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.schema.lookup;
  
  import org.apache.calcite.util.NameMap;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.Set;
  import java.util.function.BiFunction;
  
  /**
   * A case sensitive/insensitive lookup for tables, schemas, functions, types ...
   *
   * @param <T> Element type
   */
  public interface Lookup<T> {
    /**
     * Returns a named entity with a given name, or null if not found.
     *
     * @param name Name
     * @return Entity with the specified name, or null when the entity is
     *         not found.
     */
    @Nullable T get(String name);
  
    /**
     * Returns a named entity with a given name ignoring the case, or null if not found.
     *
     * @param name Name
     * @return Entity with the specified name (case insensitive),
     *         or null when the entity is not found.
     */
    @Nullable Named<T> getIgnoreCase(String name);
  
    /**
     * Returns the names of the entities in matching pattern.
     * The search is always case sensitive. This is caused by the fact that
     * {@code DatabaseMetaData.getTables(...)} doesn't support case insensitive
     * lookups.
     *
     * @return The names of all entities matching the pattern.
     */
    Set<String> getNames(LikePattern pattern);
  
    default <S> Lookup<S> map(BiFunction<T, String, S> mapper) {
      return new TransformingLookup<>(this, mapper);
    }
  
    /**
     * Helper method to call {@code Lookup.get(String)} or
     * {@code Lookup.getIgnoreCase(String)} depending on the parameter
     * caseSensitive.
     *
     * @return Entity with the specified name, or null when the entity is
     *         not found.
     */
    static <T> @Nullable T get(Lookup<T> lookup, String name, boolean caseSensitive) {
      if (caseSensitive) {
        T entry = lookup.get(name);
        if (entry == null) {
          return null;
        }
        return entry;
      }
      return Named.entityOrNull(lookup.getIgnoreCase(name));
    }
  
    /**
     * Returns an empty lookup.
     */
    static <T> Lookup<T> empty() {
      return (Lookup<T>) EmptyLookup.INSTANCE;
    }
  
    /**
     * Creates a new lookup object based on a NameMap.
     */
    static <T> Lookup<T> of(NameMap<T> map) {
      return new NameMapLookup<>(map);
    }
  
    /**
     * Concat a list of lookups.
     */
    static <T> Lookup<T> concat(Lookup<T>... lookups) {
      return new ConcatLookup<>(lookups);
    }
  }
  