import scala.util.control.TailCalls

  private val onError: PartialFunction[Throwable, TailCalls.TailRec[TestTrace[Nothing]]] = {
    case ex if NonFatal(ex) =>
      ex.setStackTrace(ex.getStackTrace.filterNot { (ste: StackTraceElement) =>
        ste.getClassName.startsWith("zio.test.TestArrow")
      })
      TailCalls.done(TestTrace.die(ex))
  }

  private def runLoop[A, B](arrow: TestArrow[A, B], in: Either[Throwable, A]): TailCalls.TailRec[TestTrace[B]] =
    TailCalls.tailcall(arrow match {
      case TestArrowF(f) =>
        try TailCalls.done(f(in))
        catch onError

      case AndThen(f, g) =>
        runLoop(f, in).flatMap { t1 =>
          t1.result match {
            case _: Result.Fail.type   => TailCalls.done(t1.asInstanceOf[TestTrace[B]])
            case Result.Die(err)       => runLoop(g, Left(err)).map(t1 >>> _)
            case Result.Succeed(value) => runLoop(g, Right(value)).map(t1 >>> _)
          }
        }

      case And(lhs, rhs) =>
        for {
          l <- runLoop(lhs, in)
          r <- runLoop(rhs, in)
        } yield l && r

      case Or(lhs, rhs) =>
        for {
          l <- runLoop(lhs, in)
          r <- runLoop(rhs, in)
        } yield l || r

      case Not(arrow) =>
        runLoop(arrow, in).map(!_)

      case Suspend(f) =>
        in match {
          case Left(exception) =>
            TailCalls.done(TestTrace.die(exception))
          case Right(value) =>
            try runLoop(f(value), in)
            catch onError
        }

      case Meta(arrow, span, parentSpan, code, location, completeCode, customLabel, genFailureDetails) =>
        runLoop(arrow, in).map {
          _.withSpan(span)
            .withCode(code)
            .withParentSpan(parentSpan)
            .withLocation(location)
            .withCompleteCode(completeCode)
            .withCustomLabel(customLabel)
            .withGenFailureDetails(genFailureDetails)
        }
    })

  def run[A, B](arrow: TestArrow[A, B], in: Either[Throwable, A]): TestTrace[B] =
    (try runLoop(arrow, in)
    catch onError).result