index.js

const express = require('express')
const bodyParser = require('body-parser')
const { BadRequestError } = require('restify-errors')
const { SerialPort } = require('serialport')

const writeInterval = 150
const httpPort = process.env.HTTP_PORT || 8080
const path = process.env.SERIAL_PORT || '/dev/ttyUSB0'
const baudRate = process.env.BAUD_RATE || 115200

const directions = {
  event_cover_open: 1,
  event_cover_close: 2,
  event_cover_stop: 0
}

// extracted for better readability
const method = '<methodName>selve.GW.iveo.commandManual</methodName>'

const serial = new SerialPort({ path, baudRate })

serial.on('error', err => console.log(`got error from SerialPort: ${err}`))

const writeQueue = []

const app = express()

app.use(bodyParser.json({ limit: 1024000 }))

app.post('/cover', (req, res, next) => {
  if (!req.body) {
    return next(new BadRequestError('no body given'))
  } else if (!req.body.event) {
    return next(new BadRequestError('no event given'))
  } else if (!req.body.event_type) {
    return next(new BadRequestError('no event_type given'))
  } else if (!req.body.event.base64) {
    return next(new BadRequestError('no base64 given'))
  } else {
    const int = directions[req.body.event_type]
    const base64 = req.body.event.base64
    writeQueue.push({ int, base64 })
    writeQueue.push({ int, base64 }) // add twice to ensure the transmission is doubled
    res.send({ OK: true })
  }
})

app.listen(httpPort, err => {
  if (err) {
    console.error('Unable to start HTTP server')
    console.error(err)
    process.exit(1)
    return
  }

  console.log(`listening on port ${httpPort}`)

  setInterval(() => {
    if (writeQueue.length) {
      const { int, base64 } = writeQueue.shift()
      const msg = `<methodCall>${method}<array><base64>${base64}</base64><int>${int}</int></array></methodCall>`
      serial.write(msg, err => err ? console.error(err) : console.log('successfully sent message'))
    }
  }, writeInterval)
})