$existingDiscountIds Array of discount IDs currently in the cart */ public function determineDiscountsToApply(int $newDiscountId, array $existingDiscountIds): DiscountApplicationResult { // If cart is empty, simply add the new discount if (empty($existingDiscountIds)) { return new DiscountApplicationResult( canApply: true, discountsToApply: [$newDiscountId], discountsToRemove: [] ); } // Get full discount information (type, priority, date_add) for all discounts $newDiscountInfo = $this->getDiscountInfo($newDiscountId); if (!$newDiscountInfo) { // If discount not found, reject it return new DiscountApplicationResult( canApply: false, discountsToApply: $existingDiscountIds, discountsToRemove: [], rejectionReason: 'Discount not found' ); } $existingDiscountsWithInfo = $this->getDiscountsWithInfo($existingDiscountIds); // Check compatibility between new discount and existing ones $compatibilityResult = $this->checkAllCompatibilities( $newDiscountId, $existingDiscountsWithInfo ); if (!$compatibilityResult['isCompatible']) { // Incompatible discounts found - resolve by priority return $this->resolveByPriority( $newDiscountInfo, $existingDiscountsWithInfo, $compatibilityResult['incompatibleDiscounts'] ); } // All discounts are compatible - return them all, sorted by priority $allDiscounts = array_merge( [$newDiscountInfo], $existingDiscountsWithInfo ); $sortedDiscounts = $this->sortDiscountsByPriority($allDiscounts); return new DiscountApplicationResult( canApply: true, discountsToApply: array_column($sortedDiscounts, 'id'), discountsToRemove: [] ); } /** * Check bidirectional compatibility between new discount and all existing discounts * * @param array $existingDiscountsWithTypes * * @return array{isCompatible: bool, incompatibleDiscounts: array} */ private function checkAllCompatibilities( int $newDiscountId, array $existingDiscountsWithTypes ): array { $incompatibleDiscounts = []; foreach ($existingDiscountsWithTypes as $existingDiscount) { $existingId = $existingDiscount['id']; // Check bidirectional compatibility $newToExisting = $this->discountTypeRepository->areDiscountsCompatible($newDiscountId, $existingId); $existingToNew = $this->discountTypeRepository->areDiscountsCompatible($existingId, $newDiscountId); if (!$newToExisting || !$existingToNew) { $incompatibleDiscounts[] = $existingDiscount; } } return [ 'isCompatible' => empty($incompatibleDiscounts), 'incompatibleDiscounts' => $incompatibleDiscounts, ]; } /** * Resolve conflicts by priority when incompatible discounts are found * * Higher priority discount wins and incompatible lower priority discounts are removed * Priority is determined by: 1) Type, 2) Priority field, 3) Creation date * * @param array $newDiscountInfo Full discount info with type, priority, date_add * @param array $existingDiscountsWithTypes * @param array $incompatibleDiscounts * * @return DiscountApplicationResult */ private function resolveByPriority( array $newDiscountInfo, array $existingDiscountsWithTypes, array $incompatibleDiscounts ): DiscountApplicationResult { $discountsToRemove = []; $discountsToKeep = []; // Check each incompatible discount using full priority comparison foreach ($incompatibleDiscounts as $incompatibleDiscount) { $comparisonResult = DiscountPriority::compareDiscounts($newDiscountInfo, $incompatibleDiscount); if ($comparisonResult < 0) { // New discount has higher priority - remove the existing one $discountsToRemove[] = $incompatibleDiscount['id']; } elseif ($comparisonResult > 0) { // Existing discount has higher priority - reject the new one return new DiscountApplicationResult( canApply: false, discountsToApply: array_column($existingDiscountsWithTypes, 'id'), discountsToRemove: [], rejectionReason: 'A higher priority incompatible discount is already applied to the cart' ); } else { // Exact same priority (extremely rare) - reject the new one (first come, first served) return new DiscountApplicationResult( canApply: false, discountsToApply: array_column($existingDiscountsWithTypes, 'id'), discountsToRemove: [], rejectionReason: 'An incompatible discount with identical priority is already applied to the cart' ); } } // Keep compatible discounts foreach ($existingDiscountsWithTypes as $existingDiscount) { if (!in_array($existingDiscount['id'], $discountsToRemove)) { $discountsToKeep[] = $existingDiscount; } } // Add new discount and sort all by priority $allDiscountsToApply = array_merge( [$newDiscountInfo], $discountsToKeep ); $sortedDiscounts = $this->sortDiscountsByPriority($allDiscountsToApply); return new DiscountApplicationResult( canApply: true, discountsToApply: array_column($sortedDiscounts, 'id'), discountsToRemove: $discountsToRemove ); } /** * Get full discount information including type, priority field, and creation date * * @return array|null Array with keys: 'id', 'discount_type', 'priority', 'date_add' */ private function getDiscountInfo(int $discountId): ?array { return $this->discountTypeRepository->getDiscountInfoForPriority($discountId); } /** * Get full discount information for multiple discounts * * @param array $discountIds * * @return array Array of discount info arrays with keys: 'id', 'discount_type', 'priority', 'date_add' */ private function getDiscountsWithInfo(array $discountIds): array { $discountsWithInfo = []; foreach ($discountIds as $discountId) { $info = $this->getDiscountInfo($discountId); if ($info) { $discountsWithInfo[] = $info; } } return $discountsWithInfo; } /** * Sort discounts by their full priority (type, priority field, creation date) * * @param array $discounts Array of discount data with 'discount_type', 'priority', 'date_add' keys * * @return array Sorted array of discounts */ private function sortDiscountsByPriority(array $discounts): array { return DiscountPriority::sortByPriority($discounts); } }