getSettings = () => {
  const settings = {};
  
  // get the current settings
  const savedCalendarSettings = JSON.parse(PropertiesService.getScriptProperties().getProperty('calendar') || '[]');
  
  // get the primary calendar
  const primaryCalendar = CalendarApp.getAllCalendars()
    .filter((cal) => cal.isMyPrimaryCalendar())
    .map((cal) => ({
      name: 'Primary calendar',
      id: cal.getId()
    }));
    
  // get the secondary calendars
  const secundaryCalendars = CalendarApp.getAllCalendars()
    .filter((cal) => cal.isOwnedByMe() && !cal.isMyPrimaryCalendar())
    .map((cal) => ({
      name: cal.getName(),
      id: cal.getId()
    }));

  // the current available calendars
  const availableCalendars = primaryCalendar.concat(secundaryCalendars);
  
  // find any calendars that were removed
  const unavailebleCalendars = [];
  savedCalendarSettings.forEach((savedCalendarSetting) => {
    if (!availableCalendars.find((availableCalendar) => availableCalendar.id === savedCalendarSetting.id)) {
      unavailebleCalendars.push(savedCalendarSetting);
    }
  });
 
  // map the current settings to the available calendars
  const calendarSettings = availableCalendars.map((availableCalendar) => {
    if (savedCalendarSettings.find((savedCalendar) => savedCalendar.id === availableCalendar.id)) {
      availableCalendar.sync = true;

    }
    return availableCalendar;
  });

  // add the calendar settings to the settings
  settings.calendarSettings = calendarSettings;

  const savedFrom = PropertiesService.getScriptProperties().getProperty('syncFrom');
  settings.syncFrom = savedFrom;
 
  const savedTo = PropertiesService.getScriptProperties().getProperty('syncTo');
  settings.syncTo = savedTo;

  const savedIsUpdateTitle = PropertiesService.getScriptProperties().getProperty('isUpdateTitle') === 'true';
  settings.isUpdateCalendarItemTitle = savedIsUpdateTitle;

  const savedIsUseCategoriesAsCalendarItemTitle = PropertiesService.getScriptProperties().getProperty('isUseCategoriesAsCalendarItemTitle') === 'true';
  settings.isUseCategoriesAsCalendarItemTitle = savedIsUseCategoriesAsCalendarItemTitle;

  const savedIsUpdateDescription = PropertiesService.getScriptProperties().getProperty('isUpdateDescription') === 'true';
  settings.isUpdateCalendarItemDescription = savedIsUpdateDescription;
  
  return settings;
}
returns the settings from the script properties