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 org.apache.calcite.rel.RelNode;
  import org.apache.calcite.util.Pair;
  import org.apache.calcite.util.Util;
  
  import com.google.common.collect.ImmutableList;
  
  import java.lang.reflect.Method;
  import java.util.Arrays;
  import java.util.Comparator;
  import java.util.List;
  import java.util.SortedMap;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.collect.ImmutableList.toImmutableList;
  
  /**
   * Definition of metadata.
   *
   * @param <M> Kind of metadata
   */
  public class MetadataDef<M extends Metadata> {
    public final Class<M> metadataClass;
    public final Class<? extends MetadataHandler<M>> handlerClass;
    public final ImmutableList<Method> methods;
  
    private MetadataDef(Class<M> metadataClass,
        Class<? extends MetadataHandler<M>> handlerClass, Method... methods) {
      this.metadataClass = metadataClass;
      this.handlerClass = handlerClass;
      this.methods =
          Arrays.stream(methods)
              .sorted(Comparator.comparing(Method::getName))
              .collect(toImmutableList());
      final SortedMap<String, Method> handlerMethods =
          MetadataHandler.handlerMethods(handlerClass);
  
      // Handler must have the same methods as Metadata, each method having
      // additional "subclass-of-RelNode, RelMetadataQuery" parameters.
      checkArgument(this.methods.size() == handlerMethods.size(),
          "handlerMethods.length = methods.length", this.methods, handlerMethods);
      Pair.forEach(this.methods, handlerMethods.values(),
          (method, handlerMethod) -> {
            final List<Class<?>> methodTypes =
                Arrays.asList(method.getParameterTypes());
            final List<Class<?>> handlerTypes =
                Arrays.asList(handlerMethod.getParameterTypes());
            checkArgument(methodTypes.size() + 2 == handlerTypes.size(),
                "methodTypes.size + 2 == handlerTypes.size", handlerMethod,
                methodTypes, handlerTypes);
            checkArgument(RelNode.class.isAssignableFrom(handlerTypes.get(0)),
                "RelNode.assignableFrom(handlerType[0])", handlerMethod,
                handlerTypes);
            checkArgument(RelMetadataQuery.class == handlerTypes.get(1),
                "handlerTypes[1] == RelMetadataQuery", handlerMethod,
                handlerTypes);
            checkArgument(methodTypes.equals(Util.skip(handlerTypes, 2)),
                "methodTypes == handlerTypes.skip(2)", handlerMethod, methodTypes,
                handlerTypes);
          });
    }
  
    /** Creates a {@link org.apache.calcite.rel.metadata.MetadataDef}. */
    public static <M extends Metadata> MetadataDef<M> of(Class<M> metadataClass,
        Class<? extends MetadataHandler<M>> handlerClass, Method... methods) {
      return new MetadataDef<>(metadataClass, handlerClass, methods);
    }
  }
  