How to migrate email templates from the local file system to the database

email-migration.js

/**
* @NOTE
* Before v3, all Mailgun email templates belonged to a separate folder in the codebase. 
* The templates were then compiled into HTML and uploaded via Mailgun's API. This made version control a pain in production. 
* It also made previewing templates difficult.
* 
* Later versions of Q3 offer an in-app email editor. 
* To use this feature, you'll need to migrate your email templates from the file system to the database. 
* You can write a script to accomplish this task.
*
* Remember: you'll need to setup permissions for the email collection and/or specify the collection name using the EMAIL_TEMPLATES_COLLECTION environment variable.
*/

// depends on your env
process.env.WEB_CONCURRENCY = 1;

const fs = require('fs');
const path = require('path');
const mongoose = require('mongoose');
const cluster = require('cluster');
const config = require('../lib/config');

// most common location for v2
const RELATIVE_PATH_TO_TEMPLATES = '../../.mailgun/templates';

// typically null, since v2 did not support multitenancy
const TENANT = null;

(async function moveTemplatesToDatabase() {  
  if (!cluster.isMaster) return;  
  await config.connect();  
  
  const data = [];
  const dir = path.resolve(__dirname, RELATIVE_PATH_TO_TEMPLATES);  

  await new Promise((resolve) => {
    fs.readdir(dir, (err, files = []) => {
      files.forEach((file) => {
        const name = file.split('.')[0];
        const filePath = path.resolve(dir, file);
        const mjml = fs.readFileSync(filePath, 'utf8').replace(/\.mjml/g, '');

        data.push({  
          active: true,
          tenant: TENANT,
          name,
          mjml,
        });
      });
  
      resolve();
    }); 
  });  

  const res = await mongoose.models.emails.create(data);  
  console.log(`Migrated ${res.length} template(s)`);
})();