friend referral feature through after sales email so both purchaser and new subscriber get discount code

Is there a code that can be used to allow this feature to work on after sales to drive more customers to site and mailing list?

What I want is when a customer has bought a product from us, they will receive and email saying refer a freind and you and your friend can get a %discount on their next purchase.

The link will send them back to our site, where their friend will subscribe. Once that happens both will receive a discount code.

is there a code out there to make this work.

That sounds like a plugin application, not something you would achieve by just adding code. Shopify and others offer things of this nature. 

https://apps.shopify.com/email-with-love

https://apps.shopify.com/discountcode-in-cart