Calendar Inviter

calendarinviter.js

CALENDAR = "Work"; 
EVENT_MATCH = /^SAP\s/;
GUEST_LIST = ['you-1@example.com', 'you-2@example.com'];
DATE_FROM = new Date('01 Jan 2014');
DATE_TO = new Date('31 Dec 2014');
FORCE_ADD = false;

function main() {
  inviteMe(CALENDAR, DATE_FROM, DATE_TO, EVENT_MATCH, GUEST_LIST, FORCE_ADD);
}

/*
* Looks for allday events in a calendar. The events must match the given title.
* For each event found, add & invite guests if required
*/
function inviteMe(calendar, from, to, event_match, guest_list, force) {

  // Assume only one calendar with the given name
  var work_cal = CalendarApp.getCalendarsByName(CALENDAR)[0];
  var events = work_cal.getEvents(from, to);
  for (var i = 0, ii = events.length; i < ii; i++) {
    var event = events[i];
    var title = event.getTitle();

    // Is the event an allday event with a title that matches?
    if (event.isAllDayEvent() && title.match(event_match)) {
      Logger.log("Event '%s' on %s", title, event.getStartTime());
      event.setGuestsCanModify(true);

      // Add and invite the guests if they're not already on the list
      var current_guests = event.getGuestList().map(function(e) { return e.getEmail(); });
      for (var g = 0, gg = guest_list.length; g < gg; g++) {
        if (force || current_guests.indexOf(guest_list[g]) < 0) {
          Logger.log("Adding guest '%s'", guest_list[g]);
          addAndInvite(event, guest_list[g]);
        }
      }
    }
  }
}


/*
* GAS Calendar libs don't currently support sending invites directly 
* when adding guests to an existing event (ticket open for 2.5 years!)
* so invite manually (ICS file via email).
*/
function addAndInvite(event, email) {
  event.addGuest(email);
  GmailApp.sendEmail(email, "Invite: " + event.getTitle(), "Please see attached calendar invitation", {
    attachments: [{fileName:"invite.ics", content:generateIcs(event)}]
  });
}


/*
* Generate a simple ICS file
*/
function generateIcs(event) {
  return "BEGIN:VCALENDAR"
          + "\r\nPRODID:-//pipetree.com//qmacro//EN"
          + "\r\nVERSION:2.0"
          + "\r\nCALSCALE:GREGORIAN"
          + "\r\nMETHOD:REQUEST"
          + "\r\nBEGIN:VEVENT"
          + "\r\nDTSTART:" + Utilities.formatDate(event.getStartTime(), "GMT", "yyyyMMdd'T'HHmmss'Z'")
          + "\r\nDTEND:" + Utilities.formatDate(event.getEndTime(), "GMT", "yyyyMMdd'T'HHmmss'Z'")
          + "\r\nUID:" + event.getId()
          + "\r\nORGANIZER:" + event.getCreators()[0]
          + "\r\nSUMMARY:" + event.getTitle()
          + "\r\nLOCATION:" + event.getLocation()
          + "\r\nDESCRIPTION:" + event.getDescription()
          + "\r\nSEQUENCE:0"
          + "\r\nSTATUS:CONFIRMED"
          + "\r\nTRANSP:OPAQUE"
          + "\r\nEND:VEVENT"
          + "\r\nEND:VCALENDAR"
          + "\r\n";
}