/*
 * 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.commons.udf.builtin;

import org.apache.iotdb.tsfile.read.common.block.column.Column;
import org.apache.iotdb.tsfile.read.common.block.column.ColumnBuilder;
import org.apache.iotdb.udf.api.UDTF;
import org.apache.iotdb.udf.api.access.Row;
import org.apache.iotdb.udf.api.collector.PointCollector;
import org.apache.iotdb.udf.api.customizer.config.UDTFConfigurations;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameters;
import org.apache.iotdb.udf.api.customizer.strategy.MappableRowByRowAccessStrategy;
import org.apache.iotdb.udf.api.type.Type;

import java.io.IOException;

public class UDTFConstPi implements UDTF {

  @Override
  public void beforeStart(UDFParameters parameters, UDTFConfigurations configurations) {
    configurations
        .setAccessStrategy(new MappableRowByRowAccessStrategy())
        .setOutputDataType(Type.DOUBLE);
  }

  @Override
  public void transform(Row row, PointCollector collector) throws Exception {
    collector.putDouble(row.getTime(), Math.PI);
  }

  @Override
  public Object transform(Row row) throws IOException {
    return Math.PI;
  }

  @Override
  public void transform(Column[] columns, ColumnBuilder builder) throws Exception {
    int colCount = columns[0].getPositionCount();

    for (int i = 0; i < colCount; i++) {
      boolean hasWritten = false;
      for (Column column : columns) {
        if (!column.isNull(i)) {
          builder.writeDouble(Math.PI);
          hasWritten = true;
          break;
        }
      }
      if (!hasWritten) {
        builder.appendNull();
      }
    }
  }
}
