Integrate web app with Canada Post shipping label generation

Hi there, I am trying to integrate shipping into a web application I'm building. The use case is as follows: 1) User visits my site and finds a product they want to buy - they purchase the product and pay for shipping from my site through a payment gateway integrated with my site 2) Upon payment acceptance, system should automatically connect with Canada Post to create a pre-paid shipping label 3) System should be able to dynamically populate BOTH the 'From' and 'To' address for the shipment, and the required payment amount should be dynamically calculated and paid to Canada Post 4) Prepaid shipping label should then be sent to an email address where a user can print it out, put it on a box and mail that box If you have done something like this in the past, I would love to hear from you and potentially work with you on this project. The web app is being built in RoR, but I'm not sure if that's a requirements for integrating with the shipping element described above. Looking forward to hearing from you!