// Server-side code
const express = require('express');
const http = require('http');
const socketIO = require('socket.io');

const app = express();
const server = http.createServer(app);
const io = socketIO(server);

let interval;
let tempo = 120; // Initial tempo (beats per minute)
let startTime; // Start time of the metronome

io.on('connection', (socket) => {
  console.log('A client connected');

  socket.on('start', () => {
    console.log('Metronome started');
    startTime = Date.now(); // Set the start time

    // Calculate the delay between each beat based on the tempo
    const delay = (60 / tempo) * 1000;

    // Send a beat event to all connected clients at the specified interval
    interval = setInterval(() => {
      const elapsedTime = Date.now() - startTime;
      io.emit('beat', elapsedTime);
    }, delay);
  });

  socket.on('stop', () => {
    console.log('Metronome stopped');
    clearInterval(interval);
  });

  socket.on('tempo', (newTempo) => {
    console.log(`Tempo set to ${newTempo} BPM`);
    tempo = newTempo;

    // If the metronome is already running, restart it with the new tempo
    if (interval) {
      clearInterval(interval);
      const delay = (60 / tempo) * 1000;
      interval = setInterval(() => {
        const elapsedTime = Date.now() - startTime;
        io.emit('beat', elapsedTime);
      }, delay);
    }
  });

  socket.on('disconnect', () => {
    console.log('A client disconnected');
    clearInterval(interval);
  });
});

server.listen(3000, () => {
  console.log('Server is running on port 3000');
});

return io;