/*
 * 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.solr.handler;

import java.util.ArrayList;
import java.util.List;

/**
 * A state manager which implements an observer pattern to notify observers
 * of a state change.
 */
abstract class CdcrStateManager {

  private List<CdcrStateObserver> observers = new ArrayList<>();

  void register(CdcrStateObserver observer) {
    this.observers.add(observer);
  }

  void callback() {
    for (CdcrStateObserver observer : observers) {
      observer.stateUpdate();
    }
  }

  interface CdcrStateObserver {

    void stateUpdate();

  }

}