import java.util.*;

// source: http://people.inf.elte.hu/pgj/fny2_msc/fny2_msc_20160407.pdf, pages 4--5

public class ZipList<T> {
    private List<T> left, right;

    public ZipList(List<T> list) {
        left = new LinkedList<>();
        right = new LinkedList<>(list);
    }

    public void move(Direction dir) {
        switch (dir) {
            case LEFT : {
                if (!left.isEmpty()) {
                    T first = left.get(0);
                    left.remove(0);
                    right.add(0, first);
                } else
                    throw new NoMoreElementException("Focus is at the beginning of the list.");
                break;
            }
            case RIGHT : {
                if (right.size() > 1) {
                    T first = right.get(0);
                    right.remove(0);
                    left.add(0, first);
                } else 
                    throw new NoMoreElementException("Focus is at the end of the list.");
                break;
            }
        }
    }

    public T get() throws EmptyFocusException {
        if (!right.isEmpty())
            return right.get(0);
        else
            throw new EmptyFocusException("The ZipList is empty.");
    }

    public void put(T elem) {
        right.add(0, elem);
    }

    public List<T> toList() {
        List<T> result = new LinkedList<>(left);
        Collections.reverse(result);
        result.addAll(right);
        return result;
    }
}