gasCalendarAddAttendeeToAllEvents.js

const EMAILS_ADD = ["john@example.com", "doe@example.co.jp"];
const EVENT_LIST_BEFORE_MONTH = 30;
const EVENT_LIST_AFTER_MONTH = 2;
const DRY_RUN = false;

function addAttendeeToAllEvents() {
  const calendarId = 'primary';
  let start = new Date();
  let end = new Date();
  start.setMonth(start.getMonth() - EVENT_LIST_BEFORE_MONTH);
  end.setMonth(end.getMonth() + EVENT_LIST_AFTER_MONTH);

  const cond = {
    timeMin: start.toISOString(),
    timeMax: end.toISOString(),
    singleEvents: false, // include recurring events themselves
    eventTypes: 'default', // exclude focusTime, fromGmail, outOfOffice and workingLocation
    showDeleted: false
  };

  let pageToken = '';
  let first = true;
  while (pageToken || first) {
    Logger.log('---');
    if (!first) {
      cond.pageToken = pageToken;
    }
    page = Calendar.Events.list(calendarId, cond);
    pageToken = page.nextPageToken;
    first = false;

    for (let event of page.items) {
      if (
        // cancelled instances of recurring events may be included in results. skip them.
        ('status' in event ? (event.status != 'cancelled') : true)
        && (
          // default of guestsCanInviteOthers is true
          ('guestsCanInviteOthers' in event ? event.guestsCanInviteOthers : true)
          || event.organizer.self
        )
        // events having recurringEventId are instances of recurring events
        // XXX: これでも recurring events が複数ヒットすることがある模様
        //      その場合は ETag が変わって Precondition Failed になる
        && !event.recurringEventId) {

        Logger.log('[%s] %s (%s)', event.id, event.summary, event.start.dateTime);

        if ('attendees' in event) { // XXX: どういう場合に attendees が含まれないのかよく分からない
          // XXX: event.attendees にグループが含まれることがありそうだが対応できていない
          attendees = event.attendees.map((attendee) => attendee.email);
          let emails = EMAILS_ADD.filter((t) => !attendees.includes(t));

          if (emails.length) {
            Logger.log('[%s] -> %s', event.id, emails)
            for (const email of emails) {
              event.attendees.push({ email: email });
            }
            if (!DRY_RUN) {
              try {
                Calendar.Events.update(
                  event,
                  calendarId,
                  event.id,
                  {},
                  { 'If-Match': event.etag }
                );
              } catch (e) {
                Logger.log(e);
              }
            }
          }
        }
      }
    }
  }
}