/*
* 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 websocket.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 org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
/**
* Sets up the timer for the multi-player snake game WebSocket example.
*/
public class SnakeTimer {
private static final Log log =
LogFactory.getLog(SnakeTimer.class);
private static Timer gameTimer = null;
static final long TICK_DELAY = 100;
private static final ConcurrentHashMap<Integer, Snake> snakes =
new ConcurrentHashMap<>();
protected static synchronized void addSnake(Snake snake) {
if (snakes.size() == 0) {
startTimer();
}
snakes.put(Integer.valueOf(snake.getId()), snake);
}
protected static Collection<Snake> getSnakes() {
return Collections.unmodifiableCollection(snakes.values());
}
protected static synchronized void removeSnake(Snake snake) {
snakes.remove(Integer.valueOf(snake.getId()));
if (snakes.size() == 0) {
stopTimer();
}
}
protected static void tick() {
StringBuilder sb = new StringBuilder();
for (Iterator<Snake> iterator = getSnakes().iterator();
iterator.hasNext();) {
Snake snake = iterator.next();
snake.update(getSnakes());
sb.append(snake.getLocationsJson());
if (iterator.hasNext()) {
sb.append(',');
}
}
broadcast(String.format("{\"type\": \"update\", \"data\" : [%s]}", sb.toString()));
}
protected static void broadcast(String message) {
for (Snake snake : getSnakes()) {
try {
snake.sendMessage(message);
} catch (IllegalStateException ise) {
// An ISE can occur if an attempt is made to write to a
// WebSocket connection after it has been closed. The
// alternative to catching this exception is to synchronise
// the writes to the clients along with the addSnake() and
// removeSnake() methods that are already synchronised.
}
}
}
public static void startTimer() {
gameTimer = new Timer(SnakeTimer.class.getSimpleName() + " Timer");
gameTimer.scheduleAtFixedRate(new TimerTask() {
@Override
public void run() {
try {
tick();
} catch (RuntimeException e) {
log.error("Caught to prevent timer from shutting down", e);
}
}
}, TICK_DELAY, TICK_DELAY);
}
public static void stopTimer() {
if (gameTimer != null) {
gameTimer.cancel();
}
}
}