import { Router } from "express";
import { createRequire } from "module";
import { getPoolStats } from "../services/browser.js";
import { pool } from "../services/db.js";

const require = createRequire(import.meta.url);
const { version: APP_VERSION } = require("../../package.json");

export const healthRouter = Router();

const HEALTH_CHECK_TIMEOUT_MS = 3000;

healthRouter.get("/", async (_req, res) => {
  const poolStats = getPoolStats();
  let databaseStatus: any;
  let overallStatus = "ok";
  let httpStatus = 200;

  // Check database connectivity with a real query and timeout
  try {
    const dbCheck = async () => {
      const client = await pool.connect();
      try {
        // Use SELECT 1 as a lightweight liveness probe
        await client.query('SELECT 1');
        const result = await client.query('SELECT version()');
        const version = result.rows[0]?.version || 'Unknown';
        const versionMatch = version.match(/PostgreSQL ([\d.]+)/);
        const shortVersion = versionMatch ? `PostgreSQL ${versionMatch[1]}` : 'PostgreSQL';
        client.release();
        return { status: "ok", version: shortVersion };
      } catch (queryErr) {
        // Destroy the bad connection so it doesn't go back to the pool
        try { client.release(true); } catch (_) {}
        throw queryErr;
      }
    };

    const timeout = new Promise<never>((_resolve, reject) =>
      setTimeout(() => reject(new Error("Database health check timed out")), HEALTH_CHECK_TIMEOUT_MS)
    );

    databaseStatus = await Promise.race([dbCheck(), timeout]);
  } catch (error: any) {
    databaseStatus = {
      status: "error",
      message: error.message || "Database connection failed"
    };
    overallStatus = "degraded";
    httpStatus = 503;
  }

  const response = {
    status: overallStatus,
    version: APP_VERSION,
    database: databaseStatus,
    pool: {
      size: poolStats.poolSize,
      active: poolStats.totalPages - poolStats.availablePages,
      available: poolStats.availablePages,
      queueDepth: poolStats.queueDepth,
      pdfCount: poolStats.pdfCount,
      restarting: poolStats.restarting,
      uptimeSeconds: Math.round(poolStats.uptimeMs / 1000),
    },
  };

  res.status(httpStatus).json(response);
});