public IEnumerable <Payment> GetMonthlyPayments(IMortgage mortgage, DateTime endAt)
{
if (endAt < mortgage.InitiatedAt)
{
yield break;
}
yield return(new Payment(mortgage, mortgage.InitiatedAt, mortgage.InitialValue, 0, 0));
var monthlyPayment = Convert.ToDecimal(mortgage.MonthlyPayment);
decimal balance = mortgage.InitialValue;
var interestRate = mortgage.PeriodicAnnualInterestRate;
var i = mortgage.InitiatedAt;
for (; balance > 0 && i < endAt; i = i.AddDays(1))
{
if (mortgage.IsMonthlyPayment(i))
{
var interestPayment = balance * interestRate / 12;
var principalPayment = monthlyPayment - interestPayment;
principalPayment = principalPayment > balance
? balance
: principalPayment;
yield return(new Payment(mortgage, i, balance, interestPayment, principalPayment));
balance -= principalPayment;
}
if (balance == 0)
{
yield break;
}
var extraPayment = mortgage.GetPrincipalOnlyPayments(i.Year, i.Month, i.Day)
.Sum();
if (extraPayment != 0)
{
extraPayment = extraPayment > balance
? balance
: extraPayment;
yield return(new Payment(mortgage, i, balance, 0, extraPayment));
balance -= extraPayment;
}
}
}
