/// <summary>
/// Calculate the loan request.
/// </summary>
/// <param name="request">The request to calculate</param>
/// <returns>A completed AmortizationResponse</returns>
/// <exception cref="ArgumentNullException">Throws when request is null.</exception>
public AmortizationResponse Calculate(AmortizationRequest request)
{
if (request is null)
{
throw new ArgumentNullException(nameof(request), "Calculator request cannot be null.");
}
var ratePerPeriod = request.RatePerPeriod;
var numberOfPeriods = request.NumberOfPeriods;
var totalPrincipal = request.TotalPrincipal;
var schedule = new AmortizationPeriod[numberOfPeriods];
Parallel.For(1, numberOfPeriods + 1, periodNumber =>
{
var principalPayment = _financial.PrincipalPayment(ratePerPeriod, periodNumber, numberOfPeriods, -totalPrincipal);
var interestPayment = _financial.InterestPayment(ratePerPeriod, periodNumber, numberOfPeriods, -totalPrincipal);
var balanceLeft = ratePerPeriod == 0 ?
totalPrincipal - (principalPayment * periodNumber) :
_financial.InterestPayment(ratePerPeriod, periodNumber + 1, numberOfPeriods, -totalPrincipal) / ratePerPeriod;
schedule[periodNumber - 1] = new AmortizationPeriod(periodNumber, interestPayment, principalPayment, balanceLeft);
});
var paymentPerPeriod = _financial.Payment(ratePerPeriod, numberOfPeriods, -totalPrincipal);
var totalInterestPaid = schedule.Sum(p => p.InterestPayment);
var totalPaid = totalPrincipal + totalInterestPaid;
return(new AmortizationResponse(paymentPerPeriod, totalInterestPaid, totalPaid, schedule, request));
}
public void InterestPaymentNoFvAtEnd()
{
var answer = _financial.InterestPayment(.05m, 2, 60, -35);
Assert.Equal(1.75m, decimal.Round(answer, 2));
}