text: /*
   * Copyright 2012-2019 the original author or 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
   *
   *      https://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 smoketest.websocket.tomcat.snake;
  
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.Timer;
  import java.util.TimerTask;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.CopyOnWriteArrayList;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /**
   * Sets up the timer for the multi-player snake game WebSocket example.
   */
  public final class SnakeTimer {
  
  	private static final long TICK_DELAY = 100;
  
  	private static final Object MONITOR = new Object();
  
  	private static final Log logger = LogFactory.getLog(SnakeTimer.class);
  
  	private static final ConcurrentHashMap<Integer, Snake> snakes = new ConcurrentHashMap<>();
  
  	private static Timer gameTimer = null;
  
  	private SnakeTimer() {
  	}
  
  	public static void addSnake(Snake snake) {
  		synchronized (MONITOR) {
  			if (snakes.isEmpty()) {
  				startTimer();
  			}
  			snakes.put(Integer.valueOf(snake.getId()), snake);
  		}
  	}
  
  	public static Collection<Snake> getSnakes() {
  		return Collections.unmodifiableCollection(snakes.values());
  	}
  
  	public static void removeSnake(Snake snake) {
  		synchronized (MONITOR) {
  			snakes.remove(Integer.valueOf(snake.getId()));
  			if (snakes.isEmpty()) {
  				stopTimer();
  			}
  		}
  	}
  
  	public static void tick() throws Exception {
  		StringBuilder sb = new StringBuilder();
  		for (Iterator<Snake> iterator = SnakeTimer.getSnakes().iterator(); iterator.hasNext();) {
  			Snake snake = iterator.next();
  			snake.update(SnakeTimer.getSnakes());
  			sb.append(snake.getLocationsJson());
  			if (iterator.hasNext()) {
  				sb.append(',');
  			}
  		}
  		broadcast(String.format("{'type': 'update', 'data' : [%s]}", sb.toString()));
  	}
  
  	public static void broadcast(String message) throws Exception {
  		Collection<Snake> snakes = new CopyOnWriteArrayList<>(SnakeTimer.getSnakes());
  		for (Snake snake : snakes) {
  			try {
  				snake.sendMessage(message);
  			}
  			catch (Throwable ex) {
  				// if Snake#sendMessage fails the client is removed
  				removeSnake(snake);
  			}
  		}
  	}
  
  	public static void startTimer() {
  		gameTimer = new Timer(SnakeTimer.class.getSimpleName() + " Timer");
  		gameTimer.scheduleAtFixedRate(new TimerTask() {
  			@Override
  			public void run() {
  				try {
  					tick();
  				}
  				catch (Throwable ex) {
  					logger.error("Caught to prevent timer from shutting down", ex);
  				}
  			}
  		}, TICK_DELAY, TICK_DELAY);
  	}
  
  	public static void stopTimer() {
  		if (gameTimer != null) {
  			gameTimer.cancel();
  		}
  	}
  
  }
  