cal.pub0.org/packages/app-store/stripepayment/api/portal.ts

import type { NextApiRequest, NextApiResponse } from "next";

import { WEBAPP_URL } from "@calcom/lib/constants";
import { getSafeRedirectUrl } from "@calcom/lib/getSafeRedirectUrl";

import { getStripeCustomerIdFromUserId } from "../lib/customer";
import stripe from "../lib/server";

export default async function handler(req: NextApiRequest, res: NextApiResponse) {
  if (req.method !== "POST" && req.method !== "GET")
    return res.status(405).json({ message: "Method not allowed" });
  const { referer } = req.headers;

  if (!referer) return res.status(400).json({ message: "Missing referrer" });

  if (!req.session?.user?.id) return res.status(401).json({ message: "Not authenticated" });

  // If accessing a user's portal
  const customerId = await getStripeCustomerIdFromUserId(req.session.user.id);
  if (!customerId) return res.status(400).json({ message: "CustomerId not found in stripe" });

  let return_url = `${WEBAPP_URL}/settings/billing`;

  if (typeof req.query.returnTo === "string") {
    const safeRedirectUrl = getSafeRedirectUrl(req.query.returnTo);
    if (safeRedirectUrl) return_url = safeRedirectUrl;
  }

  const stripeSession = await stripe.billingPortal.sessions.create({
    customer: customerId,
    return_url,
  });

  res.redirect(302, stripeSession.url);
}