zammad/app/models/observer/ticket/close_time.rb

class Observer::Ticket::CloseTime < ActiveRecord::Observer
  observe 'ticket'

  def after_create(record)
    _check(record)
  end

  def after_update(record)
    _check(record)
  end

  private
    def _check(record)
#      puts 'check close time'

      # return if we run import mode
      return if Setting.get('import_mode')

      # check if close_time is already set
      return true if record.close_time

      # check if ticket is closed now
      ticket_state = Ticket::State.lookup( :id => record.ticket_state_id )
      ticket_state_type = Ticket::StateType.lookup( :id => ticket_state.state_type_id )
      return true if ticket_state_type.name != 'closed'

      # set close_time
      record.close_time = Time.now

      # save ticket
      record.save
    end
end