content: /*
   * 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
   *
   * 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 org.apache.calcite.util;
  
  import java.util.Comparator;
  
  /**
   * Comparator that compares all strings differently, but if two strings are
   * equal in case-insensitive match they are right next to each other.
   *
   * <p>Note: strings that differ only in upper-lower case are treated by this comparator
   * as distinct.
   *
   * <p>In a collection sorted on this comparator, we can find case-insensitive matches
   * for a given string using
   * {@link #floorKey(java.lang.String)}
   * and {@link #ceilingKey(java.lang.String)}.
   */
  class CaseInsensitiveComparator implements Comparator {
    static final CaseInsensitiveComparator COMPARATOR = new CaseInsensitiveComparator();
  
    /**
     * Enables to create floor and ceiling keys for given string.
     */
    private static final class Key {
      public final String value;
      public final int compareResult;
  
      private Key(String value, int compareResult) {
        this.value = value;
        this.compareResult = compareResult;
      }
  
      @Override public String toString() {
        return value;
      }
    }
  
    Object floorKey(String key) {
      return new Key(key, -1);
    }
  
    Object ceilingKey(String key) {
      return new Key(key, 1);
    }
  
    @Override public int compare(Object o1, Object o2) {
      String s1 = o1.toString();
      String s2 = o2.toString();
      int c = s1.compareToIgnoreCase(s2);
      if (c != 0) {
        return c;
      }
      if (o1 instanceof Key) {
        return ((Key) o1).compareResult;
      }
      if (o2 instanceof Key) {
        return -((Key) o2).compareResult;
      }
      return s1.compareTo(s2);
    }
  }
  