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.sql.validate;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeField;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.Iterables;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * Checks whether two names are the same according to a case-sensitivity policy.
   *
   * @see SqlNameMatchers
   */
  public interface SqlNameMatcher {
    /** Returns whether name matching is case-sensitive. */
    boolean isCaseSensitive();
  
    /** Returns a name matches another.
     *
     * @param string Name written in code
     * @param name Name of object we are trying to match
     * @return Whether matches
     */
    boolean matches(String string, String name);
  
    /** Looks up an item in a map. */
    <K extends List<String>, V> @Nullable V get(Map<K, V> map, List<String> prefixNames,
        List<String> names);
  
    /** Returns the most recent match.
     *
     * <p>In the default implementation,
     * throws {@link UnsupportedOperationException}. */
    String bestString();
  
    /** Finds a field with a given name, using the current case-sensitivity,
     * returning null if not found.
     *
     * @param rowType    Row type
     * @param fieldName Field name
     * @return Field, or null if not found
     */
    @Nullable RelDataTypeField field(RelDataType rowType, String fieldName);
  
    /** Returns how many times a string occurs in a collection.
     *
     * <p>Similar to {@link java.util.Collections#frequency}. */
    int frequency(Iterable<String> names, String name);
  
    /** Returns a copy of a collection, removing duplicates and retaining
     * iteration order. */
    default List<String> distinctCopy(Iterable<String> names) {
      final ImmutableList.Builder<String> list = ImmutableList.builder();
      final Set<String> set = createSet();
      for (String name : names) {
        if (set.add(name)) {
          list.add(name);
        }
      }
      return list.build();
    }
  
    /** Returns the index of the first element of a collection that matches. */
    default int indexOf(Iterable<String> names, String name) {
      return Iterables.indexOf(names, n -> matches(n, name));
    }
  
    /** Creates a set that has the same case-sensitivity as this matcher. */
    Set<String> createSet();
  }
  