import { createServer, type Server } from "node:http";
import { sql } from "drizzle-orm";
import { db } from "./db.js";
import { env } from "./env.js";
import { logger } from "./logger.js";

export type HealthStatus = {
  ok: boolean;
  uptimeSec: number;
  db: "ok" | "error";
  sessions?: Record<string, number>;
};

const started = Date.now();
let getSessionCounts: () => Record<string, number> = () => ({});

export function setSessionCountsProvider(fn: () => Record<string, number>): void {
  getSessionCounts = fn;
}

export async function buildHealth(): Promise<HealthStatus> {
  let dbStatus: "ok" | "error" = "ok";
  try {
    await db.execute(sql`select 1`);
  } catch (err) {
    logger.warn({ err }, "health: db ping failed");
    dbStatus = "error";
  }
  return {
    ok: dbStatus === "ok",
    uptimeSec: Math.round((Date.now() - started) / 1000),
    db: dbStatus,
    sessions: getSessionCounts(),
  };
}

export function startHealthServer(): Server {
  const server = createServer(async (req, res) => {
    if (req.url !== "/health") {
      res.writeHead(404).end("not found");
      return;
    }
    const status = await buildHealth();
    res.writeHead(status.ok ? 200 : 503, { "content-type": "application/json" });
    res.end(JSON.stringify(status));
  });
  server.listen(env.BOT_HEALTH_PORT, () => {
    logger.info({ port: env.BOT_HEALTH_PORT }, "health server listening");
  });
  return server;
}