module Mail::CommonMessageId

def default
  return nil unless message_ids
  if message_ids.length == 1
    message_ids[0]
  else
    message_ids
  end
end

def do_decode
  "#{message_ids.map { |m| "<#{m}>" }.join(' ')}" if message_ids
end

def do_encode(field_name)
  %Q{#{field_name}: #{do_decode}\r\n}
end

def element
  @element ||= Mail::MessageIdsElement.new(value) unless value.blank?
end

def message_id
  element.message_id if element
end

def message_ids
  element.message_ids if element
end

def parse(val = value)
  unless val.blank?
    @element = Mail::MessageIdsElement.new(val)
  else
    nil
  end
end