Calculation 3.0

Spryker uses the Calculation module to calculate the cart totals that are displayed in the cart, during checkout, and 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 that 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 the following:

<?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, and each discountable item with the 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; it also 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 the total for used discount and sets it to totalDiscount in TotalsTransfer. The sum of all discountable items CalculatedDiscountTransfer gross amounts is as follows:

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
• TaxTotalsCalculatorPlugincalculates taxTotal and taxRate used from TotalTransfer::grandTotal and 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 the calculation data structure.

Quote transfer

Totals transfer

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

Tax total transfer

Item transfer

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

Calculated discount transfer

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

Product option transfer

Discount transfer

Expense transfer