Shipping.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Sales\Model\Order\Creditmemo\Total;

use Magento\Framework\Pricing\PriceCurrencyInterface;
use Magento\Tax\Model\Calculation as TaxCalculation;
use Magento\Sales\Model\Order;

/**
 * Order creditmemo shipping total calculation model
 */
class Shipping extends AbstractTotal
{
    /**
     * @var PriceCurrencyInterface
     */
    protected $priceCurrency;

    /**
     * Tax config from Tax model
     *
     * @var \Magento\Tax\Model\Config
     */
    private $taxConfig;

    /**
     * @param PriceCurrencyInterface $priceCurrency
     * @param array $data
     */
    public function __construct(
        PriceCurrencyInterface $priceCurrency,
        array $data = []
    ) {
        parent::__construct($data);
        $this->priceCurrency = $priceCurrency;
    }

    /**
     * Collects credit memo shipping totals.
     *
     * @param \Magento\Sales\Model\Order\Creditmemo $creditmemo
     * @return $this
     * @throws \Magento\Framework\Exception\LocalizedException
     */
    public function collect(\Magento\Sales\Model\Order\Creditmemo $creditmemo)
    {
        $order = $creditmemo->getOrder();

        // amounts without tax
        $orderShippingAmount = $order->getShippingAmount();
        $orderBaseShippingAmount = $order->getBaseShippingAmount();
        $allowedAmount = $orderShippingAmount - $order->getShippingRefunded();
        $baseAllowedAmount = $orderBaseShippingAmount - $order->getBaseShippingRefunded();

        // amounts including tax
        $orderShippingInclTax = $order->getShippingInclTax();
        $orderBaseShippingInclTax = $order->getBaseShippingInclTax();
        $allowedAmountInclTax =$this->getAllowedAmountInclTax($order);
        $baseAllowedAmountInclTax = $this->getBaseAllowedAmountInclTax($order);

        // Check if the desired shipping amount to refund was specified (from invoice or another source).
        if ($creditmemo->hasBaseShippingAmount()) {
            // For the conditional logic, we will either use amounts that always include tax -OR- never include tax.
            // The logic uses the 'base' currency to be consistent with what the user (admin) provided as input.
            $useAmountsWithTax = $this->isSuppliedShippingAmountInclTax($order);

            // Since the user (admin) supplied 'desiredAmount' it already has tax -OR- does not include tax
            $desiredAmount = $this->priceCurrency->round($creditmemo->getBaseShippingAmount());
            $maxAllowedAmount = ($useAmountsWithTax ? $baseAllowedAmountInclTax : $baseAllowedAmount);
            $originalTotalAmount = ($useAmountsWithTax ? $orderBaseShippingInclTax : $orderBaseShippingAmount);

            // Note: ($x < $y + 0.0001) means ($x <= $y) for floats
            if ($desiredAmount < $this->priceCurrency->round($maxAllowedAmount) + 0.0001) {
                // since the admin is returning less than the allowed amount, compute the ratio being returned
                $ratio = 0;
                if ($originalTotalAmount > 0) {
                    $ratio = $desiredAmount / $originalTotalAmount;
                }
                // capture amounts without tax
                // Note: ($x > $y - 0.0001) means ($x >= $y) for floats
                if ($desiredAmount > $maxAllowedAmount - 0.0001) {
                    $shippingAmount = $allowedAmount;
                    $baseShippingAmount = $baseAllowedAmount;
                } else {
                    $shippingAmount = $this->priceCurrency->round($orderShippingAmount * $ratio);
                    $baseShippingAmount = $this->priceCurrency->round($orderBaseShippingAmount * $ratio);
                }
                $shippingInclTax = $this->priceCurrency->round($orderShippingInclTax * $ratio);
                $baseShippingInclTax = $this->priceCurrency->round($orderBaseShippingInclTax * $ratio);
            } else {
                $maxAllowedAmount = $order->getBaseCurrency()->format($maxAllowedAmount, null, false);
                throw new \Magento\Framework\Exception\LocalizedException(
                    __('Maximum shipping amount allowed to refund is: %1', $maxAllowedAmount)
                );
            }
        } else {
            $shippingAmount = $allowedAmount;
            $baseShippingAmount = $baseAllowedAmount;
            $shippingInclTax = $this->priceCurrency->round($allowedAmountInclTax);
            $baseShippingInclTax = $this->priceCurrency->round($baseAllowedAmountInclTax);
        }

        $creditmemo->setShippingAmount($shippingAmount);
        $creditmemo->setBaseShippingAmount($baseShippingAmount);
        $creditmemo->setShippingInclTax($shippingInclTax);
        $creditmemo->setBaseShippingInclTax($baseShippingInclTax);

        $creditmemo->setGrandTotal($creditmemo->getGrandTotal() + $shippingAmount);
        $creditmemo->setBaseGrandTotal($creditmemo->getBaseGrandTotal() + $baseShippingAmount);
        return $this;
    }

    /**
     * Checks if shipping provided incl tax, tax applied after discount, and discount applied on shipping excl tax
     *
     * @param Order $order
     * @return bool
     */
    private function isShippingIncludeTaxWithTaxAfterDiscount(Order $order): bool
    {
        $calculationSequence = $this->getTaxConfig()->getCalculationSequence($order->getStoreId());
        return ($calculationSequence === TaxCalculation::CALC_TAX_AFTER_DISCOUNT_ON_EXCL
            || $calculationSequence === TaxCalculation::CALC_TAX_AFTER_DISCOUNT_ON_INCL)
            && $this->isSuppliedShippingAmountInclTax($order);
    }

    /**
     * Get allowed shipping amount to refund based on tax settings
     *
     * @param Order $order
     * @return float
     */
    private function getAllowedAmountInclTax(Order $order): float
    {
        if ($this->isShippingIncludeTaxWithTaxAfterDiscount($order)) {
            $result = $order->getShippingInclTax();
            foreach ($order->getCreditmemosCollection() as $creditmemo) {
                $result -= $creditmemo->getShippingInclTax();
            }
        } else {
            $result = ($order->getShippingAmount() - $order->getShippingRefunded()) +
                ($order->getShippingTaxAmount() - $order->getShippingTaxRefunded());
        }

        return $result;
    }

    /**
     * Get base allowed shipping amount to refund based on tax settings
     *
     * @param \Magento\Sales\Model\Order $order
     * @return float
     */
    private function getBaseAllowedAmountInclTax(\Magento\Sales\Model\Order $order): float
    {
        $result = $order->getBaseShippingInclTax();
        if ($this->isShippingIncludeTaxWithTaxAfterDiscount($order)) {
            foreach ($order->getCreditmemosCollection() as $creditmemo) {
                $result -= $creditmemo->getBaseShippingInclTax();
            }
        } else {
            $result -= $order->getBaseShippingRefunded() + $order->getBaseShippingTaxRefunded();
        }

        return max($result, 0);
    }

    /**
     * Returns whether the user specified a shipping amount that already includes tax
     *
     * @param \Magento\Sales\Model\Order $order
     * @return bool
     */
    private function isSuppliedShippingAmountInclTax($order)
    {
        // returns true if we are only displaying shipping including tax, otherwise returns false
        return $this->getTaxConfig()->displaySalesShippingInclTax($order->getStoreId());
    }

    /**
     * Get the Tax Config.
     *
     * @return \Magento\Tax\Model\Config
     *
     * @deprecated 100.1.0
     * @see \Magento\Tax\Model\Config
     */
    private function getTaxConfig()
    {
        if ($this->taxConfig === null) {
            $this->taxConfig = \Magento\Framework\App\ObjectManager::getInstance()->get(
                \Magento\Tax\Model\Config::class
            );
        }
        return $this->taxConfig;
    }
}