hb-pwa-serve/index.js

const request = require('request')
const sharp = require('sharp')
const { MongoClient, ObjectId } = require('mongodb')
const express = require('express')
const app = express()
const fs = require('fs')
const path = require('path')
const cors = require('cors')

// const resizeBox = sharp().resize(512).png()

const CTX = {
  dbHandler: null
}

const CFG = {
  port: process.env.PORT || 3000
}

app.use(cors())

app.get('/preview/:id', function (req, res) {
  CTX.dbHandler
    .collection('hboxes')
    .find({_id: ObjectId(req.params.id)})
    .project({preview: 1})
    .limit(1)
    .next(function (pErr, pDoc) {
      if (pErr) {
        return res.status(404).json(pErr)
      }
      downloadBox(pDoc._id, pDoc.preview.secure_url, res)
    })
})

app.use('/', express.static('webapp'))

MongoClient.connect('mongodb://localhost:27017', { useNewUrlParser: true }, function (pErr, pDbHandler) {
  if (pErr) {
    console.error(pErr)
    process.exit(1)
  }

  CTX.dbHandler = pDbHandler.db('hortus-box')

  app.listen(CFG.port, function () {
    console.log(`[>] pwa-server running on ${CFG.port}`)
  })
})

function downloadBox (pId, pUrl, res) {
  let cachePath = path.join('./cache', `${pId}.png`)

  fs.access(cachePath, fs.constants.F_OK, function (pErr) {
    if (pErr) {
      let wstream = fs.createWriteStream(cachePath)
      request(pUrl).pipe(wstream)
      wstream.on('finish', function () {
        resizeBox(pId, cachePath, res)
      })
    } else {
      resizeBox(pId, cachePath, res)
    }
  })
}

function resizeBox (pId, pCachePath, res) {
  let previewPath = path.join('./cache', `${pId}.preview.png`)

  fs.access(previewPath, fs.constants.F_OK, function (pErr) {
    if (pErr) {
      sharp(pCachePath)
        .resize(512)
        .toFile(previewPath, function (pErr, info) {
          if (pErr) {
            return res.status(404).json(pErr)
          }
          sendBox(previewPath, res)
        })
    } else {
      sendBox(previewPath, res)
    }
  })
}

function sendBox (pPreviewPath, res) {
  fs.createReadStream(pPreviewPath).pipe(res)
}