Explanation of Yesod route parsing - haskell

Question

I'm building a library for Yesod which, I hope, will expose an interface for Stripe, the credit card processor. (I plan on releasing it soon. I gave up on Amazon because of its poorly documented API...)
I have created a subsite and typeclass to handle the routes the Stripe API needs. I managed to figure out the "how" of what I need to do, but I don't quite understand it.
The subsite has routes defined by:
mkYesodSubData "Stripe" [parseRoutes|
/charge/#StripeId ChargeR POST
/customer/#StripeId CustomerR POST
|]
and the parent has the route defined as:
/payment/stripe StripeR Stripe appStripe
Now, I'm curious about what this line actually means. For comparison, most other routes are defined like:
/questions QuestionsR GET
As far as I understand, the route generator generates a QuestionsR data type, and dispatches /questions to getQuestionsR. But what exactly is the route generator doing with
/payment/stripe StripeR Stripe appStripe
I suppose it must be creating a StripeR type. And I know that appStripe :: App -> Stripe. But what roles do these things play? How does the parser know to ensure that StripeR takes one of the Stripe routes as an argument? What's going on behind the scenes, and is the GET case a special case of the other pattern?

Answer 1

The GET isn't really a special case as I understand it, as we are explicitly creating a Resource that is a subsite.
The line in question
/payment/stripe StripeR Stripe appStripe
Says that the resource at /payment/stripe we are going to call StripeR and it's a Stripe (which is a subsite) that can be accessed with the appStripe function.
For example, when you are defining your foundation for the subsite you do something like
data Stripe = Stripe
But you could also do
data Stripe = Stripe {
getStripeConfig :: String
}
then in the Master site you co uld do in a handler
handler :: Handler Html
handler = do
app <- getYesod
let stripeConfig = getStripeConfig $ appStripe app
...