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/*
 * Copyright The Microcks Authors.
 *
 * 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 io.github.microcks.operator;

import io.fabric8.kubernetes.client.Watcher;

import java.util.concurrent.ConcurrentHashMap;

/**
 * A simple manager for Watcher that allows registering / unregistering them so that controllers do not create multiple
 * watchers for the same resources...
 * @author laurent
 */
public class WatcherManager {

   /** Singleton's internal instance. */
   private static final WatcherManager singleton = new WatcherManager();

   /** Manager is baked by a concurrent hash map where watchers are stored according a key. */
   private final ConcurrentHashMap watchers = new ConcurrentHashMap<>();

   private WatcherManager() {
   }

   /**
    * Retrieve the current and unique instance of Watcher manager.
    * @return A WatcherManager instance
    */
   public static WatcherManager getInstance() {
      return singleton;
   }

   /**
    * Returns true if a watcher has already been registered with this key.
    * @param key The registration key for watcher
    * @return True if already present, false otherwise.
    */
   public boolean hasWatcher(WatcherKey key) {
      return watchers.containsKey(key);
   }

   /**
    * Returns registered watcher or null if none.
    * @param key The registration key for watcher
    * @return Registered watcher or null
    */
   public Watcher getWatcher(WatcherKey key) {
      return watchers.get(key);
   }

   /**
    * Register the given matcher using its key.
    * @param key     The registration key for watcher
    * @param watcher The watcher to register
    */
   public void registerWatcher(WatcherKey key, Watcher watcher) {
      watchers.put(key, watcher);
   }

   /**
    * Unregister an existing watcher if any.
    * @param key The registration key for watcher
    */
   public void unregisterWatcher(WatcherKey key) {
      watchers.remove(key);
   }
}