Kalkulator rabatu

{
  "calculations": [
    {
      "id": 1,
      "original_price": 199.99,
      "discount_type": "percentage",
      "discount_value": 20,
      "discount_amount": 40.00,
      "final_price": 159.99,
      "product_name": "Koszulka sportowa",
      "created_at": "2026-02-10 14:30:00"
    },
    {
      "id": 2,
      "original_price": 599.00,
      "discount_type": "fixed",
      "discount_value": 100,
      "discount_amount": 100.00,
      "final_price": 499.00,
      "product_name": "Buty do biegania",
      "created_at": "2026-02-10 15:45:00"
    },
    {
      "id": 3,
      "original_price": 1299.00,
      "discount_type": "percentage",
      "discount_value": 15,
      "discount_amount": 194.85,
      "final_price": 1104.15,
      "product_name": "",
      "created_at": "2026-02-11 10:20:00"
    }
  ]
}

$price = filter_var($_POST['price'] ?? '', FILTER_VALIDATE_FLOAT);
$discount = filter_var($_POST['discount'] ?? '', FILTER_VALIDATE_FLOAT);

if ($price === false || $price <= 0) {
    $errors[] = "Cena musi być liczbą dodatnią";
}

if ($discount === false || $discount < 0) {
    $errors[] = "Rabat nie może być ujemny";
}

if ($discount > 100) {
    $errors[] = "Rabat procentowy nie może przekraczać 100%";
}

// Dla rabatu kwotowego
if ($discountType === 'fixed' && $discount > $price) {
    $errors[] = "Rabat kwotowy nie może być większy niż cena";
}

function calculatePercentageDiscount(float $price, float $percent): array {
    $discountAmount = round($price * ($percent / 100), 2);
    $finalPrice = round($price - $discountAmount, 2);

    return [
        'discount_amount' => $discountAmount,
        'final_price' => $finalPrice,
    ];
}

function calculateFixedDiscount(float $price, float $fixedAmount): array {
    $discountAmount = min($fixedAmount, $price); // nie więcej niż cena
    $finalPrice = round($price - $discountAmount, 2);

    return [
        'discount_amount' => round($discountAmount, 2),
        'final_price' => $finalPrice,
    ];
}

function calculateDiscount(float $price, string $type, float $value): array {
    if ($type === 'percentage') {
        return calculatePercentageDiscount($price, $value);
    } else {
        return calculateFixedDiscount($price, $value);
    }
}

function formatPrice(float $amount): string {
    return number_format($amount, 2, ',', ' ') . ' zł';
}

function formatPercent(float $percent): string {
    return number_format($percent, 0) . '%';
}

function formatDiscountInfo(float $amount, string $type, float $value): string {
    if ($type === 'percentage') {
        return formatPrice($amount) . ' (' . formatPercent($value) . ')';
    }
    return formatPrice($amount);
}

function calculateTotalSavings(array $calculations): array {
    if (empty($calculations)) {
        return ['total' => 0, 'count' => 0, 'average' => 0];
    }

    $total = array_sum(array_column($calculations, 'discount_amount'));
    $count = count($calculations);
    $average = $total / $count;

    return [
        'total' => round($total, 2),
        'count' => $count,
        'average' => round($average, 2),
    ];
}

function getDiscountCodes(): array {
    return [
        'LATO2026' => ['type' => 'percentage', 'value' => 25],
        'NOWY10' => ['type' => 'percentage', 'value' => 10],
        'STAŁY50' => ['type' => 'fixed', 'value' => 50],
        'VIP20' => ['type' => 'percentage', 'value' => 20],
    ];
}

function applyDiscountCode(string $code): ?array {
    $codes = getDiscountCodes();
    $upperCode = strtoupper(trim($code));

    return $codes[$upperCode] ?? null;
}

// Użycie
$code = $_POST['discount_code'] ?? '';
if (!empty($code)) {
    $codeData = applyDiscountCode($code);
    if ($codeData) {
        $discountType = $codeData['type'];
        $discountValue = $codeData['value'];
    } else {
        $errors[] = "Nieprawidłowy kod rabatowy";
    }
}

function compareDiscounts(float $price, float $percentDiscount, float $fixedDiscount): array {
    $percentResult = calculatePercentageDiscount($price, $percentDiscount);
    $fixedResult = calculateFixedDiscount($price, $fixedDiscount);

    $percentBetter = $percentResult['discount_amount'] > $fixedResult['discount_amount'];

    return [
        'percentage' => $percentResult,
        'fixed' => $fixedResult,
        'better' => $percentBetter ? 'percentage' : 'fixed',
        'difference' => abs($percentResult['discount_amount'] - $fixedResult['discount_amount']),
    ];
}