server.js

import express from "express";
import Stripe from "stripe";
import path from "path";
import { fileURLToPath } from "url";

const app = express();
app.use(express.static("public"));
app.use(express.json());

// Resolve __dirname for ES modules
const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

// Load API key from environment
const stripe = new Stripe(process.env.STRIPE_SECRET_KEY);

// TODO: Replace with an existing test customer you created in Stripe
const CUSTOMER_ID = "cus_SOME_CUSTOMER_ID";

const mandateReference = `mandate_${CUSTOMER_ID}_${Date.now()}`;
const stripeAmountDue = 1500000; // example: 15000 INR
const startDate = Math.floor(Date.now() / 1000); // unix timestamp

// -------------------------------
// Create SetupIntent endpoint
// -------------------------------
app.post("/create-setup-intent", async (req, res) => {
  try {
    const setupIntent = await stripe.setupIntents.create({
      customer: CUSTOMER_ID,
      payment_method_types: ["card"],
      usage: "off_session",
      payment_method_options: {
        card: {
          mandate_options: {
            reference: mandateReference,
            description: `Test mandate for recurring payments`,
            amount: stripeAmountDue,
            amount_type: "maximum",
            currency: "usd",
            interval: "sporadic",
            start_date: startDate,
            supported_types: ["india"]
          }
        }
      }
    });

    res.json({
      clientSecret: setupIntent.client_secret,
    });
  } catch (err) {
    console.error("Error creating SetupIntent:", err);
    res.status(400).send({ error: { message: err.message } });
  }
});

// -------------------------------
// Update customer default payment method
// -------------------------------
app.post("/update-customer-payment-method", async (req, res) => {
  try {
    const { paymentMethodId } = req.body;
    
    if (!paymentMethodId) {
      return res.status(400).send({ error: { message: "paymentMethodId is required" } });
    }

    const customer = await stripe.customers.update(CUSTOMER_ID, {
      invoice_settings: { default_payment_method: paymentMethodId },
    });

    res.json({ success: true, customer });
  } catch (err) {
    console.error("Error updating customer:", err);
    res.status(400).send({ error: { message: err.message } });
  }
});

// -------------------------------
// Serve the HTML page
// -------------------------------
app.get("/", (req, res) => {
  res.sendFile(path.join(__dirname, "public/index.html"));
});

// -------------------------------

app.listen(4242, () => {
  console.log("Server running at http://localhost:4242");
  console.log("Customer dashboard link:");
  console.log(`https://dashboard.stripe.com/test/customers/${CUSTOMER_ID}`);
});