* @since 2.0
 */
@GwtCompatible
public abstract class ComparisonChain {
  private ComparisonChain() {}

  /** Begins a new chained comparison statement. See example in the class documentation. */
  public static ComparisonChain start() {
    return ACTIVE;
  }

  private static final ComparisonChain ACTIVE =
      new ComparisonChain() {
        @SuppressWarnings("unchecked") // unsafe; see discussion on supertype

    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);

    static final Ordering<?> INSTANCE = new RangeLexOrdering();

    @Override
    public int compare(Range<?> left, Range<?> right) {
      return ComparisonChain.start()
          .compare(left.lowerBound, right.lowerBound)
          .compare(left.upperBound, right.upperBound)
          .result();
    }

      // to be sorted based on the top of each iterator, with insertion order as tiebreaker
      Comparator<IndexedIterator<T>> heapComparator =
          (o1, o2) ->
              ComparisonChain.start()
                  .compare(o1.iterator.peek(), o2.iterator.peek(), itemComparator)
                  // When elements are equal, use insertion order to maintain stability