Cannot get order/transcation Id from purchase method

[WiseKodama]

Greetings,

I am trying to get an orderId / transactionId after a successful purchase.
I am initiating a purchase like so:
Glassfy.purchase(activity, sku!!, null) { transaction, error -> processPurchase(sku!!, transaction, error) }
☝️ will return a transaction, which however contains only the following fields

In order to get orderId I would need to get a Purchase object and the only way to get that seems to be via using the setPurchaseDelegate. The question here is what will trigger first and whether this is even the correct way to get it.
Can someone explain when/how setPurchaseDelegate should be used?

There is also the transactionId, which seems to be attainable only via the PurchaseHistory data. Is that the same as orderId?

Thank you in advance.