How to apply filter on finch endpoint without using finagle filters? - finch

Question

I have more than one endpoints.I am able to apply common filters on endpoints using finagle filter.But now I want to apply a filter on a specific endpoint.
How can I achieve this?

Answer 1

I had a similar question (for basic authentication filtering) that popped up while playing with redbubble's finch template which I partially solved in the following way:
class AuthenticatedEndpoint[A](e: Endpoint[A]) extends Endpoint[A] { self =>
final def apply(mapper: Mapper[A]): Endpoint[mapper.Out] = mapper(self)
final def apply(input: Input): Endpoint.Result[A] =
if (checkSession(input.request)) {
e(input)
} else {
// TODO return something meaningful to the caller (if possible?)
EndpointResult.Skipped
}
}
object AuthenticatedEndpoint {
def validSession[A](e: Endpoint[A]): Endpoint[A] = new AuthenticatedEndpoint(e)
}
(with checkSession returning true if all is well with the request). Then my api is defined as:
val api = "v1" :: loginApi :+: validSession(peopleApi :+: healthApi :+: adminApi)
This works well in the sense that requests without a session won't have access to the endpoints passed to validSession, but I have yet to find an easy way to return an error message to the caller, and I'd be curious to know if I chose the right path here.

Answer 2

This is how I got around it. It's probably not ideal but works.
class AuthenticatedEndpoint[A](e: Endpoint[A])(implicit auth: Request => Boolean) extends Endpoint[A] { self =>
final def apply(mapper: Mapper[A]): Endpoint[mapper.Out] = mapper(self)
final def apply(input: Input): Endpoint.Result[A] =
if (auth(input.request)) {
e(input)
} else {
EndpointResult.Matched[Nothing](input, Rerunnable( Unauthorized(new Exception(s"Authentication Failed."))) )
}
}
object AuthenticatedEndpoint {
def validSession[A](e: Endpoint[A]): Endpoint[A] = new AuthenticatedEndpoint(e)
}