/**
 * 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.plan.expr;

import com.google.gson.annotations.Expose;
import org.apache.tajo.datum.Datum;
import org.apache.tajo.datum.DatumFactory;
import org.apache.tajo.storage.Tuple;
import org.apache.tajo.type.Type;

public class IsNullEval extends UnaryEval {
  // persistent variables
  @Expose private boolean isNot;

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

  @Override
  public Type getValueType() {
    return Type.Bool;
  }

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

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

  @Override
  @SuppressWarnings("unchecked")
  public Datum eval(Tuple tuple) {
    super.eval(tuple);
    boolean isNull = child.eval(tuple).isNull();
    return DatumFactory.createBool(isNot ^ isNull);
  }

  public boolean isNot() {
    return isNot;
  }

  @Override
  public int hashCode() {
    final int prime = 31;
    int result = super.hashCode();
    result = prime * result + (isNot ? 1231 : 1237);
    return result;
  }

  @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;
  }
}