api: billing link returns to /account

api/src/billing.ts

@@ -235,9 +235,11 @@ export async function changePlan(request: Request, env: Env, now: number) {
   return json(publicPlan(row));
 }
 
-export async function manageBilling(request: Request, env: Env, now: number) {
+export async function manageBilling(request: Request, env: Env, now: number, origin: string) {
   const { id } = await requireMember(request, env, now);
-  const answer = await paygate(env, "POST", "/billing-link", { external_id: id });
+  // The hosted page's "Back to Floodwall" link: the account page on the site the reader came from
+  // (one of ALLOWED_ORIGINS, which Paygate also checks against the app's allowed origins).
+  const answer = await paygate(env, "POST", "/billing-link", { external_id: id, return_url: `${origin}/account` });
   if (answer.status === 404) throw new HttpError(404, MESSAGES.noBilling);
   if (answer.status !== 200 && answer.status !== 201) paygateFailed("billing link", answer);
   return json({ url: answer.body.url });

api/src/index.ts

@@ -43,7 +43,7 @@ async function route(request: Request, env: Env, origin: string | null) {
     case "POST /billing/change":
       return changePlan(request, env, now);
     case "POST /billing/manage":
-      return manageBilling(request, env, now);
+      return manageBilling(request, env, now, origin!);
     case "GET /billing/promo":
       return lookupCode(request, env, now);
     case "GET /billing/credits":

api/test/billing.test.mjs

@@ -128,7 +128,7 @@ describe("billing through Paygate", () => {
     const r = await w.call("/billing/manage", { body: {}, cookie });
     assert.equal(r.status, 200);
     assert.equal(r.body.url, "https://pay.erpai.studio/b/floodwall?t=abc");
-    assert.deepEqual(w.paygateCalls[0].body, { external_id: await userId(ADMIN) });
+    assert.deepEqual(w.paygateCalls[0].body, { external_id: await userId(ADMIN), return_url: `${SITE}/account` });
 
     answer = () => Response.json({ error: { code: "not_found" } }, { status: 404 });
     assert.equal((await w.call("/billing/manage", { body: {}, cookie })).status, 404);