NimModel

package me.dvorkin;

import java.util.Random;

public class NimModel {
    private int[] piles;
    private boolean move;

    public NimModel() {
        move = true;
        Random random = new Random();
        piles = new int[5];
        for (int i = 0; i < piles.length; i++) {
            piles[i] = random.nextInt(10) + 1;
        }
    }

    public int[] getField() {
        return piles.clone();
    }

    /**
     * @return true if first player is to move
     */
    public boolean whoMoves() {
        return move;
    }

    public boolean isOver() {
        for (int i : piles) {
            if (i != 0) {
                return false;
            }
        }
        return true;
    }

    public boolean update(int index, int amount) {
        if (index < 0 || index >= piles.length) {
            return false;
        }
        if (amount <= 0 || amount > piles[index]) {
            return false;
        }
        piles[index] -= amount;
        move ^= true;
        return true;
    }
}