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.adapter.druid;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexCall;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.sql.SqlOperator;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  /**
   * Direct operator conversion for expression like Function(exp_1,...exp_n)
   */
  public class DirectOperatorConversion implements DruidSqlOperatorConverter {
    private final SqlOperator operator;
    private final String druidFunctionName;
  
    public DirectOperatorConversion(final SqlOperator operator, final String druidFunctionName) {
      this.operator = operator;
      this.druidFunctionName = druidFunctionName;
    }
  
    @Override public SqlOperator calciteOperator() {
      return operator;
    }
  
    @Override public @Nullable String toDruidExpression(RexNode rexNode,
        RelDataType rowType, DruidQuery druidQuery) {
      final RexCall call = (RexCall) rexNode;
      final List<String> druidExpressions =
          DruidExpressions.toDruidExpressions(druidQuery, rowType,
              call.getOperands());
      if (druidExpressions == null) {
        return null;
      }
      return DruidExpressions.functionCall(druidFunctionName, druidExpressions);
    }
  }
  