Initial import of zappier-edge from zapier monorepo

tests/usage.test.ts

@@ -0,0 +1,41 @@
+import { InMemoryUsageRepo, UsageEntry } from '../src/usage';
+
+const entry = (over: Partial<UsageEntry> = {}): UsageEntry => ({
+  customerId: 'cust_1',
+  endpointId: 'transform',
+  cents: 4,
+  metadataBytes: 0,
+  attachmentBytes: 0,
+  timestamp: new Date('2026-07-27T10:00:00Z'),
+  ...over,
+});
+
+describe('InMemoryUsageRepo', () => {
+  it('records and lists entries per customer', () => {
+    const repo = new InMemoryUsageRepo();
+    repo.record(entry());
+    repo.record(entry({ customerId: 'cust_2' }));
+    expect(repo.listFor('cust_1')).toHaveLength(1);
+    expect(repo.listFor('cust_2')).toHaveLength(1);
+  });
+
+  it('filters entries by since date', () => {
+    const repo = new InMemoryUsageRepo();
+    repo.record(entry({ timestamp: new Date('2026-07-01T00:00:00Z') }));
+    repo.record(entry({ timestamp: new Date('2026-07-27T00:00:00Z') }));
+    expect(repo.listFor('cust_1', new Date('2026-07-15T00:00:00Z'))).toHaveLength(1);
+  });
+
+  it('summarizes totals by endpoint', () => {
+    const repo = new InMemoryUsageRepo();
+    repo.record(entry());
+    repo.record(entry({ endpointId: 'storage', cents: 112 }));
+    repo.record(entry());
+    const s = repo.summaryFor('cust_1');
+    expect(s.customerId).toBe('cust_1');
+    expect(s.calls).toBe(3);
+    expect(s.totalCents).toBe(120);
+    expect(s.byEndpoint.transform).toEqual({ calls: 2, cents: 8 });
+    expect(s.byEndpoint.storage).toEqual({ calls: 1, cents: 112 });
+  });
+});