Fetch the train position while travelling on a SJ train (and using their wifi) and store all data for further visualisations.

SJ-position.js

var http = require('http');
var fs = require('fs');

var dataFile = './data.json';
var dataURL = 'http://www.ombord.info/api/jsonp/position/';

var errorHandling = (e) => {
  console.log(`Got error: ${e.message}`);
  fetchData();
}

var saveData = (position) => {
  return new Promise((resolve, reject) => {
    fs.readFile(dataFile, (err, data) => {
      if(err) reject(err);

      data = JSON.parse(data);
      data.push(position);
      fs.writeFile(dataFile, JSON.stringify(data), (err) => {
        if(err) reject(err);
        console.log('data saved');
        setTimeout(resolve, 1500);
      });
    });
  });
}

var fetchData = () => {
  http.get(dataURL, (res) => {
    var data = '';
    res.setEncoding('utf8');
    res.on('data', (chunk) => data += chunk );
    res.on('end', () => {
      data = data.slice(1).slice(0, -3);
      data = JSON.parse(data);
      saveData(data).then(fetchData).catch(errorHandling);
    });
  }).on('error', errorHandling);
}

var startUp = () => {
  try {
    fs.readFileSync(dataFile);
  } catch(e) {
    fs.writeFileSync(dataFile, '[]');
  }

  fetchData();
}

startUp();