/// <summary>
/// Calculate subscription payment based on subscription level and term
/// </summary>
/// <param name="subscriptionPlan">customer's subscription plan</param>
/// <returns>subscription payment customer should pay</returns>
public double CalculatePayment(SubscriptionPlan subscriptionPlan)
{
IPaymentStrategy paymentStrategy = _paymentStrategyFactory.GetPaymentStratgey(subscriptionPlan.Level.ToString());
if (paymentStrategy == null)
{
return(-1d);
}
return(paymentStrategy.CalculatePayment(subscriptionPlan));
}