realpeterz

import play.api.libs.functional.syntax._
import play.api.libs.json.{Format, Json}

object SingleFieldFormat {
  def format[A, B](f: A => B, g: B => A)(implicit fa: Format[A]) = fa.inmap(f, g)
  // expanded:
//    syntax.toInvariantFunctorOps(fa)(Format.invariantFunctorFormat).inmap(f, g)
  // inmap's underlying:
//    Format[B](fa.map(f), Writes[B](b => fa.writes(g(b))))
}

realpeterz

import play.api.libs.json._
import scala.reflect.ClassTag

trait AdtFormat[A <: Product with Serializable] {

  type ReadByTypeFunc[C <: A] = PartialFunction[String, JsResult[C]]

  type ReadsFunc[B <: A] = JsValue => JsResult[B]

  type WriteFunc = PartialFunction[A, JsValue]