const express = require('express');
const WebSocket = require('ws');
const http = require('http');
const sqlite3 = require('sqlite3').verbose();

const app = express();
const server = http.createServer(app);
const wss = new WebSocket.Server({ server, path: '/counter-ws' });

// Initialize SQLite database
const db = new sqlite3.Database('./counter.db', (err) => {
  if (err) {
    console.error('Error opening database:', err.message);
  } else {
    console.log('Connected to SQLite database.');
    // Create counter table if it doesn't exist
    db.run(`CREATE TABLE IF NOT EXISTS counter (
      id INTEGER PRIMARY KEY CHECK (id = 1),
      value INTEGER DEFAULT 0
    )`, (err) => {
      if (err) {
        console.error('Error creating table:', err.message);
      } else {
        // Initialize counter value if not exists
        db.run(`INSERT OR IGNORE INTO counter (id, value) VALUES (1, 0)`, () => {
          // Load initial counter value
          loadCounterValue();
        });
      }
    });
  }
});

let counter = 0; // Will be loaded from database

// Function to load counter value from database
function loadCounterValue() {
  db.get(`SELECT value FROM counter WHERE id = 1`, (err, row) => {
    if (err) {
      console.error('Error loading counter value:', err.message);
    } else if (row) {
      counter = row.value;
      console.log('Loaded counter value:', counter);
    }
  });
}

app.use(express.json());

// API endpoint to get current counter value
app.get('/api/counter', (req, res) => {
  res.json({ value: counter });
});

// API endpoint to increment counter
app.post('/api/counter/increment', (req, res) => {
  counter += 1;

  // Update counter value in database
  db.run(`UPDATE counter SET value = ? WHERE id = 1`, [counter], (err) => {
    if (err) {
      console.error('Error updating counter in database:', err.message);
      res.status(500).json({ error: 'Failed to update counter' });
      return;
    }

    res.json({ value: counter });

    // Broadcast update to all connected WebSocket clients
    wss.clients.forEach(client => {
      if (client.readyState === WebSocket.OPEN) {
        client.send(JSON.stringify({ type: 'counter-update', value: counter }));
      }
    });
  });
});

// WebSocket connection handling
wss.on('connection', (ws) => {
  console.log('Client connected');

  ws.on('message', (message) => {
    const msg = Buffer.from(message).toString();
    if (msg === '{"type":"ping"}') {
      // Respond to ping to keep connection alive
      ws.send(JSON.stringify({ type: 'pong' }));
    } else {
      console.log('Received:', msg);
    }
  });

  ws.on('error', (error) => {
    console.log('WebSocket error:', error);
  });

  ws.on('close', (code, reason) => {
    console.log('Client disconnected', 'Code:', code, 'Reason:', reason.toString());
  });
});

const PORT = 3001; // API and WebSocket server port
server.listen(PORT, '127.0.0.1', () => {
  console.log(`Server running on http://127.0.0.1:${PORT}`);
});