Ecommerce solution with flexible integration?

Question

CMS

Tell me an E-commerce solution (preferably open source), which can be easily plugged into the side of the main project (nodejs), in general, it is necessary from it:
1) SSO with the main project
2) Be able to notify the project about the product purchase event
3) Possibility, in addition to ordinary products , sell (manage) subscriptions.
4) Shipping cost calculation, etc. - would be a big plus

Answer 1

opencart