
    return ImmutablePair.of(left, right);
  }

  /**
   * 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 map entry.
   * @return a pair formed from the map entry.
   * @since 3.10
   */
  public static <L, R> Pair<L, R> of(final Map.Entry<L, R> pair) {
    return ImmutablePair.of(pair);
  }

  /**
   * 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> Pair<L, R> ofNonNull(final L left, final R right) {
    return ImmutablePair.ofNonNull(left, right);
  }

  /** Constructs a new instance. */
  public Pair() {
    // empty
  }

  /**
   * Accepts this key and value as arguments to the given consumer.
   *
   * @param <E> The kind of thrown exception or error.
   * @param consumer the consumer to call.
   * @throws E Thrown when the consumer fails.
   * @since 3.13.0
   */
  public <E extends Throwable> void accept(final FailableBiConsumer<L, R, E> consumer) throws E {
    consumer.accept(getKey(), getValue());
  }

  /**
   * Applies this key and value as arguments to the given function.
   *
   * @param <V> The function return type.
   * @param <E> The kind of thrown exception or error.
   * @param function the consumer to call.
   * @return the function's return value.
   * @throws E Thrown when the consumer fails.
   * @since 3.13.0
   */
  public <V, E extends Throwable> V apply(final FailableBiFunction<L, R, V, E> function) throws E {
    return function.apply(getKey(), getValue());
  }

  /**
   * Compares the pair based on the left element followed by the right element. The types must be
   * {@link Comparable}.
   *
   * @param other the other pair, not null.
   * @return negative if this is less, zero if equal, positive if greater.
   */
  @Override
  public int compareTo(final Pair<L, R> other) {
    // Currently not used
    return 0;
  }

  /**
   * Compares this pair to another based on the two elements.
   *
   * @param obj the object to compare to, null returns false.
   * @return true if the elements of the pair are equal.
   */
  @Override
  public boolean equals(final Object obj) {
    if (obj == this) {
      return true;
    }
    if (obj instanceof Map.Entry<?, ?>) {
      final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
      return Objects.equals(getKey(), other.getKey())
          && Objects.equals(getValue(), other.getValue());
    }
    return false;
  }

  /**
   * Gets the key from this pair.
   *
   * <p>This method implements the {@code Map.Entry} interface returning the left element as the
   * key.
   *
   * @return the left element as the key, may be null.
   */
  @Override
  public final L getKey() {
    return getLeft();
  }

  /**
   * Gets the left element from this pair.
   *
   * <p>When treated as a key-value pair, this is the key.
   *
   * @return the left element, may be null.
   */
  public abstract L getLeft();

  /**
   * Gets the right element from this pair.
   *
   * <p>When treated as a key-value pair, this is the value.
   *
   * @return the right element, may be null.
   */
  public abstract R getRight();

  /**
   * Gets the value from this pair.
   *
   * <p>This method implements the {@code Map.Entry} interface returning the right element as the
   * value.
   *
   * @return the right element as the value, may be null.
   */
  @Override
  public R getValue() {
    return getRight();
  }

  /**
   * Returns a suitable hash code.
   *
   * <p>The hash code follows the definition in {@code Map.Entry}.
   *
   * @return the hash code.
   */
  @Override
  public int hashCode() {
    // See Map.Entry API specification
    return Objects.hashCode(getKey()) ^ Objects.hashCode(getValue());
  }

  /**
   * Returns a String representation of this pair using the format {@code (left,right)}.
   *
   * @return a string describing this object, not null.
   */
  @Override
  public String toString() {
    return "(" + getLeft() + ',' + getRight() + ')';
  }

  /**
   * Formats the receiver using the given format.
   *
   * <p>This uses {@link String#format(String, Object...)} to the format. Two variables may be used
   * to embed the left and right elements. Use {@code %1$s} for the left element (key) and {@code
   * %2$s} for the right element (value).
   *
   * @param format the format string, optionally containing {@code %1$s} and {@code %2$s}, not null.
   * @return the formatted string, not null.
   * @see String#format(String, Object...)
   */
  public String toString(final String format) {
    return String.format(format, getLeft(), getRight());
  }
}
