use next-iron-session to store wether a user has subscribed to a billing plan in stripe (probably using webhooks to listen for subscription creation) in javascript

To store the information whether a user has subscribed to a billing plan in Stripe using Next.js and Iron Session, you can use webhooks to listen for subscription creation events on Stripe.

Here's the step-by-step process:

1. Create a Stripe webhook:

   To create a webhook in Stripe, follow these steps:

   • Go to the Stripe Dashboard.
   • On the left sidebar, click on "Developers".
   • Click on "Webhooks".
   • Click on "Add endpoint".
     • Enter the endpoint URL where Stripe will send the webhook events.
     • Select the event type as "customer.subscription.created".
     • Click on "Add endpoint".

2. Create a Next.js API route:

   After creating the webhook, you need to create an API route in Next.js that will listen for the webhook events and update the session data accordingly.

   For example, create an API route at pages/api/stripe.js:

   index.tsx
   import ironSession from 'next-iron-session';
   import { stripe } from '../../lib/stripe';
   
   export const config = {
     api: {
       bodyParser: false,
     },
   };
   
   export default ironSession(async (req, res) => {
     const sig = req.headers['stripe-signature'];
   
     try {
       const event = stripe.webhooks.constructEvent(req.body, sig, process.env.STRIPE_WEBHOOK_SECRET);
   
       if (event.type === 'customer.subscription.created') {
         // Update session data to reflect subscription status
         req.session.set('isSubscribed', true);
         await req.session.save();
       }
   
       res.status(200).send('OK');
     } catch (error) {
       console.error(error);
       res.status(400).send(`Webhook Error: ${error.message}`);
     }
   }, {
     password: process.env.COOKIE_SECRET,
   });
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3. Store the session data:

   Update your Next.js pages to reflect the subscription status stored in the session data. For example:

   index.tsx
   import { useState, useEffect } from 'react';
   import useSWR from 'swr';
   import Layout from '../components/Layout';
   
   function Home() {
     const { data } = useSWR('/api/user', fetch);
     const [isSubscribed, setIsSubscribed] = useState(false);
   
     useEffect(() => {
       setIsSubscribed(data?.isSubscribed || false);
     }, [data]);
   
     return (
       <Layout>
         {isSubscribed ? (
           <p>You are subscribed!</p>
         ) : (
           <p>You are not subscribed.</p>
         )}
       </Layout>
     );
   }
   
   export default Home;
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   In this example, useSWR is used to fetch the session data from the Next.js API route at pages/api/user.js. The isSubscribed value from the session data is then used to render the appropriate message on the page.

4. Implement Stripe checkout:

   To allow users to subscribe to a billing plan, use the Stripe checkout form. For example:

   index.tsx
   import { loadStripe } from '@stripe/stripe-js';
   import Layout from '../components/Layout';
   
   const stripePromise = loadStripe(process.env.NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY);
   
   function Subscribe() {
     const handleClick = async () => {
       const stripe = await stripePromise;
   
       const { error } = await stripe.redirectToCheckout({
         mode: 'subscription',
         lineItems: [{ price: process.env.NEXT_PUBLIC_STRIPE_PRICE_ID, quantity: 1 }],
         successUrl: `${window.location.origin}/success`,
         cancelUrl: `${window.location.origin}/subscribe`,
         customerEmail: 'user@example.com',
       });
   
       if (error) {
         console.error(error.message);
       }
     };
   
     return (
       <Layout>
         <button onClick={handleClick}>Subscribe Now</button>
       </Layout>
     );
   }
   
   export default Subscribe;
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5. Update the subscription status:

   After a successful subscription, Stripe will send a webhook event to your API route as defined in step 2. The session data will then be updated to reflect the new subscription status, which should be reflected in your pages as defined in step 3.

Note that this is just a basic example and there may be additional configuration required. Please refer to the Next.js and Stripe documentation for more information.