zarinpal-ts

A NodeJS package, written in TypeScript, to provide access to Zarinpal's payment gateway.

Installing

Open a command prompt in the directory where package.json resides, and run this:

npm install zarinpal-ts --save

This installs the latest version of the package in your project's local node modules.

Sample codes

Sample usages of the package are located under the zarinpal-ts-sample repository.

Design

The package is a set of loosely-coupled components that enable developers to replace their own implementations, if they ever had to. More than that, the design of the package is general to most of the current web based payment providers, so the developers do not need to replace the whole package (and hence, their code) if they've switched to a new payment service; adding a few implementations, if not already been made by others, and a little modification of the application's composition root will do the job.

The design is based on these abstract entities:

• PaymentManager
• PaymentSession
• Payment

The PaymentManager is the outmost interface that provides the clients (here, the developers that use the package) with appropriate PaymentSession objects which encapsulate the payment process. That is, every payment, from the beginning to the end, takes place in a context, called PaymentSession. The job of the PaymentManager, is to create PaymentSession objects for new payments, track all active sessions, and given the HTTP request sent back from the payment server to the application (callback), return the corresponding payment session object.

The PaymentSession, enables client to set the details of the payment (held within the Payment class objects) and register it on the payment server. This is done via the register method, which takes a callback URL that determines where to navigate back the user after the payment has been done/aborted.

Since, the three steps: registration, payment, and verification are common among payment services, it's possible to use the abstraction above for payment services other than the Zarinpal's.

Usage

1. To start a payment process, first off, you need to create a new payment session by calling PaymentManager's create method:

const paymentManager = this.sessionContext("paymentManager");
const paymentSession = paymentManager.create();

Note that, PaymentManager has to be a singleton. So, here, this.sessionContext() is assumed to return from the user session data on the application server.

2. Setting up payment information:

paymentSession.payment.amount = 1000; // (In Rials.)
paymentSession.payment.description = "Showcase payment.";
paymentSession.payment.email = "[e-mail]";

3. Registering on the payment server:

const registration = await paymentSession.register(
    "http://my.domain.com/payment/callback"
);

if (registration.isSuccessful) {
    const gatewayURL = paymentSession.gateway;

    /* ...Redirecting to the "gatewayURL"... */
} else {
    const message = registration.message;

    /* ...Returning "message" to the user... */
}

4. After the user has done/abort the payment, the payment server redirects to the given callback URL at which payment verification should take place. Before proceeding to verification, it's necessary to recover the corresponding PaymentSession:

const paymentManager = this.sessionContext("paymentManager");
const paymentSession = paymentManager.get(request);

Here, request is assumed to be the original request object of IncomingMessage type.

5. Verifying the payment:

const verification = await paymentSession.verify(request);

if (verification.isSuccessful) {
    const refId = verification.refId;

    /* ...Returning "refId" to the user... */
} else {
    const message = verification.message;

    /* ...Returning "message" to the user... */
}

Composition

At startup, application should compose payment module from components. For example, for a sandboxed payment module:

import {
    ZarinpalPaymentManager,
    SandboxZarinpalPaymentSessionFactory,
    DefaultZarinpalPaymentSessionFactory,
    ZarinpalServiceConfig,
    DefaultHttpServiceInvoker,
    PaymentManager
} from "zarinpal-ts";

const zarinpalConfig = new ZarinpalServiceConfig(
    // Put your MerchantID here:
    "00000000-0000-0000-0000-000000000000"
);
const invoker = new DefaultHttpServiceInvoker();

/**
 * The line below initializes a sandboxed payment gateway. To use the actual
 * gateway replace "SandboxZarinpalPaymentSessionFactory" with
 * "DefaultZarinpalPaymentSessionFactory".
 */
const sessionFactory = new SandboxZarinpalPaymentSessionFactory(
    zarinpalConfig,
    invoker
);

const paymentManager = new ZarinpalPaymentManager(sessionFactory);

Now, paymentManager should be stored to be available for every request as a singleton.

For complete sample code, look at the zarinpal-ts-sample repository.