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export async function findFreeSlots(day: Date, rules: Availability[]) {
  const windows = rules.filter((rule) => rule.weekday === getDay(day));
  const booked = await prisma.booking.findMany({
    where: { startsAt: { gte: startOfDay(day), lt: endOfDay(day) } },
    select: { startsAt: true, endsAt: true },
  });

  return windows.flatMap((window) =>
    slotsWithin(window, day).filter(
      (slot) => !booked.some((b) => overlaps(slot, b)) && isInFuture(slot)
    )
  );
}

export function overlaps(a: Slot, b: Slot): boolean {
  return a.startsAt < b.endsAt && b.startsAt < a.endsAt;
}

export async function reserve(slot: Slot, lead: Lead) {
  const booking = await prisma.booking.create({
    data: { ...slot, leadId: lead.id, meetingUrl: await createRoom(lead) },
  });
  await sendBookingMail({ to: lead.email, booking });
  return ok(booking);
}