import { createServer, type Server } from "node:http";
import type { Logger } from "pino";
import type { HealthSnapshot } from "./processor.js";

/** GET /health (or /) → 200 {rooms, cursor, pending, lastProcessedAt}; 503 when the DB count fails. */
export function startHealthServer(port: number, snapshot: () => Promise<HealthSnapshot>, logger: Logger): Server {
  const server = createServer((req, res) => {
    if (req.method !== "GET" || (req.url !== "/" && req.url !== "/health")) {
      res.writeHead(404).end();
      return;
    }
    snapshot().then(
      (body) => {
        res.writeHead(200, { "content-type": "application/json" }).end(JSON.stringify(body));
      },
      (err: unknown) => {
        logger.warn({ err: err instanceof Error ? err.message : String(err) }, "health: snapshot failed");
        res.writeHead(503, { "content-type": "application/json" }).end(JSON.stringify({ status: "down" }));
      },
    );
  });
  server.listen(port, () => logger.info({ port }, "health: listening"));
  return server;
}