/**
 * ============LICENSE_START====================================================
 * org.onap.aaf
 * ===========================================================================
 * Copyright (c) 2018 AT&T Intellectual Property. 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.
 * ============LICENSE_END====================================================
 *
 */

package org.onap.aaf.cadi.register;

import java.util.Deque;
import java.util.Iterator;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.ConcurrentLinkedDeque;

import org.onap.aaf.cadi.client.Result;
import org.onap.aaf.misc.env.impl.BasicEnv;

public class Registrar<ENV extends BasicEnv> {
	private static final String REGISTRAR = "Registrar";
	private static final long INTERVAL = 15*60*1000L; // 15 mins
	private static final long START = 3000; // Start in 3 seconds
	private static final Object LOCK = new Object();
	private Deque<Registrant<ENV>> registrants;
	private Timer timer, erroringTimer;

	public Registrar(final ENV env, boolean shutdownHook) {
		registrants = new ConcurrentLinkedDeque<Registrant<ENV>>();

		erroringTimer = null;
		timer = new Timer(REGISTRAR,true);
		timer.schedule(new RegistrationTimerTask(env), START, INTERVAL); 
		
		if(shutdownHook) {
			Runtime.getRuntime().addShutdownHook(new Thread() {
				public void run() {
					close(env);
				}
			});
		}
	}
	
	private class RegistrationTimerTask extends TimerTask {
		private final ENV env;
		public RegistrationTimerTask(ENV env) {
			this.env = env;
		}
		@Override
		public void run() {
			for(Iterator<Registrant<ENV>> iter = registrants.iterator(); iter.hasNext();) {
				Registrant<ENV> reg = iter.next();
				Result<Void> rv = reg.update(env);
				synchronized(LOCK) {
					if(rv.isOK()) {
						if(erroringTimer!=null) {
							erroringTimer.cancel();
							erroringTimer = null;
						}
					} else {
						// Account for different Registrations not being to same place
						if(erroringTimer==null) {
							erroringTimer =  new Timer(REGISTRAR + " error re-check ",true);
							erroringTimer.schedule(new RegistrationTimerTask(env),20000,20000);
						}
					}
				}
			}
		}
	}
	
	public void register(Registrant<ENV> r) {
		registrants.addLast(r);
	}
	
	public void deregister(Registrant<ENV> r) {
		registrants.remove(r);
	}

	public void close(ENV env) {
		timer.cancel();

		Registrant<ENV> r;
		while(registrants.peek()!=null) {
			r = registrants.pop();
			r.cancel(env);
		}
	}
}