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.fun;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.sql.SqlCallBinding;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlOperatorBinding;
  import org.apache.calcite.sql.type.SqlTypeUtil;
  import org.apache.calcite.sql.validate.SqlValidatorUtil;
  import org.apache.calcite.util.Pair;
  import org.apache.calcite.util.Util;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  import static org.apache.calcite.util.Static.RESOURCE;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Definition of the MAP constructor,
   * <code>MAP [&lt;key&gt;, &lt;value&gt;, ...]</code>.
   *
   * <p>This is an extension to standard SQL.
   */
  public class SqlMapValueConstructor extends SqlMultisetValueConstructor {
    public SqlMapValueConstructor() {
      // no need to deduce NULL operand type
      super("MAP", SqlKind.MAP_VALUE_CONSTRUCTOR, null);
    }
  
    @SuppressWarnings("argument.type.incompatible")
    @Override public RelDataType inferReturnType(SqlOperatorBinding opBinding) {
      Pair<@Nullable RelDataType, @Nullable RelDataType> type =
          getComponentTypes(
              opBinding.getTypeFactory(), opBinding.collectOperandTypes());
  
      // explicit cast elements to component type if they are not same
      SqlValidatorUtil.adjustTypeForMapConstructor(type, opBinding);
  
      return SqlTypeUtil.createMapType(
          opBinding.getTypeFactory(),
          requireNonNull(type.left, "inferred key type"),
          requireNonNull(type.right, "inferred value type"),
          false);
    }
  
    @Override public boolean checkOperandTypes(
        SqlCallBinding callBinding,
        boolean throwOnFailure) {
      final List<RelDataType> argTypes = SqlTypeUtil.deriveType(callBinding, callBinding.operands());
      if (argTypes.isEmpty()) {
        throw callBinding.newValidationError(RESOURCE.mapRequiresTwoOrMoreArgs());
      }
      if (argTypes.size() % 2 > 0) {
        throw callBinding.newValidationError(RESOURCE.mapRequiresEvenArgCount());
      }
      final Pair<@Nullable RelDataType, @Nullable RelDataType> componentType =
          getComponentTypes(
              callBinding.getTypeFactory(), argTypes);
      if (null == componentType.left || null == componentType.right) {
        if (throwOnFailure) {
          throw callBinding.newValidationError(RESOURCE.needSameTypeParameter());
        }
        return false;
      }
      return true;
    }
  
    private static Pair<@Nullable RelDataType, @Nullable RelDataType> getComponentTypes(
        RelDataTypeFactory typeFactory,
        List<RelDataType> argTypes) {
      return Pair.of(
          typeFactory.leastRestrictive(Util.quotientList(argTypes, 2, 0)),
          typeFactory.leastRestrictive(Util.quotientList(argTypes, 2, 1)));
    }
  }
  