/// <summary>
/// The interest accrued on the loan (calculated based on the number of days from the <see cref="PrincipalEffectiveDate"/>)
/// </summary>
/// <param name="asOf">The date to calculate accrued interest for</param>
/// <returns>The interest accrued on the loan as of the provided date.</returns>
/// <exception cref="InvalidOperationException">When the provided <paramref name="asOf"/> date is before the loan's <see cref="PrincipalEffectiveDate"/>.</exception>
public decimal CalculateInterest(DateTime asOf)
{
if (asOf < PrincipalEffectiveDate)
{
throw new InvalidOperationException();
}
var total = 0.00m;
for (var i = PrincipalEffectiveDate.Year; i <= asOf.Year; i++)
{
if (i == PrincipalEffectiveDate.Year)
{
var dateDiff = 0;
if (PrincipalEffectiveDate.Year == asOf.Year)
{
dateDiff = (asOf - PrincipalEffectiveDate).Days;
}
else
{
dateDiff = (new DateTime(PrincipalEffectiveDate.Year, 12, 31) - PrincipalEffectiveDate).Days;
}
total += ((Principal * InterestRate) / (decimal)PrincipalEffectiveDate.DaysInYear()) * dateDiff;
continue;
}
if (i == asOf.Year)
{
var dateDiff = (asOf - new DateTime(asOf.Year, 1, 1)).Days;
total += ((Principal * InterestRate) / (decimal)asOf.DaysInYear()) * dateDiff;
continue;
}
var daysInYear = new DateTime(i, 1, 1).DaysInYear();
total += (Principal * InterestRate);
}
return(total);
}
/// <summary>
/// Calcuates the amount of interest accruing daily on the loan based on the number of days in the year.
/// </summary>
/// <returns></returns>
public decimal CurrentDailyInterestRate()
{
return((Principal * InterestRate) / (decimal)PrincipalEffectiveDate.DaysInYear());
}
