TypeClassPractice

// JSON AST
sealed trait JSON
case object JSNull extends JSON
case class JSString(get: String) extends JSON
case class JSNumber(get: Int) extends JSON
case class JSObject(get: Map[String, JSON]) extends JSON

final case class Person(name: String, email: String)

// Given any value, write it to JSON AST
// JSONWriter is the typeclass
trait JsonWriter[A]{
  def write(value: A): JSON
}

// These are instances of our typeclasse
object JsonWriterInstances{
  implicit val stringWriter: JsonWriter[String] = {
    new JsonWriter[String] {
      def write(a: String) = JSString(a)
    }
  }

  implicit val numberWriter: JsonWriter[Int] = {
    new JsonWriter[Int]{
      def write(a: Int) = JSNumber(a)
    }
  }

  implicit val personWriter: JsonWriter[Person] = {
    new JsonWriter[Person] {
      def write(a: Person) = JSObject(Map(
      "name" -> JSString(a.name),
      "email" -> JSString(a.email)
      ))
    }
  }
}

object JSON { // You want this toJson method to take your implicit JsonWriter because then you don't need separate toJson methods for each type.
  def toJson[A](a: A)(implicit jsonWriter: JsonWriter[A]): JSON = jsonWriter.write(a)
}


object Main {
  import JsonWriterInstances._
  def main(args: Array[String]): Unit = {
   println(JSON.toJson("HI"))
  }
}