paybaji

Official Node.js SDK for the paybaji payment gateway. Accept bKash, Nagad, Rocket, Upay, and Tap payments from your Bangladeshi customers by verifying their user-submitted transaction IDs against the merchant device's SMS feed. No funds custody — paybaji just confirms the payment happened and notifies your server.

npm install paybaji

Requires Node.js 18+ (uses globalThis.fetch). Server-side only — keep the secret key off the browser.

Quick start

import { Paybaji } from 'paybaji';

const paybaji = new Paybaji({
  publicKey:  process.env.PAYBAJI_PUBLIC_KEY!,
  secretKey:  process.env.PAYBAJI_SECRET_KEY!,
  hmacSecret: process.env.PAYBAJI_HMAC_SECRET!,   // for verifyWebhook()
  // apiBaseUrl defaults to https://api.paybaji.com
});

// 1. On every deposit-page render, ask what payment options are live for your brand.
//    The wallet is randomly load-balanced across your active MFS pool.
const options = await paybaji.getPaymentOptions();
// → [{ provider: 'bkash', channel: 'personal', channel_label: 'Send Money',
//      wallet: { id, phone_number, label }, wallet_count }, ...]

// 2. When the user picks a method and submits their deposit amount:
const payment = await paybaji.initiatePayment({
  mfsAccountId: options[0].wallet.id,
  amount: 500.00,
  endUserRef: 'order_42',                  // echoed back on the webhook
  successUrl: 'https://example.com/paid',  // optional
  failUrl:    'https://example.com/failed' // optional
});

// 3. Redirect the user to paybaji's hosted checkout.
return Response.redirect(payment.checkout_url, 303);

The user lands on paybaji's checkout, sees the wallet number + amount, sends from their MFS app, and pastes the TrxID. paybaji matches against the merchant's incoming SMS and fires a signed webhook to your server.

Webhook handler (Express)

import express from 'express';
import { paybaji } from './paybaji';

const app = express();

// IMPORTANT: capture the RAW body before any JSON parsing — the signature
// is computed over the exact bytes paybaji sent.
app.post(
  '/paybaji/webhook',
  express.raw({ type: 'application/json' }),
  (req, res) => {
    const rawBody = req.body.toString('utf8');
    const sig = req.header('x-paybaji-signature');

    if (!paybaji.verifyWebhook(rawBody, sig)) {
      return res.status(401).send('bad signature');
    }

    const event = JSON.parse(rawBody) as import('paybaji').WebhookPayload;
    // event.status === 'matched'
    // event.end_user_ref === your `endUserRef` from initiatePayment
    // event.txn_id is the TrxID the user submitted
    //
    // Idempotency: paybaji retries up to 10 times. Dedupe on event.id.
    creditOrderIdempotent(event.end_user_ref, event.amount);

    res.status(200).send('ok');
  },
);

Webhook handler (Next.js Route Handler)

// app/api/paybaji-webhook/route.ts
import type { NextRequest } from 'next/server';
import { paybaji } from '@/lib/paybaji';
import type { WebhookPayload } from 'paybaji';

export async function POST(req: NextRequest): Promise<Response> {
  const rawBody = await req.text();           // raw bytes for signature
  const sig = req.headers.get('x-paybaji-signature');

  if (!paybaji.verifyWebhook(rawBody, sig)) {
    return new Response('bad signature', { status: 401 });
  }

  const event = JSON.parse(rawBody) as WebhookPayload;
  await creditOrderIdempotent(event.end_user_ref, event.amount);

  return new Response('ok', { status: 200 });
}

Polling fallback

If your endpoint can't accept inbound webhooks (e.g. behind a corporate firewall), call getPaymentStatus until the status is final (matched, expired, or failed):

const status = await paybaji.getPaymentStatus(paymentId);
// status.status, status.submittedTxnId, status.matchedAt

API reference

new Paybaji(config)

| Field | Type | Notes | |---|---|---| | publicKey | string | Required. pk_test_… or pk_live_… | | secretKey | string | Required. Never expose to a browser. | | hmacSecret | string? | Required only if you call verifyWebhook(). | | apiBaseUrl | string? | Defaults to https://api.paybaji.com. Override for self-hosted. | | fetch | typeof fetch? | Inject a custom fetch (useful for tests). |

Methods

| Method | Returns | |---|---| | getPaymentOptions() | Promise<PaymentOption[]> — currently active (provider, channel) groups with one randomly-picked wallet each | | initiatePayment(input) | Promise<InitiateResponse> — includes checkout_url to redirect the user to | | getPaymentStatus(paymentId) | Promise<PaymentStatusResponse> | | verifyWebhook(rawBody, signatureHeader) | boolean — true iff the HMAC matches AND timestamp is within ±5 min |

All network methods throw PaybajiError on non-2xx responses (the error carries .status and .body).

Authentication recipe (for reference)

Every outgoing request is signed with three headers:

X-Brand-Key:  pk_test_xxxxxxxxxxxx
X-Timestamp:  1716906000
X-Signature:  hex(HMAC_SHA256(secretKey, `${timestamp}.${rawBody}`))

GET requests sign over an empty body (""). The SDK handles all of this for you.

Webhook signature format

X-Paybaji-Signature: t=1716906321,v1=ab12cd34...

v1 = hex(HMAC_SHA256(hmacSecret, "${t}.${rawBody}")). Verify against the raw bytes you received — re-stringifying parsed JSON will fail the signature.

TypeScript

Full types are bundled. Import what you need:

import type {
  PaybajiConfig,
  PaymentOption,
  InitiateInput,
  InitiateResponse,
  PaymentStatusResponse,
  WebhookPayload,
  PaybajiProvider,
  PaybajiChannel,
  PaybajiStatus,
} from 'paybaji';

License

MIT