Initial import of zappier-edge from zapier monorepo

tests/invoicing.test.ts

@@ -0,0 +1,86 @@
+import { buildInvoice, Invoice } from '../src/invoicing';
+import { Customer } from '../src/auth';
+import { TierConfig } from '../src/pricing';
+import { UsageEntry } from '../src/usage';
+
+const pro: TierConfig = { id: 'pro', name: 'Pro', multiplier: 0.5, monthlyCreditCents: 1000 };
+
+const customer: Customer = {
+  id: 'cust_2',
+  name: 'Grace',
+  tierId: 'pro',
+  apiKey: 'key-grace',
+  stripeCustomerId: 'cus_123',
+};
+
+const entry = (endpointId: string, cents: number): UsageEntry => ({
+  customerId: customer.id,
+  endpointId,
+  cents,
+  metadataBytes: 0,
+  attachmentBytes: 0,
+  timestamp: new Date('2026-07-10T12:00:00Z'),
+});
+
+describe('buildInvoice', () => {
+  it('groups usage entries into lines per endpoint, sorted', () => {
+    const inv = buildInvoice({
+      customer,
+      period: '2026-07',
+      sequence: 1,
+      tier: pro,
+      entries: [entry('transform', 3), entry('storage', 6), entry('transform', 3)],
+    });
+    expect(inv.lines).toEqual([
+      { endpointId: 'storage', calls: 1, cents: 6 },
+      { endpointId: 'transform', calls: 2, cents: 6 },
+    ]);
+    expect(inv.totalCents).toBe(12);
+  });
+
+  it('applies a partial monthly credit', () => {
+    const inv = buildInvoice({
+      customer,
+      period: '2026-07',
+      sequence: 1,
+      tier: pro,
+      entries: [entry('storage', 1500)],
+    });
+    expect(inv.totalCents).toBe(1500);
+    expect(inv.creditCents).toBe(1000);
+    expect(inv.billableCents).toBe(500);
+  });
+
+  it('floors billable at zero when credit exceeds usage', () => {
+    const inv = buildInvoice({
+      customer,
+      period: '2026-07',
+      sequence: 1,
+      tier: pro,
+      entries: [entry('storage', 400)],
+    });
+    expect(inv.creditCents).toBe(400);
+    expect(inv.billableCents).toBe(0);
+  });
+
+  it('formats the id as INV-<period>-<padded sequence> and starts as draft', () => {
+    const inv = buildInvoice({ customer, period: '2026-07', sequence: 7, tier: pro, entries: [] });
+    expect(inv.id).toBe('INV-2026-07-0007');
+    expect(inv.status).toBe('draft');
+    expect(inv.billingType).toBe('stripe');
+  });
+
+  it('carries purchase-order billing fields', () => {
+    const poCustomer: Customer = { ...customer, billingType: 'purchase_order' };
+    const inv = buildInvoice({
+      customer: poCustomer,
+      period: '2026-07',
+      sequence: 2,
+      tier: pro,
+      entries: [entry('storage', 2000)],
+      poNumber: 'PO-9982',
+    });
+    expect(inv.billingType).toBe('purchase_order');
+    expect(inv.poNumber).toBe('PO-9982');
+  });
+});