const express = require('express');
const { MongoClient } = require('mongodb');
const cors = require('cors');
const path = require('path');

const app = express();
const PORT = process.env.PORT || 3001;

// Middleware
app.use(cors());
app.use(express.json());

// Serve static files from React build
app.use(express.static(path.join(__dirname, '..', 'dist')));

// MongoDB connection - using host.docker.internal for Docker networking
const mongoHost = process.env.MONGO_HOST || 'host.docker.internal';
const uri = `mongodb://admin:MongoPass2024!@${mongoHost}:27017/?authSource=admin`;
const client = new MongoClient(uri);

let db;
let amigosCollection;
const clients = new Set();

function sseHeaders(res) {
  res.setHeader('Content-Type', 'text/event-stream');
  res.setHeader('Cache-Control', 'no-cache');
  res.setHeader('Connection', 'keep-alive');
  res.flushHeaders && res.flushHeaders();
}

function sendEvent(res, event, data) {
  if (event) res.write(`event: ${event}\n`);
  res.write(`data: ${JSON.stringify(data)}\n\n`);
}

function broadcast(event, data) {
  for (const res of clients) {
    try {
      sendEvent(res, event, data);
    } catch (_) {
      // ignore write errors; client will be removed on close
    }
  }
}

// Connect to MongoDB
async function connectDB() {
  try {
    await client.connect();
    console.log('Connected to MongoDB');
    db = client.db('testdb');
    amigosCollection = db.collection('amigos');
  } catch (error) {
    console.error('Error connecting to MongoDB:', error);
    // Retry connection after 5 seconds
    setTimeout(connectDB, 5000);
  }
}

// API Routes
// Get all amigos
app.get('/api/amigos', async (req, res) => {
  try {
    if (!amigosCollection) {
      return res.status(503).json({ error: 'Database not connected' });
    }
    const amigos = await amigosCollection.find({}).toArray();
    res.json(amigos);
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

// Add new amigo
app.post('/api/amigos', async (req, res) => {
  try {
    if (!amigosCollection) {
      return res.status(503).json({ error: 'Database not connected' });
    }
    
    const { nombre } = req.body;
    if (!nombre) {
      return res.status(400).json({ error: 'Nombre es requerido' });
    }
    
    const result = await amigosCollection.insertOne({ nombre });
    res.status(201).json({ 
      message: 'Amigo agregado exitosamente',
      id: result.insertedId,
      nombre 
    });

    // Notify SSE clients about the new friend
    broadcast('amigoAdded', { id: result.insertedId, nombre });
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

// Server-Sent Events for realtime updates
app.get('/api/events', async (req, res) => {
  sseHeaders(res);
  clients.add(res);

  // Send initial snapshot
  try {
    if (amigosCollection) {
      const amigos = await amigosCollection.find({}).toArray();
      sendEvent(res, 'init', { amigos });
    } else {
      sendEvent(res, 'init', { amigos: [] });
    }
  } catch (_) {
    sendEvent(res, 'init', { amigos: [] });
  }

  req.on('close', () => {
    clients.delete(res);
    try { res.end(); } catch (_) {}
  });
});

// Health check endpoint
app.get('/health', (req, res) => {
  res.json({ 
    status: 'ok', 
    mongodb: amigosCollection ? 'connected' : 'disconnected' 
  });
});

// Serve React app for all other routes
app.use((req, res) => {
  res.sendFile(path.join(__dirname, '..', 'dist', 'index.html'));
});

// Start server
connectDB().then(() => {
  app.listen(PORT, '0.0.0.0', () => {
    console.log(`Server running on http://0.0.0.0:${PORT}`);
    console.log(`MongoDB host: ${mongoHost}`);
  });
});