add product tag to a shopify discount script

[girlmeetschic]

Hi There, thanks in advance for help.  I have a working shopify discount script but need to add a product tag(s) to it and cannot seem to find a solution that works.  Here is the script:

DISCOUNT_AMOUNT = 40

if (Input.cart.line_items.size > 1)
line_item = Input.cart.line_items.sort_by { |line_item| line_item.variant.price }.last
if line_item.quantity > 1
line_item = line_item.split(take: 1)
Input.cart.line_items << line_item
end
line_item.change_line_price(line_item.line_price * (1.0 - (DISCOUNT_AMOUNT / 100.0)), message: "#{DISCOUNT_AMOUNT}% off!")
end

Output.cart = Input.cart

I need this to reflect products with specific tag.  If qualified item(s) is in the cart and it is the highest priced item, discount will be applied to that item.

Advise?