Initial import of zappier-account-balance from zapier monorepo

src/books.js

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+/**
+ * Source of truth for prepaid balances, CS credits, usage, and payments.
+ */
+export class AccountBooks {
+  constructor() {
+    /** @type {Record<string, number>} */
+    this.prepaid = {};
+    /** @type {Record<string, string>} */
+    this.veraeUserIds = {};
+    /** @type {Record<string, string>} */
+    this.names = {};
+    this.credits = [];
+    this.usage = [];
+    this.payments = [];
+  }
+
+  remember(customerId, veraeUserId, name) {
+    if (customerId && veraeUserId) this.veraeUserIds[customerId] = veraeUserId;
+    if (customerId && name) this.names[customerId] = name;
+  }
+
+  prepaidCents(customerId) {
+    return this.prepaid[customerId] ?? 0;
+  }
+
+  adjust({ customerId, cents, reason, agent, kind = 'credit', veraeUserId, name }) {
+    this.remember(customerId, veraeUserId, name);
+    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) {
+    this.remember(entry.customerId, entry.veraeUserId, entry.name);
+    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',
+    });
+  }
+
+  lookup(idOrName) {
+    if (this.names[idOrName] || this.prepaid[idOrName] != null || this.veraeUserIds[idOrName]) {
+      return this.statement(idOrName);
+    }
+    const want = String(idOrName || '').toLowerCase();
+    const hit = Object.entries(this.names).find(([, n]) => String(n).toLowerCase() === want);
+    return this.statement(hit ? hit[0] : idOrName);
+  }
+
+  statement(customerId) {
+    const match = (rows) => rows.filter((r) => r.customerId === customerId).slice(0, 100);
+    return {
+      customerId,
+      name: this.names[customerId],
+      veraeUserId: this.veraeUserIds[customerId],
+      prepaidCents: this.prepaidCents(customerId),
+      credits: match(this.credits),
+      usage: match(this.usage),
+      payments: match(this.payments),
+    };
+  }
+
+  dump() {
+    return {
+      prepaid: this.prepaid,
+      veraeUserIds: this.veraeUserIds,
+      names: this.names,
+      credits: this.credits,
+      usage: this.usage,
+      payments: this.payments,
+    };
+  }
+
+  load(raw) {
+    if (!raw || typeof raw !== 'object') return this;
+    this.prepaid = raw.prepaid || {};
+    this.veraeUserIds = raw.veraeUserIds || {};
+    this.names = raw.names || {};
+    this.credits = Array.isArray(raw.credits) ? raw.credits : [];
+    this.usage = Array.isArray(raw.usage) ? raw.usage : [];
+    this.payments = Array.isArray(raw.payments) ? raw.payments : [];
+    return this;
+  }
+}
+
+export function handle(subject, payload, books) {
+  const p = payload || {};
+  if (subject.endsWith('customer.put')) {
+    books.remember(p.customerId, p.veraeUserId, p.name);
+    return books.lookup(p.customerId);
+  }
+  if (subject.endsWith('balance.get') || subject.endsWith('statement.get')) {
+    books.remember(p.customerId, p.veraeUserId, p.name);
+    return books.lookup(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}`);
+}

src/persist.js

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+import fs from 'node:fs';
+import path from 'node:path';
+
+export function booksPath() {
+  return (
+    process.env.BOOKS_PATH ||
+    path.join(process.env.FLEET_STATE_DIR || process.cwd(), 'data', 'books.json')
+  );
+}
+
+export function loadInto(books) {
+  const p = booksPath();
+  if (!fs.existsSync(p)) return books;
+  try {
+    books.load(JSON.parse(fs.readFileSync(p, 'utf8')));
+  } catch {
+    /* keep empty */
+  }
+  return books;
+}
+
+export function saveFrom(books) {
+  const p = booksPath();
+  fs.mkdirSync(path.dirname(p), { recursive: true });
+  const tmp = `${p}.tmp`;
+  fs.writeFileSync(tmp, JSON.stringify(books.dump(), null, 2));
+  fs.renameSync(tmp, p);
+}

src/server.js

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+#!/usr/bin/env node
+import http from 'node:http';
+import { AccountBooks, handle } from './books.js';
+import { SUBJECTS } from './subjects.js';
+import { loadInto, saveFrom } from './persist.js';
+
+const PORT = Number(process.env.PORT || process.env.FLEET_HEALTH_PORT || 3010);
+const BIND = process.env.FLEET_HEALTH_BIND || '0.0.0.0';
+const books = loadInto(new AccountBooks());
+
+function apply(subject, payload) {
+  const out = handle(subject, payload, books);
+  saveFrom(books);
+  return out;
+}
+let natsOk = false;
+
+async function startNats() {
+  const url = process.env.NATS_URL;
+  if (!url) return;
+  const { connect, StringCodec } = await import('nats');
+  const nc = await connect({ servers: url.split(','), name: 'zappier-account-balance' });
+  const sc = StringCodec();
+  const reply = async (sub, fn) => {
+    for await (const m of sub) {
+      let payload = {};
+      try {
+        payload = JSON.parse(sc.decode(m.data) || '{}');
+      } catch {
+        payload = {};
+      }
+      const out = fn(payload);
+      saveFrom(books);
+      if (m.reply) m.respond(sc.encode(JSON.stringify(out)));
+    }
+  };
+  reply(nc.subscribe(SUBJECTS.STATEMENT_GET, { queue: SUBJECTS.QUEUE }), (p) =>
+    apply(SUBJECTS.STATEMENT_GET, p),
+  );
+  reply(nc.subscribe(SUBJECTS.BALANCE_GET, { queue: SUBJECTS.QUEUE }), (p) =>
+    apply(SUBJECTS.BALANCE_GET, p),
+  );
+  reply(nc.subscribe(SUBJECTS.BALANCE_ADJUST, { queue: SUBJECTS.QUEUE }), (p) =>
+    apply(SUBJECTS.BALANCE_ADJUST, p),
+  );
+  reply(nc.subscribe(SUBJECTS.CUSTOMER_PUT, { queue: SUBJECTS.QUEUE }), (p) =>
+    apply(SUBJECTS.CUSTOMER_PUT, p),
+  );
+  (async () => {
+    for await (const m of nc.subscribe(SUBJECTS.USAGE_RECORDED)) {
+      apply(SUBJECTS.USAGE_RECORDED, JSON.parse(sc.decode(m.data) || '{}'));
+    }
+  })();
+  // payment.recorded / credit.applied are fan-out events. Prepaid mutations
+  // go through balance.adjust so publishers can both pub and request-reply.
+  natsOk = true;
+  process.stdout.write(`account-balance nats ${url}\n`);
+}
+
+function readBody(req) {
+  return new Promise((resolve) => {
+    const chunks = [];
+    req.on('data', (c) => chunks.push(c));
+    req.on('end', () => {
+      try {
+        resolve(JSON.parse(Buffer.concat(chunks).toString('utf8') || '{}'));
+      } catch {
+        resolve({});
+      }
+    });
+  });
+}
+
+const server = http.createServer(async (req, res) => {
+  const url = new URL(req.url || '/', `http://127.0.0.1:${PORT}`);
+  const json = (code, obj) => {
+    res.writeHead(code, { 'content-type': 'application/json' });
+    res.end(JSON.stringify(obj));
+  };
+  try {
+    if (req.method === 'GET' && url.pathname === '/health') {
+      return json(200, { ok: true, role: 'zappier-account-balance', nats: natsOk, subjects: SUBJECTS });
+    }
+    const st = url.pathname.match(/^\/statement\/([^/]+)$/);
+    if (req.method === 'GET' && st) {
+      return json(200, books.lookup(decodeURIComponent(st[1])));
+    }
+    if (req.method === 'POST' && url.pathname === '/customer') {
+      const body = await readBody(req);
+      return json(200, apply(SUBJECTS.CUSTOMER_PUT, body));
+    }
+    if (req.method === 'POST' && url.pathname === '/adjust') {
+      const body = await readBody(req);
+      return json(200, apply(SUBJECTS.BALANCE_ADJUST, body));
+    }
+    json(404, { error: 'not found' });
+  } catch (err) {
+    json(500, { error: err.message });
+  }
+});
+
+server.listen(PORT, BIND, () => {
+  process.stdout.write(`zappier-account-balance http://${BIND}:${PORT}/\n`);
+});
+startNats().catch((err) => {
+  process.stderr.write(`nats optional: ${err.message}\n`);
+});

src/subjects.js

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+/** Internal billing bus. Zapier cloud never subscribes. */
+export const SUBJECTS = {
+  BALANCE_GET: 'verae.billing.balance.get',
+  BALANCE_ADJUST: 'verae.billing.balance.adjust',
+  STATEMENT_GET: 'verae.billing.statement.get',
+  USAGE_RECORDED: 'verae.billing.usage.recorded',
+  PAYMENT_RECORDED: 'verae.billing.payment.recorded',
+  CREDIT_APPLIED: 'verae.billing.credit.applied',
+  CUSTOMER_PUT: 'verae.billing.customer.put',
+  QUEUE: 'account-balance',
+};