Calculation 3.0

Spryker uses the Calculation module to calculate the cart totals that are displayed in the cart/checkout or when the order is placed.

The Calculation module extensively uses plugins to inject calculation algorithms.

How calculation works

There is already a list of plugins which populate quote transfer with corresponding data. Calculations are executed every time the content of the cart is updated.

If manual recalculation of cart is required, then CalculationFacade::recalculate can be called from Zed or CalculationClient::recalculate from Yves with prepared Calculation Data Structure. When the recalculation operation is called, the calculator runs the calculator plugin stack and each plugin modifies the QuoteTransfer (calculates discounts, adds sum gross prices, calculates taxes). Most plugins require the unitGrossPrice and the quantity to be provided.

Calculator plugins

Calculator plugins are registered in the CalculationDependencyProvider::getCalculatorStack() method. This method can be extended on the project level and the plugin stack can be updated with your own plugins. Each calculator must implement CalculatorPluginInterface.

For more information see:

<?php
interface CalculatorPluginInterface
{
    /**
     * @param QuoteTransfer $quoteTransfer
     *
    public function recalculate(QuoteTransfer $quoteTransfer);
}

• RemoveTotalsCalculatorPlugin—resets quote totals, sets TotalsTransfer empty.
• RemoveAllCalculatedDiscountsCalculatorPlugin—resets every CalculatedDiscountTransfer.
• ItemGrossAmountsCalculatorPlugin—calculates sumGrossPrice for each ItemTransfer.

ItemTransfer::sumGrossPrice = ItemTransfer::unitGrossPrice * ItemTransfer::quantity

• ProductOptionGrossSumCalculatorPlugin—calculates unitGrossPriceWithProductOptions, sumGrossPriceWithProductOptions for ItemTransfer and sumGrossPrice for ProductOptionTransfer—calculates unitGrossPriceWithProductOptions, sumGrossPriceWithProductOptions for ItemTransfer and sumGrossPrice for ProductOptionTransfer.

ProductOptionTransfer::sumGrossPrice = ProductOptionTransfer::unitGrossPrice * ProductOptionTransfer::quantity
ItemTransfer::unitGrossPriceWithProductOptions = sum(ProductOptionTransfer::unitGrossPrice) + ItemTransfer::unitGrossPrice
ItemTransfer::sumGrossPriceWithProductOptions = sum(ProductOptionTransfer::sumGrossPrice) + ItemTransfer:sumGrossPrice

• SubtotalTotalsCalculatorPlugin—sums each of the sumGrossPriceWithProductOptions items. TotalsTransfer::subtotal = sum(ItemTransfer::sumGrossPriceWithProductOptions)
• ExpensesGrossSumAmountCalculatorPlugin—calculates sumGrossPrice for each item. ExpenseTransfer::sumGrossPrice = ExpenseTransfer::unitGrossPrice * ExpenseTransfer::quantity
• ExpenseTotalsCalculatorPlugin—calculates expenseTotal in TotalsTransfer. TotalsTransfer::expenseTotal = sum(ExpenseTransfer::sumGrossPrice)
• DiscountCalculatorPlugin—applies discounts to current QuoteTransfer each discountable item with property calculatedDiscounts, gets discounts filled. Also, voucherDiscounts and cartRuleDiscounts are populated with additional used discount data for order level.

• SumGrossCalculatedDiscountAmountCalculatorPlugin—calculates and sets ItemTransfer amounts after discounts to sumGrossPriceWithProductOptionAndDiscountAmounts and unitGrossPriceWithProductOptionAndDiscountAmounts; sets expense amounts after discounts to unitGrossPriceWithDiscounts and sumGrossPriceWithDiscounts.

ItemTransfer::unitGrossPriceWithProductOptionAndDiscountAmounts = ItemTransfer::unitGrossPriceWithProductOptions— (sum(ItemTransfer:calculatedDiscounts::unitGrossPrice) + sum(ProductOptionTransfer::calculatedDiscounts::unitGrossPrice))
ItemTransfer::sumGrossPriceWithProductOptionAndDiscountAmounts = ItemTransfer::sumGrossPriceWithProductOptions— (sum(ItemTransfer:calculatedDiscounts::sumGrossPrice) + sum(ProductOptionTransfer::calculatedDiscounts::sumGrossPrice))

• DiscountTotalsCalculatorPlugin—calculates total for discounts used and sets it to totalDiscount in TotalsTransfer. Sum all discountable item CalculatedDiscountTransfer gross amounts:

TotalsTransfer:discountTotal += sum(ItemTransfer::CalculateDiscountTransfer::sumGrossAmount +
ItemTransfer::ProductOptionTransfer::CalculateDiscountTransfer::sumGrossAmount + ExpenseTransfer::sumGrossAmount)
GrandTotalTotalsCalculatorPlugin—Calculates grandTotal in TotalsTransfer.
TotalsTransfer:grandTotal = TotalsTransfer::subtotal + TotalsTransfer:expenseTotal

• GrandTotalWithDiscountsCalculatorPlugin —calculates GrandTotal after discounts in TotalsTransfer. TotalsTransfer:grandTotal = TotalsTransfer::subtotal + TotalsTransfer:expenseTotal - TotalsTransfer::discountTotal
• TaxTotalsCalculatorPlugin—calculates taxTotal and taxRate used from TotalTransfer::grandTotal, sets it in TotalsTransfer::TaxTotalsTransfer.

TaxableItems = ItemTransfer, ProductOptionTransfer, ExpenseTransfer. TaxTotalsTransfer::taxRate = sum(TaxableItems) / TaxableItems TaxTotalsTransfer::taxAmount = round((TotalsTransfer::grandTotal * TaxTotalsTransfer::taxRate) / TaxTotalsTransfer::taxRate / 100)

Calculation data structure

This section describes calculation data structure.

Quote transfer

Totals transfer

TotalsTransfer is a data object holding cart totals, subtotal, expenses (shipping), discount total and grand total. Here should the amounts for order level be stored.

Tax total transfer

TaxTotalsTransfer holds taxRate and taxAmount used for grandTotal.

Item transfer

ItemTransfer is a cart item transfer, holds single product information.

Calculated discount transfer

Each item which can have discounts applied have calculatedDiscounts property added which holds the collection of discounts for each discount type.

Product option transfer

ProductOptionTransfer, some items may have product option collection attached which also have amounts calculated.

Discount transfer

DiscountTransfer is a collection of discounts used in all QuoteTransfer discountable items. It can be voucherDiscounts or cartRuleDiscounts.

Expense transfer