server.js

// server.js
require('dotenv').config();
const express = require('express');
const os = require('os');
const pkg = require('./package.json');
const { connectDB, getLogsCollection } = require('./db/mongoClient');
const requestLogger = require('./middleware/requestLogger');
const proxyRouter = require('./proxy/router');
const rateLimiter = require('./middleware/rateLimiter');

const app = express();
const PORT = process.env.PORT || 3000;

// Record start time for uptime calculation
const startTime = Date.now();

// Health check endpoint
app.get('/health', async (req, res) => {
  let dbStatus = 'unknown';

  try {
    const logsCollection = await getLogsCollection();
    await logsCollection.estimatedDocumentCount(); // ping db
    dbStatus = 'connected';
  } catch (err) {
    dbStatus = 'disconnected';
  }

  res.status(200).json({
    status: 'ok',
    db: dbStatus,
    uptime: `${Math.floor(process.uptime())}s`,
    memory: process.memoryUsage().rss,
    version: pkg.version,
    hostname: os.hostname(),
  });
});

// Prometheus-style metrics endpoint
app.get('/metrics', (req, res) => {
  const mem = process.memoryUsage();
  const uptime = process.uptime();

  res.set('Content-Type', 'text/plain');
  res.send(
    `# HELP app_uptime_seconds Uptime in seconds\n` +
    `app_uptime_seconds ${uptime}\n` +
    `# HELP app_memory_rss_bytes Resident memory usage\n` +
    `app_memory_rss_bytes ${mem.rss}\n` +
    `# HELP app_memory_heap_used_bytes Heap used\n` +
    `app_memory_heap_used_bytes ${mem.heapUsed}\n` +
    `# HELP app_memory_heap_total_bytes Heap total\n` +
    `app_memory_heap_total_bytes ${mem.heapTotal}\n`
  );
});

async function startServer() {
  try {
    await connectDB();

    app.use(rateLimiter); // ✅ Add rate limiter globally

    const logsCollection = await getLogsCollection();
    app.use(requestLogger(logsCollection));

    app.use(proxyRouter);

    app.listen(PORT, () => {
      console.log(`🚀 Reverse proxy running at http://localhost:${PORT}`);
    });
  } catch (err) {
    console.error('❌ Failed to start server:', err.message);
    process.exit(1);
  }
}

startServer();