FINERACT-1981: Fix interest calculation logic (rounding issues with sub interest periods)

fineract-progressive-loan/src/main/java/org/apache/fineract/portfolio/loanproduct/calc/ProgressiveEMICalculator.java

@@ -499,7 +499,7 @@ public final class ProgressiveEMICalculator implements EMICalculator {
         final DaysInMonthType daysInMonthType = DaysInMonthType.fromInt(loanProductRelatedDetail.getDaysInMonthType());
         final PeriodFrequencyType repaymentFrequency = loanProductRelatedDetail.getRepaymentPeriodFrequencyType();
 
-        final BigDecimal daysInYear = BigDecimal.valueOf(daysInYearType.getNumberOfDays(interestPeriodFromDate));
+        BigDecimal daysInYear = BigDecimal.valueOf(daysInYearType.getNumberOfDays(interestPeriodFromDate));
         final BigDecimal actualDaysInPeriod = BigDecimal
                 .valueOf(DateUtils.getDifferenceInDays(interestPeriodFromDate, interestPeriodDueDate));
         final BigDecimal calculatedDaysInPeriod = BigDecimal
@@ -611,7 +611,7 @@ public final class ProgressiveEMICalculator implements EMICalculator {
         final PeriodFrequencyType repaymentFrequency = loanProductRelatedDetail.getRepaymentPeriodFrequencyType();
         final BigDecimal repaymentEvery = BigDecimal.valueOf(loanProductRelatedDetail.getRepayEvery());
 
-        final BigDecimal daysInYear = BigDecimal.valueOf(daysInYearType.getNumberOfDays(interestPeriodFromDate));
+        BigDecimal daysInYear = BigDecimal.valueOf(daysInYearType.getNumberOfDays(interestPeriodFromDate));
         final BigDecimal actualDaysInPeriod = BigDecimal
                 .valueOf(DateUtils.getDifferenceInDays(interestPeriodFromDate, interestPeriodDueDate));
         final BigDecimal calculatedDaysInPeriod = BigDecimal

fineract-progressive-loan/src/main/java/org/apache/fineract/portfolio/loanproduct/calc/data/InterestPeriod.java

@@ -103,20 +103,19 @@ public class InterestPeriod implements Comparable<InterestPeriod> {
         this.chargebackInterest = MathUtil.plus(this.chargebackInterest, chargebackInterest, mc);
     }
 
-    public Money getCalculatedDueInterest() {
+    public BigDecimal getCalculatedDueInterest() {
         if (isPaused) {
-            return chargebackInterest;
+            return chargebackInterest.getAmount();
         }
 
         long lengthTillPeriodDueDate = getLengthTillPeriodDueDate();
-        final Money interestDueTillRepaymentDueDate = Money.of(outstandingLoanBalance.getCurrencyData(), lengthTillPeriodDueDate == 0 //
+        final BigDecimal interestDueTillRepaymentDueDate = lengthTillPeriodDueDate == 0 //
                 ? BigDecimal.ZERO //
                 : getOutstandingLoanBalance().getAmount() //
                         .multiply(getRateFactorTillPeriodDueDate(), mc) //
                         .divide(BigDecimal.valueOf(lengthTillPeriodDueDate), mc) //
-                        .multiply(BigDecimal.valueOf(getLength()), mc),
-                mc); //
-        return MathUtil.plus(chargebackInterest, interestDueTillRepaymentDueDate, mc);
+                        .multiply(BigDecimal.valueOf(getLength()), mc); //
+        return MathUtil.add(chargebackInterest.getAmount(), interestDueTillRepaymentDueDate, mc);
     }
 
     public long getLength() {

fineract-progressive-loan/src/main/java/org/apache/fineract/portfolio/loanproduct/calc/data/ProgressiveLoanInterestScheduleModel.java

@@ -296,8 +296,7 @@ public class ProgressiveLoanInterestScheduleModel {
      * @return
      */
     public Money getTotalDueInterest() {
-        return repaymentPeriods().stream().flatMap(rp -> rp.getInterestPeriods().stream().map(InterestPeriod::getCalculatedDueInterest))
-                .reduce(zero(), Money::plus);
+        return repaymentPeriods().stream().map(RepaymentPeriod::getCalculatedDueInterest).reduce(zero(), Money::plus);
     }
 
     /**

fineract-progressive-loan/src/main/java/org/apache/fineract/portfolio/loanproduct/calc/data/RepaymentPeriod.java

@@ -149,8 +149,8 @@ public final class RepaymentPeriod {
     }
 
     private Money calculateCalculatedDueInterest() {
-        Money calculatedDueInterest = getInterestPeriods().stream().map(InterestPeriod::getCalculatedDueInterest).reduce(getZero(mc),
-                (m1, m2) -> m1.plus(m2, mc));
+        Money calculatedDueInterest = Money.of(emi.getCurrencyData(),
+                getInterestPeriods().stream().map(InterestPeriod::getCalculatedDueInterest).reduce(BigDecimal.ZERO, BigDecimal::add), mc);
         if (getPrevious().isPresent()) {
             calculatedDueInterest = calculatedDueInterest.add(getPrevious().get().getUnrecognizedInterest(), mc);
         }