billing skeleton: bun + hono + sqlite, seed + happy path

src/db.ts

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+import { Database } from "bun:sqlite";
+import { join } from "node:path";
+
+export const db = new Database(join(import.meta.dir, "..", "data.db"), { create: true });
+db.exec("PRAGMA journal_mode = WAL;");
+db.exec("PRAGMA foreign_keys = ON;");
+
+// Migrate: schema is idempotent (CREATE TABLE IF NOT EXISTS)
+db.exec(await Bun.file(join(import.meta.dir, "schema.sql")).text());
+
+// Seed once, only if empty
+const { n } = db.query<{ n: number }, []>("SELECT count(*) AS n FROM customers").get()!;
+if (n === 0) {
+  db.transaction(() => {
+    db.run(
+      `INSERT INTO customers (id, name, email) VALUES
+       ('cus_ada',   'Ada Lovelace',   'ada@example.com'),
+       ('cus_grace', 'Grace Hopper',   'grace@example.com')`,
+    );
+    db.run(
+      `INSERT INTO plans (id, name, amount_cents, currency, interval) VALUES
+       ('plan_basic', 'Basic',  1000, 'usd', 'month'),
+       ('plan_pro',   'Pro',    5000, 'usd', 'month')`,
+    );
+    db.run(
+      `INSERT INTO subscriptions (id, customer_id, plan_id, status, current_period_start, current_period_end) VALUES
+       ('sub_1', 'cus_ada', 'plan_pro', 'active', datetime('now'), datetime('now', '+1 month'))`,
+    );
+    db.run(
+      `INSERT INTO invoices (id, subscription_id, customer_id, amount_cents, currency, status, due_at) VALUES
+       ('inv_1', 'sub_1', 'cus_ada', 5000, 'usd', 'open', datetime('now', '+14 days'))`,
+    );
+  })();
+  console.log("seeded database");
+}
+
+// `bun run db:reset` executes this file directly after deleting data.db
+if (import.meta.main) {
+  console.log("db ready:", db.filename);
+}

src/index.ts

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+import { Hono } from "hono";
+import { logger } from "hono/logger";
+import { z } from "zod";
+import { db } from "./db";
+
+const app = new Hono();
+app.use(logger());
+
+app.get("/health", (c) => c.json({ ok: true }));
+
+// --- Customers -------------------------------------------------------------
+
+app.get("/customers", (c) => {
+  return c.json(db.query("SELECT * FROM customers ORDER BY created_at").all());
+});
+
+app.get("/customers/:id/invoices", (c) => {
+  const rows = db
+    .query("SELECT * FROM invoices WHERE customer_id = ? ORDER BY created_at DESC")
+    .all(c.req.param("id"));
+  return c.json(rows);
+});
+
+// --- Subscriptions (happy path: subscribe -> first invoice) -----------------
+
+const CreateSubscription = z.object({
+  customer_id: z.string(),
+  plan_id: z.string(),
+});
+
+app.post("/subscriptions", async (c) => {
+  const parsed = CreateSubscription.safeParse(await c.req.json().catch(() => null));
+  if (!parsed.success) return c.json({ error: z.treeifyError(parsed.error) }, 400);
+  const { customer_id, plan_id } = parsed.data;
+
+  const customer = db.query("SELECT id FROM customers WHERE id = ?").get(customer_id);
+  if (!customer) return c.json({ error: "customer not found" }, 404);
+
+  const plan = db
+    .query<{ id: string; amount_cents: number; currency: string; interval: string }, [string]>(
+      "SELECT * FROM plans WHERE id = ?",
+    )
+    .get(plan_id);
+  if (!plan) return c.json({ error: "plan not found" }, 404);
+
+  const subId = `sub_${crypto.randomUUID().slice(0, 8)}`;
+  const invId = `inv_${crypto.randomUUID().slice(0, 8)}`;
+
+  db.transaction(() => {
+    db.run(
+      `INSERT INTO subscriptions (id, customer_id, plan_id, status, current_period_start, current_period_end)
+       VALUES (?, ?, ?, 'active', datetime('now'), datetime('now', ?))`,
+      [subId, customer_id, plan_id, `+1 ${plan.interval}`],
+    );
+    db.run(
+      `INSERT INTO invoices (id, subscription_id, customer_id, amount_cents, currency, status, due_at)
+       VALUES (?, ?, ?, ?, ?, 'open', datetime('now', '+14 days'))`,
+      [invId, subId, customer_id, plan.amount_cents, plan.currency],
+    );
+  })();
+
+  const subscription = db.query("SELECT * FROM subscriptions WHERE id = ?").get(subId);
+  const invoice = db.query("SELECT * FROM invoices WHERE id = ?").get(invId);
+  return c.json({ subscription, invoice }, 201);
+});
+
+export default {
+  port: Number(process.env.PORT ?? 3000),
+  fetch: app.fetch,
+};
+
+console.log(`listening on http://localhost:${process.env.PORT ?? 3000}`);

src/schema.sql

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+CREATE TABLE IF NOT EXISTS customers (
+  id         TEXT PRIMARY KEY,
+  name       TEXT NOT NULL,
+  email      TEXT NOT NULL UNIQUE,
+  created_at TEXT NOT NULL DEFAULT (datetime('now'))
+);
+
+CREATE TABLE IF NOT EXISTS plans (
+  id           TEXT PRIMARY KEY,
+  name         TEXT NOT NULL,
+  amount_cents INTEGER NOT NULL,
+  currency     TEXT NOT NULL DEFAULT 'usd',
+  interval     TEXT NOT NULL DEFAULT 'month' CHECK (interval IN ('month', 'year'))
+);
+
+CREATE TABLE IF NOT EXISTS subscriptions (
+  id                   TEXT PRIMARY KEY,
+  customer_id          TEXT NOT NULL REFERENCES customers(id),
+  plan_id              TEXT NOT NULL REFERENCES plans(id),
+  status               TEXT NOT NULL DEFAULT 'active' CHECK (status IN ('active', 'past_due', 'canceled')),
+  current_period_start TEXT NOT NULL,
+  current_period_end   TEXT NOT NULL,
+  created_at           TEXT NOT NULL DEFAULT (datetime('now'))
+);
+
+CREATE TABLE IF NOT EXISTS invoices (
+  id              TEXT PRIMARY KEY,
+  subscription_id TEXT NOT NULL REFERENCES subscriptions(id),
+  customer_id     TEXT NOT NULL REFERENCES customers(id),
+  amount_cents    INTEGER NOT NULL,
+  currency        TEXT NOT NULL DEFAULT 'usd',
+  status          TEXT NOT NULL DEFAULT 'open' CHECK (status IN ('open', 'paid', 'void')),
+  due_at          TEXT NOT NULL,
+  created_at      TEXT NOT NULL DEFAULT (datetime('now'))
+);
+
+CREATE INDEX IF NOT EXISTS idx_subscriptions_customer ON subscriptions(customer_id);
+CREATE INDEX IF NOT EXISTS idx_invoices_customer ON invoices(customer_id);