Cart discount based on cart item count and only for items that are not in sale

Here is a custom hooked function that will apply to cart a discount, if there is 5 or more items in cart and no products on sale:

add_action('woocommerce_cart_calculate_fees' , 'custom_discount', 10, 1);function custom_discount( $cart ){    if ( is_admin() && ! defined( 'DOING_AJAX' ) )        return;    // Only when there is 5 or more items in cart    if( $cart->get_cart_contents_count() >= 5):        // 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 = $cart->subtotal * -0.1;        ## Applied discount (no products on sale) ##        if(!$is_on_sale )            $cart->add_fee( '10% discount', $discount);    endif;}

This code goes in function.php file of your active child theme (or theme) or also in any plugin file.

This code is tested and works perfectly.