/*
 * Copyright (C) 2009 The Guava Authors
 *
 * 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 com.google.common.collect;

import static com.google.common.base.MoreObjects.toStringHelper;
import static com.google.common.truth.Truth.assertThat;
import static com.google.common.truth.Truth.assertWithMessage;
import static java.lang.Integer.signum;
import static java.util.Comparator.comparing;
import static java.util.Comparator.naturalOrder;
import static java.util.Comparator.nullsLast;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.primitives.Booleans;
import java.util.Comparator;
import junit.framework.AssertionFailedError;
import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit test for {@link ComparisonChain}.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public class ComparisonChainTest extends TestCase {
  private static final DontCompareMe DONT_COMPARE_ME = new DontCompareMe();

  private static class DontCompareMe implements Comparable<DontCompareMe> {
    @Override
    public int compareTo(DontCompareMe o) {
      throw new AssertionFailedError();
    }
  }

  @SuppressWarnings("deprecation")
  public void testCompareBooleans() {
    assertThat(
            ComparisonChain.start()
                .compare(true, true)
                .compare(true, Boolean.TRUE)
                .compare(Boolean.TRUE, true)
                .compare(Boolean.TRUE, Boolean.TRUE)
                .result())
        .isEqualTo(0);
  }

  public void testDegenerate() {
    // kinda bogus, but who cares?
    assertThat(ComparisonChain.start().result()).isEqualTo(0);
  }

  public void testOneEqual() {
    assertThat(ComparisonChain.start().compare("a", "a").result()).isEqualTo(0);
  }

  public void testOneEqualUsingComparator() {
    assertThat(ComparisonChain.start().compare("a", "A", String.CASE_INSENSITIVE_ORDER).result())
        .isEqualTo(0);
  }

  public void testManyEqual() {
    assertThat(
            ComparisonChain.start()
                .compare(1, 1)
                .compare(1L, 1L)
                .compareFalseFirst(true, true)
                .compare(1.0, 1.0)
                .compare(1.0f, 1.0f)
                .compare("a", "a", Ordering.usingToString())
                .result())
        .isEqualTo(0);
  }

  public void testShortCircuitLess() {
    assertThat(
            ComparisonChain.start()
                .compare("a", "b")
                .compare(DONT_COMPARE_ME, DONT_COMPARE_ME)
                .result())
        .isLessThan(0);
  }

  public void testShortCircuitGreater() {
    assertThat(
            ComparisonChain.start()
                .compare("b", "a")
                .compare(DONT_COMPARE_ME, DONT_COMPARE_ME)
                .result())
        .isGreaterThan(0);
  }

  public void testShortCircuitSecondStep() {
    assertThat(
            ComparisonChain.start()
                .compare("a", "a")
                .compare("a", "b")
                .compare(DONT_COMPARE_ME, DONT_COMPARE_ME)
                .result())
        .isLessThan(0);
  }

  public void testCompareFalseFirst() {
    assertThat(ComparisonChain.start().compareFalseFirst(true, true).result()).isEqualTo(0);
    assertThat(ComparisonChain.start().compareFalseFirst(true, false).result()).isGreaterThan(0);
    assertThat(ComparisonChain.start().compareFalseFirst(false, true).result()).isLessThan(0);
    assertThat(ComparisonChain.start().compareFalseFirst(false, false).result()).isEqualTo(0);
  }

  public void testCompareTrueFirst() {
    assertThat(ComparisonChain.start().compareTrueFirst(true, true).result()).isEqualTo(0);
    assertThat(ComparisonChain.start().compareTrueFirst(true, false).result()).isLessThan(0);
    assertThat(ComparisonChain.start().compareTrueFirst(false, true).result()).isGreaterThan(0);
    assertThat(ComparisonChain.start().compareTrueFirst(false, false).result()).isEqualTo(0);
  }

  enum TriState {
    FALSE,
    MAYBE,
    TRUE,
  }

  static class Foo {
    private final String aString;
    private final int anInt;
    private final @Nullable TriState anEnum;

    Foo(String aString, int anInt, @Nullable TriState anEnum) {
      this.aString = aString;
      this.anInt = anInt;
      this.anEnum = anEnum;
    }

    @Override
    public String toString() {
      return toStringHelper(this)
          .add("aString", aString)
          .add("anInt", anInt)
          .add("anEnum", anEnum)
          .toString();
    }
  }

  /** Validates that the Comparator equivalent we document is correct. */
  @J2ktIncompatible // TODO b/315311435 - J2kt cannot emulate Comparator<C>.<U>thenComparing()
  public void testComparatorEquivalent() {
    Comparator<Foo> comparatorUsingComparisonChain =
        (a, b) ->
            ComparisonChain.start()
                .compare(a.aString, b.aString)
                .compare(a.anInt, b.anInt)
                .compare(a.anEnum, b.anEnum, Ordering.natural().nullsLast())
                .result();
    Comparator<Foo> comparatorUsingComparatorMethods =
        comparing((Foo foo) -> foo.aString)
            .thenComparing(foo -> foo.anInt)
            .thenComparing(foo -> foo.anEnum, nullsLast(naturalOrder()));
    ImmutableList<Foo> instances =
        ImmutableList.of(
            new Foo("a", 1, TriState.TRUE),
            new Foo("a", 2, TriState.TRUE),
            new Foo("b", 1, TriState.FALSE),
            new Foo("b", 1, TriState.TRUE),
            new Foo("b", 1, null));
    for (Foo a : instances) {
      for (Foo b : instances) {
        int comparedUsingComparisonChain = signum(comparatorUsingComparisonChain.compare(a, b));
        int comparedUsingComparatorMethods = signum(comparatorUsingComparatorMethods.compare(a, b));
        assertWithMessage("%s vs %s", a, b)
            .that(comparedUsingComparatorMethods)
            .isEqualTo(comparedUsingComparisonChain);
      }
    }
  }

  static class Bar {
    private final boolean isBaz;

    Bar(boolean isBaz) {
      this.isBaz = isBaz;
    }

    boolean isBaz() {
      return isBaz;
    }
  }

  /**
   * Validates that {@link Booleans#trueFirst()} and {@link Booleans#falseFirst()} can be used with
   * {@link Comparator} when replacing {@link ComparisonChain#compareTrueFirst} and {@link
   * ComparisonChain#compareFalseFirst}, as we document.
   */
  public void testTrueFirstFalseFirst() {
    Bar trueBar = new Bar(true);
    Bar falseBar = new Bar(false);

    assertThat(ComparisonChain.start().compareTrueFirst(trueBar.isBaz(), falseBar.isBaz()).result())
        .isLessThan(0);
    Comparator<Bar> trueFirstComparator = comparing(Bar::isBaz, Booleans.trueFirst());
    assertThat(trueFirstComparator.compare(trueBar, falseBar)).isLessThan(0);

    assertThat(
            ComparisonChain.start().compareFalseFirst(falseBar.isBaz(), trueBar.isBaz()).result())
        .isLessThan(0);
    Comparator<Bar> falseFirstComparator = comparing(Bar::isBaz, Booleans.falseFirst());
    assertThat(falseFirstComparator.compare(falseBar, trueBar)).isLessThan(0);
  }
}