const http = require('http')

const fs = require('fs')

const path = require('path')

const util = require('util')

const port = process.env.PORT || 7010

const allowedExtensions = ['.css', '.js', '.ico', '.html']

exports.startServer = () => {

const server = http.createServer((req, res) => {

serve(req, res).catch((e) => {

console.error(e)

res.writeHead(500)

res.end('Internal error')

})

}).listen({

host: 'localhost',

port

})

console.log('Listening on', server.address())

}

async function serve (req, res) {

let filePath = null

try {

filePath = await util.promisify(fs.realpath)(path.normalize('.' + req.url))

} catch (e) {

return notFound(res, e)

}

console.log('Real path: ', filePath)

if (!path.dirname(filePath).startsWith(path.dirname(__filename))) {

return internal(res, 'Invalid path')

}

if (allowedExtensions.indexOf(path.extname(filePath)) === -1) {

return internal(res, 'Invalid path')

}

try {

const file = fs.createReadStream(filePath, 'utf8')

res.writeHead(200, { 'Content-Type': 'html' })

file.pipe(res)

} catch (e) {

return notFound(res, e)

}

}

function internal (res, e) {

res.writeHead(500)

res.end(e)

}

function notFound (res, e) {

res.writeHead(404)

res.end('Not found: ' + e)

}

if (require.main === module) {

exports.startServer()

}