Payment-Gateway-Stripe-Paypal-Using-Dependency-Inversion

This Repo Related to Online Payment Service With Stripe and Paypal Following SOLID Principles With Focus On Dependency Inversion Principle And How To Use it in Real Case Senario You Can More Details at my Article Here
Dependency Inversion With Payment Gateways Stripe/Paypal Using Nodejs

Dependency Inversion Idea

• High level Modules should not depend on low level modules Both Should Depend on Abstractions ?
• That's Means Code Depends on The Wrapper We Created Not The Actual Implementation Of Dependcies We Are Using
• Here We Don't Want Our Code Depends On How Stripe/Paypal Works
• So If We Want Switch Between Stripe/Paypal We Will Change The Wrapper And it's Going To Be Easy Then

Problem

• Change Payment Gateway From Stripe >> Paypal Will Be Very Hard and We Will Change tons Of Code
• Our Code Depends on the Actual Implementation Of The Payment Service and This Going to be Hard to Maintain
• Test Everything From Scratch Again
• Making any Transaction Going To Be Really Hard to Trace Later

Solution

• Create Intermediate Layer This Layer Going to Be Wrapper Around Payment Gateway Services
• e.g StripeServiceWrapper, PaypalServiceWrapper
• So We Just Abstract the Payment Gateways Idea Using These Wrappers it's
• Our Code Now Depends On These Wrappers Not The Actual Implementation Of Dependency We're Using

Let's Start By Some Code Snippets

Payment Store Here We Are Going to Inject The Wrapper And Makes The Transaction With Anyone We Want Easily

import PaymentService from "./PaymentService";
class PaymentStore {
  constructor(paymentWrapper) {
    this.paymentWrapper = paymentWrapper;
    this.paymentService = new PaymentService();
  }

  async makeTransaction(chargeData) {
    const charge = await this.paymentWrapper.createCharge(chargeData);
    await this.paymentService.addNewCharge(charge);
    return charge;
  }
}

export default PaymentStore;

Stripe Wrapper

import Stripe from "stripe";
import mockPayment from "./Stripe/mockPayment";
class StripeServiceWrapper {
  constructor() {
    this.stripe = new Stripe(process.env.STRIPE_SECRET_KEY);
  }
  async createCharge() {
    const { amount, currency, description, source } = mockPayment;
    const charge = await this.stripe.charges.create({
      amount,
      currency,
      description,
      source,
    });
    return charge;
  }

  async createCustomer(customerData) {
    const { name, email, source, address, phone } = customerData;
    const customer = await stripe.customers.create({
      address,
      name,
      email,
      phone,
      source,
    });
    return customer;
  }
}

export default StripeServiceWrapper;

Paypal Wrapper

import paypal from "paypal-rest-sdk";
import "./PayPal/PayPalConfig";

class PayPalServiceWrapper {
  createCharge({ payment_object, paymentId }) {
    return new Promise(function (resolve, reject) {
      paypal.payment.execute(paymentId, payment_object, function (error, payment) {
        if (error) reject(error);
        else {
          const { id, transactions } = payment;
          resolve({ id, amount: parseInt(transactions[0].amount.total) });
        }
      });
    });
  }

  paymentExecutionLink(paymentObject) {
    return new Promise(function (resolve, reject) {
      paypal.payment.create(paymentObject, function (error, payment) {
        if (error) reject(error);
        else resolve(payment);
      });
    });
  }

  getRedirectLink(links) {
    for (let i = 0; i < links.length; i++) {
      if (links[i].rel === "approval_url") return links[i].href;
    }
  }
}

export default PayPalServiceWrapper;

So Now At Our Controller It's Going to Be Very Easy To Switch From Stripe To Paypal

const post = async (req, res) => {
  const store = new PaymentStore(new StripeServiceWrapper());
  await store.makeTransaction();
  return res.status(200).send({SUCCESS_MESSAGE});
};

How To Start

• npm install
• Make Account At Stripe https://dashboard.stripe.com/login
• Set Environment Variables at .env STRIPE_PUBLISH_KEY & STRIPE_SECRET_KEY
• Signup at Paypal https://developer.paypal.com/developer/accounts/
• Set Environment Variables at .env PAYPAL_CLIENT_ID & PAYPAL_SECRET
• Hit Stripe End Point http://localhost:3000/payment/ With Empty Post Request
• Hit http://localhost:3000/payment/paypal With Empty Post Request