/*
 * 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.phoenix.parse;

import java.sql.SQLException;
import java.util.Collections;
import java.util.List;
import org.apache.phoenix.compile.ColumnResolver;

/**
 * Node representing the IS NULL and IS NOT NULL expressions in SQL
 * @since 0.1
 */
public class IsNullParseNode extends UnaryParseNode {
  private final boolean negate;

  IsNullParseNode(ParseNode expr, boolean negate) {
    super(expr);
    this.negate = negate;
  }

  public boolean isNegate() {
    return negate;
  }

  @Override
  public <T> T accept(ParseNodeVisitor<T> visitor) throws SQLException {
    List<T> l = Collections.emptyList();
    if (visitor.visitEnter(this)) {
      l = acceptChildren(visitor);
    }
    return visitor.visitLeave(this, l);
  }

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

  @Override
  public boolean equals(Object obj) {
    if (this == obj) return true;
    if (!super.equals(obj)) return false;
    if (getClass() != obj.getClass()) return false;
    IsNullParseNode other = (IsNullParseNode) obj;
    if (negate != other.negate) return false;
    return true;
  }

  @Override
  public void toSQL(ColumnResolver resolver, StringBuilder buf) {
    getChildren().get(0).toSQL(resolver, buf);
    buf.append(" IS");
    if (negate) buf.append(" NOT");
    buf.append(" NULL ");
  }
}
