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.rel.metadata;
  
  import com.google.common.collect.ImmutableSortedMap;
  
  import java.lang.reflect.Method;
  import java.util.Arrays;
  import java.util.SortedMap;
  
  import static org.apache.calcite.util.ReflectUtil.isStatic;
  
  /**
   * Marker interface for a handler of metadata.
   *
   * @param <M> Kind of metadata
   */
  public interface MetadataHandler<M extends Metadata> {
    MetadataDef<M> getDef();
  
    /**
     * Finds handler methods defined by a {@link MetadataHandler},
     * and returns a map keyed by method name.
     *
     * <p>Ignores static and synthetic methods,
     * and the {@link MetadataHandler#getDef()} method.
     *
     * <p>Methods must have unique names.
     *
     * @param handlerClass the handler class to inspect
     * @return handler methods
     */
    static SortedMap<String, Method> handlerMethods(
        Class<? extends MetadataHandler<?>> handlerClass) {
      final ImmutableSortedMap.Builder<String, Method> map =
          ImmutableSortedMap.naturalOrder();
      Arrays.stream(handlerClass.getDeclaredMethods())
          .filter(m -> !m.getName().equals("getDef"))
          .filter(m -> !m.isSynthetic())
          .filter(m -> !isStatic(m))
          .forEach(m -> map.put(m.getName(), m));
      return map.build();
    }
  }
  