core/src/main/java/org/apache/calcite/sql/validate/SqlNameMatcher.java

/*
 * 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();
}