Create Booking

const idempotencyKey = `booking-${userId}-${Date.now()}`;

// If this request fails and is retried with the same key,
// it will return the original booking instead of creating a duplicate

const { slots } = await getAvailability({...});

// Verify the slot still exists
const slotAvailable = slots.some(
  s => s.startsAt === selectedStart && s.endsAt === selectedEnd
);

if (!slotAvailable) {
  throw new Error('Selected slot is no longer available');
}

try {
  const booking = await createBooking(data);
  return { success: true, booking };
} catch (error) {
  if (error.status === 409) {
    // Fetch fresh availability
    const newSlots = await getAvailability({...});
    return {
      success: false,
      error: 'That time was just booked',
      alternatives: newSlots.slice(0, 5)
    };
  }
  throw error;
}

function validateContact(contact) {
  if (!contact.name?.trim()) {
    throw new Error('Name is required');
  }

  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  if (!emailRegex.test(contact.email)) {
    throw new Error('Invalid email format');
  }

  // Phone is optional but validate if provided
  if (contact.phone) {
    const phoneRegex = /^\+?[\d\s-()]+$/;
    if (!phoneRegex.test(contact.phone)) {
      throw new Error('Invalid phone format');
    }
  }
}

const { booking } = await createBooking(data);

await sendEmail({
  to: booking.contact.email,
  subject: `Booking Confirmed - ${booking.service_name}`,
  body: `
    Your appointment is confirmed!

    Confirmation #: ${booking.confirmation_number}
    Service: ${booking.service_name}
    Date: ${formatDate(booking.start_at)}
    Time: ${formatTime(booking.start_at)}
    Location: ${booking.location.value}

    To cancel or reschedule, visit:
    https://yoursite.com/manage-booking?confirmation=${booking.confirmation_number}
  `
});