Initial import of zappier-edge from zapier monorepo

src/billing/stripe.ts

@@ -0,0 +1,41 @@
+import { UsageEntry } from '../usage';
+
+export const METER_EVENT_NAME = 'zappier.api_cents';
+
+export interface MeterEventClient {
+  createMeterEvent(params: {
+    eventName: string;
+    customerId: string;
+    value: string;
+    /** Stripe-side dedup key; events with the same identifier are dropped. */
+    identifier?: string;
+  }): Promise<void>;
+}
+
+export function computeBillableCents(entries: UsageEntry[], monthlyCreditCents: number): number {
+  const totalCents = entries.reduce((sum, e) => sum + e.cents, 0);
+  return Math.max(0, totalCents - monthlyCreditCents);
+}
+
+export function computeDelta(billableCents: number, previouslyReportedCents: number): number {
+  return Math.max(0, billableCents - previouslyReportedCents);
+}
+
+// Public API: retained for API compatibility. The monthly billing job now uses
+// the delta-based path in src/jobs/report-usage.ts (reportMonthlyUsage), which
+// shares computeBillableCents with this function. Do not remove.
+export async function reportUsage(
+  client: MeterEventClient,
+  stripeCustomerId: string,
+  entries: UsageEntry[],
+  monthlyCreditCents: number,
+): Promise<number> {
+  const billable = computeBillableCents(entries, monthlyCreditCents);
+  if (billable <= 0) return 0;
+  await client.createMeterEvent({
+    eventName: METER_EVENT_NAME,
+    customerId: stripeCustomerId,
+    value: String(billable),
+  });
+  return billable;
+}