Next.js

FIANTO_APP_ID=fian_app_...
FIANTO_APP_SECRET=fian_sk_live_...
FIANTO_WEBHOOK_SECRET=whsec_...
# FIANTO_BASE_URL is optional: set it only for a self-hosted or local fianto backend.

// app/api/checkout/route.ts
import { Checkout } from '@fianto/nextjs';

const PRICES: Record<string, { amount: string; description: string }> = {
  beans: { amount: '10.00', description: 'Coffee beans, 1 kg' },
};

export const POST = Checkout({
  createSession: async (request) => {
    const body = (await request.json().catch(() => null)) as { item?: string } | null;
    const price = body?.item ? PRICES[body.item] : undefined;
    if (!price) return new Response('Unknown item', { status: 400 }); // a Response refuses the request

    return {
      mode: 'payment',
      order_id: `order_${crypto.randomUUID()}`, // use your own order's id
      amount: price.amount,
      description: price.description,
      success_url: 'https://shop.example/thank-you',
      cancel_url: 'https://shop.example/cart',
    };
  },
  // Only needed when a caller does not send Sec-Fetch-Site: same-origin, for example behind a proxy.
  allowedOrigins: ['https://shop.example'],
  onError: (error) => console.error('fianto checkout failed', error),
});

// app/api/webhooks/fianto/route.ts
import { Webhooks } from '@fianto/nextjs';

export const POST = Webhooks({
  secret: process.env.FIANTO_WEBHOOK_SECRET,
  onOrderPaid: async (event) => {
    // Record event.id in the same database transaction as the fulfilment,
    // and skip ids you have already seen.
    console.log('paid', event.data.order_id, event.id);
  },
  onVerificationError: (error) => console.warn('fianto webhook rejected:', error.reason),
  onError: (error, event) => console.error('fianto webhook failed:', event.id, error),
});

// app/buy-button.tsx
'use client';

import { FiantoButton, fetchCheckoutSession } from '@fianto/react';

export function BuyButton() {
  return (
    <FiantoButton
      session={() => fetchCheckoutSession('/api/checkout', { body: { item: 'beans' } })}
      onResult={(result) => console.log(result.status)}
      onError={(error) => console.error(error)}
    />
  );
}