// 1. Create checkout session
stripe.checkout.sessions.create({
  customer: "cus_1234567890",
  line_items: [
    {
      price: "price_1MotwRLkdIwHu7ixYcPLm5uZ",
      quantity: 1,
    },
  ],
  success_url: "https://useautumn.com",
  mode: "subscription",
});

// 2. Update subscription (upgrades)
const currentSub = await stripe.subscriptions.retrieve(subscriptionId)

const newSubItems = currentSub.items.map((item) => ({
  id: item.id,
  deleted: true,
}));

newSubItems.push({
  price: "price_1MotwRLkdIwHu7ixYcPLm5uZ", // new price
  quantity: 1,
})

await stripe.subscriptions.update(subscriptionId, { 
  items: newSubItems,
  proration_behavior: "create_prorations",
});

// 3. One time payments / add ons
stripe.invoices.create({
  customer: "cus_1234567890",
  items: [
    {
      price: "price_1MotwRLkdIwHu7ixYcPLm5uZ",
      quantity: 1,
    }
  ],
})

// 4. Schedule downgrade
stripe.subscriptionSchedules.create({
  customer: "cus_1234567890",
  start_date: endOfBillingPeriod,
  phases: [
    {
      items: [{
        price: "price_1MotwRLkdIwHu7ixYcPLm5uZ",
        quantity: 1,
      }],
      default_payment_method: paymentMethod?.id,
    },
  ],
})