Correct per diem time calculation for same-day expenses

src/libs/PerDiemRequestUtils.ts

@@ -1,4 +1,4 @@
-import {addDays, differenceInDays, differenceInMinutes, format, startOfDay} from 'date-fns';
+import {addDays, differenceInDays, differenceInMinutes, format, isSameDay, startOfDay} from 'date-fns';
 import lodashSortBy from 'lodash/sortBy';
 import type {OnyxCollection, OnyxEntry} from 'react-native-onyx';
 import Onyx from 'react-native-onyx';
@@ -258,6 +258,16 @@ function getTimeDifferenceIntervals(transaction: OnyxEntry<Transaction>) {
     const customUnitRateDate = transaction?.comment?.customUnit?.attributes?.dates ?? {start: '', end: ''};
     const startDate = new Date(customUnitRateDate.start);
     const endDate = new Date(customUnitRateDate.end);
+
+    if (isSameDay(startDate, endDate)) {
+        const hourDiff = differenceInMinutes(endDate, startDate) / 60;
+        return {
+            firstDay: hourDiff,
+            tripDays: 0,
+            lastDay: undefined,
+        };
+    }
+
     const firstDayDiff = differenceInMinutes(startOfDay(addDays(startDate, 1)), startDate);
     const tripDaysDiff = differenceInDays(startOfDay(endDate), startOfDay(addDays(startDate, 1)));
     const lastDayDiff = differenceInMinutes(endDate, startOfDay(endDate));

tests/unit/getTimeDifferenceIntervalsTest.ts

@@ -0,0 +1,82 @@
+import {addDays, differenceInDays, differenceInMinutes, startOfDay} from 'date-fns';
+import type {OnyxEntry} from 'react-native-onyx';
+import {getTimeDifferenceIntervals} from '@libs/PerDiemRequestUtils';
+import type Transaction from '@src/types/onyx/Transaction';
+
+describe('getTimeDifferenceIntervals', () => {
+    const createMockTransaction = (startDate: string, endDate: string): OnyxEntry<Transaction> =>
+        ({
+            comment: {
+                customUnit: {
+                    attributes: {
+                        dates: {
+                            start: startDate,
+                            end: endDate,
+                        },
+                    },
+                },
+            },
+        } as OnyxEntry<Transaction>);
+
+    it('calculates hours for same-day transactions', () => {
+        // Given a transaction that starts and ends on the same day
+        const startDate = '2024-03-20T09:00:00Z';
+        const endDate = '2024-03-20T17:00:00Z';
+        const transaction = createMockTransaction(startDate, endDate);
+
+        const result = getTimeDifferenceIntervals(transaction);
+
+        // When we calculate the time difference intervals
+        const expectedHours = differenceInMinutes(new Date(endDate), new Date(startDate)) / 60;
+
+        // Then we should get the correct number of hours for a single day, there should be no trip days and no last day
+        expect(result).toEqual({
+            firstDay: expectedHours,
+            tripDays: 0,
+            lastDay: undefined,
+        });
+    });
+
+    it('calculates hours spanning two days', () => {
+        // Given a transaction that spans across two days
+        const startDate = '2024-03-20T14:00:00Z';
+        const endDate = '2024-03-21T16:00:00Z';
+        const transaction = createMockTransaction(startDate, endDate);
+
+        const result = getTimeDifferenceIntervals(transaction);
+
+        // When we calculate the time difference intervals
+        const startDateTime = new Date(startDate);
+        const firstDayDiff = differenceInMinutes(startOfDay(addDays(startDateTime, 1)), startDateTime);
+        const lastDayDiff = differenceInMinutes(new Date(endDate), startOfDay(new Date(endDate)));
+
+        // Then we should get the correct split of hours, there should be no trip days
+        expect(result).toEqual({
+            firstDay: firstDayDiff / 60,
+            tripDays: 0,
+            lastDay: lastDayDiff / 60,
+        });
+    });
+
+    it('calculates hours for multi-day trips', () => {
+        // Given a transaction that spans multiple days
+        const startDate = '2024-03-20T16:00:00Z';
+        const endDate = '2024-03-23T14:00:00Z';
+        const transaction = createMockTransaction(startDate, endDate);
+
+        const result = getTimeDifferenceIntervals(transaction);
+
+        // When we calculate the time difference intervals
+        const startDateTime = new Date(startDate);
+        const firstDayDiff = differenceInMinutes(startOfDay(addDays(startDateTime, 1)), startDateTime);
+        const tripDaysDiff = differenceInDays(startOfDay(new Date(endDate)), startOfDay(addDays(startDateTime, 1)));
+        const lastDayDiff = differenceInMinutes(new Date(endDate), startOfDay(new Date(endDate)));
+
+        // Then we should get the correct hours split, there should be trip days and last day
+        expect(result).toEqual({
+            firstDay: firstDayDiff / 60,
+            tripDays: tripDaysDiff,
+            lastDay: lastDayDiff / 60,
+        });
+    });
+});