index.js

const express = require('express');
const path = require('path');
const helmet = require('helmet')

const app = express();
const NEXCHANGE_ROOT = process.env.NEXCHANGE_ROOT
const ICO_ROOT = process.env.ICO_ROOT

//Helmet helps you secure your Express apps by setting various HTTP headers.
app.use(helmet())
app.use('/ico', express.static(path.resolve(ICO_ROOT)));
app.use(express.static(path.resolve(NEXCHANGE_ROOT), {index: false}));

function getCur(qParam) {
    return qParam.toUpperCase().substr(-3);
}

app.get('/ico', (req, res) => {
  res.sendFile(path.resolve(ICO_ROOT, 'index.html'));
});

// Handling lowercase order Ids
var orderUppercase = (req, res, next) => {

  if (req.params.orderId) {
    const orderIdUP =  req.params.orderId.toUpperCase()
    if (req.params.orderId != orderIdUP) {
      res.redirect('/order/' + orderIdUP)
    }
    else {
      next()
    }
  }
};

// General handler for the rest of the URLs
var generalHandler = (req, res) => {

  let redirectRequired = false;
  let params = {};
  if (req.query.cur_from && req.query.cur_to) {
    redirectRequired = true;
    req.query.pair = getCur(req.query.cur_to) + getCur(req.query.cur_from);
    delete req.query['cur_to'];
    delete req.query['cur_from'];
  }

  if (req.query.lang && req.query.lang !== req.query.lang.toLowerCase()) {
    redirectRequired = true;
    req.query.lang =  req.query.lang.toLowerCase()
  }

  if (redirectRequired) {
    params = req.query;
    params = Object.keys(params).map(key => key + '=' + params[key]).join('&');
    res.redirect(req.path + '?' + params);
    return;
  }

  res.sendFile(path.resolve(process.env.NEXCHANGE_ROOT, 'index.html'));
};

// Convert order ids to uppercase
app.get('/order/:orderId', [orderUppercase, generalHandler]
);

// For all other cases
app.get('*', generalHandler);


app.listen(3000, () => console.log('Nexchange Frontend Proxy is listening on port 3000!'));