import { NextResponse } from "next/server";
import { getPayload } from "payload";
import config from "@payload-config";
import { getAvailableSlots } from "@/lib/booking/slots";

export const dynamic = "force-dynamic";

/** GET /api/booking/slots?offer=<slug>&from=YYYY-MM-DD&to=YYYY-MM-DD */
export async function GET(request: Request) {
  const { searchParams } = new URL(request.url);
  const offerSlug = searchParams.get("offer");
  const fromParam = searchParams.get("from");
  const toParam = searchParams.get("to");

  if (!offerSlug) {
    return NextResponse.json({ error: "offer ist erforderlich." }, { status: 400 });
  }

  try {
    const payload = await getPayload({ config });
    const { docs } = await payload.find({
      collection: "offers",
      where: { slug: { equals: offerSlug } },
      limit: 1,
      overrideAccess: false,
    });
    const offer = docs[0];
    if (!offer || !offer.bookable || !offer.durationMinutes) {
      return NextResponse.json({ error: "Dieses Angebot ist nicht buchbar." }, { status: 404 });
    }

    const from = fromParam ? new Date(fromParam) : new Date();
    from.setHours(0, 0, 0, 0);
    const to = toParam ? new Date(toParam) : new Date(from.getTime() + 21 * 24 * 60 * 60 * 1000);
    to.setHours(23, 59, 59, 999);

    // Cap the range so this can't be abused to run an expensive scan.
    const maxRangeMs = 62 * 24 * 60 * 60 * 1000;
    if (to.getTime() - from.getTime() > maxRangeMs) {
      return NextResponse.json({ error: "Zeitraum zu groß." }, { status: 400 });
    }

    const slotsByDay = await getAvailableSlots(payload, { durationMinutes: offer.durationMinutes, from, to });

    const result: Record<string, { start: string; end: string }[]> = {};
    for (const [day, slots] of slotsByDay) {
      result[day] = slots.map((s) => ({ start: s.start.toISOString(), end: s.end.toISOString() }));
    }

    return NextResponse.json({ durationMinutes: offer.durationMinutes, slots: result });
  } catch (error) {
    console.error("booking slots failed", error);
    return NextResponse.json({ error: "Verfügbarkeiten konnten nicht geladen werden." }, { status: 500 });
  }
}