import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;

public class Environment {

	Set<Point> living = new HashSet<Point>();

	Map<Point, AtomicInteger> neighbours = new HashMap<>();

	public Environment(Set<Point> ps) {
		living = ps;
	}

	public Environment next() {
		Environment ret = new Environment(new HashSet<Point>());

		for (Entry<Point, AtomicInteger> entry : neighbours.entrySet()) {
			if (entry.getValue().get() == 3 || (entry.getValue().get() == 2 && living.contains(entry.getKey()))) {
				ret.living.add(entry.getKey());
			}
		}
		return ret;
	}

	public void increment(Point p) {
		AtomicInteger val = neighbours.get(p);
		if (val == null) {
			synchronized (neighbours) {
				val = neighbours.get(p);
				if (val == null) {
					neighbours.put(p, new AtomicInteger(1));
				} else {
					val.getAndIncrement();
				}
			}
		} else {
			val.getAndIncrement();
		}
	}

	public Set<Point> getPoints() {
		return living;
	}

}