app/agent/reference.scala

package agent

import controllers.Prism
import play.api.mvc.Call

case class Reference[T](
    arn: String,
    fields: Map[String, String] = Map.empty,
    prism: Prism
)(implicit arnLookup: ArnLookup[T]) {
  def dereference(implicit arnLookup: ArnLookup[T]): Option[(Label, T)] =
    arnLookup.item(arn, prism)
  def call(implicit arnLookup: ArnLookup[T]): Call = arnLookup.call(arn)
}

trait ArnLookup[T] {
  def item(arn: String, prism: Prism): Option[(Label, T)]
  def call(arn: String): Call
}