import "reflect-metadata";
import { NestFactory } from "@nestjs/core";
import { AppModule } from "./app.module.js";
import { GlobalErrorFilter } from "./shared/errors/global-error.filter.js";
import { initTracer, shutdownTracer } from "./shared/observability/tracer.js";
import { logger } from "./shared/observability/logger.js";
import { env } from "./config/env.js";
import { metricsRegistry } from "./shared/observability/metrics.js";
import type { Request, Response } from "express";

async function bootstrap(): Promise<void> {
  initTracer();

  const app = await NestFactory.create(AppModule, {
    logger: ["log", "error", "warn"],
  });

  app.useGlobalFilters(new GlobalErrorFilter());
  app.enableShutdownHooks();

  // Prometheus 指标端点：不鉴权，供 Prometheus 抓取。
  app.getHttpAdapter().get("/metrics", async (_req: Request, res: Response) => {
    res.set("Content-Type", metricsRegistry.contentType);
    res.end(await metricsRegistry.metrics());
  });

  await app.listen(env.PORT);
  logger.info({ port: env.PORT }, "Teacher BFF started");

  process.on("SIGTERM", async () => {
    await app.close();
    await shutdownTracer();
  });
}

bootstrap().catch((err: unknown) => {
  logger.error({ err }, "Failed to start Teacher BFF");
  process.exit(1);
});
