Uploading a file from web-based platform to S3 bucket using NodeJS - Callback Hell

Question

This code checks user permissions for uploading file, and if user can upload, then the file undergoes a check to see if it exists in SharePoint. If so then the file is pulled and uploaded to S3 bucket. This all works fine, but I have been told all these catches create callback hell. I've been trying to implement promises but I am very confused on how to change these callbacks to promises. Appreciate any help.

//////////////////
// Dependencies //
//////////////////
const path = require('path');
const fs = require('fs');
const ping = require('tcp-ping');
const Semaphore = require('mysql-semaphore');
const dateFormat = require('dateformat');
const randomstring = require("randomstring");
const rimraf = require("rimraf");
const docx4js = require('docx4js');
var sppull = require("sppull").sppull;
const storage = require('azure-storage');
///////////////////////////////
// Sequelize database models //
///////////////////////////////
const Sequelize = require('sequelize');
const sequelize = require('../util/database');
const Op = Sequelize.Op;
const ProjectContacts = sequelize.import('../models/db/project_contact');
////////////////////////
// Local dependencies //
////////////////////////
const { parseJsonFile, encrypt, makeDirs, waitForLock, pullFromSharePoint, decrypt, doesFileExistSp } = require('../util/common');
const { getNormalizedFilepath, updateTAndCCleanup, convertDocxToHtml, insertNewTCVersion, waitForFileUpload } = require('../util/update-t-and-c-helper');
const { listContainers, createContainer, uploadString, uploadLocalFile, listBlobs, downloadBlob } = require('../util/blob-helper');
const createError = require('../util/error-management').createErrorFlow;
const { getProjectPath, saveMetadata, copyFileSpToS3Cleanup } = require('../util/copy-to-s3-helper');
const { getTimeTaken, formatLockKey, saveFileToSp, createFolderIfNotExists, createFolderPathRecursively, processExcelFileRequest } = require('../util/common');
const logger = require('../util/logger')(module);

const fileName = req.body.fileName.trim();
const spSite = req.body.spSite;
const spFolder = req.body.spFolder;
const email = req.body.email_address;
const downloadPath = req.body.S3Path;
const spFile = `${spFolder}/${fileName}`;
const before = Date.now();
const uploadFolderName = 'upload';
const siteUrl = `${process.env.SP_URL}/sites/${spSite}/`;
const creds = {
 username: process.env.SP_USER,
 password: decrypt(process.env.SP_PASSWORD)
};

ProjectContacts.findAll({ where: { can_upload_files: 1, email_address: email }, attributes: ['email_address', 'project_id', 'can_upload_files'] })
 .then(projectContacts => {
 if (projectContacts.length > 0) { //If email can upload, proceed
 doesFileExistSp(creds, spSite, siteUrl, spFile) //Check if file exists in SharePoint
 .then(exists => {
 if (exists) {
 logger.info(`DOWNLOAD PATH: ${downloadPath}`);
 logger.info(`FILENAME: ${fileName}`);
 const sppullContext = {
 siteUrl: siteUrl, //SharePoint URL
 creds: {
 username: process.env.SP_USER,
 password: decrypt(process.env.SP_PASSWORD)
 }
 };
 const sppullOptions = {
 spRootFolder: spFolder, // The folder path for the file in SharePoint
 dlRootFolder: downloadPath, // Where the file is saved locally
 strictObjects: [fileName], // Only download the fileName specified as a query parameter
 muteConsole: true
 };
 pullFromSharePoint(sppullContext, sppullOptions)
 .then(filepath => { //Pull file with fileName from SharePoint
 logger.info(`FILE NOW IN PATH: ${filepath}`);
 // Create the upload directory within the project directory.
 const s3UploadFolder = path.join(downloadPath, uploadFolderName);
 makeDirs(s3UploadFolder)
 .then(() => { //creates upload folder in s3
 function saveMetadataCallback(errorObj) { //callback for saveMetadata which checks for errors, semaphore/locks not being used
 if (errorObj) {
 const filepath = path.join(downloadPath, fileName);
 copyFileSpToS3Cleanup(filepath, semaphore, lockKey).then(() => {
 const error = createError(errorObj.errorMsg, errorObj.statusCode, errorObj.origErr);
 return next(errorObj);
 }).catch(errorObj => {
 const error = createError(errorObj.errorMsg, errorObj.statusCode, errorObj.origErr);
 return next(error);
 });
 }
 }
 saveMetadata(saveMetadataCallback); // Save the metadata info.json files.
 }).catch(err => {
 const filepath = path.join(downloadPath, fileName);
 copyFileSpToS3Cleanup(filepath, semaphore, lockKey)
 .then(() => {
 const error = createError('Unable to create upload directory', 500, err);
 return next(error);
 }).catch(errorObj => {
 const error = createError(errorObj.errorMsg, errorObj.statusCode, errorObj.origErr);
 return next(error);
 });
 });
 return res.status(200).json({
 message: `${fileName} has been uploaded to ${filepath}`
 })
 }).catch(errorObj => {
 const filepath = path.join(downloadPath, fileName);
 copyFileSpToS3Cleanup(filepath, semaphore, lockKey)
 .then(() => {
 const error = createError(errorObj.errorMsg, errorObj.statusCode, errorObj.origErr);
 return next(error);
 }).catch(errorObj => {
 const error = createError(errorObj.errorMsg, errorObj.statusCode, errorObj.origErr);
 return next(error);
 });
 });
 } else {
 const error = createError('File does not exist!');
 return next(error);
 }
 }).catch(err => {
 const error = createError('File does not exist!');
 return next(error);
 })
 } else {
 logger.error(`${email} does not have permission to upload`);
 return res.status(401).json({
 message: `${email} does not have permission to upload`
 });
 }
 });

• konijn: Can you add your requires in there? Otherwise it will be hard to know what functions you wrote, and what functions you call from 3rd party libraries.
• Mike Brant: Show the whole module file. The code context is important here.
• Omi in a hellcat: Added. Let me know if I should add some of the local dependencies code, to clarify it even more.
• konijn: Almost spit out my coffee when I saw creds.password, then I saw it was fine
• Omi in a hellcat: lol! I'm being extra careful to not post the credentials.

Answer 1

Got it using promises:

//Finds if project_contact email has permission to upload
 function findProjectContacts() {
 return new Promise((resolve, reject) => {
 ProjectContacts.findAll({ where: { can_upload_files: 1, email_address: email }, attributes: ['email_address', 'project_id', 'can_upload_files'] })
 .then(projectContacts => {
 if (projectContacts.length > 0) {
 return resolve(true);
 }
 else {
 const error = createError(`${email} does not have permission to upload!`, 401);
 return reject(error);
 }
 })
 .catch(err => {
 const error = createError(`${email} does not have permission to upload!`, 401, err);
 return reject(error)
 })
 })
 }
 //Checks if file exists in SharePoint
 function findFile() {
 return new Promise((resolve, reject) => {
 doesFileExistSp(creds, spSite, siteUrl, spFile).then(exists => {
 if (!exists) {
 const error = createError(`${filename} does not exist in ${spFolder}`, 404);
 return reject(error);
 } else {
 return resolve(true);
 }
 }).catch(err => {
 const error = createError(`${filename} does not exist in ${spFolder} `, 404, err);
 return reject(error);
 });
 });
 }
 //Pulls file from SharePoint to download into specified filepath
 function pullFile() {
 return new Promise((resolve, reject) => {
 const sppullContext = {
 siteUrl: siteUrl, //SharePoint URL
 creds: creds
 };
 const sppullOptions = {
 spRootFolder: spFolder, // The folder path for the file in SharePoint
 dlRootFolder: downloadPath, // Where the file is saved locally
 strictObjects: [filename], // Only download the filename specified as a query parameter
 muteConsole: true
 };
 pullFromSharePoint(sppullContext, sppullOptions) //Pull file with filename from SharePoint
 .then(filepath => {
 if (!fs.existsSync(filepath)) {
 const error = createError(`${filepath} does not exist`, 404);
 return reject(error);
 }
 else {
 logger.info(`FILE NOW IN PATH: ${filepath}`);
 const s3UploadFolder = path.join(downloadPath, uploadFolderName);
 makeDirs(s3UploadFolder);
 }
 return resolve(true);
 });
 });
 }
 findProjectContacts()
 .then(permission => {
 if (permission === true)
 return findFile();
 })
 .then(fileFound => {
 if (fileFound === true)
 return pullFile();
 }).then(fileCopied => {
 if (fileCopied === true)
 logger.info(`${filename} has been uploaded`);
 return res.status(200).json({
 message: `${filename} has been uploaded`
 });
 }).catch(errorObj => {
 return next(errorObj);
 })
}