Alert::resolveTriggerProperty

private function resolveTriggerProperty()
{
	if ($this->triggerMode === self::TRIGGER_DATE) {
		return DateTimePropertyType::getInstance(
			'TRIGGER',
			$this->triggerDate,
			true
		)->addParameter(new Parameter('VALUE', 'DATE-TIME'));
	}

	$property = LengthPropertyType::getInstance('TRIGGER', $this->triggerInterval);

	if ($this->triggerMode === self::TRIGGER_END) {
		return $property->addParameter(new Parameter('RELATED', 'END'));
	}

	return $property;
}