Json.scala

import util.parsing.json.JSON
import io.Source

import scala.language.dynamics

object Example extends App{
  val json = """{
         "name" : "Adam Slodowy",
         "active": "true",
         "roles" : [ "teacher", "admin" ],
         "lessons" : [ { "id": 1 }, { "id": 2 } ],
         "security" : { "id" : 123, "login": "adams" }
      }"""

  val adam = JsonElement.parse(json).get
  case class Lesson(teacher: String, id: Int, name: String, active : Boolean = true)
  
  val lesson = Lesson(adam.name, adam.lessons.at(1).id, adam.lessons.at(1).name, adam.active)
  // will create Lesson("Adam Slodowy", 2, "", true ) - see the implicit conversions
  
}

trait JsonElement extends Dynamic{ self =>
  def selectDynamic(field: String) : JsonElement = EmptyElement
  def applyDynamic(field: String)(i: Int) : JsonElement = EmptyElement
  def toList : List[String] = sys.error(s"$this is not a list.")
  def asString: String = sys.error(s"$this has no string representation.")
  def length$ : Int = sys.error(s"$this has no length")
}


object JsonElement{

  def ^(s: String) = {
    require(!s.isEmpty, "Element is empty")
    s
  }

  implicit def toString(e: JsonElement) : String = e.asString
  implicit def toBoolean(e: JsonElement) : Boolean = (^(e.asString)).toBoolean
  implicit def toBigDecimal(e: JsonElement) : BigDecimal = BigDecimal(^(e.asString))
  implicit def toDouble(e: JsonElement) : Double = ^(e.asString).toDouble
  implicit def toFloat(e: JsonElement) : Float = ^(e.asString).toFloat
  implicit def toByte(e: JsonElement) : Byte = ^(e.asString).stripSuffix(".0").toByte
  implicit def toShort(e: JsonElement) : Short = ^(e.asString).stripSuffix(".0").toShort
  implicit def toInt(e: JsonElement) : Int = ^(e.asString).stripSuffix(".0").toInt
  implicit def toLong(e: JsonElement) : Long = ^(e.asString).stripSuffix(".0").toLong
  implicit def toList(e: JsonElement) : List[String] = e.toList



  def parse(json: String) = JSON.parseFull(json) map (JsonElement(_))

  def apply(any : Any) : JsonElement = any match {
    case x : Seq[Any] => new ArrayElement(x)
    case x : Map[String, Any] => new ComplexElement(x)
    case x => new PrimitiveElement(x)
  }
}

case class PrimitiveElement(x: Any) extends JsonElement{
  override def asString = x.toString
}

case object EmptyElement extends JsonElement{
  override def asString = ""
  override def toList = Nil
}

case class ArrayElement(private val x: Seq[Any]) extends JsonElement{
  private lazy val elements = x.map((JsonElement(_))).toArray

  override def applyDynamic(field: String)(i: Int) : JsonElement = elements.lift(i).getOrElse(EmptyElement)
  override def toList : List[String] = elements map (_.asString) toList
  override def length$ : Int = elements.length
}

case class ComplexElement(private val fields : Map[String, Any]) extends JsonElement{
  override def selectDynamic(field: String) : JsonElement = fields.get(field) map(JsonElement(_)) getOrElse(EmptyElement)
}