Fix bi-weekly+ recurring tasks reverting to weekly (#844) (#890)

Author: chrisvel

backend/modules/tasks/operations/recurring.js

@@ -152,18 +152,21 @@ async function calculateNextIterations(task, startFromDate, userTimezone) {
                 const weekdays = Array.isArray(task.recurrence_weekdays)
                     ? task.recurrence_weekdays
                     : JSON.parse(task.recurrence_weekdays);
-                let found = false;
-                for (let daysAhead = 1; daysAhead <= 7; daysAhead++) {
-                    const testDate = new Date(nextDate);
-                    testDate.setUTCDate(testDate.getUTCDate() + daysAhead);
-                    if (weekdays.includes(testDate.getUTCDay())) {
-                        nextDate = testDate;
-                        found = true;
-                        break;
-                    }
-                }
-                if (!found) {
-                    nextDate.setUTCDate(nextDate.getUTCDate() + interval * 7);
+                const sorted = [...weekdays].sort((a, b) => a - b);
+                const currentDay = nextDate.getUTCDay();
+                const laterInWeek = sorted.filter((d) => d > currentDay);
+                if (laterInWeek.length > 0) {
+                    nextDate.setUTCDate(
+                        nextDate.getUTCDate() + (laterInWeek[0] - currentDay)
+                    );
+                } else {
+                    const daysToNextFirst =
+                        (7 - currentDay + sorted[0]) % 7 || 7;
+                    nextDate.setUTCDate(
+                        nextDate.getUTCDate() +
+                            daysToNextFirst +
+                            (interval - 1) * 7
+                    );
                 }
             } else if (
                 task.recurrence_weekday !== null &&
@@ -213,28 +216,26 @@ async function calculateNextIterations(task, startFromDate, userTimezone) {
 
             // Handle multiple weekdays
             if (task.recurrence_weekdays) {
-                // Sequelize getter already parses JSON, so it's already an array
                 const weekdays = Array.isArray(task.recurrence_weekdays)
                     ? task.recurrence_weekdays
                     : JSON.parse(task.recurrence_weekdays);
+                const interval = task.recurrence_interval || 1;
+                const sorted = [...weekdays].sort((a, b) => a - b);
+                const currentDay = nextDate.getUTCDay();
+                const laterInWeek = sorted.filter((d) => d > currentDay);
 
-                // Find next matching weekday
-                let found = false;
-                for (let daysAhead = 1; daysAhead <= 7; daysAhead++) {
-                    const testDate = new Date(nextDate);
-                    testDate.setUTCDate(testDate.getUTCDate() + daysAhead);
-                    const testWeekday = testDate.getUTCDay();
-
-                    if (weekdays.includes(testWeekday)) {
-                        nextDate = testDate;
-                        found = true;
-                        break;
-                    }
-                }
-
-                if (!found) {
-                    // Fallback: add 7 days
-                    nextDate.setUTCDate(nextDate.getUTCDate() + 7);
+                if (laterInWeek.length > 0) {
+                    nextDate.setUTCDate(
+                        nextDate.getUTCDate() + (laterInWeek[0] - currentDay)
+                    );
+                } else {
+                    const daysToNextFirst =
+                        (7 - currentDay + sorted[0]) % 7 || 7;
+                    nextDate.setUTCDate(
+                        nextDate.getUTCDate() +
+                            daysToNextFirst +
+                            (interval - 1) * 7
+                    );
                 }
             } else {
                 // Old behavior for single weekday

backend/modules/tasks/recurringTaskService.js

@@ -68,16 +68,22 @@ const calculateWeeklyRecurrence = (fromDate, interval, weekday, weekdays) => {
         : null;
 
     if (parsedWeekdays && parsedWeekdays.length > 0) {
-        // Find the next matching weekday from tomorrow onward
-        for (let daysAhead = 1; daysAhead <= 7; daysAhead++) {
-            const testDate = new Date(nextDate);
-            testDate.setUTCDate(testDate.getUTCDate() + daysAhead);
-            if (parsedWeekdays.includes(testDate.getUTCDay())) {
-                return testDate;
-            }
+        const sorted = [...parsedWeekdays].sort((a, b) => a - b);
+        const currentDay = nextDate.getUTCDay();
+
+        // Find next weekday later in the current week
+        const laterInWeek = sorted.filter((d) => d > currentDay);
+        if (laterInWeek.length > 0) {
+            nextDate.setUTCDate(
+                nextDate.getUTCDate() + (laterInWeek[0] - currentDay)
+            );
+        } else {
+            // Wrap to first weekday of next cycle (interval weeks ahead)
+            const daysToNextFirst = (7 - currentDay + sorted[0]) % 7 || 7;
+            nextDate.setUTCDate(
+                nextDate.getUTCDate() + daysToNextFirst + (interval - 1) * 7
+            );
         }
-        // Fallback: advance by interval weeks
-        nextDate.setUTCDate(nextDate.getUTCDate() + interval * 7);
     } else if (weekday !== null && weekday !== undefined) {
         const currentWeekday = nextDate.getUTCDay();
         const daysUntilTarget = (weekday - currentWeekday + 7) % 7;

backend/tests/integration/recurring-tasks.test.js

@@ -295,6 +295,68 @@ describe('Recurring Tasks', () => {
                 expect(nextDueDate.getUTCDay()).toBe(2); // Tuesday
             });
 
+            it('should respect bi-weekly interval with multiple weekdays (Issue #844)', async () => {
+                // Use a fixed Tuesday: 2026-02-10
+                const tuesday = new Date(Date.UTC(2026, 1, 10, 0, 0, 0, 0));
+                expect(tuesday.getUTCDay()).toBe(2); // Sanity: Tuesday
+
+                const task = await Task.create({
+                    name: 'Bi-weekly Tue/Thu Task',
+                    recurrence_type: 'weekly',
+                    recurrence_interval: 2,
+                    recurrence_weekdays: [2, 4], // Tuesday, Thursday
+                    due_date: tuesday,
+                    user_id: user.id,
+                    status: Task.STATUS.NOT_STARTED,
+                });
+
+                // Tuesday -> Thursday (same cycle week)
+                const next1 = calculateNextDueDate(task, tuesday);
+                expect(next1.getUTCDay()).toBe(4); // Thursday
+                expect(next1.toISOString().split('T')[0]).toBe('2026-02-12');
+
+                // Thursday -> next cycle Tuesday (skip 1 week, land on week 3's Tuesday)
+                const next2 = calculateNextDueDate(task, next1);
+                expect(next2.getUTCDay()).toBe(2); // Tuesday
+                expect(next2.toISOString().split('T')[0]).toBe('2026-02-24');
+
+                // Tuesday (week 3) -> Thursday (week 3, same cycle)
+                const next3 = calculateNextDueDate(task, next2);
+                expect(next3.getUTCDay()).toBe(4); // Thursday
+                expect(next3.toISOString().split('T')[0]).toBe('2026-02-26');
+
+                // Thursday (week 3) -> Tuesday (week 5)
+                const next4 = calculateNextDueDate(task, next3);
+                expect(next4.getUTCDay()).toBe(2); // Tuesday
+                expect(next4.toISOString().split('T')[0]).toBe('2026-03-10');
+            });
+
+            it('should respect tri-weekly interval with single weekday via weekdays array (Issue #844)', async () => {
+                // Use a fixed Monday: 2026-02-09
+                const monday = new Date(Date.UTC(2026, 1, 9, 0, 0, 0, 0));
+                expect(monday.getUTCDay()).toBe(1);
+
+                const task = await Task.create({
+                    name: 'Every 3 weeks on Monday',
+                    recurrence_type: 'weekly',
+                    recurrence_interval: 3,
+                    recurrence_weekdays: [1], // Monday only
+                    due_date: monday,
+                    user_id: user.id,
+                    status: Task.STATUS.NOT_STARTED,
+                });
+
+                // Monday Feb 9 -> Monday Mar 2 (3 weeks later)
+                const next1 = calculateNextDueDate(task, monday);
+                expect(next1.getUTCDay()).toBe(1);
+                expect(next1.toISOString().split('T')[0]).toBe('2026-03-02');
+
+                // Monday Mar 2 -> Monday Mar 23 (3 weeks later)
+                const next2 = calculateNextDueDate(task, next1);
+                expect(next2.getUTCDay()).toBe(1);
+                expect(next2.toISOString().split('T')[0]).toBe('2026-03-23');
+            });
+
             it('should handle three weekdays (Mon/Wed/Fri)', async () => {
                 // Use a fixed Monday: 2026-02-09
                 const monday = new Date(Date.UTC(2026, 1, 9, 0, 0, 0, 0));