public static void AddInterest(this InstallmentPlanRow row, decimal interest, string description)
{
row.Description = row.Description + ", " + description;
row.InterestRepayment += interest;
row.Annuity += interest;
row.NetCashFlow += interest;
row.DiscountedNetCashFlow += interest;
}
public static InstallmentPlanCalculationResult CalculateInstallmentPlan(SimpleLoanCalculationRequest request)
{
if (request.NumberOfInstallments == 0)
{
request.NumberOfInstallments = 1;
}
if (request.CalculationTarget == CalculationTarget.Term)
{
request.NumberOfInstallments = 12 * 200; // this will be cut off
}
//request.StardDate = request.StardDate.Date;
// default installment schedule
if (request.InstallmentSchedule == null)
{
request.InstallmentSchedule = new SimpleSchedule();
request.InstallmentSchedule.DayOfMonth = request.StardDate.Day;
request.InstallmentSchedule.FrequencyPeriod = 1;
request.InstallmentSchedule.FrequencyUnitOfTime = SimpleUnitOfTime.M;
}
if (request.InstallmentSchedule.DayOfMonth == 0)
{
request.InstallmentSchedule.DayOfMonth = request.StardDate.Day;
}
// default interest schedule
if (request.InterestSchedule == null)
{
request.InterestSchedule = new SimpleSchedule();
request.InterestSchedule.DayOfMonth = request.InstallmentSchedule.DayOfMonth;
request.InterestSchedule.FrequencyPeriod = request.InstallmentSchedule.FrequencyPeriod;
request.InterestSchedule.FrequencyUnitOfTime = request.InstallmentSchedule.FrequencyUnitOfTime;
}
int dayOfMonth = request.InstallmentSchedule.DayOfMonth;
DateTime startDate = request.StardDate;
DateTime repaymentPeriodStartDate = request.StardDate;
DateTime firstInstallmentDate = new DateTime(startDate.Year, startDate.Month, dayOfMonth);
DateTime firstInterestDate = new DateTime(startDate.Year, startDate.Month, request.InterestSchedule.DayOfMonth);
if (firstInterestDate <= startDate)
{
firstInterestDate = firstInterestDate.AddMonths(1);
}
if (firstInstallmentDate < startDate)
{
firstInstallmentDate = firstInstallmentDate.AddMonths(1);
}
Decimal intercalarInterest = 0;
if (request.RegularInterest.Count != 1)
{
throw new NotImplementedException("Currently support only single interest rate entry");
}
var inr = request.RegularInterest.FirstOrDefault();
if (firstInstallmentDate == startDate)
{
firstInstallmentDate = firstInstallmentDate.AddPeriod(request.InstallmentSchedule.FrequencyPeriod, request.InstallmentSchedule.FrequencyUnitOfTime);
}
if (firstInterestDate == startDate)
{
firstInterestDate = firstInterestDate.AddPeriod(request.InterestSchedule.FrequencyPeriod, request.InterestSchedule.FrequencyUnitOfTime);
}
// for days 29..31
firstInstallmentDate = firstInstallmentDate.MoveTo(request.InstallmentSchedule.DayOfMonth);
firstInterestDate = firstInterestDate.MoveTo(request.InterestSchedule.DayOfMonth);
bool hasIntercalar = false;
if (startDate.AddDays(request.MinimumDaysForFirstInstallment) > firstInstallmentDate)
{
// This means that date of first interest calculation and first installment will differ
// Intercalar period must be forced
repaymentPeriodStartDate = firstInterestDate;
firstInstallmentDate = repaymentPeriodStartDate.AddPeriod(request.InstallmentSchedule.FrequencyPeriod, request.InstallmentSchedule.FrequencyUnitOfTime);
hasIntercalar = true;
}
decimal annuity = request.Amount / request.NumberOfInstallments;
if (request.RepaymentType == RepaymentType.FixedAnnuity)
{
if (request.CalculationTarget == CalculationTarget.Amount)
{
decimal dummyAmount = 100000;
annuity = (decimal)CalculateAnnuity(repaymentPeriodStartDate, firstInstallmentDate,
request.NumberOfInstallments, request.InstallmentSchedule.FrequencyPeriod, request.InstallmentSchedule.FrequencyUnitOfTime,
inr.RatePercentage, inr.RateUnitOfTime, inr.IsCompound, inr.CalendarBasis, (double)dummyAmount, request.AdjustFirstInstallment);
request.Amount = Math.Round(dummyAmount / annuity * request.Annuity, 2, MidpointRounding.ToEven);
annuity = request.Annuity;
}
}
if (request.CalculationTarget == CalculationTarget.Annuity && request.RepaymentType == RepaymentType.FixedAnnuity)
{
annuity = (decimal)CalculateAnnuity(repaymentPeriodStartDate, firstInstallmentDate,
request.NumberOfInstallments, request.InstallmentSchedule.FrequencyPeriod, request.InstallmentSchedule.FrequencyUnitOfTime,
inr.RatePercentage, inr.RateUnitOfTime, inr.IsCompound, inr.CalendarBasis, (double)request.Amount, request.AdjustFirstInstallment);
}
else if (request.CalculationTarget == CalculationTarget.Annuity && request.RepaymentType == RepaymentType.FixedPrincipalRepayment)
{
annuity = request.Amount / request.NumberOfInstallments;
}
else if (request.CalculationTarget == CalculationTarget.Annuity && request.RepaymentType == RepaymentType.Bullet)
{
annuity = request.Amount;
request.NumberOfInstallments = 1;
}
else
{
annuity = request.Annuity;
}
annuity = Math.Round(annuity, 2, MidpointRounding.ToEven);
if (hasIntercalar && inr != null)
{
intercalarInterest = InterestCalculation.CalculateInterest(startDate, firstInterestDate, firstInterestDate, inr.RatePercentage, inr.RateUnitOfTime.CharLiteral(), inr.IsCompound, inr.CalendarBasis, (double)request.Amount).TotalInterest;
intercalarInterest = Math.Round(intercalarInterest, 2, MidpointRounding.ToEven);
}
InstallmentPlanCalculationResult result = new InstallmentPlanCalculationResult
{
NumberOfInstallments = request.NumberOfInstallments,
Annuity = annuity,
Amount = request.Amount,
Rows = new List <InstallmentPlanRow>()
};
// Disbursement row
InstallmentPlanRow row = new InstallmentPlanRow
{
Ordinal = 0,
Date = startDate,
ActivityKind = ActivityKind.Disbursement,
Description = "Disbursement",
Disbursement = request.Amount,
NetCashFlow = -request.Amount
};
row.DiscountedNetCashFlow = row.NetCashFlow;
row.OutstandingBalance = request.Amount;
result.Rows.Add(row);
int ordinal = 1;
bool addIntercalarToFirstInstallment = false;
// Intercalary interest
if (firstInterestDate != firstInstallmentDate && intercalarInterest != 0)
{
if (request.IntercalarInterestRepaymentType == IntercalarInterestRepaymentType.AfterIntercalarPeriod)
{
row = new InstallmentPlanRow
{
Ordinal = ordinal,
Date = firstInterestDate,
Description = "Intercalar interest",
ActivityKind = ActivityKind.InterestPayment,
InterestRepayment = intercalarInterest,
OutstandingBalance = request.Amount,
StartingBalance = request.Amount,
Annuity = intercalarInterest,
NetCashFlow = intercalarInterest,
DiscountedNetCashFlow = intercalarInterest
};
result.Rows.Add(row);
ordinal++;
}
else if (request.IntercalarInterestRepaymentType == IntercalarInterestRepaymentType.WithDisbursement)
{
row.AddInterest(intercalarInterest, "Intercalar interest");
}
else
{
// As this row is still not created, we leave this for later
addIntercalarToFirstInstallment = true;
}
}
DateTime d1 = repaymentPeriodStartDate;
DateTime d2 = firstInstallmentDate;
decimal outstanding = request.Amount;
#region new way
DateTime maturityDate = firstInstallmentDate.AddPeriod(request.InstallmentSchedule.FrequencyPeriod * (request.NumberOfInstallments - 1), request.InstallmentSchedule.FrequencyUnitOfTime);
maturityDate = maturityDate.MoveTo(request.InstallmentSchedule.DayOfMonth); // correction for day of month 29..31
SortedDictionary <DateTime, InstlCalcRow> calcDates = new SortedDictionary <DateTime, InstlCalcRow>();
DateTime d = firstInterestDate;
if (intercalarInterest != 0) // if there was intercalar interest calculated, then skip this date
{
d1 = firstInterestDate;
d = d.AddPeriod(request.InterestSchedule.FrequencyPeriod, request.InterestSchedule.FrequencyUnitOfTime);
d = d.MoveTo(request.InterestSchedule.DayOfMonth); // correction for day of month 29..31
}
while (d < maturityDate)
{
calcDates.Add(d, new InstlCalcRow()
{
HasInterestRepayment = true
});
d = d.AddPeriod(request.InterestSchedule.FrequencyPeriod, request.InterestSchedule.FrequencyUnitOfTime);
d = d.MoveTo(request.InterestSchedule.DayOfMonth); // correction for day of month 29..31
}
d = firstInstallmentDate;
while (d < maturityDate)
{
if (calcDates.ContainsKey(d))
{
calcDates[d].HasPrincipalRepayment = true;
}
else
{
calcDates.Add(d, new InstlCalcRow()
{
HasInterestRepayment = request.ForceInterestWithInstallment, HasPrincipalRepayment = true
});
}
d = d.AddPeriod(request.InstallmentSchedule.FrequencyPeriod, request.InstallmentSchedule.FrequencyUnitOfTime);
d = d.MoveTo(request.InstallmentSchedule.DayOfMonth); // correction for day of month 29..31
}
// on maturity date we have to add interest and principal
calcDates.Add(maturityDate, new InstlCalcRow()
{
HasInterestRepayment = true, HasPrincipalRepayment = true
});
decimal inrCalc = 0;
decimal inrBase = 0;
bool installmentAdjusted = false;
bool suddenEnd = false;
decimal minimalInstallment = 1; // TODO: read from configuration
foreach (var calcDate in calcDates)
{
d2 = calcDate.Key;
inrBase = outstanding;
if (inr.IsCompound)
{
inrBase = outstanding + inrCalc;
}
inrCalc = inrCalc + Math.Round(InterestCalculation.CalculateInterest(d1, d2, d2, inr.RatePercentage, inr.RateUnitOfTime.CharLiteral(), inr.IsCompound, inr.CalendarBasis, (double)inrBase).TotalInterest, 2, MidpointRounding.ToEven);
decimal inrRepayment = 0;
if (calcDate.Value.HasInterestRepayment)
{
inrRepayment = inrCalc;
inrCalc = 0;
}
row = new InstallmentPlanRow
{
Ordinal = ordinal,
Date = d2,
ActivityKind = ActivityKind.Repayment,
Description = "Repayment",
StartingBalance = outstanding,
InterestRepayment = inrRepayment
};
if (calcDate.Value.HasPrincipalRepayment)
{
if (d2 == maturityDate) // if last installment
{
row.PrincipalRepayment = outstanding;
}
else if (request.AdjustFirstInstallment && !installmentAdjusted && d2 < maturityDate && request.RepaymentType == RepaymentType.FixedAnnuity)
{
// We calculate PrincipalRepayment using dummy interest from simplified installment plan where all periods are equal
var dummyDate = d2.AddPeriod(-request.InstallmentSchedule.FrequencyPeriod, request.InstallmentSchedule.FrequencyUnitOfTime);
var dummyInterest = InterestCalculation.CalculateInterest(dummyDate, d2, d2, inr.RatePercentage, inr.RateUnitOfTime.CharLiteral(), inr.IsCompound, inr.CalendarBasis, (double)outstanding).TotalInterest;
dummyInterest = Math.Round(dummyInterest, 2, MidpointRounding.ToEven);
row.PrincipalRepayment = annuity - dummyInterest;
installmentAdjusted = true;
}
else if (request.RepaymentType == RepaymentType.FixedAnnuity)
{
row.PrincipalRepayment = annuity - row.InterestRepayment;
}
else // fixed principal repayment
{
row.PrincipalRepayment = annuity;
}
if (row.PrincipalRepayment > outstanding - minimalInstallment)
{
// break before reaching maturityDate (for example when calculating term)
// minimalInstallment is used to avoid insignificant amounts in last installment
row.PrincipalRepayment = outstanding;
result.NumberOfInstallments = calcDates.Count(it => it.Key < d2 && it.Value.HasPrincipalRepayment) + 1;
maturityDate = d2;
suddenEnd = true;
// force interest repayment if there wasn't one...
row.InterestRepayment += inrCalc;
inrCalc = 0;
}
}
else
{
row.PrincipalRepayment = 0;
}
row.Annuity = row.PrincipalRepayment + row.InterestRepayment + row.Fee;
row.OutstandingBalance = outstanding -= row.PrincipalRepayment;
row.NetCashFlow = row.PrincipalRepayment + row.InterestRepayment + row.Fee;
row.DiscountedNetCashFlow = row.PrincipalRepayment + row.InterestRepayment + row.Fee;
result.Rows.Add(row);
if (suddenEnd)
{
break;
}
ordinal++;
d1 = d2;
}
#endregion
if (addIntercalarToFirstInstallment)
{
var firstInstallment = result.Rows.FirstOrDefault(it => it.Date == firstInstallmentDate);
if (firstInstallment != null)
{
firstInstallment.AddInterest(intercalarInterest, "Intercalar interest");
}
}
// Now fees
if (request.Fees != null)
{
if (!request.FeeCurrencyConversionDone && !string.IsNullOrEmpty(request.Currency))
{
AssecoCurrencyConvertion.CurrencyConverter currencyConverter = new AssecoCurrencyConvertion.CurrencyConverter();
foreach (var feeEntry in request.Fees)
{
if (!string.IsNullOrWhiteSpace(feeEntry.Currency) && feeEntry.Currency != request.Currency)
{
feeEntry.FixedAmountInDealCurrency = currencyConverter.CurrencyConvert(feeEntry.FixedAmount, feeEntry.Currency, request.Currency, request.StardDate.ToString("o", System.Globalization.CultureInfo.InvariantCulture), request.FeeCurrencyConversionMethod);
feeEntry.LowerLimitInDealCurrency = currencyConverter.CurrencyConvert(feeEntry.LowerLimit, feeEntry.Currency, request.Currency, request.StardDate.ToString("o", System.Globalization.CultureInfo.InvariantCulture), request.FeeCurrencyConversionMethod);
feeEntry.UpperLimitInDealCurrency = currencyConverter.CurrencyConvert(feeEntry.UpperLimit, feeEntry.Currency, request.Currency, request.StardDate.ToString("o", System.Globalization.CultureInfo.InvariantCulture), request.FeeCurrencyConversionMethod);
}
else
{
feeEntry.FixedAmountInDealCurrency = feeEntry.FixedAmount;
feeEntry.LowerLimitInDealCurrency = feeEntry.LowerLimit;
feeEntry.UpperLimitInDealCurrency = feeEntry.UpperLimit;
}
}
}
List <FeeEntry> newFeeDates = new List <FeeEntry>();
foreach (var feeEntry in request.Fees.Where(it => it.Frequency != FeeConditionFrequency.EventTriggered))
{
d = feeEntry.Date;
while (d < maturityDate)
{
switch (feeEntry.Frequency)
{
case FeeConditionFrequency.Monthly:
d = d.AddMonths(1);
break;
case FeeConditionFrequency.Quarterly:
d = d.AddMonths(3);
break;
case FeeConditionFrequency.Semiyearly:
d = d.AddMonths(6);
break;
case FeeConditionFrequency.Yearly:
d = d.AddYears(1);
break;
default:
break;
}
// TODO: check if d is last date and if it should be applied
bool applyFeeOnLastDate = false;
if ((d <= maturityDate) && (applyFeeOnLastDate || d < d1))
{
FeeEntry f = new FeeEntry
{
CalculationBasisType = feeEntry.CalculationBasisType,
Currency = feeEntry.Currency,
Date = d,
FixedAmount = feeEntry.FixedAmount,
Frequency = feeEntry.Frequency,
Kind = feeEntry.Kind,
LowerLimit = feeEntry.LowerLimit,
Name = feeEntry.Name,
Percentage = feeEntry.Percentage,
ServiceCode = feeEntry.ServiceCode,
TariffCode = feeEntry.TariffCode,
UpperLimit = feeEntry.UpperLimit,
FixedAmountInDealCurrency = feeEntry.FixedAmountInDealCurrency,
LowerLimitInDealCurrency = feeEntry.LowerLimitInDealCurrency,
UpperLimitInDealCurrency = feeEntry.UpperLimitInDealCurrency
};
newFeeDates.Add(f);
}
}
}
foreach (var feeEntry in request.Fees.Union(newFeeDates))
{
row = result.Rows.Where(it => it.Date == feeEntry.Date).LastOrDefault();
if (row == null)
{
row = new InstallmentPlanRow();
var prevDate = result.Rows.Where(it => it.Date < feeEntry.Date).Max(it => it.Date);
int index = 0;
if (prevDate != null)
{
var prevRow = result.Rows.Where(it => it.Date == prevDate).LastOrDefault();
index = result.Rows.IndexOf(prevRow) + 1;
row.StartingBalance = prevRow.StartingBalance;
row.OutstandingBalance = prevRow.OutstandingBalance;
}
result.Rows.Insert(index, row);
row.Ordinal = 9999999; // we will have to renumerate this.
row.Description = feeEntry.Name;
}
else
{
row.Description = row.Description + ", " + feeEntry.Name;
}
decimal feeBasis = request.Amount;
if (feeEntry.CalculationBasisType == CalculationBasisType.AccountBalance)
{
feeBasis = row.OutstandingBalance; // as we calculate for future period
}
decimal fee = feeEntry.FixedAmountInDealCurrency + feeEntry.Percentage / 100 * feeBasis;
if (feeEntry.UpperLimitInDealCurrency > 0 && fee > feeEntry.UpperLimitInDealCurrency)
{
fee = feeEntry.UpperLimitInDealCurrency;
}
if (fee < feeEntry.LowerLimitInDealCurrency)
{
fee = feeEntry.LowerLimitInDealCurrency;
}
fee = Math.Round(fee, 2, MidpointRounding.ToEven);
row.Fee += fee;
row.NetCashFlow += fee;
row.DiscountedNetCashFlow = row.NetCashFlow;
// TODO: Add installment plan column OtherPayments (Druge isplate) to support this
/*
* if (row.Disbursement > 0 && request.payFeeFromDisbursement)
* {
* row.Disbursement -= fee;
* row.OtherPayments += fee;
*
* }
*/
}
}
// TODO: Check if there are rows with row.Ordinal = 9999999 and renumerate
// At the end, APR calculation
List <NetCashFlowItem> cashFlow = result.Rows.Select(it => new NetCashFlowItem()
{
Date = it.Date,
NetCashFlow = -it.NetCashFlow,
DiscountedNetCashFlow = -it.DiscountedNetCashFlow
}).ToList();
result.APR = InterestCalculation.CalculateEffectiveInterestRate(cashFlow);
// Update DiscountedNetCashFlow
foreach (var item in result.Rows)
{
item.DiscountedNetCashFlow = InterestCalculation.CalculateDiscountedNetCashFlow((double)item.NetCashFlow, (double)result.APR, item.Date, startDate);
}
return(result);
}