import { addCalendarDays, organizerDate, readCalendar } from "../../_lib/calendar-feed";
import { readSettings } from "../../_lib/store";

export const dynamic = "force-dynamic";

export async function GET() {
  const { calendars } = await readSettings();
  const feeds = calendars.filter((calendar) => calendar.enabled);
  if (!feeds.length) {
    return Response.json({ items: [], calendarsAvailable: 0, calendarsTotal: 0, updatedAt: new Date().toISOString() }, { status: 503 });
  }

  const now = Date.now();
  const windowStart = now - 45 * 24 * 60 * 60 * 1_000;
  const horizon = now + 60 * 24 * 60 * 60 * 1_000;
  const today = organizerDate(new Date(now));
  const windowStartDate = addCalendarDays(today, -45);
  const horizonDate = addCalendarDays(today, 60);
  const results = await Promise.allSettled(
    feeds.map((feed, feedIndex) =>
      readCalendar(feed.url, { feedIndex, tone: feed.tone, nameOverride: feed.name }, windowStart, horizon, windowStartDate, horizonDate),
    ),
  );
  const successful = results.filter((result): result is PromiseFulfilledResult<Awaited<ReturnType<typeof readCalendar>>> => result.status === "fulfilled");
  const items = successful
    .flatMap((result) => result.value.items)
    .filter((item, index, all) => all.findIndex((candidate) => candidate.id === item.id) === index)
    .sort((left, right) => {
      const leftValue = left.allDay ? `${left.start}T00:00:00` : left.start;
      const rightValue = right.allDay ? `${right.start}T00:00:00` : right.start;
      return leftValue.localeCompare(rightValue);
    })
    .slice(0, 160);

  return Response.json(
    {
      items,
      calendarsAvailable: successful.length,
      calendarsTotal: feeds.length,
      updatedAt: new Date().toISOString(),
    },
    {
      status: successful.length ? 200 : 503,
      headers: { "Cache-Control": "private, max-age=60, stale-while-revalidate=240" },
    },
  );
}