sealed trait DB[T, InnerContext[_], HanderReturnType] {
  type InnerHandler = Handler[HanderReturnType, InnerContext]
  type OuterHandler = Handler[InnerContext[HanderReturnType], Try]
  type Mapped[T] = DB[T, InnerContext, HanderReturnType]

  val value: Try[InnerContext[T]]

  def map[R](f: T => R): Mapped[R]
  def flatMap[R](f: T => Mapped[R]): Mapped[R]

  def purify: DB.Pure[InnerContext[T]] = DbPure(value)
  def reify: Try[InnerContext[T]] = value

  def run[R <: HanderReturnType](f: T => R)(implicit innerHandler: InnerHandler, outerHandler: OuterHandler): R
}