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package sjsonnet

/**
 * Typeclasses for easy conversion between [[Val]]s and Scala data types
 */
sealed abstract class ReadWriter[T] {
  def apply(t: Val): T
  def write(pos: Position, t: T): Val
}
object ReadWriter {
  implicit def OptionReadWriter[T](implicit r: ReadWriter[T]): ReadWriter[Option[T]] =
    new ReadWriter[Option[T]] {
      def apply(t: Val): Option[T] = t match {
        case Val.Null(_) => None
        case other       => Some(r(other))
      }

      def write(pos: Position, t: Option[T]): Val = t match {
        case None    => Val.Null(pos)
        case Some(v) => r.write(pos, v)
      }
    }
  implicit object StringRead extends ReadWriter[String] {
    def apply(t: Val): String = t.asString
    def write(pos: Position, t: String): sjsonnet.Val.Str = Val.Str(pos, t)
  }
  implicit object BooleanRead extends ReadWriter[Boolean] {
    def apply(t: Val): Boolean = t.asBoolean
    def write(pos: Position, t: Boolean): sjsonnet.Val.Bool = Val.bool(pos, t)
  }
  implicit object IntRead extends ReadWriter[Int] {
    def apply(t: Val): Int = t.asInt
    def write(pos: Position, t: Int): sjsonnet.Val.Num = Val.Num(pos, t.toDouble)
  }
  implicit object LongRead extends ReadWriter[Long] {
    def apply(t: Val): Long = t.asLong
    def write(pos: Position, t: Long): sjsonnet.Val.Num = Val.Num(pos, t.toDouble)
  }
  implicit object DoubleRead extends ReadWriter[Double] {
    def apply(t: Val): Double = t.asDouble
    def write(pos: Position, t: Double): sjsonnet.Val.Num = Val.Num(pos, t)
  }
  implicit object ValRead extends ReadWriter[Val] {
    def apply(t: Val): Val = t
    def write(pos: Position, t: Val): Val = t
  }
  implicit object ObjRead extends ReadWriter[Val.Obj] {
    def apply(t: Val): Val.Obj = t.asObj
    def write(pos: Position, t: Val.Obj): sjsonnet.Val.Obj = t
  }
  implicit object ArrRead extends ReadWriter[Val.Arr] {
    def apply(t: Val): Val.Arr = t.asArr
    def write(pos: Position, t: Val.Arr): sjsonnet.Val.Arr = t
  }
  implicit object FuncRead extends ReadWriter[Val.Func] {
    def apply(t: Val): Val.Func = t.asFunc
    def write(pos: Position, t: Val.Func): sjsonnet.Val.Func = t
  }
  implicit object BuiltinRead extends ReadWriter[Val.Builtin] {
    def apply(t: Val): Val.Builtin = t.asInstanceOf[Val.Builtin]
    def write(pos: Position, t: Val.Builtin): sjsonnet.Val.Builtin = t
  }
  implicit object LiteralRead extends ReadWriter[Val.Literal] {
    def apply(t: Val): Val.Literal = t match {
      case literal: Val.Literal => literal
      case other =>
        Error.fail("Wrong parameter type: expected Val.Literal" + ", got " + other.prettyName)
    }

    def write(pos: Position, t: Val.Literal): sjsonnet.Val.Literal = t
  }
}