/*
 * 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.druid.sql.calcite.planner;

import org.apache.calcite.util.Pair;
import org.apache.druid.sql.calcite.rel.DruidQuery;

import java.util.ArrayList;
import java.util.List;

/**
 * Utility class for queries
 */
public class QueryUtils
{

  private QueryUtils()
  {
  }

  /**
   * Builds the mappings for queryColumn to outputColumn
   * @param fieldMapping The field mappings
   * @param druidQuery The Druid query
   * @return Mappings for queryColumn to outputColumn
   */
  public static List<ColumnMapping> buildColumnMappings(
      final List<Pair<Integer, String>> fieldMapping,
      final DruidQuery druidQuery
  )
  {
    final List<ColumnMapping> columnMappings = new ArrayList<>();
    for (final Pair<Integer, String> entry : fieldMapping) {
      final String queryColumn = druidQuery.getOutputRowSignature().getColumnName(entry.getKey());
      final String outputColumn = entry.getValue();
      columnMappings.add(new ColumnMapping(queryColumn, outputColumn));
    }

    return columnMappings;
  }
}
