/*
 * ToroDB
 * Copyright © 2014 8Kdata Technology (www.8kdata.com)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package com.torodb.kvdocument.values;

import com.torodb.kvdocument.types.NullType;

/**
 *
 */
public class KvNull extends KvValue<KvNull> {

  private static final long serialVersionUID = 4583557874141119051L;

  private KvNull() {
  }

  public static KvNull getInstance() {
    return KvNullHolder.INSTANCE;
  }

  @Override
  public KvNull getValue() {
    return this;
  }

  @Override
  public Class<? extends KvNull> getValueClass() {
    return KvNull.class;
  }

  @Override
  public NullType getType() {
    return NullType.INSTANCE;
  }

  @Override
  public String toString() {
    return "null";
  }

  @Override
  public boolean equals(Object obj) {
    return obj == this || obj != null && obj instanceof KvNull;
  }

  @Override
  public int hashCode() {
    return System.identityHashCode(this);
  }

  @Override
  public <R, A> R accept(KvValueVisitor<R, A> visitor, A arg) {
    return visitor.visit(this, arg);
  }

  private static class KvNullHolder {

    private static final KvNull INSTANCE = new KvNull();
  }

  //@edu.umd.cs.findbugs.annotations.SuppressFBWarnings(value = "UPM_UNCALLED_PRIVATE_METHOD")
  private Object readResolve() {
    return KvNull.getInstance();
  }
}