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";

type Body = {
  offerSlug?: unknown;
  start?: unknown;
  appointmentType?: unknown;
  message?: unknown;
};

export async function POST(request: Request) {
  let body: Body;
  try {
    body = await request.json();
  } catch {
    return NextResponse.json({ error: "Ungültige Anfrage." }, { status: 400 });
  }

  const offerSlug = typeof body.offerSlug === "string" ? body.offerSlug : "";
  const startISO = typeof body.start === "string" ? body.start : "";
  const appointmentType = body.appointmentType === "online" ? "online" : "onsite";
  const message = typeof body.message === "string" ? body.message.trim().slice(0, 2000) : "";

  if (!offerSlug || !startISO) {
    return NextResponse.json({ error: "Angebot und Termin sind erforderlich." }, { status: 400 });
  }

  try {
    const payload = await getPayload({ config });
    const { user } = await payload.auth({ headers: request.headers });
    if (!user || user.collection !== "customers") {
      return NextResponse.json({ error: "Bitte melde dich an, um einen Termin anzufragen." }, { status: 401 });
    }

    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 start = new Date(startISO);
    if (Number.isNaN(start.getTime()) || start < new Date()) {
      return NextResponse.json({ error: "Bitte wähle einen gültigen, zukünftigen Termin." }, { status: 400 });
    }
    const end = new Date(start.getTime() + offer.durationMinutes * 60_000);

    // Re-validate the slot is actually free right now (defense against a
    // stale slot list) — the hard, race-safe check still runs again when
    // Anna confirms (see collections/BookingRequests.ts).
    const dayStart = new Date(start);
    dayStart.setHours(0, 0, 0, 0);
    const dayEnd = new Date(start);
    dayEnd.setHours(23, 59, 59, 999);
    const slotsByDay = await getAvailableSlots(payload, {
      durationMinutes: offer.durationMinutes,
      from: dayStart,
      to: dayEnd,
    });
    const key = dayStart.toISOString().slice(0, 10);
    const isStillFree = (slotsByDay.get(key) ?? []).some((s) => s.start.getTime() === start.getTime());
    if (!isStillFree) {
      return NextResponse.json({ error: "Dieser Termin ist leider nicht mehr verfügbar." }, { status: 409 });
    }

    await payload.create({
      collection: "booking-requests",
      data: {
        user: user.id,
        offer: offer.id,
        date: start.toISOString(),
        startTime: start.toISOString(),
        endTime: end.toISOString(),
        appointmentType,
        status: "pending",
        userMessage: message || undefined,
      },
    });

    return NextResponse.json({ ok: true });
  } catch (error) {
    console.error("booking request failed", error);
    return NextResponse.json({ error: "Die Anfrage konnte nicht gesendet werden. Bitte versuche es später erneut." }, { status: 500 });
  }
}