/**
 * 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.tajo.engine.eval;

import com.google.gson.annotations.Expose;
import org.apache.tajo.catalog.CatalogUtil;
import org.apache.tajo.catalog.Schema;
import org.apache.tajo.common.TajoDataTypes;
import org.apache.tajo.common.TajoDataTypes.DataType;
import org.apache.tajo.datum.Datum;
import org.apache.tajo.datum.DatumFactory;
import org.apache.tajo.storage.Tuple;

public class IsNullEval extends BinaryEval {
  // it's just a hack to emulate a binary expression
  private final static ConstEval DUMMY_EVAL = new ConstEval(DatumFactory.createBool(true));
  private static final DataType RES_TYPE = CatalogUtil.newSimpleDataType(TajoDataTypes.Type.BOOLEAN);

  // persistent variables
  @Expose private boolean isNot;

  public IsNullEval(boolean not, EvalNode predicand) {
    super(EvalType.IS_NULL, predicand, DUMMY_EVAL);
    this.isNot = not;
  }

  @Override
  public DataType getValueType() {
    return RES_TYPE;
  }

  @Override
  public String getName() {
    return "?";
  }

  @Override
  public String toString() {
    return leftExpr + " IS " + (isNot ? "NOT NULL" : "NULL");
  }

  @Override
  public Datum eval(Schema schema, Tuple tuple) {
    boolean isNull = leftExpr.eval(schema, tuple).isNull();
    return DatumFactory.createBool(isNot ^ isNull);
  }

  public boolean isNot() {
    return isNot;
  }

  @Override
  public boolean equals(Object obj) {
    if (obj instanceof IsNullEval) {
      IsNullEval other = (IsNullEval) obj;
      return super.equals(other) && isNot == other.isNot();
    } else {
      return false;
    }
  }

  public Object clone() throws CloneNotSupportedException {
    IsNullEval isNullEval = (IsNullEval) super.clone();
    isNullEval.isNot = isNot;

    return isNullEval;
  }
}