Initial commit

src/app.ts

@@ -0,0 +1,74 @@
+import express, { type ErrorRequestHandler } from "express";
+import { randomUUID } from "node:crypto";
+import { pinoHttp } from "pino-http";
+import type { Logger } from "pino";
+import type { Config } from "./lib/config.js";
+import type { Db } from "./lib/db.js";
+import type { Flags } from "./lib/flags.js";
+import type { Cache } from "./lib/redis.js";
+import {
+  staticRuntimeConfig,
+  type RuntimeConfig,
+} from "./lib/runtime-config.js";
+import { adminRouter } from "./routes/admin.js";
+import { healthRouter } from "./routes/health.js";
+import { logDemoRouter } from "./routes/log-demo.js";
+import { rootRouter } from "./routes/root.js";
+
+export interface Deps {
+  config: Config;
+  logger: Logger;
+  db?: Db;
+  cache?: Cache;
+  flags?: Flags;
+  runtimeConfig?: RuntimeConfig;
+}
+
+export function createApp({
+  config,
+  logger,
+  db,
+  cache,
+  flags,
+  runtimeConfig = staticRuntimeConfig(),
+}: Deps) {
+  const app = express();
+  app.disable("x-powered-by");
+
+  app.use(
+    pinoHttp({
+      logger,
+      genReqId: (req, res) => {
+        const incoming = req.headers["x-request-id"];
+        const id =
+          (Array.isArray(incoming) ? incoming[0] : incoming) ?? randomUUID();
+        res.setHeader("X-Request-Id", id);
+        return id;
+      },
+      // Keep the logging contract flat and small: req.id/method/url,
+      // res.statusCode, responseTime.
+      serializers: {
+        req: (req) => ({ id: req.id, method: req.method, url: req.url }),
+        res: (res) => ({ statusCode: res.statusCode }),
+      },
+      autoLogging: {
+        ignore: (req) => req.url === "/healthz" || req.url === "/readyz",
+      },
+    }),
+  );
+
+  app.use(healthRouter({ db, cache }));
+  app.use(rootRouter({ config, db, cache, flags, runtimeConfig }));
+  app.use(adminRouter({ runtimeConfig }));
+  app.use(logDemoRouter());
+
+  // Express identifies error handlers by arity; keep all four args.
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  const onError: ErrorRequestHandler = (err, req, res, _next) => {
+    req.log.error({ err }, "unhandled error");
+    res.status(500).json({ error: "internal error" });
+  };
+  app.use(onError);
+
+  return app;
+}