worker.js

/**
 * forceCalendar core as a server-side scheduling engine on Cloudflare Workers.
 *
 * Workers ban eval and dynamic code generation — @forcecalendar/core is
 * pure ES modules with zero dependencies, so it deploys unmodified.
 *
 * Endpoints:
 *   GET /occurrences?rrule=FREQ=WEEKLY;BYDAY=MO,WE;COUNT=10&start=2026-01-05T09:00:00Z
 *       -> JSON array of expanded occurrences
 *   GET /ics?rrule=...&start=...&title=Standup
 *       -> downloadable iCalendar file
 */
import { Calendar, RecurrenceEngine, ICSHandler } from '@forcecalendar/core';

function eventFromQuery(params) {
  const start = new Date(params.get('start') || Date.now());
  const durationMin = Number(params.get('duration') || 60);
  return {
    id: 'evt-1',
    title: params.get('title') || 'Recurring event',
    start,
    end: new Date(start.getTime() + durationMin * 60000),
    recurring: true,
    recurrenceRule: params.get('rrule') || 'FREQ=DAILY;COUNT=7',
    timeZone: params.get('tz') || 'UTC'
  };
}

export default {
  async fetch(request) {
    const url = new URL(request.url);
    const event = eventFromQuery(url.searchParams);
    const rangeStart = new Date(url.searchParams.get('from') || event.start);
    const rangeEnd = new Date(
      url.searchParams.get('to') || rangeStart.getTime() + 366 * 86400000
    );

    if (url.pathname === '/occurrences') {
      const occurrences = RecurrenceEngine.expandEvent(event, rangeStart, rangeEnd, 500);
      return Response.json({
        rule: event.recurrenceRule,
        count: occurrences.length,
        occurrences: occurrences.map(o => ({ start: o.start, end: o.end }))
      });
    }

    if (url.pathname === '/ics') {
      const calendar = new Calendar({ timeZone: event.timeZone });
      calendar.addEvent(event);
      const ics = new ICSHandler(calendar).export({ calendarName: event.title });
      return new Response(ics, {
        headers: {
          'Content-Type': 'text/calendar; charset=utf-8',
          'Content-Disposition': 'attachment; filename="event.ics"'
        }
      });
    }

    return Response.json({
      usage: ['/occurrences?rrule=FREQ=WEEKLY;BYDAY=MO,WE;COUNT=10&start=2026-01-05T09:00:00Z', '/ics?rrule=FREQ=DAILY;COUNT=5&title=Standup']
    });
  }
};