/*
 * 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.iotdb.db.utils.columngenerator;

import org.apache.iotdb.db.queryengine.execution.aggregation.timerangeiterator.ITimeRangeIterator;

import org.apache.tsfile.block.column.Column;
import org.apache.tsfile.read.common.block.column.LongColumn;

import java.util.Optional;

/**
 * This class is used to generate a time column in INT64 where the value would increase in a way of
 * sliding-window. It's only designed for group by time now.
 */
public class SlidingTimeColumnGenerator extends ColumnGenerator {

  private final ITimeRangeIterator timeRangeIterator;

  public SlidingTimeColumnGenerator(ITimeRangeIterator timeRangeIterator) {
    this.timeRangeIterator = timeRangeIterator;
  }

  // Construct endTime column according to timeRangeIterator.
  @Override
  public Column[] generate(int positionCount) {
    long[] values = new long[positionCount];
    int index = 0;
    while (index < positionCount && timeRangeIterator.hasNextTimeRange()) {
      // Get the endTime in the timeRange, it's always the maxTime because the ordering in GROUP BY
      // TIME only allows ascending.
      values[index++] = timeRangeIterator.nextTimeRange().getMax();
    }
    return new Column[] {new LongColumn(positionCount, Optional.empty(), values)};
  }
}
