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.SqlCall;
  import org.apache.calcite.sql.SqlCallBinding;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlOperatorBinding;
  import org.apache.calcite.sql.SqlSpecialOperator;
  import org.apache.calcite.sql.SqlWriter;
  import org.apache.calcite.sql.type.InferTypes;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.ReturnTypes;
  import org.apache.calcite.sql.type.SqlOperandTypeInference;
  import org.apache.calcite.sql.type.SqlTypeUtil;
  
  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 SQL:2003 standard MULTISET constructor, <code>MULTISET
   * [&lt;expr&gt;, ...]</code>.
   *
   * <p>Derived classes construct other kinds of collections.
   *
   * @see SqlMultisetQueryConstructor
   */
  public class SqlMultisetValueConstructor extends SqlSpecialOperator {
    //~ Constructors -----------------------------------------------------------
  
    public SqlMultisetValueConstructor() {
      this("MULTISET", SqlKind.MULTISET_VALUE_CONSTRUCTOR);
    }
  
    protected SqlMultisetValueConstructor(String name, SqlKind kind) {
      this(name, kind, InferTypes.FIRST_KNOWN);
    }
  
    protected SqlMultisetValueConstructor(
        String name, SqlKind kind,
        @Nullable SqlOperandTypeInference operandTypeInference) {
      super(
          name,
          kind, MDX_PRECEDENCE,
          false,
          ReturnTypes.ARG0,
          operandTypeInference,
          OperandTypes.VARIADIC);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public RelDataType inferReturnType(
        SqlOperatorBinding opBinding) {
      RelDataType type =
          getComponentType(
              opBinding.getTypeFactory(),
              opBinding.collectOperandTypes());
      requireNonNull(type, "inferred multiset value");
      return SqlTypeUtil.createMultisetType(
          opBinding.getTypeFactory(),
          type,
          false);
    }
  
    protected @Nullable RelDataType getComponentType(
        RelDataTypeFactory typeFactory,
        List<RelDataType> argTypes) {
      return typeFactory.leastRestrictive(argTypes);
    }
  
    @Override public boolean checkOperandTypes(
        SqlCallBinding callBinding,
        boolean throwOnFailure) {
      final List<RelDataType> argTypes =
          SqlTypeUtil.deriveType(callBinding, callBinding.operands());
      if (argTypes.isEmpty()) {
        throw callBinding.newValidationError(RESOURCE.requireAtLeastOneArg());
      }
      final RelDataType componentType =
          getComponentType(
              callBinding.getTypeFactory(),
              argTypes);
      if (null == componentType) {
        if (throwOnFailure) {
          throw callBinding.newValidationError(RESOURCE.needSameTypeParameter());
        }
        return false;
      }
      return true;
    }
  
    @Override public void unparse(
        SqlWriter writer,
        SqlCall call,
        int leftPrec,
        int rightPrec) {
      writer.keyword(getName()); // "MULTISET" or "ARRAY"
      final SqlWriter.Frame frame = writer.startList("[", "]");
      for (SqlNode operand : call.getOperandList()) {
        writer.sep(",");
        operand.unparse(writer, leftPrec, rightPrec);
      }
      writer.endList(frame);
    }
  }
  