Calendar & iCal

discendo-sdk/scheduling/calendar provides two pure, dependency-free utilities:

1. Evaluating whether an assignment, quiz, or content node is locked, open, or closed at a given instant.
2. Generating RFC 5545 standard iCalendar (.ics) feeds of course due dates for calendar apps (Google Calendar, Apple Calendar, Outlook).

Self-contained

This submodule has no database requirements, no constructor arguments, and no side effects.

---

At a Glance

Import	import { CalendarService, toIcal } from 'discendo-sdk/scheduling/calendar'
Repositories	None
Events	None
Permissions	None (pure calculation functions)

---

Evaluating Availability Windows (getAvailability)

type AvailabilityState = "locked" | "open" | "closed";

interface AvailabilityWindow {
  opensAt?: Date; // If omitted, open from the beginning of time
  closesAt?: Date; // If omitted, never closes
}

The State Machine:

import { CalendarService } from "discendo-sdk/scheduling/calendar";

const calendar = new CalendarService();

const window = {
  opensAt: new Date("2026-10-10T09:00:00Z"),
  closesAt: new Date("2026-10-17T23:59:59Z"),
};

calendar.getAvailability(window, new Date("2026-10-05T00:00:00Z")); // 'locked'
calendar.getAvailability(window, new Date("2026-10-12T12:00:00Z")); // 'open'
calendar.getAvailability(window, new Date("2026-10-18T00:00:00Z")); // 'closed'

Invariants:

• Inclusive boundaries: Exactly at opensAt, the state is already 'open'. Exactly at closesAt, it remains 'open'; one millisecond later, it becomes 'closed'.
• Pure comparisons: Compares UTC epoch timestamps, avoiding timezone offset confusion.

---

iCalendar Export (toIcal)

Generates standard .ics calendar content for assignment deadlines and exam schedules:

import { toIcal } from "discendo-sdk/scheduling/calendar";

const icsString = toIcal([
  {
    id: "asg-lab1",
    title: "CS101: Lab 1 Submission Deadline",
    dueAt: new Date("2026-10-15T23:59:00Z"),
  },
  {
    id: "exam-midterm",
    title: "CS101: Midterm Exam",
    dueAt: new Date("2026-10-22T14:00:00Z"),
  },
]);

Sample Output:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//DiscendoLMS//discendo-sdk//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
UID:asg-lab1@discendo-lms
DTSTAMP:20261013T200000Z
DTSTART:20261015T235900Z
SUMMARY:CS101: Lab 1 Submission Deadline
END:VEVENT
BEGIN:VEVENT
UID:exam-midterm@discendo-lms
DTSTAMP:20261013T200000Z
DTSTART:20261022T140000Z
SUMMARY:CS101: Midterm Exam
END:VEVENT
END:VCALENDAR

---

Serving iCal Feeds in HTTP Handlers

You can serve this as a live subscription feed for students in an API endpoint:

app.get("/api/users/:userId/calendar.ics", async (c) => {
  const userId = c.req.param("userId");
  const assignments = await db.assignments.findDueDatesForUser(userId);

  const ics = toIcal(
    assignments.map((a) => ({
      id: a.id,
      title: `${a.courseCode}: ${a.title}`,
      dueAt: a.dueAt,
    })),
  );

  return c.text(ics, 200, {
    "Content-Type": "text/calendar; charset=utf-8",
    "Content-Disposition": 'inline; filename="calendar.ics"',
  });
});