basketitembase_onfiledmodify.php

<?php
  
  protected function onFieldModify($name, $oldValue, $value)
	{
		$result = new Result();

		if ($name == "QUANTITY" && $value != 0)
		{
			$value = (float)$value;
			$oldValue = (float)$oldValue;
			$deltaQuantity = $value - $oldValue;

			/** @var Basket $basket */
			$basket = $this->getCollection();
			$context = $basket->getContext();

			/** @var Result $r */
			$r = Internals\Catalog\Provider::getAvailableQuantityAndPriceByBasketItem($this, $context);
			if (!$r->isSuccess())
			{
				$result->addErrors($r->getErrors());
				$result->setData($r->getData());

				return $result;
			}

			$providerData = $r->getData();

			$bImportMode = \Bitrix\Main\Context::getCurrent()->getRequest()->get('mode') == 'import';

			if ($this->getField('SUBSCRIBE') !== 'Y' && !$bImportMode)
			{
				if (array_key_exists('AVAILABLE_QUANTITY', $providerData) && $providerData['AVAILABLE_QUANTITY'] > 0)
				{
					$availableQuantity = $providerData['AVAILABLE_QUANTITY'];
				}
				else
				{
						$result->addError(
								new ResultError(
										Localization\Loc::getMessage(
												'SALE_BASKET_ITEM_WRONG_AVAILABLE_QUANTITY',
												array('#PRODUCT_NAME#' => $this->getField('NAME'))
										),
										'SALE_BASKET_ITEM_WRONG_AVAILABLE_QUANTITY'
								)
						);

						return $result;
				}
			}
			else
			{
				$availableQuantity = $value;
			}

			if (!empty($providerData['PRICE_DATA']))
			{
				if (isset($providerData['PRICE_DATA']['CUSTOM_PRICE']))
				{
					$this->setField('CUSTOM_PRICE', $providerData['PRICE_DATA']['CUSTOM_PRICE']);
				}
			}

			if ($value != 0
				&& (($deltaQuantity > 0) && (roundEx($availableQuantity, SALE_VALUE_PRECISION) < roundEx($value, SALE_VALUE_PRECISION))   // plus
				|| ($deltaQuantity < 0) && (roundEx($availableQuantity, SALE_VALUE_PRECISION) > roundEx($value, SALE_VALUE_PRECISION)))
			)   // minus
			{
				if ($deltaQuantity > 0)
				{
					$mess = Localization\Loc::getMessage(
						'SALE_BASKET_AVAILABLE_FOR_PURCHASE_QUANTITY',
						array(
							'#PRODUCT_NAME#' => $this->getField('NAME'),
							'#AVAILABLE_QUANTITY#' => $availableQuantity
						)
					);
				}
				else
				{
					$mess = Localization\Loc::getMessage(
						'SALE_BASKET_AVAILABLE_FOR_DECREASE_QUANTITY',
						array(
							'#PRODUCT_NAME#' => $this->getField('NAME'),
							'#AVAILABLE_QUANTITY#' => $availableQuantity
						)
					);
				}

				$result->addError(new ResultError($mess, "SALE_BASKET_AVAILABLE_QUANTITY"));
				$result->setData(array("AVAILABLE_QUANTITY" => $availableQuantity, "REQUIRED_QUANTITY" => $deltaQuantity));

				return $result;
			}

			/** @var BasketItemCollection $collection */
			$collection = $this->getCollection();

			/** @var BasketBase $basket */
			$basket = $collection->getBasket();

			if ((!$basket->getOrder() || $basket->getOrderId() == 0) && !($collection instanceof BundleCollection))
			{
				if ($this->getField("CUSTOM_PRICE") != "Y" && $value > 0)
				{
					$r = $basket->refresh(RefreshFactory::createSingle($this->getBasketCode()));
					if (!$r->isSuccess())
					{
						$result->addErrors($r->getErrors());
						return $result;
					}
				}
			}

			if ($this->getField("CUSTOM_PRICE") != "Y")
			{

				$providerName = $this->getProviderName();
				if (strval($providerName) == '')
				{
					$providerName = $this->getCallbackFunction();
				}


				if (!empty($providerData['PRICE_DATA']))
				{
					if (isset($providerData['PRICE_DATA']['PRICE']))
					{
						$this->setField('PRICE', $providerData['PRICE_DATA']['PRICE']);
					}

					if (isset($providerData['PRICE_DATA']['BASE_PRICE']))
					{
						$this->setField('BASE_PRICE', $providerData['PRICE_DATA']['BASE_PRICE']);
					}

					if (isset($providerData['PRICE_DATA']['DISCOUNT_PRICE']))
					{
						$this->setField('DISCOUNT_PRICE', $providerData['PRICE_DATA']['DISCOUNT_PRICE']);
					}
				}
				elseif ($providerName && !$this->isCustom())
				{
					$result->addError(
						new ResultError(
							Localization\Loc::getMessage(
								'SALE_BASKET_ITEM_WRONG_PRICE',
								array('#PRODUCT_NAME#' => $this->getField('NAME'))
							),
							'SALE_BASKET_ITEM_WRONG_PRICE'
						)
					);

					return $result;
				}
			}
		}

		$r = parent::onFieldModify($name, $oldValue, $value);
		if ($r->isSuccess())
		{
			if (($name === 'BASE_PRICE') || ($name === 'DISCOUNT_PRICE'))
			{
				if ($this->getField('CUSTOM_PRICE') !== 'Y')
				{
					$price = $this->getField('BASE_PRICE') - $this->getField('DISCOUNT_PRICE');
					$r = $this->setField('PRICE', $price);
					if (!$r->isSuccess())
						$result->addErrors($r->getErrors());
				}
			}
		}
		else
		{
			$result->addErrors($r->getErrors());
		}

		return $result;
	}