Shipping rate by distance, charge flat rate conditionally

add_filter('wpali_distance_shipping_rate', 'wpali_add_base_price_to_rate', 10, 2);
function wpali_add_base_price_to_rate($rate, $obj)
{
    if (!empty($rate['meta_data']['value'])) {
        $meters = $rate['meta_data']['value'];
        $distance_in_km = $meters * 0.001;
        $distance_in_km = round($distance, 2);
        if($distance_in_km > 10 ){
            $price_per_km = $rate['cost'] / $distance_in_km;
            $cost_per_first_10km = 29;
            $cost_per_remaining_kms = ( $distance_in_km - 10 ) * $price_per_km;
            $rate['cost'] = $cost_per_first_10km + $cost_per_remaining_kms;
        }else{
            $rate['label'] = 'Fixed distance rate';
            $rate['cost'] = 29;
        }
    }
    return $rate;
}