function has_bought() {
    // Get all customer orders
    $customer_orders = get_posts( array(
        'numberposts' => 1, // one order is enough
        'meta_key'    => '_customer_user',
        'meta_value'  => get_current_user_id(),
        'post_type'   => 'shop_order', // WC orders post type
        'post_status' => 'wc-completed', // Only orders with "completed" status
        'fields'      => 'ids', // Return Ids "completed"
    ) );

    // return "true" when customer has already at least one order (false if not)
   return count($customer_orders) > 0 ? true : false; 
}