package class5_3_QueueInterface;

/** Sorry... forgot to save yesterday's version... it was just getting started, anyhow */
// TODO: Untested code!

public class CircularQueue<E> implements Queue<E> {
    private final int MAX_SIZE = 5; // Smaller value makes testing easier

    int indFront = 0; // The "front of the line" i.e. first items to come off
    int indRear = -1; // The "back of the line" i.e. most recently arrived items.

    E[] array = (E[]) new Object[MAX_SIZE];

    @Override
    public E poll() {
        if(isEmpty()) {
            return null;
        }

        E result = array[indFront];
        indFront++;
        if(indFront >= array.length) {
            indFront = 0;
        }
        // TODO Edge case? +1?
        if(indFront == indRear) {
            // Queue is again empty!
            indFront = 0;
            indRear = -1;
        }

        return result;
    }

    @Override
    public boolean offer(E e) {
        // TODO: HW
        return false;
    }

    @Override
    public E peek() {
        if(isEmpty()) {
            return null;
        }

        return array[indFront];
    }

    @Override
    public boolean isEmpty() {
        return (indRear < 0);
    }

    /**
     * Returns true if no more elements can be added to the array.
     * @return true if full
     */
    private boolean isFull() {
        return ((indRear+1)%array.length == indFront);
    }
}