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 { Cache } from "./lib/redis.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;
}

export function createApp({ config, logger, db, cache }: 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 }));
  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;
}