Reservair/includes/Services/Forms/Pricing/RsvFormPriceCalculator.php

<?php

/** Computes a form's total price as the sum of its elements' prices, reduced by membership discount. */
class RsvFormPriceCalculator {
    public function calculate(RsvFormDefinition $definition, RsvFormData $data): float {
        global $rsv_form_price_registry;

        $total = 0.0;

        foreach ($definition->getElements() as $element) {
            $calculator = $rsv_form_price_registry->get($element->getType());
            if ($calculator === null) {
                continue; // Unpriced element type contributes nothing.
            }

            $total += (float) $calculator($element, $data->getValue($element->getName()));
        }

        $pct = (new RsvMembershipService())->discount_for($definition, $data);
        return $total * (1.0 - max(0.0, min(100.0, $pct)) / 100.0);
    }
}