// Di dalam fungsi generateQRIS() pada file create_transaction.php
function generateQRIS($nominal, $idProduk, $idMesin) {
    $endpoint = MAYAR_ENDPOINT . '/qrcode/create';
    
    // --- TITIPKAN DATA MESIN DI METADATA MAYAR ---
    $payload = json_encode([
        'name'   => "Vending " . $idProduk, 
        'amount' => (int)$nominal,
        'metadata' => [
            'mesin_id' => $idMesin,
            'prod_id'  => $idProduk
        ]
    ]);

    $ch = curl_init($endpoint);
    // ... (setting curl seperti biasa) ...
    $response = curl_exec($ch);
    $res = json_decode($response, true);
    $url_qris = $res['data']['url'] ?? $res['url'] ?? null;

    if ($url_qris) {
        return ['status' => 'success', 'url' => $url_qris];
    }
    return ['status' => 'error', 'msg' => $response];
}