Webhook Basic

Webhook is used to received notification about the status of the checkout, let's try a minimal example of a webhook endpoint

Creating a POST endpoint

We will be using Nextjs in this example, but you can use any framework of your choice

api/webhook/route.ts

import { NextRequest, NextResponse } from "next/server";
 
export const POST = async (req: NextRequest) => {
  return NextResponse.json("Hello from /api/webhook!")
}

Get the checkout data

The webhook will attach a checkoutId in the request body. We can use this ID to query the full checkout and transaction data for further processing

api/webhook/route.ts

import { NextRequest, NextResponse } from "next/server";
import { checkitout } from "@/lib/checkitout";
 
export const POST = async (req: NextRequest) => {
  const { checkoutId } = await req.json();
 
  // if there is no checkoutId
  if (!checkoutId) {
    return NextResponse.json(
      { message: "Invalid checkoutId" },
      { status: 400 },
    );
  }
 
  const { error, data } = await checkitout.findOne(checkoutId);
 
  if (error || !data) {
    // unable to query checkout
    return NextResponse.json({ message: "No checkout found" }, { status: 500 });
  }
 
  return NextResponse.json("Hello from /api/webhook!")
}

We will follow a security principle called Zero Trust, in simple term, do not trust the webhook. So with the checkout data that we queried, we will use it to verify that there is least one successful transaction.

api/webhook/route.ts

import { NextRequest, NextResponse } from "next/server";
import { checkitout } from "@/lib/checkitout";
 
export const POST = async (req: NextRequest) => {
  const { checkoutId } = await req.json();
 
  if (!checkoutId) {
    return NextResponse.json(
      { message: "Invalid checkoutId" },
      { status: 400 },
    );
  }
 
  const { error, data } = await checkitout.findOne(checkoutId);
 
  if (error || !data) {
    // unable to query checkout
    return NextResponse.json({ message: "No checkout found" }, { status: 500 });
  }
 
  const isPaid = data.transactions.some((t) => t.status === "SUCCESS");
 
  if (!isPaid) {
    return NextResponse.json(
      { message: "Invalid webhook, checkout has no successful transaction" },
      { status: 400 },
    );
  }
 
  return NextResponse.json("Hello from /api/webhook!")
}

Process your business logic

In this step, you can process your business logic, such as updating subscription status. etc.

api/webhook/route.ts

import { NextRequest, NextResponse } from "next/server";
import { checkitout } from "@/lib/checkitout";
 
export const POST = async (req: NextRequest) => {
  const { checkoutId } = await req.json();
 
  if (!checkoutId) {
    return NextResponse.json(
      { message: "Invalid checkoutId" },
      { status: 400 },
    );
  }
 
  const { error, data } = await checkitout.findOne(checkoutId);
 
  if (error || !data) {
    // unable to query checkout
    return NextResponse.json({ message: "No checkout found" }, { status: 500 });
  }
 
  const isPaid = data.transactions.some((t) => t.status === "SUCCESS");
 
  if (!isPaid) {
    return NextResponse.json(
      { message: "Invalid webhook, checkout has no successful transaction" },
      { status: 400 },
    );
  }
 
  const someResult = await doBusinessLogic(...);
 
  if (someResult.error) {
    // return error status code to indicate failed webhook
    return NextResponse.json({ message: "Something went really wrong :(" }, { status: 500 })
  }
 
  // return successful status code to indicate successful webhook
  return NextResponse.json({ message: "OK" })
}

Webhook will be considered SUCCESSFUL if the returned status code is in range of 200
Webhook will be considered FAILED if the returned status code is of error ones, e.g. 400, 500

Webhook Basic

Creating a POST endpoint

Get the checkout data

Verify the checkout status

Process your business logic

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