FINERACT-1971: Fix EMI Calculator: Last Unpaid Repayment Period Handling.

call calculateLastUnpaidRepaymentPeriodEMI recursively when emi would be less than zero to adjust remaining emi correction for previous period.

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

@@ -307,7 +307,13 @@ public final class ProgressiveEMICalculator implements EMICalculator {
         Money diff = totalDisbursedAmount.plus(totalDueInterest, mc).minus(totalEMI, mc);
         Optional<RepaymentPeriod> findLastUnpaidRepaymentPeriod = scheduleModel.repaymentPeriods().stream().filter(rp -> !rp.isFullyPaid())
                 .reduce((first, second) -> second);
-        findLastUnpaidRepaymentPeriod.ifPresent(repaymentPeriod -> repaymentPeriod.setEmi(repaymentPeriod.getEmi().add(diff, mc)));
+        findLastUnpaidRepaymentPeriod.ifPresent(repaymentPeriod -> {
+            repaymentPeriod.setEmi(repaymentPeriod.getEmi().add(diff, mc));
+            if (repaymentPeriod.getEmi().isLessThanZero()) {
+                repaymentPeriod.setEmi(repaymentPeriod.getEmi().zero());
+                calculateLastUnpaidRepaymentPeriodEMI(scheduleModel);
+            }
+        });
     }
 
     private void calculateOutstandingBalance(ProgressiveLoanInterestScheduleModel scheduleModel) {

fineract-progressive-loan/src/test/java/org/apache/fineract/portfolio/loanproduct/calc/ProgressiveEMICalculatorTest.java

@@ -1132,6 +1132,64 @@ class ProgressiveEMICalculatorTest {
         checkPeriod(interestSchedule, 5, 0, 16.89, 0.003950916667, 0.07, 16.82, 0.0);
     }
 
+    @Test
+    public void soma_test_disbursedAmt1000_dayInYears360_daysInMonthDoesntMatter_repayEvery15Days() {
+
+        final List<LoanScheduleModelRepaymentPeriod> expectedRepaymentPeriods = List.of(
+                repayment(1, LocalDate.of(2024, 1, 1), LocalDate.of(2024, 2, 1)),
+                repayment(2, LocalDate.of(2024, 2, 1), LocalDate.of(2024, 3, 1)),
+                repayment(3, LocalDate.of(2024, 3, 1), LocalDate.of(2024, 4, 1)),
+                repayment(4, LocalDate.of(2024, 4, 1), LocalDate.of(2024, 5, 1)),
+                repayment(5, LocalDate.of(2024, 5, 1), LocalDate.of(2024, 6, 1)),
+                repayment(6, LocalDate.of(2024, 6, 1), LocalDate.of(2024, 7, 1)),
+                repayment(7, LocalDate.of(2024, 7, 1), LocalDate.of(2024, 8, 1)),
+                repayment(8, LocalDate.of(2024, 8, 1), LocalDate.of(2024, 9, 1)),
+                repayment(9, LocalDate.of(2024, 9, 1), LocalDate.of(2024, 10, 1)),
+                repayment(10, LocalDate.of(2024, 10, 1), LocalDate.of(2024, 11, 1)),
+                repayment(11, LocalDate.of(2024, 11, 1), LocalDate.of(2024, 12, 1)),
+                repayment(12, LocalDate.of(2024, 12, 1), LocalDate.of(2025, 1, 1)));
+
+        final BigDecimal interestRate = BigDecimal.valueOf(25);
+        final Integer installmentAmountInMultiplesOf = null;
+
+        Mockito.when(loanProductRelatedDetail.getAnnualNominalInterestRate()).thenReturn(interestRate);
+        Mockito.when(loanProductRelatedDetail.getDaysInYearType()).thenReturn(DaysInYearType.ACTUAL.getValue());
+        Mockito.when(loanProductRelatedDetail.getDaysInMonthType()).thenReturn(DaysInMonthType.ACTUAL.getValue());
+        Mockito.when(loanProductRelatedDetail.getRepaymentPeriodFrequencyType()).thenReturn(PeriodFrequencyType.MONTHS);
+        Mockito.when(loanProductRelatedDetail.getRepayEvery()).thenReturn(1);
+        Mockito.when(loanProductRelatedDetail.getCurrencyData()).thenReturn(currency);
+
+        final ProgressiveLoanInterestScheduleModel interestSchedule = emiCalculator.generatePeriodInterestScheduleModel(
+                expectedRepaymentPeriods, loanProductRelatedDetail, installmentAmountInMultiplesOf, mc);
+
+        final Money disbursedAmount = toMoney(1000.0);
+        LocalDate disbursementDate = LocalDate.of(2024, 1, 1);
+
+        emiCalculator.addDisbursement(interestSchedule, disbursementDate, disbursedAmount);
+
+        for (int i = 0; i < 12; i++) {
+            LocalDate dueDate = expectedRepaymentPeriods.get(i).getDueDate();
+            PeriodDueDetails dueAmounts = emiCalculator.getDueAmounts(interestSchedule, dueDate, disbursementDate);
+            Money duePrincipal = dueAmounts.getDuePrincipal();
+            if (duePrincipal.isGreaterThanZero()) {
+                emiCalculator.payPrincipal(interestSchedule, dueDate, disbursementDate, duePrincipal);
+            }
+        }
+
+        checkPeriod(interestSchedule, 0, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 1, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 2, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 3, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 4, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 5, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 6, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 7, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 8, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 9, 95.02, 0.0, 95.02, 0.0, true);
+        checkPeriod(interestSchedule, 10, 49.8, 0.0, 49.8, 0.0, true);
+        checkPeriod(interestSchedule, 11, 0.0, 0.0, 0.0, 0.0, true);
+    }
+
     @Test
     public void test_dailyInterest_disbursedAmt1000_dayInYears360_daysInMonth30_repayIn1Month() {
 
@@ -1298,6 +1356,18 @@ class ProgressiveEMICalculatorTest {
                 remaingBalance);
     }
 
+    private static void checkPeriod(final ProgressiveLoanInterestScheduleModel interestScheduleModel, final int repaymentIdx,
+            final double emiValue, final double interestDueCumulated, final double principalDue, final double remainingBalance,
+            final boolean fullyRepaid) {
+        final RepaymentPeriod repaymentPeriod = interestScheduleModel.repaymentPeriods().get(repaymentIdx);
+
+        Assertions.assertEquals(emiValue, toDouble(repaymentPeriod.getEmi()));
+        Assertions.assertEquals(interestDueCumulated, toDouble(repaymentPeriod.getDueInterest()));
+        Assertions.assertEquals(principalDue, toDouble(repaymentPeriod.getDuePrincipal()));
+        Assertions.assertEquals(remainingBalance, toDouble(repaymentPeriod.getOutstandingLoanBalance()));
+        Assertions.assertEquals(fullyRepaid, repaymentPeriod.isFullyPaid());
+    }
+
     private static void checkPeriod(final ProgressiveLoanInterestScheduleModel interestScheduleModel, final int repaymentIdx,
             final int interestIdx, final double emiValue, final double rateFactor, final double interestDue,
             final double interestDueCumulated, final double principalDue, final double remaingBalance) {

integration-tests/src/test/java/org/apache/fineract/integrationtests/BaseLoanIntegrationTest.java

@@ -1075,6 +1075,10 @@ public abstract class BaseLoanIntegrationTest {
         return new Installment(principalAmount, interestAmount, null, null, totalOutstandingAmount, completed, dueDate, null, null);
     }
 
+    protected Installment fullyRepaidInstallment(double principalAmount, double interestAmount, String dueDate) {
+        return new Installment(principalAmount, interestAmount, null, null, 0.0, true, dueDate, null, null);
+    }
+
     protected Installment installment(double principalAmount, double interestAmount, double feeAmount, double totalOutstandingAmount,
             Boolean completed, String dueDate) {
         return new Installment(principalAmount, interestAmount, feeAmount, null, totalOutstandingAmount, completed, dueDate, null, null);

integration-tests/src/test/java/org/apache/fineract/integrationtests/LoanInterestRefundTest.java

@@ -218,6 +218,127 @@ public class LoanInterestRefundTest extends BaseLoanIntegrationTest {
         });
     }
 
+    @Test
+    public void verifyInterestRefundCreatedForMerchantIssuedRefundDay22HighInterest12month() {
+        AtomicReference<Long> loanIdRef = new AtomicReference<>();
+        runAt("1 January 2021", () -> {
+            PostLoanProductsResponse loanProduct = loanProductHelper
+                    .createLoanProduct(create4IProgressive().daysInMonthType(DaysInMonthType.ACTUAL) //
+                            .daysInYearType(DaysInYearType.ACTUAL) //
+                            .addSupportedInterestRefundTypesItem(SupportedInterestRefundTypesItem.MERCHANT_ISSUED_REFUND) //
+                            .recalculationRestFrequencyType(RecalculationRestFrequencyType.DAILY) //
+            );
+            Long loanId = applyAndApproveProgressiveLoan(client.getClientId(), loanProduct.getResourceId(), "1 January 2021", 1000.0, 26.0,
+                    12, null);
+            Assertions.assertNotNull(loanId);
+            loanIdRef.set(loanId);
+            disburseLoan(loanId, BigDecimal.valueOf(1000), "1 January 2021");
+        });
+        runAt("22 January 2021", () -> {
+            Long loanId = loanIdRef.get();
+            PostLoansLoanIdTransactionsResponse postLoansLoanIdTransactionsResponse = loanTransactionHelper
+                    .makeLoanRepayment("MerchantIssuedRefund", "22 January 2021", 1000F, loanId.intValue());
+            Assertions.assertNotNull(postLoansLoanIdTransactionsResponse);
+            Assertions.assertNotNull(postLoansLoanIdTransactionsResponse.getResourceId());
+
+            verifyTransactions(loanId, transaction(1000.0, "Disbursement", "01 January 2021"), //
+                    transaction(14.96, "Accrual", "22 January 2021"), //
+                    transaction(14.96, "Interest Refund", "22 January 2021"), //
+                    transaction(1000.0, "Merchant Issued Refund", "22 January 2021") //
+            );
+            verifyRepaymentSchedule(loanId, installment(1000.0, null, "01 January 2021"), //
+                    fullyRepaidInstallment(80.52, 14.96, "01 February 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 March 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 April 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 May 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 June 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 July 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 August 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 September 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 October 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 November 2021"), //
+                    fullyRepaidInstallment(60.16, 0.0, "01 December 2021"), //
+                    fullyRepaidInstallment(0.0, 0.0, "01 January 2022") //
+            );
+        });
+    }
+
+    @Test
+    public void verifyFullMerchantIssuedRefundOnDay0HighInterest12month() {
+        runAt("1 January 2021", () -> {
+            PostLoanProductsResponse loanProduct = loanProductHelper
+                    .createLoanProduct(create4IProgressive().daysInMonthType(DaysInMonthType.ACTUAL) //
+                            .daysInYearType(DaysInYearType.ACTUAL) //
+                            .addSupportedInterestRefundTypesItem(SupportedInterestRefundTypesItem.MERCHANT_ISSUED_REFUND) //
+                            .recalculationRestFrequencyType(RecalculationRestFrequencyType.DAILY) //
+            );
+            Long loanId = applyAndApproveProgressiveLoan(client.getClientId(), loanProduct.getResourceId(), "1 January 2021", 1000.0, 26.0,
+                    12, null);
+            Assertions.assertNotNull(loanId);
+            disburseLoan(loanId, BigDecimal.valueOf(1000), "1 January 2021");
+            PostLoansLoanIdTransactionsResponse postLoansLoanIdTransactionsResponse = loanTransactionHelper
+                    .makeLoanRepayment("MerchantIssuedRefund", "1 January 2021", 1000F, loanId.intValue());
+            Assertions.assertNotNull(postLoansLoanIdTransactionsResponse);
+            Assertions.assertNotNull(postLoansLoanIdTransactionsResponse.getResourceId());
+
+            verifyTransactions(loanId, transaction(1000.0, "Disbursement", "01 January 2021"), //
+                    transaction(1000.0, "Merchant Issued Refund", "01 January 2021") //
+            );
+            verifyRepaymentSchedule(loanId, installment(1000.0, null, "01 January 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 February 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 March 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 April 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 May 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 June 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 July 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 August 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 September 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 October 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 November 2021"), //
+                    fullyRepaidInstallment(45.2, 0.0, "01 December 2021"), //
+                    fullyRepaidInstallment(0.0, 0.0, "01 January 2022") //
+            );
+        });
+    }
+
+    @Test
+    public void verifyRepaymentDay0HighInterest12month() {
+        runAt("1 January 2021", () -> {
+            PostLoanProductsResponse loanProduct = loanProductHelper
+                    .createLoanProduct(create4IProgressive().daysInMonthType(DaysInMonthType.ACTUAL) //
+                            .daysInYearType(DaysInYearType.ACTUAL) //
+                            .addSupportedInterestRefundTypesItem(SupportedInterestRefundTypesItem.MERCHANT_ISSUED_REFUND) //
+                            .recalculationRestFrequencyType(RecalculationRestFrequencyType.DAILY) //
+            );
+            Long loanId = applyAndApproveProgressiveLoan(client.getClientId(), loanProduct.getResourceId(), "1 January 2021", 1000.0, 26.0,
+                    12, null);
+            Assertions.assertNotNull(loanId);
+            disburseLoan(loanId, BigDecimal.valueOf(1000), "1 January 2021");
+            PostLoansLoanIdTransactionsResponse postLoansLoanIdTransactionsResponse = loanTransactionHelper.makeLoanRepayment("Repayment",
+                    "1 January 2021", 1000F, loanId.intValue());
+            Assertions.assertNotNull(postLoansLoanIdTransactionsResponse);
+            Assertions.assertNotNull(postLoansLoanIdTransactionsResponse.getResourceId());
+
+            verifyTransactions(loanId, transaction(1000.0, "Disbursement", "01 January 2021"), //
+                    transaction(1000.0, "Repayment", "01 January 2021") //
+            );
+            verifyRepaymentSchedule(loanId, installment(1000.0, null, "01 January 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 February 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 March 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 April 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 May 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 June 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 July 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 August 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 September 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 October 2021"), //
+                    fullyRepaidInstallment(95.48, 0.0, "01 November 2021"), //
+                    fullyRepaidInstallment(45.2, 0.0, "01 December 2021"), //
+                    fullyRepaidInstallment(0.0, 0.0, "01 January 2022") //
+            );
+        });
+    }
+
     @Test
     public void verifyUC01() {
         AtomicReference<Long> loanIdRef = new AtomicReference<>();