Any way to sync discounts to Google shopping (created via a 3rd party app) without changing compare at price

So i am building a discount app in which i want a similar feature like in native shopify discounts, to sync the discounted prices to google shopping (without changing the compare at price of the discounted products).

What is the best way to do so, without requiring the google OAuth from the merchants(who will use my app).
Is there a way i can use some shopify api etc. to do so.