typeclass api

import argonaut._
import Argonaut._

case class Session0(request: Int, data: Int) extends Session[Int, Int]
case class Session1(request: Int, data: String) extends Session[Int, String]
case class Session2(request: Int, data: Session0) extends Session[Int, Session0]

implicit def Session0CodecJson: CodecJson[Session0] =
  casecodec2(Session0.apply, Session0.unapply)("request", "data")
implicit def Session1CodecJson: CodecJson[Session1] =
  casecodec2(Session1.apply, Session1.unapply)("request", "data")
implicit def Session2CodecJson: CodecJson[Session2] =
  casecodec2(Session2.apply, Session2.unapply)("request", "data")

def toJson[A <: Session[_,_] : argonaut.CodecJson](s: A): argonaut.Json = 
  implicitly[CodecJson[A]].encode(s)
  
scala> toJson(Session2(1, Session0(1, 1)))
res7: argonaut.Json = {"request":1,"data":{"request":1,"data":1}}