How to create an event on every organisation member calendar? - google-apps-script

Question

I need to create an event in everyone's calendar of my organization. This event is a reminder of an action everyone needs to take before a certain date, but this date is not the same every month, so I can't do a recurring event. I don't want to add everyone as attendee because I want everyone keep the event on the calendar and not just answer "don't participate" and forgot to do what they need to do at the good time.
To do this, I already wrote a code that gets every active account from the organisation, gets the start date, end date, event title and event description from a google sheet. It works for my calendar and calendars of people I add manually on my list "other calendars" in google calendar. But the script doesn't create the event in agendas of people in my organisation not present on my "other calendar" list.
function getAllPeopleFromDirectory() {
var pageToken;
var page;
var usersId = [];
do {
page = AdminDirectory.Users.list({
domain:'mydomain.com',
orderBy: 'givenName',
maxResults: 400,
query: "orgUnitPath=/ isSuspended=False",
pageToken: pageToken
});
var users = page.users;
if(users) {
for (var i=0; i< users.length; i++) {
var user = users[i];
usersId.push(user.primaryEmail);
}
} else {
Logger.log('No users found.');
}
pageToken = page.nextPageToken;
} while(pageToken);
if (usersId.length != 0){
setUpReminder(usersId);
}
}
function setUpReminder(calendarIDs) {
var ss = SpreadsheetApp.openById("SPREADSHEET_ID");
var sheet = ss.getSheetByName('reminder');
var range = sheet.getDataRange();
var values = range.getValues();
for (var i = 0; i < calendarIDs.length; i++) {
setUpCalendar(values, range, calendarIDs[i]);
}
}
function setUpCalendar(values, range, calendarId) {
var cal = CalendarApp.getCalendarById(calendarId);
for (var i = 1; i < values.length; i++) {
var session = values[i];
var date = new Date(session[1]);
var now = new Date();
if (date.getMonth() == now.getMonth()) {
var title = session[4];
var start = joinDateAndTime(session[1], session[2]);
var end = joinDateAndTime(session[1], session[3]);
var options = {location: session[5], sendInvites: false, description: session[8]};
var event = cal.createEvent(title, start, end, options).setGuestsCanSeeGuests(true);
}
}
range.setValues(values);
}
function joinDateAndTime(date, time) {
date = new Date(date);
date.setHours(time.getHours());
date.setMinutes(time.getMinutes());
return date;
}
When I call "CalendarApp.getCalendarById" with everyone who isn't on my other calendars, the function returns null so cal.createEvent raises an error...
Does anyone have an idea how to make this correctly?
Maybe I can add and remove people to my other calendar every time I run the script, it's not the best solution but if someone knows how to do this, it would be cool!

Answer 1

Instead of fetching user-specific (primary) calendars and updating them with events one-by-one, a better approach is to create a custom calendar (aka. a secondary calendar) that's shared among all the users under your GSuite domain.
Here's an excerpt from the Calendar API reference documentation:
...you can explicitly create any number of other calendars; these calendars can be modified, deleted, and shared among multiple users.
So, all you need do is update the secondary calendar and its events will be reflected in your users' calendar view (but only if your users have the custom calendar enabled).
See Primary Calendars and other calendars
See Sharing Calendars.