// Copyright 2017 The Nomulus Authors. All Rights Reserved.
//
// Licensed 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 google.registry.dns.writer;

import static com.google.common.base.Preconditions.checkState;

import java.util.concurrent.atomic.AtomicBoolean;

/**
 * A base implementation of {@link DnsWriter} that protects against multiple calls to commit().
 */
public abstract class BaseDnsWriter implements DnsWriter {

  private final AtomicBoolean committedAlready = new AtomicBoolean(false);

  @Override
  public final void commit() {
    checkState(committedAlready.compareAndSet(false, true), "commit() has already been called");
    commitUnchecked();
  }

  /** Commits DNS updates. This can never be called more than once. */
  protected abstract void commitUnchecked();
}