const express = require('express');
const fs = require('fs');
const path = require('path');

const app = express();
const PORT = 9201;
const ALERTS_FILE = path.join(__dirname, 'alerts.json');

app.use(express.json());

// Load/save alerts
function loadAlerts() {
  try { return JSON.parse(fs.readFileSync(ALERTS_FILE, 'utf8')); }
  catch { return []; }
}
function saveAlerts(alerts) {
  fs.writeFileSync(ALERTS_FILE, JSON.stringify(alerts, null, 2));
}

// SSE clients
const sseClients = new Set();

// Serve dashboard
app.get('/', (req, res) => {
  res.sendFile(path.join(__dirname, 'index.html'));
});

// List alerts
app.get('/api/alerts', (req, res) => {
  res.json(loadAlerts().slice(-50).reverse());
});

// Push alert
app.post('/api/alerts', (req, res) => {
  const { message, priority = 'info' } = req.body;
  if (!message) return res.status(400).json({ error: 'message required' });
  const alert = {
    id: Date.now().toString(36) + Math.random().toString(36).slice(2, 6),
    message,
    priority,
    timestamp: new Date().toISOString()
  };
  const alerts = loadAlerts();
  alerts.push(alert);
  // Keep last 100
  if (alerts.length > 100) alerts.splice(0, alerts.length - 100);
  saveAlerts(alerts);
  // Notify SSE clients
  for (const client of sseClients) {
    client.write(`data: ${JSON.stringify(alert)}\n\n`);
  }
  res.status(201).json(alert);
});

// SSE stream
app.get('/api/alerts/stream', (req, res) => {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    'Connection': 'keep-alive',
  });
  res.write('data: {"type":"connected"}\n\n');
  sseClients.add(res);
  req.on('close', () => sseClients.delete(res));
});

app.listen(PORT, '0.0.0.0', () => {
  console.log(`Alert dashboard running on http://0.0.0.0:${PORT}`);
});