Discount as fee at first order exclude product on sale and if is applied a coupon disable fee

Discount as fee at first order exclude product on sale and if is applied a coupon disable fee.php

<?php

/**
 * Discount as fee at first order exclude product on sale and if is applied a coupon disable fee
 */ 


add_action('woocommerce_cart_calculate_fees' , 'custom_discount', 10, 1);
function custom_discount( $cart ){

    if ( is_admin() && ! defined( 'DOING_AJAX' ) || ! is_user_logged_in() )
        return;

	
	// Getting "completed" customer orders
    $customer_orders = get_posts( array(
        'numberposts' => -1,
        '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 status "completed"
    ) );
	
	  // Orders count
    $customer_orders_count = count($customer_orders);
	
	
        // Initialising variable
        $is_on_sale = false;

        // Iterating through each item in cart
        foreach( $cart->get_cart() as $cart_item ){
            // Getting an instance of the product object
            $product =  $cart_item['data'];

            // If a cart item is on sale, $is_on_sale is true and we stop the loop
            if($product->is_on_sale()){
                $is_on_sale = true;
                break;
            }
        }

        ## Discount calculation ##
        $discount = (-10 / 100) * WC()->cart->get_subtotal(); // or WC()->cart->get_total_ex_tax()

        ## Applied discount (no products on sale) ##
        if(!$is_on_sale AND empty($customer_orders) || $customer_orders_count == 0){
            $cart->add_fee( 'Sconto sul primo ordine', $discount);
        }
  
  ## Se c'è un coupon nel carrello disabilita la tassa ##
  elseif( ( is_cart() || is_checkout() ) && sizeof( WC()->cart->get_applied_coupons() ) > 0){
$cart->fees_api()->set_fees($fees);
}
}