api.js

const MongoClient = require('mongodb').MongoClient
const http = require('http')
const url = require('url')
const fs = require('fs')

const DB_URL = 'mongodb://localhost:27017/currency'

http.createServer(function (req, res) {
  const q = url.parse(req.url, true)
  pathname = url.parse(req.url).pathname
  if (pathname.match(/^\/style.css\/$/) || pathname.match(/^\/style.css$/)) {
    res.writeHead(200, { 'Content-type': 'text/css' })
    const fileContents = fs.readFileSync('./style.css', { encoding: 'utf8' })
    res.write(fileContents)
    res.end()
  } else if (req.url === '/') {
    fs.readFile('./home.html', null, function (err, data) {
      if (err) {
        res.writeHead(404)
        res.write('Contents you are looking are Not Found')
        res.end()
      } else {
        res.write(data)
        res.end()
      }
    })
  } else if (pathname.match(/^\/api\/latest\/$/) || pathname.match(/^\/api\/latest$/)) {
    MongoClient.connect(DB_URL, { useUnifiedTopology: true }, function (err, dbo) {
      const db = dbo.db('currency')
      const collection = db.collection('prices')
      fields = { base: 1, date: 1, _id: 0, rates: 1 }
      query = { base: 'EUR' }

      if (q.query.base) {
        query = { base: q.query.base.toUpperCase() }
      }
      if (q.query.symbols) {
        fields = { base: 1, date: 1, _id: 0 }
        symbols = q.query.symbols.split(',')
        for (each in symbols) {
          symbol = 'rates.' + symbols[each].toUpperCase()
          fields[symbol] = 1
        }
      }
      const cursor = collection.find(query, { fields: fields }).sort({ date: -1 }).limit(1).toArray(function (err, result) {
        if (err) throw err
        dbo.close()
        if (result[0]) {
          currency_keys = Object.keys(result[0]['rates'])
          for (let key of currency_keys) {
            result[0]['rates'][key] = parseFloat(result[0]['rates'][key])
          }
          res.writeHead(200, { 'Content-Type': 'text/json' })
          res.write(JSON.stringify(result[0]))
        } else {
          res.writeHead(400, { 'Content-Type': 'text/json' })
          res.write(JSON.stringify({ error: 'Invalid base or symbols' }))
        }
        res.end()
      })
    })
  } else if (pathname.match(/^\/api\/\d{4}([./-])\d{2}\1\d{2}$/)) {
    MongoClient.connect(DB_URL, function (err, dbo) {
      const db = dbo.db('currency')
      const collection = db.collection('prices')
      fields = { base: 1, date: 1, _id: 0, rates: 1 }
      query = { base: 'EUR', date: { $lte: req.url.split('/api/')[1].split('?')[0].toString() } }
      if (q.query.base) {
        query.base = q.query.base.toUpperCase()
      }
      if (q.query.symbols) {
        fields = { base: 1, date: 1, _id: 0 }
        symbols = q.query.symbols.split(',')
        for (each in symbols) {
          symbol = 'rates.' + symbols[each].toUpperCase()
          fields[symbol] = 1
        }
      }
      const cursor = collection.find(query, { fields: fields }).sort({ date: -1 }).toArray(function (err, result) {
        if (err) {
          throw err
        }
        dbo.close()
        if (result[0]) {
          res.writeHead(200, { 'Content-Type': 'application/json' })
          res.write(JSON.stringify(result[0]))
        } else {
          res.writeHead(400, { 'Content-Type': 'application/json' })
          res.write(JSON.stringify({ error: 'Invalid base or symbols' }))
        }
        res.end()
      })
    })
  } else {
    res.writeHead(404)
    res.write('Contents you are looking are Not Found')
    res.end()
  }
}).listen(8080)