Routes in Express to process and upload files via Multer to Google Drive

files.js

module.exports = (Router, Joi, fileOperations) => {

  const { services } = require('../common/configurations')

  // Diagnostics.

  const factoryForDiagnostics = require('../mixins/diagnostics')
  const diagnostics = factoryForDiagnostics({ log4js: fileOperations.log4js, nameOfChannel: 'default', level: 'debug' })

  // Mixins.

  const MixinAssets = require('../mixins/assets')

  // Modules.

  const factoryForS3 = require('../modules/aws/s3')
  const moduleForS3 = factoryForS3(fileOperations.aws, services.aws)
  
  // Controllers.

  const factoryForFiles = require('../controllers/files.js')
  const controllerForFiles = factoryForFiles(Joi, fileOperations)

  // Middleware.

  const { authenticate } = require('../middleware/routes')

  const date = new Date()
  const [y, m, d] = [
    // Year.
    (() => date.getFullYear())(),
    // Month.
    (() => date.getMonth() + 1)(),
    // Day.
    (() => date.getDate())()
  ]

  // Create a regular expression based on the allowable file extensions stored in a mixin.
  let byExtension = `/\.(${MixinAssets().allowedToUploadByExtension.join('|')})$/`
  
  Router.get('/google/drive/files/list', authenticate, (req, res) => {
    controllerForFiles.getAllFilesFromDrive(req, res)
  })
  
  Router.post('/assets/files/upload/:fileExtension', authenticate, (req, res) => {
    const fileFilter = function(req, file, returnFunction) {
      if (!file.originalname.match(byExtension) && !MixinAssets().allowedToUploadByMimeType.includes(file.mimetype)) {
        req.fileValidationError = 'Please choose a file of an allowed type to upload'
        returnFunction(new Error("File isn't an allowed type"), false)
      }
      returnFunction(null, true)
    }
    let uploadViaMulter = fileOperations.multer({
      fileFilter,
      limits: {
        fileSize: 1024 * 1024 * 2 // 2 megabytes.
      }
    }).single('fileToUpload')
    uploadViaMulter(req, res, (uploadViaMulterError) => {
      try {
        if (req.fileValidationError) {
          if (process.env.ENV !== 'production') console.error('Multer: A fileValidationError', req.fileValidationError)
          return res.status(500).json(req.fileValidationError)
        } else if (!req.file) {
          if (process.env.ENV !== 'production') console.error('Multer: Not a valid file', uploadViaMulterError)
          return res.status(500).json(uploadViaMulterError)
        } else if (uploadViaMulterError instanceof fileOperations.multer.MulterError) {
          if (process.env.ENV !== 'production') console.error('Multer: MulterError', uploadViaMulterError)
          return res.status(500).json(uploadViaMulterError)
        } else if (uploadViaMulterError) {
          if (process.env.ENV !== 'production') console.error('Multer: Misc. Error', uploadViaMulterError)
          return res.status(500).json(uploadViaMulterError)
        }

        const FactoryForGoogle = require('../modules/api/google')
        return FactoryForGoogle({
          typeOfAction: 'isDefault'
        }).uploadFileToDrive({
          userId: req.body.userId,
          fileToUpload: req.file
        })

      } catch (error) {
        if (process.env.ENV !== 'production') console.error(error)
        diagnostics.error(`routes/files.js /assets/files/upload/:fileExtension ${error}`)
        return res.status(500).json(error)
      }
    })
  })

  /**
   * 
   * Uilities.
   * 
   */

  Router.post('/assets/files/download', authenticate, (req, res) => {
    controllerForFiles.downloadExistingFile(req, res)
  })

  Router.post('/assets/files/delete', authenticate, (req, res) => {
    controllerForFiles.removeExistingFile(req, res)
  })

  return Router

}

A work in progress, one that allows someone to upload files to the appropriate endpoint.