private static PaymentSchedule RoundPayments(PaymentSchedule paymentSchedule, int digitsAfterZero)
{
var resultPaymentSchedule = new PaymentSchedule();
var deltaMainDebt = 0M;
var deltaInterest = 0M;
var deltaOverdueMainDebt = 0M;
var deltaOverdueInterest = 0M;
if (paymentSchedule.Payments.Any())
{
var lastPmt = paymentSchedule.Payments.Last();
foreach (var payment in paymentSchedule.Payments)
{
if (payment == null)
{
continue;
}
var newMainDebt = 0M;
var newInterest = 0M;
var newOverdueMainDebt = 0M;
var newOverdueInterest = 0M;
if (payment != lastPmt)
{
newMainDebt = Math.Round(payment.MainDebtAmount, digitsAfterZero);
newInterest = Math.Round(payment.AccruedInterestAmount, digitsAfterZero);
newOverdueMainDebt = Math.Round(payment.OverdueMainDebtAmount, digitsAfterZero);
newOverdueInterest = Math.Round(payment.OverdueInterestAmount, digitsAfterZero);
deltaMainDebt += payment.MainDebtAmount - newMainDebt;
deltaInterest += payment.AccruedInterestAmount - newInterest;
deltaOverdueMainDebt += payment.OverdueMainDebtAmount - newOverdueMainDebt;
deltaOverdueInterest += payment.OverdueInterestAmount - newOverdueInterest;
}
else
{
newMainDebt = Math.Round(payment.MainDebtAmount + deltaMainDebt, digitsAfterZero);
newInterest = Math.Round(payment.AccruedInterestAmount + deltaInterest, digitsAfterZero);
newOverdueMainDebt = Math.Round(payment.OverdueMainDebtAmount + deltaOverdueMainDebt, digitsAfterZero);
newOverdueInterest = Math.Round(payment.OverdueInterestAmount + deltaOverdueInterest, digitsAfterZero);
}
resultPaymentSchedule.AddPayment(new Payment
{
MainDebtAmount = newMainDebt,
AccruedInterestAmount = newInterest,
OverdueMainDebtAmount = newOverdueMainDebt,
OverdueInterestAmount = newOverdueInterest,
AccruedOn = payment.AccruedOn,
ShouldBePaidBefore = payment.ShouldBePaidBefore,
});
}
}
return(resultPaymentSchedule);
}
public static PaymentSchedule CalculateAnnuitySchedule(Tariff tariff, decimal loanAmount, int term, DateTime?startDate)
{
var rate = tariff.InterestRate * tariff.PmtFrequency / 12;
var helpCoeff = PowDecimal(1 + rate, term);
var annuityCoeff = (rate * helpCoeff) / (helpCoeff - 1);
var monthlyPayment = loanAmount * annuityCoeff;
var schedule = new PaymentSchedule();
var remainMainDebt = loanAmount;
for (var i = 0; i < term; i++)
{
var pmtInterest = remainMainDebt * rate;
var pmtMainDebt = monthlyPayment - pmtInterest;
var accruedDate = CalculateAccrualDate(startDate, i + 1);
var payBefore = CalculatePaymentDate(startDate, i + 1);
if (startDate.HasValue && payBefore > startDate.Value.AddMonths(term))
{
payBefore = startDate.Value.AddMonths(term);
}
if (i == 0 && startDate.HasValue)
{
pmtInterest *= ((30 - startDate.Value.Day + 1) / 30M);
}
if (i + 1 == term && startDate.HasValue)
{
pmtInterest += pmtInterest * ((startDate.Value.Day - 1) / 30M);
}
var pmt = new Payment
{
MainDebtAmount = pmtMainDebt,
AccruedInterestAmount = pmtInterest,
AccruedOn = accruedDate,
ShouldBePaidBefore = payBefore
};
schedule.AddPayment(pmt);
remainMainDebt -= pmtMainDebt;
}
return(RoundPayments(schedule, 2));
}
private static PaymentSchedule CalculateStandardSchedule(Tariff tariff, decimal loanAmount, int term, DateTime?startDate)
{
var rate = tariff.InterestRate * tariff.PmtFrequency / 12;
var pmtMainDebt = loanAmount / term;
var schedule = new PaymentSchedule();
var remainMainDebt = loanAmount;
for (var i = 0; i < term; i++)
{
var pmtInterest = remainMainDebt * rate;
var payBefore = CalculatePaymentDate(startDate, i + 1);
if (i == 0 && startDate.HasValue)
{
pmtInterest *= ((30 - startDate.Value.Day + 1) / 30M);
}
if (i + 1 == term && startDate.HasValue)
{
pmtInterest += pmtInterest * ((startDate.Value.Day - 1) / 30M);
}
if (startDate.HasValue && payBefore > startDate.Value.AddMonths(term))
{
payBefore = startDate.Value.AddMonths(term);
}
var pmt = new Payment
{
MainDebtAmount = pmtMainDebt,
AccruedInterestAmount = pmtInterest,
AccruedOn = CalculateAccrualDate(startDate, i),
ShouldBePaidBefore = payBefore
};
schedule.AddPayment(pmt);
remainMainDebt -= pmtMainDebt;
}
return(RoundPayments(schedule, 2));
}