setFileForMatrixify

public function setFileForMatrixify()
{
    $skuList = json_decode(request()->input('ids'));
    $today = date('Y-m-d');
    $this->path = 'public/shopify/';

    // Initialize CSV file
    $filename = "automatic-shopify-{$today}.csv";
    $file = fopen(storage_path("app/{$this->path}{$filename}"), 'w');
    fputcsv($file, $this->headers());

    // Process in small chunks (50 SKUs at a time)
    $chunkSize = 50;
    $totalChunks = ceil(count($skuList) / $chunkSize);

    for ($i = 0; $i < $totalChunks; $i++) {
        $skuChunk = array_slice($skuList, $i * $chunkSize, $chunkSize);

        // Fetch products for this chunk
        $products = Product::whereIn('sku', $skuChunk)
            ->where('is_active', 1)
            ->select('id', 'category_id')
            ->get();

        foreach ($products as $product) {
            // Use switch for PHP 7.2 compatibility
            switch ((int)$product->category_id) {
                case 1:
                case 3:
                    $method = 'primary';
                    break;
                case 2:
                    $method = 'secondary';
                    break;
                case 4:
                    $method = 'protein';
                    break;
                case 5:
                    $method = 'lifeSience';
                    break;
                case 6:
                    $method = 'flow';
                    break;
                default:
                    $method = null;
                    break;
            }

            if ($method) {
                $content = $this->{$method}($product->id);
                foreach ($content as $row) {
                    if ($this->isValidRow($row)) {
                        fputcsv($file, $this->escapeRow($row));
                    }
                }
            }
        }

        // Free up memory after each chunk
        unset($products, $content);
        gc_collect_cycles();
    }

    fclose($file);
    return response()->json(['filename' => $filename]);
}