feat: app health endpoint succeeds (E00-S02-T03)

apps/server/src/index.ts

@@ -1,8 +1,69 @@
 /**
  * @personal-blog/server — EPPP public server application.
  *
- * Bootstrap placeholder so apps/ is a real workspace package that compiles
- * under tsconfig.base.json. The Fastify 5 application shell (and its real
- * exports) lands in a later story.
+ * [E00-S02-T03] minimal serving process: a small HTTP server built on Node's
+ * `node:http` (no runtime dependencies yet) that answers the application
+ * health endpoint. `GET /health` reports a healthy application — HTTP 200 with
+ * `{"status":"ok"}` — so the Compose stack's `app` service stays up and the
+ * health endpoint succeeds once the stack is running.
+ *
+ * The Fastify 5 application shell (and the real HTTP API) lands in a later
+ * story; this bootstrap keeps the application health-checkable until then.
  */
-export {};
+
+import { createServer, type IncomingMessage, type ServerResponse } from 'node:http';
+
+/** Port the server listens on; `PORT` overrides the container default (3000). */
+const PORT = resolvePort(process.env.PORT);
+
+/** Health payload — reports a healthy application. */
+const HEALTH_PAYLOAD = JSON.stringify({ status: 'ok' });
+
+/** Payload for any route that is not the health endpoint. */
+const NOT_FOUND_PAYLOAD = JSON.stringify({ error: 'not found' });
+
+/**
+ * Resolves the listen port from `PORT` (default 3000, matching the Dockerfile
+ * `EXPOSE 3000` and the compose `:3000` container port). A non-numeric or
+ * out-of-range override falls back to the default so a bad `PORT` value cannot
+ * crash the process at startup.
+ */
+function resolvePort(raw: string | undefined): number {
+  const port = Number(raw ?? 3000);
+  return Number.isInteger(port) && port > 0 && port <= 65535 ? port : 3000;
+}
+
+/** Writes a JSON response with an explicit content-length. */
+function sendJson(res: ServerResponse, statusCode: number, body: string): void {
+  res.writeHead(statusCode, {
+    'Content-Type': 'application/json; charset=utf-8',
+    'Content-Length': Buffer.byteLength(body),
+  });
+  res.end(body);
+}
+
+/**
+ * Routes one request. The application only serves the health endpoint at this
+ * stage; anything else is a 404 so misconfiguration is loud.
+ */
+function handleRequest(req: IncomingMessage, res: ServerResponse): void {
+  if (req.method === 'GET' && (req.url ?? '/') === '/health') {
+    sendJson(res, 200, HEALTH_PAYLOAD);
+    return;
+  }
+  sendJson(res, 404, NOT_FOUND_PAYLOAD);
+}
+
+const server = createServer(handleRequest);
+
+server.listen(PORT, () => {
+  console.log(`@personal-blog/server listening on http://0.0.0.0:${PORT} (health: GET /health)`);
+});
+
+// `docker stop` (Compose down) and Ctrl-C send SIGTERM/SIGINT — close the
+// server and exit cleanly instead of being killed mid-request.
+for (const signal of ['SIGTERM', 'SIGINT'] as const) {
+  process.on(signal, () => {
+    server.close(() => process.exit(0));
+  });
+}