Include last date also for sip payment

lib/contract/frequency.dart

@@ -7,24 +7,3 @@ enum Frequency {
   halfYearly,
   yearly,
 }
-
-DateTime getNextOccurrenceDateTime(DateTime dateTime, Frequency frequency) {
-  switch (frequency) {
-    case Frequency.daily:
-      return DateTime(dateTime.year, dateTime.month, dateTime.day + 1);
-    case Frequency.weekly:
-      return DateTime(dateTime.year, dateTime.month, dateTime.day + 7);
-    case Frequency.biweekly:
-      return DateTime(dateTime.year, dateTime.month, dateTime.day + 14);
-    case Frequency.monthly:
-      return DateTime(dateTime.year, dateTime.month + 1, dateTime.day);
-    case Frequency.quarterly:
-      return DateTime(dateTime.year, dateTime.month + 3, dateTime.day);
-    case Frequency.halfYearly:
-      return DateTime(dateTime.year, dateTime.month + 6, dateTime.day);
-    case Frequency.yearly:
-      return DateTime(dateTime.year + 1, dateTime.month + 6, dateTime.day);
-    default:
-      throw Exception('Invalid frequency');
-  }
-}

lib/domain/models/sip.dart

@@ -24,15 +24,37 @@ class Sip {
 
   List<Payment> getFuturePayment({required final DateTime till}) {
     final List<Payment> payments = [];
-    final DateTime? endDate = this.endDate;
-    for (var i = executedTill ?? startDate;
-        i.isBefore(till) && (endDate == null || i.isBefore(endDate));
-        i = getNextOccurrenceDateTime(i, frequency)) {
-      payments.add(Payment.from(amount: amount, createdOn: i));
+    DateTime nextPaymentDate = executedTill ?? startDate;
+
+    while (nextPaymentDate.compareTo(till) <= 0 &&
+        (endDate == null || nextPaymentDate.compareTo(endDate!) < 0)) {
+      payments.add(Payment.from(amount: amount, createdOn: nextPaymentDate));
+      nextPaymentDate = _getNextOccurrenceDateTime(nextPaymentDate, frequency);
     }
     return payments;
   }
 
+  DateTime _getNextOccurrenceDateTime(DateTime dateTime, Frequency frequency) {
+    switch (frequency) {
+      case Frequency.daily:
+        return DateTime(dateTime.year, dateTime.month, dateTime.day + 1);
+      case Frequency.weekly:
+        return DateTime(dateTime.year, dateTime.month, dateTime.day + 7);
+      case Frequency.biweekly:
+        return DateTime(dateTime.year, dateTime.month, dateTime.day + 14);
+      case Frequency.monthly:
+        return DateTime(dateTime.year, dateTime.month + 1, dateTime.day);
+      case Frequency.quarterly:
+        return DateTime(dateTime.year, dateTime.month + 3, dateTime.day);
+      case Frequency.halfYearly:
+        return DateTime(dateTime.year, dateTime.month + 6, dateTime.day);
+      case Frequency.yearly:
+        return DateTime(dateTime.year + 1, dateTime.month + 6, dateTime.day);
+      default:
+        throw Exception('Invalid frequency');
+    }
+  }
+
   factory Sip.from({required final SipDO sipDO}) => Sip._(
       id: sipDO.id,
       investmentId: sipDO.investmentId,

test/domain/models/sip_test.dart

@@ -0,0 +1,58 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:wealth_wave/api/db/app_database.dart';
+import 'package:wealth_wave/contract/frequency.dart';
+import 'package:wealth_wave/domain/models/sip.dart';
+
+void main() {
+  group('Sip', () {
+    test('should return correct future payments for daily frequency', () {
+      final sip = Sip.from(
+        sipDO: SipDO(
+          id: 1,
+          investmentId: 1,
+          description: "Test SIP",
+          amount: 100.0,
+          startDate: DateTime(2023, 1, 1),
+          endDate: null,
+          frequency: Frequency.daily,
+          executedTill: null,
+        ),
+      );
+
+      final payments = sip.getFuturePayment(till: DateTime(2023, 1, 5));
+
+      expect(payments.length, 5);
+      expect(payments[0].amount, 100.0);
+      expect(payments[0].createdOn, DateTime(2023, 1, 1));
+      expect(payments[1].createdOn, DateTime(2023, 1, 2));
+      expect(payments[2].createdOn, DateTime(2023, 1, 3));
+      expect(payments[3].createdOn, DateTime(2023, 1, 4));
+      expect(payments[4].createdOn, DateTime(2023, 1, 5));
+    });
+
+    test('should return correct future payments for monthly frequency', () {
+      final sip = Sip.from(
+        sipDO: SipDO(
+          id: 1,
+          investmentId: 1,
+          description: "Test SIP",
+          amount: 100.0,
+          startDate: DateTime(2023, 1, 1),
+          endDate: null,
+          frequency: Frequency.monthly,
+          executedTill: null,
+        ),
+      );
+
+      final payments = sip.getFuturePayment(till: DateTime(2023, 5, 1));
+
+      expect(payments.length, 5);
+      expect(payments[0].amount, 100.0);
+      expect(payments[0].createdOn, DateTime(2023, 1, 1));
+      expect(payments[1].createdOn, DateTime(2023, 2, 1));
+      expect(payments[2].createdOn, DateTime(2023, 3, 1));
+      expect(payments[3].createdOn, DateTime(2023, 4, 1));
+      expect(payments[4].createdOn, DateTime(2023, 5, 1));
+    });
+  });
+}