Next.js

npm install @swft-checkout/nextjs @swft-checkout/js

App Router (Server Action)

app/checkout/actions.ts

'use server'
import { swftCheckout } from '@swft-checkout/nextjs'

export async function checkout(cartItems: CartItem[]) {
  await swftCheckout({
    merchantApiKey: process.env.SWFT_MERCHANT_API_KEY!,
    currency: 'GBP',
    lineItems: cartItems.map(item => ({
      name:       item.name,
      quantity:   item.quantity,
      price:      item.price,
      product_id: item.id,
    })),
    shippingMethods: [
      { id: 'standard', label: 'Standard Shipping (3-5 days)', cost: 499 },
      { id: 'express',  label: 'Express Shipping (next day)',  cost: 999 },
    ],
    subtotal: cartItems.reduce((s, i) => s + i.price * i.quantity, 0),
  })
  // swftCheckout calls redirect() — never returns
}

app/cart/page.tsx

import { checkout } from './actions'

export default function CartPage({ items }: { items: CartItem[] }) {
  return (
    <form action={checkout.bind(null, items)}>
      <button type="submit">Checkout with Swft →</button>
    </form>
  )
}

Webhook handler (App Router)

app/api/webhooks/swft/route.ts

import { createSwftWebhookHandler } from '@swft-checkout/nextjs'

export const POST = createSwftWebhookHandler(
  process.env.SWFT_WEBHOOK_SECRET!,
  async (payload) => {
    if (payload.event === 'payment_succeeded') {
      await createOrder({ ...payload })
    }
  }
)