This SCREAMS to be moved to a model -_-

helper.rb

    def participation_options(invitation)
      options = []
      options << :yes   if invitation.can_change_to_yes? || invitation.can_buy_tickets? || invitation.participation == :yes
      options << :maybe if invitation.can_change_to_maybe? || invitation.participation == :maybe
      options << :no    if invitation.can_change_to_no? || invitation.participation == :no
      options
    end