set up initial backend

.gitignore

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+node_modules
+dist

backend/db.ts

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+import type { Knex } from "knex";
+
+import { getKnex } from "./knex";
+import { asyncLocalStorage } from "./store";
+
+type KnexRepoFn<T, Args extends unknown[]> = (
+  knex: Knex,
+  ...args: Args
+) => Promise<T>;
+
+type UseKnex = <T, Args extends unknown[]>(
+  fn: KnexRepoFn<T, Args>
+) => (...args: Args) => Promise<T>;
+
+export const useKnex: UseKnex = (fn) => {
+  return async (...args) => {
+    const store = asyncLocalStorage.getStore();
+    const logger = store?.get("logger");
+
+    store?.get("logger")?.debug({ args }, `Starting ${fn.name}`);
+
+    args.push(logger);
+
+    const knex = getKnex();
+    try {
+      return await fn(knex, ...args);
+    } catch (err) {
+      logger?.error(err);
+      throw err;
+    } finally {
+      logger?.debug(`Finished ${fn.name}`);
+    }
+  };
+};

backend/knex.ts

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+import knex, { type Knex } from "knex";
+
+let db: Knex | null = null;
+
+export function getKnex() {
+  if (!db) {
+    db = knex({
+      connection: process.env.DB_URL,
+      client: "pg",
+    });
+  }
+
+  return db;
+}
+
+export function closeKnex() {
+  db?.destroy();
+  db = null;
+}

backend/logging.ts

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+import pino from "pino";
+
+export const logger = pino({
+  level: "debug",
+});