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.model;
  
  import com.fasterxml.jackson.annotation.JsonCreator;
  import com.fasterxml.jackson.annotation.JsonProperty;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Function schema element.
   *
   * @see JsonRoot Description of schema elements
   */
  public class JsonFunction {
    /** Name of this function.
     *
     * <p>Required.
     */
    public final String name;
  
    /** Name of the class that implements this function.
     *
     * <p>Required.
     */
    public final String className;
  
    /** Name of the method that implements this function.
     *
     * <p>Optional.
     *
     * <p>If specified, the method must exist (case-sensitive) and Calcite
     * will create a scalar function. The method may be static or non-static, but
     * if non-static, the class must have a public constructor with no parameters.
     *
     * <p>If "*", Calcite creates a function for every method
     * in this class.
     *
     * <p>If not specified, Calcite looks for a method called "eval", and
     * if found, creates a a table macro or scalar function.
     * It also looks for methods "init", "add", "merge", "result", and
     * if found, creates an aggregate function.
     */
    public final @Nullable String methodName;
  
    /** Path for resolving this function.
     *
     * <p>Optional.
     */
    public final @Nullable List<String> path;
  
    @JsonCreator
    public JsonFunction(
        @JsonProperty("name") String name,
        @JsonProperty(value = "className", required = true) String className,
        @JsonProperty("methodName") @Nullable String methodName,
        @JsonProperty("path") @Nullable List<String> path) {
      this.name = name;
      this.className = requireNonNull(className, "className");
      this.methodName = methodName;
      this.path = path;
    }
  
    public void accept(ModelHandler handler) {
      handler.visit(this);
    }
  }
  