/*
 * 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.drill.exec.store.druid;

import org.apache.drill.common.exceptions.ExecutionSetupException;
import org.apache.drill.common.expression.SchemaPath;
import org.apache.drill.exec.ops.ExecutorFragmentContext;
import org.apache.drill.exec.physical.impl.BatchCreator;
import org.apache.drill.exec.physical.impl.ScanBatch;
import org.apache.drill.exec.record.CloseableRecordBatch;
import org.apache.drill.exec.record.RecordBatch;
import org.apache.drill.exec.store.RecordReader;
import org.apache.drill.shaded.guava.com.google.common.base.Preconditions;
import org.apache.drill.shaded.guava.com.google.common.collect.Lists;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;

public class DruidScanBatchCreator implements BatchCreator<DruidSubScan> {

  private static final Logger logger = LoggerFactory.getLogger(DruidScanBatchCreator.class);

  @Override
  public CloseableRecordBatch getBatch(ExecutorFragmentContext context, DruidSubScan subScan, List<RecordBatch> children) throws ExecutionSetupException {
    Preconditions.checkArgument(children.isEmpty());
    List<RecordReader> readers = Lists.newArrayList();
    List<SchemaPath> columns;

    for (DruidSubScan.DruidSubScanSpec scanSpec : subScan.getScanSpec()) {
      try {
        columns = subScan.getColumns();
        readers.add(new DruidRecordReader(scanSpec, columns, subScan.getMaxRecordsToRead(), context, subScan.getStorageEngine()));
      } catch (Exception ex) {
        throw new ExecutionSetupException(ex);
      }
    }
    logger.debug("Number of record readers initialized - {}", readers.size());
    return new ScanBatch(subScan, context, readers);
  }
}
