OpenChat::getLoadContextMessage

public function getLoadContextMessage(): Message
{
	$startMessageId = 0;

	if ($this->getSelfRelation() === null)
	{
		$startMessageId = $this->getLastMessageId();
	}
	else
	{
		$startMessageId = $this->getMarkedId() ?: $this->getLastId();
	}

	return (new BitrixImV2Message($startMessageId))->setChatId($this->getId())->setMessageId($startMessageId);
}