I have been working on import modules for eBay and Amazon. The idea is that if you have an existing storefront at either of these providers, you can import your inventory and sell them at your own custom storefront. The concern I have is, after selling an item on VC, I would have to make sure to adjust the inventory at eBay. And likewise, if an item is sold on eBay, the VC inventory would not be updated until the next scheduled import (perhaps run hourly).
With these concerns in mind, I wonder if I might be going about this the wrong way. Would it be possible for me to author a custom "catalog provider" class, that, instead of retrieving catalog items from the database, would retrieve them real-time via the eBay/Amazon APIs? (Perhaps backed by a cache)
So I guess in summary my question is, is there support/guidance for creating a custom catalog type in VirtoCommerce?
Import/export is a preferred approach for getting a listing data. eBay also provides client alerts https://developer.ebay.com/devzone/client-alerts/docs/Concepts/ClientAlertsAPIGuide.html, which allows you to pull the data every minute about various alerts, like when item is sold. You can use that to get the inventory. So in case it is critical for you to get up to date inventory information, I would use combination of more realtime inventory APIs and import/export.
As of creating an external catalog provider, it is possible but will be much more effort than doing import/export.
Also, we have a parter who is developing integration with eBay/amazon, the project is open source: http://spreadbot.net.