Shipping rate by distance custom snippet

// Code for https://codecanyon.net/item/shipping-rate-by-distance-for-woocommerce/21671361
// Charge a base shipping price if distance is below xx KM/mile, and a base price + per KM/mile rate otherwise
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'])) {
        $meters = $rate['meta_data'];
        $distance_in_km = $meters * 0.001;
        $distance_in_km = round($distance_in_km, 2);
    } else {
        $distance_in_km = null;
    }

    if ($distance_in_km !== null) {
        if ($distance_in_km < 20) {
            $rate['cost'] = 70;
        } else {
            $price_per_km = $rate['cost'] / $distance_in_km;
            $cost_per_first_20km = 70;
            $cost_per_remaining_kms = ($distance_in_km - 20) * $price_per_km;
            $rate['cost'] = $cost_per_first_20km + $cost_per_remaining_kms;
        }
    }

    return $rate;
}