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/*
 * Copyright 2007 Google Inc.
 *
 * Licensed 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
 *
 * http://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 java.util;

import static javaemul.internal.InternalPreconditions.checkNotNull;

import java.io.Serializable;
import java.util.function.Function;
import java.util.function.ToDoubleFunction;
import java.util.function.ToIntFunction;
import java.util.function.ToLongFunction;

/**
 * An interface used a basis for implementing custom ordering. [Sun
 * docs]
 *
 * @param  the type to be compared.
 */
@FunctionalInterface
public interface Comparator {

  int compare(T a, T b);

  @Override
  boolean equals(Object other);

  default Comparator reversed() {
    return new Comparators.ReversedComparator(this);
  }

  default Comparator thenComparing(Comparator other) {
    checkNotNull(other);
    return (Comparator & Serializable) (a, b) -> {
      int c = compare(a, b);
      return (c != 0) ? c : other.compare(a, b);
    };
  }

  default  Comparator thenComparing(Function keyExtractor,
      Comparator keyComparator) {
    return thenComparing(comparing(keyExtractor, keyComparator));
  }

  default > Comparator thenComparing(
      Function keyExtractor) {
    return thenComparing(comparing(keyExtractor));
  }

  default Comparator thenComparingInt(ToIntFunction keyExtractor) {
    return thenComparing(comparingInt(keyExtractor));
  }

  default Comparator thenComparingLong(ToLongFunction keyExtractor) {
    return thenComparing(comparingLong(keyExtractor));
  }

  default Comparator thenComparingDouble(ToDoubleFunction keyExtractor) {
    return thenComparing(comparingDouble(keyExtractor));
  }

  static  Comparator comparing(Function keyExtractor,
      Comparator keyComparator) {
    checkNotNull(keyExtractor);
    checkNotNull(keyComparator);
    return (Comparator & Serializable) (a, b) ->
        keyComparator.compare(keyExtractor.apply(a), keyExtractor.apply(b));
  }

  static > Comparator comparing(
      Function keyExtractor) {
    return comparing(keyExtractor, naturalOrder());
  }

  static Comparator comparingDouble(ToDoubleFunction keyExtractor) {
    checkNotNull(keyExtractor);
    return (Comparator & Serializable) (a, b) ->
        Double.compare(keyExtractor.applyAsDouble(a), keyExtractor.applyAsDouble(b));
  }

  static  Comparator comparingInt(ToIntFunction keyExtractor) {
    checkNotNull(keyExtractor);
    return (Comparator & Serializable) (a, b) ->
        Integer.compare(keyExtractor.applyAsInt(a), keyExtractor.applyAsInt(b));
  }

  static  Comparator comparingLong(ToLongFunction keyExtractor) {
    checkNotNull(keyExtractor);
    return (Comparator & Serializable) (a, b) ->
        Long.compare(keyExtractor.applyAsLong(a), keyExtractor.applyAsLong(b));
  }

  static > Comparator naturalOrder() {
    return Comparators.naturalOrder();
  }

  static  Comparator nullsFirst(Comparator comparator) {
    return new Comparators.NullComparator<>(true, comparator);
  }

  static  Comparator nullsLast(Comparator comparator) {
    return new Comparators.NullComparator<>(false, comparator);
  }

  static > Comparator reverseOrder() {
    return Comparators.reverseNaturalOrder();
  }
}