Generator kodow rabatowych

{
  "codes": [
    {
      "id": 1,
      "code": "RABAT2026XY",
      "discount_type": "percent",
      "discount_value": 15,
      "valid_until": "2026-03-31",
      "is_used": false,
      "created_at": "2026-02-17 10:30:00"
    },
    {
      "id": 2,
      "code": "PROMO50ZL",
      "discount_type": "amount",
      "discount_value": 50,
      "valid_until": "2026-02-28",
      "is_used": true,
      "used_at": "2026-02-20 14:15:00",
      "created_at": "2026-02-17 11:00:00"
    }
  ]
}

function generateCode($length = 8) {
    $characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
    $code = '';
    for ($i = 0; $i < $length; $i++) {
        $code .= $characters[random_int(0, strlen($characters) - 1)];
    }
    return $code;
}

function isCodeUnique($code, $existingCodes) {
    foreach ($existingCodes as $existing) {
        if ($existing['code'] === $code) {
            return false;
        }
    }
    return true;
}

// Generuj aż do uzyskania unikalnego kodu
do {
    $newCode = generateCode(8);
} while (!isCodeUnique($newCode, $data['codes']));

$validUntil = new DateTime($_POST['valid_until']);
$today = new DateTime();

if ($validUntil < $today) {
    $errors[] = "Data waznosci musi być w przyszłości";
}

$data = json_decode(file_get_contents('codes.json'), true) ?? ['codes' => []];
$data['codes'][] = [
    'id' => count($data['codes']) + 1,
    'code' => $newCode,
    'discount_type' => $_POST['discount_type'],
    'discount_value' => (float)$_POST['discount_value'],
    'valid_until' => $_POST['valid_until'],
    'is_used' => false,
    'created_at' => date('Y-m-d H:i:s')
];
file_put_contents('codes.json', json_encode($data, JSON_PRETTY_PRINT));