content: /*
   * Copyright 2002-2018 the original author or 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
   *
   *      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.avro.util.springframework;
  
  import org.apache.avro.reflect.Nullable;
  
  import java.util.Comparator;
  
  /**
   * A Comparator that will safely compare nulls to be lower or higher than other
   * objects. Can decorate a given Comparator or work on Comparables.
   *
   * @author Keith Donald
   * @author Juergen Hoeller
   * @since 1.2.2
   * @param <T> the type of objects that may be compared by this comparator
   * @see Comparable
   */
  class NullSafeComparator<T> implements Comparator<T> {
  
    /**
     * A shared default instance of this comparator, treating nulls lower than
     * non-null objects. see Comparators#nullsLow()
     */
    @SuppressWarnings("rawtypes")
    public static final NullSafeComparator NULLS_LOW = new NullSafeComparator<>(true);
  
    /**
     * A shared default instance of this comparator, treating nulls higher than
     * non-null objects. see Comparators#nullsHigh()
     */
    @SuppressWarnings("rawtypes")
    public static final NullSafeComparator NULLS_HIGH = new NullSafeComparator<>(false);
  
    private final Comparator<T> nonNullComparator;
  
    private final boolean nullsLow;
  
    /**
     * Create a NullSafeComparator that sorts {@code null} based on the provided
     * flag, working on Comparables.
     * <p>
     * When comparing two non-null objects, their Comparable implementation will be
     * used: this means that non-null elements (that this Comparator will be applied
     * to) need to implement Comparable.
     * <p>
     * As a convenience, you can use the default shared instances:
     * {@code NullSafeComparator.NULLS_LOW} and
     * {@code NullSafeComparator.NULLS_HIGH}.
     *
     * @param nullsLow whether to treat nulls lower or higher than non-null objects
     * @see Comparable
     * @see #NULLS_LOW
     * @see #NULLS_HIGH
     */
    @SuppressWarnings("unchecked")
    private NullSafeComparator(boolean nullsLow) {
      this.nonNullComparator = ComparableComparator.INSTANCE;
      this.nullsLow = nullsLow;
    }
  
    /**
     * Create a NullSafeComparator that sorts {@code null} based on the provided
     * flag, decorating the given Comparator.
     * <p>
     * When comparing two non-null objects, the specified Comparator will be used.
     * The given underlying Comparator must be able to handle the elements that this
     * Comparator will be applied to.
     *
     * @param comparator the comparator to use when comparing two non-null objects
     * @param nullsLow   whether to treat nulls lower or higher than non-null
     *                   objects
     */
    public NullSafeComparator(Comparator<T> comparator, boolean nullsLow) {
      // Assert.notNull(comparator, "Non-null Comparator is required");
      this.nonNullComparator = comparator;
      this.nullsLow = nullsLow;
    }
  
    @Override
    public int compare(@Nullable T o1, @Nullable T o2) {
      if (o1 == o2) {
        return 0;
      }
      if (o1 == null) {
        return (this.nullsLow ? -1 : 1);
      }
      if (o2 == null) {
        return (this.nullsLow ? 1 : -1);
      }
      return this.nonNullComparator.compare(o1, o2);
    }
  
    @Override
    @SuppressWarnings("unchecked")
    public boolean equals(@Nullable Object other) {
      if (this == other) {
        return true;
      }
      if (!(other instanceof NullSafeComparator)) {
        return false;
      }
      NullSafeComparator<T> otherComp = (NullSafeComparator<T>) other;
      return (this.nonNullComparator.equals(otherComp.nonNullComparator) && this.nullsLow == otherComp.nullsLow);
    }
  
    @Override
    public int hashCode() {
      return this.nonNullComparator.hashCode() * (this.nullsLow ? -1 : 1);
    }
  
    @Override
    public String toString() {
      return "NullSafeComparator: non-null comparator [" + this.nonNullComparator + "]; "
          + (this.nullsLow ? "nulls low" : "nulls high");
    }
  
  }
  