feat: initial backend service template

src/lib/config.ts

@@ -0,0 +1,25 @@
+import { z } from "zod";
+
+const schema = z.object({
+  PORT: z.coerce.number().int().positive().default(3000),
+  SERVICE_NAME: z.string().min(1, "SERVICE_NAME is required"),
+  LOG_LEVEL: z
+    .enum(["fatal", "error", "warn", "info", "debug", "trace", "silent"])
+    .default("info"),
+  GIT_SHA: z.string().default("dev"),
+  DATABASE_URL: z.string().url().optional(),
+  REDIS_URL: z.string().url().optional(),
+});
+
+export type Config = z.infer<typeof schema>;
+
+export function parseConfig(env: NodeJS.ProcessEnv): Config {
+  const result = schema.safeParse(env);
+  if (!result.success) {
+    const problems = result.error.issues
+      .map((i) => `  ${i.path.join(".")}: ${i.message}`)
+      .join("\n");
+    throw new Error(`Invalid environment:\n${problems}`);
+  }
+  return result.data;
+}

src/lib/db.ts

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+import pg from "pg";
+
+export interface Db {
+  query: pg.Pool["query"];
+  ping(): Promise<void>;
+  close(): Promise<void>;
+}
+
+export function createDb(connectionString: string): Db {
+  const pool = new pg.Pool({
+    connectionString,
+    max: 5,
+    connectionTimeoutMillis: 2000,
+  });
+  // Idle-client errors must not crash the process.
+  pool.on("error", () => {});
+  return {
+    query: pool.query.bind(pool) as pg.Pool["query"],
+    async ping() {
+      await pool.query("SELECT 1");
+    },
+    close: () => pool.end(),
+  };
+}

src/lib/logger.ts

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+import pino from "pino";
+import type { Config } from "./config.js";
+
+// Logging contract: one JSON object per line on stdout with level, time,
+// msg, service, version. Level is emitted as a label, time as ISO-8601.
+export function createLogger(config: Config): pino.Logger {
+  return pino({
+    level: config.LOG_LEVEL,
+    base: { service: config.SERVICE_NAME, version: config.GIT_SHA },
+    messageKey: "msg",
+    timestamp: pino.stdTimeFunctions.isoTime,
+    formatters: { level: (label) => ({ level: label }) },
+  });
+}

src/lib/redis.ts

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+import { Redis } from "ioredis";
+
+export interface Cache {
+  incr(key: string): Promise<number>;
+  ping(): Promise<void>;
+  close(): Promise<void>;
+}
+
+export function createCache(url: string): Cache {
+  const client = new Redis(url, {
+    maxRetriesPerRequest: 1,
+    connectTimeout: 2000,
+    enableOfflineQueue: false,
+    lazyConnect: false,
+  });
+  client.on("error", () => {});
+  return {
+    incr: (key) => client.incr(key),
+    async ping() {
+      await client.ping();
+    },
+    async close() {
+      client.disconnect();
+    },
+  };
+}