Add NATS account-balance SoT and statement review for customers, CS, and sales

Internal billing now uses verae.billing.* request-reply and pubs. zappier-account-balance tracks prepaid, credits, usage, and payments. Portal, admin, CS, and sales all review the same statement. Independent Forgejo repos stay split via push-module-repos.

packages/zappier-account-balance/src/books.js

@@ -0,0 +1,89 @@
+/**
+ * Source of truth for prepaid balances, CS credits, usage, and payments.
+ */
+export class AccountBooks {
+  constructor() {
+    /** @type {Record<string, number>} */
+    this.prepaid = {};
+    this.credits = [];
+    this.usage = [];
+    this.payments = [];
+  }
+
+  prepaidCents(customerId) {
+    return this.prepaid[customerId] ?? 0;
+  }
+
+  adjust({ customerId, cents, reason, agent, kind = 'credit' }) {
+    const delta = Math.trunc(Number(cents) || 0);
+    const next = this.prepaidCents(customerId) + delta;
+    this.prepaid[customerId] = next;
+    const row = {
+      id: `adj_${Date.now().toString(36)}_${Math.random().toString(36).slice(2, 6)}`,
+      customerId,
+      cents: delta,
+      reason: reason || kind,
+      agent: agent || 'system',
+      kind,
+      at: new Date().toISOString(),
+      prepaidCents: next,
+    };
+    if (kind === 'payment' || kind === 'reload') this.payments.unshift(row);
+    else this.credits.unshift(row);
+    return row;
+  }
+
+  recordUsage(entry) {
+    const cents = Number(entry.cents) || 0;
+    const customerId = entry.customerId;
+    const next = this.prepaidCents(customerId) - cents;
+    this.prepaid[customerId] = next;
+    const row = {
+      customerId,
+      endpointId: entry.endpointId || 'unknown',
+      cents,
+      at: entry.at || new Date().toISOString(),
+      prepaidCents: next,
+    };
+    this.usage.unshift(row);
+    return row;
+  }
+
+  recordPayment(entry) {
+    return this.adjust({
+      customerId: entry.customerId,
+      cents: Number(entry.cents) || 0,
+      reason: entry.reason || 'payment',
+      agent: entry.agent || 'payments',
+      kind: 'payment',
+    });
+  }
+
+  statement(customerId) {
+    const match = (rows) => rows.filter((r) => r.customerId === customerId).slice(0, 100);
+    return {
+      customerId,
+      prepaidCents: this.prepaidCents(customerId),
+      credits: match(this.credits),
+      usage: match(this.usage),
+      payments: match(this.payments),
+    };
+  }
+}
+
+export function handle(subject, payload, books) {
+  const p = payload || {};
+  if (subject.endsWith('balance.get') || subject.endsWith('statement.get')) {
+    return books.statement(p.customerId);
+  }
+  if (subject.endsWith('balance.adjust') || subject.endsWith('credit.applied')) {
+    return books.adjust(p);
+  }
+  if (subject.endsWith('usage.recorded')) {
+    return books.recordUsage(p);
+  }
+  if (subject.endsWith('payment.recorded')) {
+    return books.recordPayment(p);
+  }
+  throw new Error(`unknown billing subject ${subject}`);
+}