FINERACT-1981: EMI Calculation

2024-06-11 16:44:48 +02:00
parent d502dfa437
commit f0deb111cb
4 changed files with 204 additions and 85 deletions
@@ -16,29 +16,25 @@
 * specific language governing permissions and limitations
 * under the License.
 */
-package org.apache.fineract.portfolio.loanproduct.calc.emi;
+package org.apache.fineract.portfolio.loanproduct.calc;

 import java.math.BigDecimal;
-import java.math.MathContext;
+import java.util.List;
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import lombok.Getter;

-public class FnValueFunctions {
+@AllArgsConstructor(access = AccessLevel.PACKAGE)
+public class EMICalculationResult {

-    protected FnValueFunctions() {}
+    @Getter
+    private final BigDecimal equalMonthlyInstallmentValue;
+    private final List<BigDecimal> repaymentPeriodRateFactorMinus1List;

-    /**
-     * To calculate the function value for each period, we are going to use the next formula:
-     *
-     * fn = 1 + fnValueFrom * rateFactorEnd
-     *
-     * @param previousFnValue
-     *
-     * @param currentRateFactor
-     *
-     * @param mathContext
-     *
-     */
-    public static BigDecimal fnValue(final BigDecimal previousFnValue, final BigDecimal currentRateFactor, final MathContext mc) {
-        return BigDecimal.ONE.add(previousFnValue.multiply(currentRateFactor, mc));
+    public BigDecimal getRateFactorMinus1ForRepaymentPeriod(Integer repaymentPeriodNumber) {
+        return repaymentPeriodNumber != null && repaymentPeriodNumber > 0
+                && repaymentPeriodNumber <= repaymentPeriodRateFactorMinus1List.size()
+                        ? repaymentPeriodRateFactorMinus1List.get(repaymentPeriodNumber - 1)
+                        : BigDecimal.ZERO;
    }
-
 }
@@ -0,0 +1,150 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.fineract.portfolio.loanproduct.calc;
+
+import java.math.BigDecimal;
+import java.math.MathContext;
+import java.util.List;
+import org.springframework.stereotype.Component;
+
+@Component
+public class EMICalculator {
+
+    /**
+     * Calculate EMI parts and return an EMI calculation result object with repayment installment rate factors
+     *
+     * @param repaymentPeriodDays
+     *            List of day gaps between periods (zero interest period values should be 0)
+     * @param principal
+     * @param interestRate
+     * @param daysInYear
+     * @param mc
+     * @return
+     */
+    public EMICalculationResult calculateEMI(final List<Integer> repaymentPeriodDays, final BigDecimal principal,
+            final BigDecimal interestRate, final Integer daysInYear, final MathContext mc) {
+        final List<BigDecimal> rateFactorList = getRateFactorList(repaymentPeriodDays, interestRate, daysInYear, mc);
+        final BigDecimal rateFactorN = calculateRateFactorN(rateFactorList, mc);
+        final BigDecimal fnResult = calculateFnResult(rateFactorList, mc);
+
+        final BigDecimal emiValue = calculateEMIValue(rateFactorN, principal, fnResult, mc);
+        final List<BigDecimal> rateFactorMinus1List = getRateFactorMinus1List(rateFactorList, mc);
+
+        return new EMICalculationResult(emiValue, rateFactorMinus1List);
+    }
+
+    /**
+     * Calculate rate factors from repayment periods
+     *
+     * @param repaymentPeriodDays
+     * @param interestRate
+     * @param daysInYear
+     * @param mc
+     * @return
+     */
+    List<BigDecimal> getRateFactorList(final List<Integer> repaymentPeriodDays, final BigDecimal interestRate, final Integer daysInYear,
+            final MathContext mc) {
+        return repaymentPeriodDays.stream().map(daysInPeriod -> rateFactor(interestRate, daysInPeriod, daysInYear, mc)).toList();
+    }
+
+    /**
+     * Rate factor -1 values
+     *
+     * @param rateFactors
+     * @param mc
+     * @return
+     */
+    List<BigDecimal> getRateFactorMinus1List(final List<BigDecimal> rateFactors, final MathContext mc) {
+        return rateFactors.stream().map(it -> it.subtract(BigDecimal.ONE, mc)).toList();
+    }
+
+    /**
+     * Calculate Rate Factor Product from rate factors
+     *
+     * @param rateFactors
+     * @param mc
+     * @return
+     */
+    BigDecimal calculateRateFactorN(final List<BigDecimal> rateFactors, final MathContext mc) {
+        return rateFactors.stream().reduce(BigDecimal.ONE, (BigDecimal acc, BigDecimal value) -> acc.multiply(value, mc));
+    }
+
+    /**
+     * Summarize Fn values
+     *
+     * @param rateFactors
+     * @param mc
+     * @return
+     */
+    BigDecimal calculateFnResult(final List<BigDecimal> rateFactors, final MathContext mc) {
+        return rateFactors.stream().skip(1).reduce(BigDecimal.ONE,
+                (BigDecimal previousValue, BigDecimal rateFactor) -> fnValue(previousValue, rateFactor, mc));
+    }
+
+    /**
+     * Calculate the EMI (Equal Monthly Installment) value
+     *
+     * @param rateFactorN
+     * @param principal
+     * @param fnResult
+     * @param mc
+     * @return
+     */
+    BigDecimal calculateEMIValue(final BigDecimal rateFactorN, final BigDecimal principal, final BigDecimal fnResult,
+            final MathContext mc) {
+        return rateFactorN.multiply(principal, mc).divide(fnResult, mc);
+    }
+
+    /**
+     * To calculate the monthly payment, we first need to calculate something called the Rate Factor. We're going to be
+     * using simple interest. The Rate Factor for simple interest is calculated by the following formula:
+     *
+     *
+     * R = 1 + (r * d / y)
+     *
+     * @param interestRate
+     *            (r)
+     * @param daysInPeriod
+     *            (d)
+     * @param daysInYear
+     *            (y)
+     */
+    BigDecimal rateFactor(final BigDecimal interestRate, final Integer daysInPeriod, final Integer daysInYear, final MathContext mc) {
+        final BigDecimal daysPeriod = BigDecimal.valueOf(daysInPeriod);
+        final BigDecimal daysYear = BigDecimal.valueOf(daysInYear);
+
+        return BigDecimal.ONE.add(interestRate.multiply(daysPeriod.divide(daysYear, mc), mc), mc);
+    }
+
+    /**
+     * To calculate the function value for each period, we are going to use the next formula:
+     *
+     * fn = 1 + fnValueFrom * rateFactorEnd
+     *
+     * @param previousFnValue
+     *
+     * @param currentRateFactor
+     *
+     * @param mc
+     *
+     */
+    BigDecimal fnValue(final BigDecimal previousFnValue, final BigDecimal currentRateFactor, final MathContext mc) {
+        return BigDecimal.ONE.add(previousFnValue.multiply(currentRateFactor, mc), mc);
+    }
+}
@@ -1,50 +0,0 @@
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements. See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership. The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied. See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-package org.apache.fineract.portfolio.loanproduct.calc.ratefactor;
-
-import java.math.BigDecimal;
-import java.math.MathContext;
-
-public class RateFactorFunctions {
-
-    protected RateFactorFunctions() {}
-
-    /**
-     * To calculate the monthly payment, we first need to calculate something called the Rate Factor. We're going to be
-     * using simple interest. The Rate Factor for simple interest is calculated by the following formula:
-     *
-     *
-     * R = 1 + (r * d / y)
-     *
-     * @param interestRate
-     *            (r)
-     * @param daysInPeriod
-     *            (d)
-     * @param daysInYear
-     *            (y)
-     */
-    public static BigDecimal rateFactor(final BigDecimal interestRate, final Long daysInPeriod, final Integer daysInYear,
-            final MathContext mc) {
-        final BigDecimal daysPeriod = BigDecimal.valueOf(daysInPeriod);
-        final BigDecimal daysYear = BigDecimal.valueOf(daysInYear);
-
-        return BigDecimal.ONE.add(interestRate.multiply(daysPeriod.divide(daysYear, mc), mc), mc);
-    }
-
-}