Serve the API

With our back end functionality defined, it’s time to actually serve the API. The code in apis/index.js defines the REST HTTP endpoints for the IoT Center API. Express.js routing¹ is used in conjunction with the helper functions documented above.

In the following import statements, functions imported from authorizations.js, and env.js (covered above):

const env = require('../env')
// const {stringify} = require('yaml')
const {
  getIoTAuthorization,
  createIoTAuthorization,
  getIoTAuthorizations,
  getDeviceId,
  deleteAuthorization,
} = require('../influxdb/authorizations')

(Source)

We also need to import the Router() method from Express, in order to serve the REST API. Do this by adding:

const express = require('express')
const router = express.Router()

API paths

Express handles HTTP verbs and paths.

We need our server to:

• register new devices
• return information about current devices
• list all register devices
• delete device registrations

We can accomplish this using three API endpoints: a GET /env/:deviceId, a GET /devices; DELETE /devices/:deviceId

Describe or register device

GET /env/:deviceId

Return environment for a specific device by its ID.

This will either run createIoTAuthorization if none exists, or getIoTAuthorization. It also handles registration.

router.get(
  '/env/:deviceId',
  handleError(async (req, res) => {
    const deviceId = req.params.deviceId
    let authorization = await getIoTAuthorization(deviceId)
    let registered = false
    if (!authorization) {
      if (req.query.register !== 'false') {
        authorization = await createIoTAuthorization(deviceId)
        registered = true
      } else {
        res.status(403)
        return res.json({
          id: deviceId,
          registered,
        })
      }
    }
    [*snip*]
  })
)

(Source)

This creates an authorization if it doesn’t exist:

if (req.query.register !== 'false') {
  authorization = await createIoTAuthorization(deviceId)
  registered = true

List devices

GET /devices

Gets a list of registered devices used in web UI to provide a list devices. It contains deviceId.

router.get(
  '/devices',
  handleError(async (_req, res) => {
    const authorizations = await getIoTAuthorizations()
    res.json(
      authorizations.map((a) => ({
        key: a.id,
        deviceId: getDeviceId(a),
        createdAt: a.createdAt,
      }))
    )
  })
)

(Source)

Delete device

DELETE /devices/:deviceId

Remove a device identified by device_id. It also deletes the associated authorization token from InfluxDB.

router.delete(
  '/devices/:deviceId',
  handleError(async (req, res) => {
    const deviceId = req.params.deviceId
    const authorizations = await getIoTAuthorizations()
    for (const a of authorizations) {
      if (getDeviceId(a) === deviceId) {
        await deleteAuthorization(a.id)
        res.status(204)
        res.send('Device authorization removed')
        return
      }
    }
    res.status(404)
    res.send(`Device ${deviceId} not found!`)
  })
)

(Source)