Issue #2901178: Add TaxRatePercentage::calculateTaxAmount()

Author: bojanz

modules/tax/src/Plugin/Commerce/TaxType/LocalTaxTypeBase.php

@@ -6,7 +6,6 @@
 use Drupal\commerce_order\Adjustment;
 use Drupal\commerce_order\Entity\OrderInterface;
 use Drupal\commerce_order\Entity\OrderItemInterface;
-use Drupal\commerce_price\Calculator;
 use Drupal\commerce_price\RounderInterface;
 use Drupal\commerce_store\Entity\StoreInterface;
 use Drupal\commerce_tax\TaxZone;
@@ -147,12 +146,8 @@ public function apply(OrderInterface $order) {
       foreach ($rates as $zone_id => $rate) {
         $zone = $zones[$zone_id];
         $unit_price = $order_item->getUnitPrice();
-        $percentage = $rate->getPercentage()->getNumber();
-        $tax_amount = $unit_price->multiply($percentage);
-        if ($prices_include_tax) {
-          $divisor = Calculator::add('1', $percentage);
-          $tax_amount = $tax_amount->divide($divisor);
-        }
+        $percentage = $rate->getPercentage();
+        $tax_amount = $percentage->calculateTaxAmount($unit_price, $prices_include_tax);
         if ($this->shouldRound()) {
           $tax_amount = $this->rounder->round($tax_amount);
         }
@@ -169,7 +164,7 @@ public function apply(OrderInterface $order) {
           'type' => 'tax',
           'label' => $zone->getDisplayLabel(),
           'amount' => $negate ? $tax_amount->multiply('-1') : $tax_amount,
-          'percentage' => $percentage,
+          'percentage' => $percentage->getNumber(),
           'source_id' => $this->entityId . '|' . $zone->getId() . '|' . $rate->getId(),
           'included' => !$negate && $this->isDisplayInclusive(),
         ]));

modules/tax/src/TaxRatePercentage.php

@@ -2,6 +2,8 @@
 
 namespace Drupal\commerce_tax;
 
+use Drupal\commerce_price\Calculator;
+use Drupal\commerce_price\Price;
 use Drupal\Core\Datetime\DrupalDateTime;
 
 /**
@@ -108,4 +110,24 @@ public function getEndDate() {
     return $this->endDate;
   }
 
+  /**
+   * Calculates the tax amount for the given price.
+   *
+   * @param \Drupal\commerce_price\Price $price
+   *   The price.
+   * @param bool $included
+   *   Whether tax is already included in the price.
+   *
+   * @return \Drupal\commerce_price\Price
+   *   The unrounded tax amount.
+   */
+  public function calculateTaxAmount(Price $price, $included = FALSE) {
+    $tax_amount = $price->multiply($this->number);
+    if ($included) {
+      $divisor = Calculator::add('1', $this->number);
+      $tax_amount = $tax_amount->divide($divisor);
+    }
+    return $tax_amount;
+  }
+
 }

modules/tax/tests/src/Kernel/TaxRatePercentageTest.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\commerce_tax\Kernel;
 
+use Drupal\commerce_price\Price;
 use Drupal\commerce_tax\TaxRatePercentage;
 use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Tests\commerce\Kernel\CommerceKernelTestBase;
@@ -60,4 +61,21 @@ public function testValid() {
     $this->assertEquals(new DrupalDateTime($definition['end_date']), $percentage->getEndDate());
   }
 
+  /**
+   * @covers ::calculateTaxAmount
+   */
+  public function testCalculation() {
+    $definition = [
+      'number' => '0.20',
+      'start_date' => '2012-01-01',
+    ];
+    $percentage = new TaxRatePercentage($definition);
+
+    $tax_amount = $percentage->calculateTaxAmount(new Price('12', 'USD'), FALSE);
+    $this->assertEquals(new Price('2.4', 'USD'), $tax_amount);
+
+    $tax_amount = $percentage->calculateTaxAmount(new Price('12', 'USD'), TRUE);
+    $this->assertEquals(new Price('2', 'USD'), $tax_amount);
+  }
+
 }