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.sql.type;
  
  import org.apache.calcite.linq4j.function.Functions;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  
  import java.util.List;
  import java.util.function.Function;
  import java.util.function.IntFunction;
  import java.util.function.Predicate;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Operand type-checking strategy user-defined functions (including user-defined
   * aggregate functions, table functions, and table macros).
   *
   * <p>UDFs have a fixed number of parameters is fixed. Per
   * {@link SqlOperandMetadata}, this interface provides the name and types of
   * each parameter.
   *
   * @see OperandTypes#operandMetadata
   */
  public class OperandMetadataImpl extends FamilyOperandTypeChecker
      implements SqlOperandMetadata {
    private final Function<RelDataTypeFactory, List<RelDataType>>
        paramTypesFactory;
    private final IntFunction<String> paramNameFn;
  
    //~ Constructors -----------------------------------------------------------
  
    /** Package private. Create using {@link OperandTypes#operandMetadata}. */
    OperandMetadataImpl(List<SqlTypeFamily> families,
        Function<RelDataTypeFactory, List<RelDataType>> paramTypesFactory,
        IntFunction<String> paramNameFn, Predicate<Integer> optional) {
      super(families, optional);
      this.paramTypesFactory =
          requireNonNull(paramTypesFactory, "paramTypesFactory");
      this.paramNameFn = paramNameFn;
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public boolean isFixedParameters() {
      return true;
    }
  
    @Override public List<RelDataType> paramTypes(RelDataTypeFactory typeFactory) {
      return paramTypesFactory.apply(typeFactory);
    }
  
    @Override public List<String> paramNames() {
      return Functions.generate(families.size(), paramNameFn);
    }
  }
  