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

app.use((req, res, next) => {
  const date = new Date();
  const data = `${date}:\nmethod: ${req.method}; url: ${req.url}; User-Agent: ${req.get('user-agent')}\n\n`;
  fs.appendFile('server.log', data, err => {
      if (err) throw new Error(err);
      console.log(data);
  });
  next();
});

app.get('/', (req, res) =>{
  res.send('Server log');
});

app.listen(3000);