/// <summary>
/// Initializes a new instance of the <see cref="LoanCalculationOutputStreamWriter"/> class.
/// </summary>
/// <param name="context">The context.</param>
/// <param name="output">The output.</param>
public LoanCalculationOutputStreamWriter(LoanContext context, LoanCalculationOutput output)
{
this.context = context;
this.output = output;
}
/// <summary>
/// Calculates the loan using the context.
/// </summary>
/// <returns></returns>
public LoanCalculationOutput Calculate()
{
LoanCalculationOutput result = new LoanCalculationOutput();
bool firstIteration = true;
double balance = context.Balance;
double monthlyInterest = 0.0d;
DateTime currentDate = context.StartDate;
// we will calculate interest from the first of the month
DateTime calcInterestStartDate = new DateTime(currentDate.Year, currentDate.Month, 1);
result.InterestStartDate = calcInterestStartDate;
// loop through dates, caculating interest daily etc
while (true)
{
// if min repay day
if (currentDate.Day == context.MinRepaymentDay && balance > 0.0d)
{
balance = ProcessMinRepayment(balance, context.MinRepaymentAmount, currentDate, monthlyInterest, result);
}
// if extra repay day
if (currentDate.Day == context.ExtraRepaymentDay && context.ExtraRepaymentAmount > 0.0d && balance > 0.0d)
{
balance = ProcessExtraRepayment(balance, context.ExtraRepaymentAmount, currentDate, result);
}
// if balance is zero or less - we are done!
if (balance <= 0.0d)
{
result.LoanEndsDate = currentDate;
break;
}
// calculate the daily interest
monthlyInterest += CalculateDailyInterest(balance, context.InterestRate);
// if this is the first iteration and we did not start on the first of the month
// let's calculate the interest for the days back to the first
if (firstIteration && context.StartDate.Day != 1)
{
int daysToMonthStart = currentDate.Day - 1;
monthlyInterest += (monthlyInterest * daysToMonthStart);
firstIteration = false;
}
// if we have reached the max date of DateTime, let's throw back an error
if((currentDate.Ticks + TimeSpan.TicksPerDay) >= DateTime.MaxValue.Ticks)
{
result.Failure = true;
result.FailureMessage = string.Format("Calculations for your loan got to the end-of-time date {0}...and still not paid off. Your situation, sorry to say, is hopeless.", currentDate.ToShortDateString());
return (result);
}
// move date forward
DateTime nextDate = currentDate.AddDays(1);
// if end of month
if (currentDate.Month != nextDate.Month)
{
balance = ProcessEndOfMonth(currentDate, monthlyInterest, balance, result);
// reset interest to zero
monthlyInterest = 0.0d;
}
currentDate = nextDate;
}
SetTargetEndDateAccuracy(result.LoanEndsDate, context.TargetEndDate, result);
return (result);
}
/// <summary>
/// Sets the target end date accuracy.
/// </summary>
/// <param name="actualEndDate">The actual end date.</param>
/// <param name="targetEndDate">The target end date.</param>
/// <param name="result">The result.</param>
private void SetTargetEndDateAccuracy(DateTime actualEndDate, DateTime targetEndDate, LoanCalculationOutput result)
{
TimeSpan difference = actualEndDate - targetEndDate;
result.TargetEndDateMissedInDays = Math.Abs((int)difference.TotalDays);
}
/// <summary>
/// Processes the minimum repayment.
/// </summary>
/// <param name="balance">The balance.</param>
/// <param name="context">The context.</param>
/// <param name="currentDate">The current date.</param>
/// <param name="monthlyInterest">The monthly interest.</param>
/// <param name="result">The result.</param>
private double ProcessMinRepayment(double balance, double minRepaymentAmount, DateTime currentDate, double monthlyInterest, LoanCalculationOutput result)
{
// add min repay transaction
if ((balance + monthlyInterest) <= minRepaymentAmount)
{
double finalRepayment = 0.0d;
balance += monthlyInterest;
finalRepayment = balance;
balance -= finalRepayment;
LoanTransaction transaction = new LoanTransaction(currentDate, TransactionType.FinalRepayment, finalRepayment, 0.0d, balance);
result.Transactions.Add(transaction);
}
else
{
balance -= minRepaymentAmount;
LoanTransaction transaction = new LoanTransaction(currentDate, TransactionType.MinimumRepayment, minRepaymentAmount, 0.0d, balance);
result.Transactions.Add(transaction);
}
return (balance);
}
/// <summary>
/// Processes the extra repayment.
/// </summary>
/// <param name="balance">The balance.</param>
/// <param name="extraRepaymentAmount">The extra repayment amount.</param>
/// <param name="currentDate">The current date.</param>
/// <param name="result">The result.</param>
private double ProcessExtraRepayment(double balance, double extraRepaymentAmount, DateTime currentDate, LoanCalculationOutput result)
{
if(balance >= extraRepaymentAmount)
{
// add extra repay transaction (if amount is more than 0)
balance -= extraRepaymentAmount;
LoanTransaction transaction = new LoanTransaction(currentDate, TransactionType.ExtraRepayment, extraRepaymentAmount, 0.0d, balance);
result.Transactions.Add(transaction);
}
return (balance);
}
/// <summary>
/// Processes the end of month.
/// </summary>
/// <param name="currentDate">The current date.</param>
/// <param name="monthlyInterest">The monthly interest.</param>
/// <param name="balance">The balance.</param>
/// <param name="result">The result.</param>
private double ProcessEndOfMonth(DateTime currentDate, double monthlyInterest, double balance, LoanCalculationOutput result)
{
// add interest charged transaction
balance += monthlyInterest;
// calculate the total interest paid
result.TotalInterestPaid += monthlyInterest;
LoanTransaction transaction = new LoanTransaction(currentDate, TransactionType.InterestCharged, 0.0d, monthlyInterest, balance);
result.Transactions.Add(transaction);
return (balance);
}