✨ Adds functions on prices (#48)

* ✨ Adds functions on prices

* Adds percentages functions

* rounding prices to cent precision

* add precision to Price

Author: YevicT

component/Money/Price.php

@@ -9,14 +9,66 @@ class Price
     public function __construct(
         public readonly float $amount,
         public readonly ?Currency $currency,
-        public readonly ?string $unit
+        public readonly ?string $unit,
+        public readonly ?int $precision = 2
     ) {
     }
 
+    public function add(self $price): self
+    {
+        if ($this->currency !== $price->currency) {
+            throw new \InvalidArgumentException('Cannot add prices with different currencies.');
+        }
+
+        if ($this->unit !== $price->unit) {
+            throw new \InvalidArgumentException('Cannot add prices with different units.');
+        }
+
+        return new self(
+            amount: round($this->amount + $price->amount, $this->precision),
+            currency: $this->currency,
+            unit: $this->unit,
+            precision: $this->precision
+        );
+    }
+
+    public function subtract(self $price): self
+    {
+        if ($this->currency !== $price->currency) {
+            throw new \InvalidArgumentException('Cannot subtract prices with different currencies.');
+        }
+
+        if ($this->unit !== $price->unit) {
+            throw new \InvalidArgumentException('Cannot subtract prices with different units.');
+        }
+
+        return new self(
+            amount: round($this->amount - $price->amount, $this->precision),
+            currency: $this->currency,
+            unit: $this->unit,
+            precision: $this->precision
+        );
+    }
+
+    public function multiply(float $factor): self
+    {
+        return new self(
+            amount: round($this->amount * $factor, $this->precision),
+            currency: $this->currency,
+            unit: $this->unit,
+            precision: $this->precision
+        );
+    }
+
+    public function applyPercentage(float $percentage): self
+    {
+        return $this->multiply(1 + $percentage / 100);
+    }
+
     public function getFormatted(
         bool $espaceInsecable = true
     ): string {
-        $price = number_format($this->amount, 2, ',', ' ');
+        $price = number_format($this->amount, $this->precision, ',', ' ');
 
         if ($this->currency) {
             $price .= ' ' . $this->currency->getLabel();

test/Money/PriceTest.php

@@ -13,7 +13,7 @@ public function testInterface(): void
     {
         $price = new Price(1234.56, Currency::EUR, 'kg');
 
-        $this->assertEquals('1 234,56 €/kg', (string)$price);
+        $this->assertEquals('1 234,56 €/kg', (string) $price);
 
         $this->assertIsFloat($price->amount);
         $this->assertEquals(1234.56, $price->amount);
@@ -22,6 +22,56 @@ public function testInterface(): void
         $this->assertEquals(Currency::EUR, $price->currency);
 
         $this->assertIsString($price->unit);
-        $this->assertEquals('kg', (string)$price->unit);
+        $this->assertEquals('kg', (string) $price->unit);
+    }
+
+    public function testAdd(): void
+    {
+        $price1 = new Price(100, Currency::EUR, 'Mwh');
+        $price2 = new Price(50, Currency::EUR, 'Mwh');
+
+        $result = $price1->add($price2);
+
+        $this->assertEquals(150, $result->amount);
+        $this->assertEquals(Currency::EUR, $result->currency);
+        $this->assertEquals('Mwh', $result->unit);
+    }
+
+    public function testsubtract(): void
+    {
+        $price1 = new Price(100, Currency::EUR, 'Mwh');
+        $price2 = new Price(50, Currency::EUR, 'Mwh');
+
+        $result = $price1->subtract($price2);
+
+        $this->assertEquals(50, $result->amount);
+        $this->assertEquals(Currency::EUR, $result->currency);
+        $this->assertEquals('Mwh', $result->unit);
+    }
+
+    public function testMultiply(): void
+    {
+        $price = new Price(100, Currency::EUR, 'Mwh');
+
+        $result = $price->multiply(2);
+
+        $this->assertEquals(200, $result->amount);
+        $this->assertEquals(Currency::EUR, $result->currency);
+        $this->assertEquals('Mwh', $result->unit);
+    }
+
+    public function testApplyPercentage(): void
+    {
+        $price = new Price(100, Currency::EUR, 'Mwh');
+
+        $result = $price->applyPercentage(10);
+        $this->assertEquals(110.00, $result->amount);
+        $this->assertEquals(Currency::EUR, $result->currency);
+        $this->assertEquals('Mwh', $result->unit);
+
+        $result = $price->applyPercentage(-10);
+        $this->assertEquals(90.00, $result->amount);
+        $this->assertEquals(Currency::EUR, $result->currency);
+        $this->assertEquals('Mwh', $result->unit);
     }
 }