podcastdistributiona/lib/billing/webhooks/paypal.ts

import { z } from "zod";
import { upsertSubscription } from "../subscription";
import { planFromPaypalPlan } from "../catalog";
import { PLAN_ORDER, type PlanKey } from "../plans";

interface PaypalResource {
  id?: string;
  plan_id?: string;
  custom_id?: string;
  billing_info?: { next_billing_time?: string };
}

interface PaypalEvent {
  event_type: string;
  resource: PaypalResource;
}

// custom_id is attacker-influenceable JSON; validate it strictly and never trust
// it to default to a paid plan.
const customSchema = z.object({
  subjectId: z.string().min(1),
  subjectType: z.enum(["user", "organization"]),
  plan: z.enum(PLAN_ORDER as [PlanKey, ...PlanKey[]]),
});

function parseCustom(
  custom?: string
): { subjectId: string; subjectType: "user" | "organization"; plan: PlanKey } | null {
  if (!custom) return null;
  let raw: unknown;
  try {
    raw = JSON.parse(custom);
  } catch {
    return null;
  }
  const parsed = customSchema.safeParse(raw);
  if (!parsed.success) {
    console.warn("[paypal] invalid custom_id payload, skipping");
    return null;
  }
  return parsed.data;
}

async function sync(resource: PaypalResource, status: string) {
  const subId = resource.id;
  if (!subId) return;
  const custom = parseCustom(resource.custom_id);
  const planFromId = resource.plan_id ? planFromPaypalPlan(resource.plan_id) : null;
  const plan = (custom?.plan || planFromId || "free") as PlanKey;
  const referenceId = custom?.subjectId;
  if (!referenceId) {
    console.warn("[paypal] subscription without custom subjectId, skipping", subId);
    return;
  }
  await upsertSubscription({
    provider: "paypal",
    referenceId,
    plan,
    status,
    paypalSubscriptionId: subId,
    paypalPlanId: resource.plan_id ?? null,
    periodEnd: resource.billing_info?.next_billing_time
      ? new Date(resource.billing_info.next_billing_time)
      : null,
  });
}

export async function handlePaypalEvent(event: PaypalEvent): Promise<void> {
  switch (event.event_type) {
    case "BILLING.SUBSCRIPTION.ACTIVATED":
    case "BILLING.SUBSCRIPTION.UPDATED":
    case "BILLING.SUBSCRIPTION.RE-ACTIVATED":
      await sync(event.resource, "active");
      break;
    case "BILLING.SUBSCRIPTION.SUSPENDED":
      await sync(event.resource, "paused");
      break;
    case "BILLING.SUBSCRIPTION.CANCELLED":
    case "BILLING.SUBSCRIPTION.EXPIRED":
      await sync(event.resource, "canceled");
      break;
    default:
      break;
  }
}