DiscountBase::getCurrency

protected function getCurrency()
{
	if ($this->isOrderExists())
		return $this->order->getCurrency();
	$result = null;
	if ($this->isBasketExist())
	{
		if ($this->isBasketNotEmpty())
		{
			/** @var BasketItemBase $basketItem */
			$basketItem = $this->basket->rewind();
			$result = $basketItem->getCurrency();
			unset($basketItem);
		}
		else
		{
			$result = $this->getSiteCurrency();
		}
	}
	return $result;
}