Obtain OAuth2 refresh token from existing authorization - google-apps-script

Question

Is it possible to obtain an OAuth2 refresh token of a user that has previously provided authorization, without having to ask for authorization again?
Context:
I have a Google Apps Script add-on that has obtained authorization for a number of scopes (including the ability to run when they are not present - see below screenshot). I am extending the project to include a Google App Engine web application that requires access to the same scopes (no additional scopes required). I am hoping to utilize the existing scopes that have previously been granted without having to request them again.
Ability to run when they are not present screenshot:
Any guidance on whether it is possible and the best approach is appreciated.

Answer 1

In order to get a Refresh token you must request offline access when the user is authenticating this way the user is asked if they are willing for your application to have off line access to their data. Think of it as an extra scope of permissions.
If you need a refresh token and didnt obtain it at the time you authenticated your user then your going to have to request authentication again.

Answer 2

You can use a time trigger to refresh the token every hour and then save this token into your database (make sure the user had authorized your script to create the trigger)
Whenever you need to do something that needs a user's authorization, you just need to use this token without asking the user
For example:
export const generateOAuthToken = () => {
try {
const user = Session.getEffectiveUser()
let accessToken
let error = ''
try {
accessToken = ScriptApp.getOAuthToken()
} catch (err) {
error = err.message
}
// Connect to database
const db = connectDatabase()
if (error === '') {
// Generate new token and save to database
// ... here
} else {
// Save the error to display to the user
}
} catch (err) {
console.error(err)
}
}
export const setupOAuthTrigger = () => {
const form = FormApp.getActiveForm()
const triggers = ScriptApp.getUserTriggers(form)
// Create a new trigger if required; delete existing trigger if it is not needed.
let existingTrigger = null
for (let i = 0; i < triggers.length; i += 1) {
if (triggers[i].getEventType() === ScriptApp.EventType.CLOCK) {
existingTrigger = triggers[i]
break
}
}
// TODO: Optimize this later, at the moment it's for cleaning up trigger in case of error
if (existingTrigger) {
ScriptApp.deleteTrigger(existingTrigger)
}
// Trigger every hour
ScriptApp.newTrigger('generateOAuthToken')
.timeBased()
.everyHours(1)
.create()
}