/*
 * 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.queryengine.transformation.dag.transformer.unary;

import org.apache.iotdb.db.exception.query.QueryProcessException;
import org.apache.iotdb.db.queryengine.transformation.api.LayerPointReader;
import org.apache.iotdb.db.queryengine.transformation.api.YieldableState;
import org.apache.iotdb.tsfile.file.metadata.enums.TSDataType;

import java.io.IOException;

public class IsNullTransformer extends UnaryTransformer {
  private final boolean isNot;

  public IsNullTransformer(LayerPointReader layerPointReader, boolean isNot) {
    super(layerPointReader);
    this.isNot = isNot;
  }

  @Override
  public TSDataType getDataType() {
    return TSDataType.BOOLEAN;
  }

  @Override
  public final YieldableState yieldValue() throws Exception {
    final YieldableState yieldableState = layerPointReader.yield();
    if (!YieldableState.YIELDABLE.equals(yieldableState)) {
      return yieldableState;
    }

    if (!isLayerPointReaderConstant) {
      cachedTime = layerPointReader.currentTime();
    }

    transformAndCache();

    layerPointReader.readyForNext();
    return YieldableState.YIELDABLE;
  }

  /*
   * currNull = true, isNot = false -> cachedBoolean = true;
   * currNull = false, isNot = true -> cachedBoolean = true;
   * currNull = true, isNot = true -> cachedBoolean = false;
   * currNull = false, isNot = false -> cachedBoolean = false.
   * So we need use '^' here.
   */
  @Override
  protected void transformAndCache() throws QueryProcessException, IOException {
    cachedBoolean = layerPointReader.isCurrentNull() ^ isNot;
  }
}