/**
* Add one line
*
* @param BillLine $line
*
* @return BaseBill
*/
public function addLine(BillLine $line)
{
$line->setBill($this);
$this->totalHt += $line->getUnitPrice() * $line->getQuantity() / (1 + $line->getDiscount() / 100);
$this->lines->add($line);
return $this;
}