How to collapse of Spray Directives

Question

How can one collapse these directives as much as possible?

I was able to collapse three directives into mainHeader but how can include authenticate and responseWithMediaType as well?

val mainHeaders = cors & headerValueByName("Access_Token") & headerValueByName("Tenant_Name")

override def getLayer = path("api" / Segment / "model" / "layers") { modeledSystemName =>
    mainHeaders { (accessToken, tenantName) =>
      authenticate(validate(accessToken)) { authInfo =>
        respondWithMediaType(`application/json`) {
          get {
            onComplete(service.getlayers(modeledSystemName, tenantName)) {
              case Success(layers) => complete(layers)
              //case Success(None) => complete(NotFound, "Release version not found")
              case Failure(ex) => complete(InternalServerError, s"An error occurred: ${ex.getMessage}")
            }
          }
        }
      }
    }
  }

Answer 1

Spray routes are super compossible so you can do whatever you want. For example I would write this route like this:

val authWithHeader = headerValueByName("Access_Token")
  .flatMap(accessToken => authenticate(validate(accessToken)))

val authenticatedJsonRoute = cors &
  authWithHeader &
  headerValueByName("Tenant_Name") &
  respondWithMediaType(MediaTypes.`application/json`)

override val getLayer =
  (get & path("api" / Segment / "model" / "layers")) { modeledSystemName =>
    authenticatedJsonRoute { (authInfo, tenantName) =>
      onComplete(service.getlayers(modeledSystemName, tenantName)) {
        case Success(layers) => complete(layers)
        //case Success(None) => complete(NotFound, "Release version not found")
        case Failure(ex) => complete(InternalServerError, s"An error occurred: ${ex.getMessage}")
      }
    }
  }

Let me explain this code. First, I created the directive authWithHeader that reads header value and then do authentication with this value. It is super simple and all magic done by flatMap.

Then, I created authenticatedJsonRoute which is just a composition of other simple directives. Composition magic is done with & operator (I pronounce it as "and then" in this context) and those directives will be executed in order.

Lastly, I used my composed directive, authenticatedJsonRoute, in a complete route getLayer.