Revise paste userdb nodejs version

const http = require('http')
const sqlite3 = require('sqlite3')
const hostname = '127.0.0.1'
const port = 3000;

var db = null;

const open = (filename) => {
  db = new sqlite3.Database(filename);
}

const close = () => {
  db.run("pragma analysis_limit = 100");
  db.run("pragma optimize");
  db.close();
}

const ensure = (filename) => {
  if (db == null) { open(filename); }
}

const create = (filename) => {
  ensure(filename);
  db.run("pragma trusted_schema = false")
  db.run("pragma journal_mode = WAL")
  // can't figure out how to config defensive from node

db.serialize(() => {
    db.run("drop table if exists users")
      .run(`create table users(username text primary key not null,
                               plainpass text not null)`)
  })
}

const uuid = (cb) => {
  db.get("select lower(hex(randomblob(16))) as uuid", cb)
}

const create_user = (username, plainpass) => {
  db.run(`insert into users values('${username}', '${plainpass}')`)
}

const valid_plainpass = (username, checkpass, valid, invalid) => {
  db.get(`select plainpass from users where username='${username}'`, (err, row) => {
    if (row && row.plainpass === checkpass)
      valid()
    else
      invalid()
  })
}

const web_create_user = (req, res) => {
  uuid((err, row) => {
    const username = row.uuid
    uuid((err, row) => {
      const plainpass = row.uuid
      create_user(username, plainpass)
      res.writeHead(200, { 'Content-Type': 'text/plain' })
      res.end(`Created user ${username} with pass ${plainpass}`)
    })
  })
}

const web_check_password = (req, res) => {
  uuid((err, row) => {
    const username = row.uuid
    uuid((err, row) => {
      const plainpass = row.uuid
      const valid = () => {
        res.writeHead(200, { 'Content-Type': 'text/plain' })
        res.end(`Checked user ${username} with pass ${plainpass}: valid`)
      }
      const invalid = () => {
        res.writeHead(200, { 'Content-Type': 'text/plain' })
        res.end(`Checked user ${username} with pass ${plainpass}: invalid`)
      }

valid_plainpass(username, plainpass, valid, invalid)
    })
  })
}

const web_default = (req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' })
  res.end(`Try paths /create or /check`)

}

const dbfile = "test-js-userdb.sqlite"
create(dbfile);

const server = http.createServer((req, res) => {
  switch (req.url) {
    case "/create": return web_create_user(req, res)
    case "/check": return web_check_password(req, res)
    default: return web_default(req, res)

}
})

server.listen(port, hostname, () => {
  console.log(`listening at http://${hostname}:${port}`)
})