feat: replace custom discount with absolute value in favor of percentage

tests/Controller/Api/AccommodationBookingControllerTest.php

@@ -56,7 +56,7 @@ class AccommodationBookingControllerTest extends TestCase
         $booking->setAccommodationDiscount(10);
         $booking->setBoardServiceDiscount(20);
         $booking->setAdditionalServicesDiscount(30);
-        $booking->setTotalDiscount(5);
+        $booking->setTotalDiscountAmount(5000);
         $booking->setTotalDiscountLabel('Treuerabatt');
         $booking->setStatus(AccommodationBookingStatus::Confirmed);
         $booking->setOrigin(AccommodationBookingOrigin::Direct);
@@ -129,7 +129,7 @@ class AccommodationBookingControllerTest extends TestCase
             'accommodationDiscount' => 10,
             'boardServiceDiscount' => 20,
             'additionalServicesDiscount' => 30,
-            'totalDiscount' => 5,
+            'totalDiscountAmount' => 5000,
             'totalDiscountLabel' => 'Treuerabatt',
             'totalPrice' => 11111,
             'pricingCurrency' => 'EUR',

tests/Form/Admin/Groups/AccommodationBookingTypeTest.php

@@ -74,13 +74,13 @@ class AccommodationBookingTypeTest extends TestCase
     }
 
     /**
-     * The label is printed verbatim on the customer's PDF, so a percentage without one is
+     * The label is printed verbatim on the customer's PDF, so an amount without one is
      * refused — and in the Default group, so that even a draft cannot store the pair half-set.
      */
     public function testTotalDiscountRequiresALabel(): void
     {
         $booking = new AccommodationBooking();
-        $booking->setTotalDiscount(5);
+        $booking->setTotalDiscountAmount(5000);
 
         $violations = $this->validate($booking, ['Default']);
 
@@ -91,17 +91,17 @@ class AccommodationBookingTypeTest extends TestCase
     public function testALabelledTotalDiscountPassesValidation(): void
     {
         $booking = new AccommodationBooking();
-        $booking->setTotalDiscount(5);
+        $booking->setTotalDiscountAmount(5000);
         $booking->setTotalDiscountLabel('Treuerabatt');
 
         self::assertCount(0, $this->validate($booking, ['Default']));
     }
 
     /**
-     * The reverse is harmless — without a percentage the label never reaches a breakdown row —
+     * The reverse is harmless — without an amount the label never reaches a breakdown row —
      * so it is deliberately left valid rather than blocking a half-typed edit.
      */
-    public function testALabelWithoutAPercentageIsAccepted(): void
+    public function testALabelWithoutAnAmountIsAccepted(): void
     {
         $booking = new AccommodationBooking();
         $booking->setTotalDiscountLabel('Treuerabatt');

tests/Service/AccommodationBookingBreakdownCalculatorTest.php

@@ -101,33 +101,32 @@ class AccommodationBookingBreakdownCalculatorTest extends TestCase
 
     /**
      * On its own the total discount has nothing to sit below, so no subtotal row is offered and
-     * the percentage applies to the plain total.
+     * the amount comes straight off the plain total.
      */
     public function testTotalDiscountAloneAppliesToTheTotalWithoutASubtotal(): void
     {
         $booking = new AccommodationBooking();
-        $booking->setTotalDiscount(10);
+        $booking->setTotalDiscountAmount(1235);
         $booking->setTotalDiscountLabel('Treuerabatt');
 
         $breakdown = $this->createCalculator()->withDiscounts($booking, $this->breakdown());
 
         self::assertSame([], $breakdown['discounts']);
-        self::assertSame(['label' => 'Treuerabatt', 'percent' => 10, 'amount' => 1235], $breakdown['totalDiscountDetails']);
+        self::assertSame(['label' => 'Treuerabatt', 'amount' => 1235], $breakdown['totalDiscountDetails']);
         self::assertNull($breakdown['discountSubtotal']);
         self::assertSame(12345 - 1235, $breakdown['discountedTotal']);
     }
 
     /**
-     * The worked example from the specification: the total discount compounds on the subtotal
-     * left by the section discounts, not on the gross total — 5 % of 930,00 € is 46,50 €, where
-     * 5 % of the gross 1.000,00 € would have been 50,00 €.
+     * The worked example from the specification: a fixed 50,00 € off the 930,00 € left by the
+     * section discounts, which is where the Zwischensumme row comes from.
      */
-    public function testTotalDiscountCompoundsOnTheSubtotalAfterSectionDiscounts(): void
+    public function testTotalDiscountIsSubtractedFromTheSubtotalAfterSectionDiscounts(): void
     {
         $booking = new AccommodationBooking();
         $booking->setAccommodationDiscount(10);
         $booking->setBoardServiceDiscount(5);
-        $booking->setTotalDiscount(5);
+        $booking->setTotalDiscountAmount(5000);
         $booking->setTotalDiscountLabel('Treuerabatt');
 
         $breakdown = $this->createCalculator()->withDiscounts($booking, [
@@ -138,14 +137,30 @@ class AccommodationBookingBreakdownCalculatorTest extends TestCase
 
         // accommodation: 60000*10% = 6000, board: 20000*5% = 1000 → subtotal 93000
         self::assertSame(93000, $breakdown['discountSubtotal']);
-        self::assertSame(['label' => 'Treuerabatt', 'percent' => 5, 'amount' => 4650], $breakdown['totalDiscountDetails']);
-        self::assertSame(88350, $breakdown['discountedTotal']);
+        self::assertSame(['label' => 'Treuerabatt', 'amount' => 5000], $breakdown['totalDiscountDetails']);
+        self::assertSame(88000, $breakdown['discountedTotal']);
+    }
+
+    /**
+     * A sum larger than the price is clamped rather than refused: prices move after the discount
+     * was agreed, and a negative total would be worse than a free stay.
+     */
+    public function testTotalDiscountLargerThanTheSubtotalIsClampedToIt(): void
+    {
+        $booking = new AccommodationBooking();
+        $booking->setTotalDiscountAmount(20000);
+        $booking->setTotalDiscountLabel('Treuerabatt');
+
+        $breakdown = $this->createCalculator()->withDiscounts($booking, $this->breakdown());
+
+        self::assertSame(['label' => 'Treuerabatt', 'amount' => 12345], $breakdown['totalDiscountDetails']);
+        self::assertSame(0, $breakdown['discountedTotal']);
     }
 
     public function testTotalDiscountThatAmountsToNothingIsSkipped(): void
     {
         $booking = new AccommodationBooking();
-        $booking->setTotalDiscount(20);
+        $booking->setTotalDiscountAmount(2000);
         $booking->setTotalDiscountLabel('Treuerabatt');
 
         $breakdown = $this->createCalculator()->withDiscounts($booking, ['total' => 0]);