import * as ical from 'node-ical';
import type { AgendaEvent } from '../todayview';

export async function fetchICSAgenda(
  urls: string[]
): Promise<AgendaEvent[]> {
  const now = new Date();
  const startOfDay = new Date(now);
  startOfDay.setHours(0, 0, 0, 0);
  const endOfDay = new Date(now);
  endOfDay.setHours(23, 59, 59, 999);

  const allEvents = (
    await Promise.all(urls.map((url) => fetchOne(url, startOfDay, endOfDay)))
  ).flat();

  allEvents.sort((a, b) => a.sortKey - b.sortKey);

  return allEvents.map(({ sortKey, ...event }) => event);
}

interface RawAgendaEvent extends AgendaEvent {
  sortKey: number;
}

async function fetchOne(
  url: string,
  start: Date,
  end: Date
): Promise<RawAgendaEvent[]> {
  const resp = await fetch(url, {
    headers: [['User-Agent', 'private TRMNL fetcher']],
  });
  const data = await resp.text();
  const parsed = Object.values(await ical.async.parseICS(data)).filter(
    (a) => a?.type === 'VEVENT'
  );

  const events: RawAgendaEvent[] = [];

  for (const event of parsed) {
    for (const instance of ical.expandRecurringEvent(event, {
      from: start,
      to: end,
      excludeExdates: true,
      expandOngoing: true,
      includeOverrides: true,
    })) {
      if (instance.isFullDay) continue;

      const startTime = formatTime(instance.start);
      const endTime = formatTime(instance.end);
      const location = (instance.event as any).location ?? '';

      events.push({
        start: startTime,
        end: endTime,
        title: (instance.summary as string) ?? '',
        where: location,
        kind: '',
        sortKey: instance.start.valueOf(),
      });
    }
  }

  return events;
}

function formatTime(d: Date): string {
  return `${String(d.getHours()).padStart(2, '0')}:${String(d.getMinutes()).padStart(2, '0')}`;
}