Initial import of zappier-edge from zapier monorepo

src/invoicing.ts

@@ -0,0 +1,106 @@
+import { Customer } from './auth';
+import { TierConfig } from './pricing';
+import { UsageEntry } from './usage';
+
+export interface InvoiceLine {
+  endpointId: string;
+  calls: number;
+  cents: number;
+}
+
+export interface Invoice {
+  /** INV-<period>-<zero-padded sequence>, e.g. INV-2026-07-0007 */
+  id: string;
+  customerId: string;
+  /** Billing period, YYYY-MM */
+  period: string;
+  status: 'draft' | 'issued' | 'paid';
+  lines: InvoiceLine[];
+  /** Gross usage in cents (sum of lines, before credit). */
+  totalCents: number;
+  /** Monthly credit actually consumed. */
+  creditCents: number;
+  /** totalCents − creditCents, floored at 0. */
+  billableCents: number;
+  billingType: 'stripe' | 'purchase_order';
+  poNumber?: string;
+  issuedAtMs?: number;
+  dueAtMs?: number;
+  paidAtMs?: number;
+}
+
+export interface InvoiceRepo {
+  save(invoice: Invoice): void;
+  get(id: string): Invoice | undefined;
+  list(filter: {
+    customerId?: string;
+    period?: string;
+    status?: Invoice['status'];
+  }): Invoice[];
+  /** 1-based sequence for the next invoice id within a period. */
+  nextSequence(period: string): number;
+}
+
+/** Test/dev adapter; production uses SqliteInvoiceRepo. */
+export class InMemoryInvoiceRepo implements InvoiceRepo {
+  private invoices = new Map<string, Invoice>();
+
+  save(invoice: Invoice): void {
+    this.invoices.set(invoice.id, { ...invoice, lines: invoice.lines.map((l) => ({ ...l })) });
+  }
+
+  get(id: string): Invoice | undefined {
+    return this.invoices.get(id);
+  }
+
+  list(filter: {
+    customerId?: string;
+    period?: string;
+    status?: Invoice['status'];
+  }): Invoice[] {
+    return [...this.invoices.values()]
+      .filter((i) => (filter.customerId ? i.customerId === filter.customerId : true))
+      .filter((i) => (filter.period ? i.period === filter.period : true))
+      .filter((i) => (filter.status ? i.status === filter.status : true))
+      .sort((a, b) => a.id.localeCompare(b.id));
+  }
+
+  nextSequence(period: string): number {
+    return [...this.invoices.values()].filter((i) => i.period === period).length + 1;
+  }
+}
+
+export function buildInvoice(args: {
+  customer: Customer;
+  period: string;
+  sequence: number;
+  entries: UsageEntry[];
+  tier: TierConfig;
+  poNumber?: string;
+}): Invoice {
+  const { customer, period, sequence, entries, tier, poNumber } = args;
+  const byEndpoint = new Map<string, InvoiceLine>();
+  for (const e of entries) {
+    const line = byEndpoint.get(e.endpointId) ?? { endpointId: e.endpointId, calls: 0, cents: 0 };
+    line.calls += 1;
+    line.cents += e.cents;
+    byEndpoint.set(e.endpointId, line);
+  }
+  const lines = [...byEndpoint.values()].sort((a, b) =>
+    a.endpointId.localeCompare(b.endpointId),
+  );
+  const totalCents = lines.reduce((sum, l) => sum + l.cents, 0);
+  const creditCents = Math.min(totalCents, tier.monthlyCreditCents);
+  return {
+    id: `INV-${period}-${String(sequence).padStart(4, '0')}`,
+    customerId: customer.id,
+    period,
+    status: 'draft',
+    lines,
+    totalCents,
+    creditCents,
+    billableCents: totalCents - creditCents,
+    billingType: customer.billingType ?? 'stripe',
+    ...(poNumber !== undefined ? { poNumber } : {}),
+  };
+}