public class OrderDeliverer
{
    private List completedOrders = new List();
    private IOrderStreamer orderStreamer;
    private Warehouse warehouse;
    private Double promoters;
    private Double detractors;
    private Action deliveredOrderAction;

    public OrderDeliverer(Warehouse warehouse, IOrderStreamer orderStreamer)
    {
        this.warehouse = warehouse;
        this.orderStreamer = orderStreamer;
    }

    public virtual void ProcessOrder()
    {
        // Artificially advance the time to the next order waiting to be created
        // This is a fail safe, just in case the the processing of orders don't advance time enough
        if (!warehouse.HasOrders)
        {
            orderStreamer.AdvanceTime();
        }

        // Keep processing orders while there are orders
        if (warehouse.HasOrders)
        {
            Order order;

            // If there isn't time for delivery the order should be moved to next day delivery
            if (!warehouse.HasTimeToDeliverNextOrder(orderStreamer.CurrentTime))
            {
                warehouse.MoveNextOrderToNextDay();
            }
            else if (warehouse.TrySendNextOrder(out order)) // Try to send the order out of the warehouse
            {
                // Create a delivered order and track its status and times
                DeliveredOrder outboundOrder = new DeliveredOrder(order.Id);
                outboundOrder.OrderPlaced = order.Created;
                outboundOrder.DepartureTime = orderStreamer.CurrentTime;
                outboundOrder.DeliveredTime = outboundOrder.DepartureTime;

                // Time traveled to the destination
                double travelMinutes = warehouse.GetOrderDeliveryMinutes(order);
                outboundOrder.DeliveredTime = outboundOrder.DeliveredTime.AddMinutes(travelMinutes);

                // Total time traveled, includes to destination and returning back to the warehouse 
                travelMinutes += warehouse.GetOrderReturnMinutes(order);

                completedOrders.Add(outboundOrder);
                deliveredOrderAction(outboundOrder);

                switch (outboundOrder.GetRating())
                {
                    case OrderHelper.RatingType.Detractor:
                        detractors++;
                        break;

                    case OrderHelper.RatingType.Promoter:
                        promoters++;
                        break;
                }

                warehouse.DockDrone();

                // Update the mock global time (will also bring more new orders depending on the time)
                orderStreamer.AddMinutesToTime(travelMinutes);
            }
        }
    }

    public void OnDeliveredOrder(Action deliveredAction)
    {
        deliveredOrderAction += deliveredAction;
    }

    /// 
    /// The number of orders successfully delivered
    /// 
    /// Returns an int for the count of delivered orders
    public int GetNumberOfCompleted()
    {
        return completedOrders.Count;
    }

    public double GetNps()
    {
        double nps = 0;

        if (completedOrders.Count > 0)
        {
            double promoterPercent = (promoters / completedOrders.Count) * 100;
            double detractorPercent = (detractors / completedOrders.Count) * 100;
            int decimalPlaces = 2;

            nps = Math.Round(promoterPercent - detractorPercent, decimalPlaces);
        }

        return nps;
    }
}