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package izumi.functional.bio

import cats.effect.kernel.Outcome
import izumi.fundamentals.platform.language.Quirks.Discarder
import zio.ZIO
import zio.stacktracer.TracingImplicits.disableAutoTrace

sealed trait Exit[+E, +A] {
  def map[B](f: A => B): Exit[E, B]
  def leftMap[E1](f: E => E1): Exit[E1, A]
  def flatMap[E1 >: E, B](f: A => Exit[E1, B]): Exit[E1, B]
  def toThrowableEither(implicit ev: E <:< Throwable): Either[Throwable, A]
}

object Exit {

  /** Tracing information about the error `E` */
  trait Trace[+E] {
    def asString: String

    /** The returned Throwable must contain some mention of the error `E`, if not the original error fully */
    def toThrowable: Throwable

    /**
      * Try to Unsafely Mutate the contained Throwable (if any) to attach this Trace's debugging information to it and return it.
      *
      * If the Throwable cannot be mutated to attach tracing information to it, may create a new Throwable with the tracing information.
      *
      * The returned Throwable must contain some mention of the error `E`, if not the original error fully.
      *
      * @note may mutate arbitrary Throwables contained in the trace, discard all throwables that came from the same source
      * @param conv convert any contained typed errors into a Throwable
      */
    def unsafeAttachTraceOrReturnNewThrowable(conv: E => Throwable): Throwable

    final def unsafeAttachTraceOrReturnNewThrowable(): Throwable = unsafeAttachTraceOrReturnNewThrowable(TypedError(_))

    def map[E1](f: E => E1): Trace[E1]

    override final def toString: String = asString
  }
  object Trace {
    def forTypedError[E](error: E): Trace[E] = error match {
      case t: Throwable => ThrowableTrace(t)
      case e => ThrowableTrace(TypedError(e))
    }

    def forUnknownError: Trace[Nothing] = new Trace[Nothing] {
      override val asString: String = ""
      override def toThrowable: Throwable = new RuntimeException(asString)
      override def unsafeAttachTraceOrReturnNewThrowable(conv: Nothing => Throwable): Throwable = toThrowable
      override def map[E1](f: Nothing => E1): Trace[E1] = this
    }

    final case class ZIOTrace[+E](cause: zio.Cause[E]) extends Trace[E] {
      override def asString: String = cause.prettyPrint
      override def toThrowable: Throwable = zio.FiberFailure(cause)
      override def unsafeAttachTraceOrReturnNewThrowable(conv: E => Throwable): Throwable = {
        val zio2ThrowableWithSuppressedAttached = cause.squashTraceWith {
          case t: Throwable => t
          case e => conv(e)
        }
        if (zio2ThrowableWithSuppressedAttached.getSuppressed.isEmpty) {
          // Throwable has disabled suppression, return full cause instead (add stackless like its added in squashTraceWith, NB stackless removes Throwable stacktraces, not monadic traces)
          zio.FiberFailure(zio.Cause.stackless(cause))
        } else {
          zio2ThrowableWithSuppressedAttached
        }
      }
      override def map[E1](f: E => E1): Trace[E1] = ZIOTrace(cause.map(f))
    }

    final case class ThrowableTrace(toThrowable: Throwable) extends Trace[Nothing] {
      override def asString: String = {
        import java.io.{PrintWriter, StringWriter}
        val sw = new StringWriter
        val pw = new PrintWriter(sw)
        toThrowable.printStackTrace(pw)
        sw.toString
      }
      override def unsafeAttachTraceOrReturnNewThrowable(conv: Nothing => Throwable): Throwable = toThrowable
      override def map[E1](f: Nothing => E1): Trace[E1] = this
    }
  }

  sealed trait Uninterrupted[+E, +A] extends Exit[E, A]

  final case class Success[+A](value: A) extends Exit.Uninterrupted[Nothing, A] {
    override def map[B](f: A => B): Success[B] = Success(f(value))
    override def leftMap[E1](f: Nothing => E1): this.type = this
    override def flatMap[E1 >: Nothing, B](f: A => Exit[E1, B]): Exit[E1, B] = f(value)
    override def toThrowableEither(implicit ev: Nothing <:< Throwable): Either[Throwable, A] = Right(value)
  }

  sealed trait Failure[+E] extends Exit[E, Nothing] {
    def trace: Trace[E]

    def toEither: Either[List[Throwable], E]
    def toEitherCompound: Either[Throwable, E]

    final def toThrowable(implicit ev: E <:< Throwable): Throwable = toEitherCompound.fold(identity, ev)
    final def toThrowable(conv: E => Throwable): Throwable = toEitherCompound.fold(identity, conv)

    override final def map[B](f: Nothing => B): this.type = this
    override final def flatMap[E1 >: E, B](f: Nothing => Exit[E1, B]): this.type = this
  }

  sealed trait FailureUninterrupted[+E] extends Exit.Failure[E] with Exit.Uninterrupted[E, Nothing]

  final case class Error[+E](error: E, trace: Trace[E]) extends Exit.FailureUninterrupted[E] {
    override def toEither: Right[Nothing, E] = Right(error)
    override def toEitherCompound: Right[Nothing, E] = Right(error)
    override def toThrowableEither(implicit ev: E <:< Throwable): Either[Throwable, Nothing] = Left(ev(error))
    override def leftMap[E1](f: E => E1): Error[E1] = Error[E1](f(error), trace.map(f))
  }

  final case class Termination(compoundException: Throwable, allExceptions: List[Throwable], trace: Trace[Nothing]) extends Exit.FailureUninterrupted[Nothing] {
    override def toEither: Left[List[Throwable], Nothing] = Left(allExceptions)
    override def toEitherCompound: Left[Throwable, Nothing] = Left(compoundException)
    override def toThrowableEither(implicit ev: Nothing <:< Throwable): Either[Throwable, Nothing] = Left(compoundException)
    override def leftMap[E1](f: Nothing => E1): this.type = this
  }
  object Termination {
    def apply(exception: Throwable, trace: Trace[Nothing]): Termination = new Termination(exception, List(exception), trace)
  }

  final case class Interruption(compoundException: Throwable, otherExceptions: List[Throwable], trace: Trace[Nothing]) extends Exit.Failure[Nothing] {
    override def toEither: Left[List[Throwable], Nothing] = Left(List(compoundException))
    override def toEitherCompound: Left[Throwable, Nothing] = Left(compoundException)
    override def toThrowableEither(implicit ev: Nothing <:< Throwable): Either[Throwable, Nothing] = Left(compoundException)
    override def leftMap[E1](f: Nothing => E1): this.type = this
  }
  object Interruption {
    def apply(otherExceptions: List[Throwable], trace: Trace[Nothing]): Interruption = new Interruption(trace.toThrowable, otherExceptions, trace)
  }

  object ZIOExit {
    def toExit[E, A](result: zio.Exit[E, A])(outerInterruptionConfirmed: Boolean): Exit[E, A] = result match {
      case zio.Exit.Success(v) =>
        Success(v)
      case zio.Exit.Failure(cause) =>
        toExit(cause)(outerInterruptionConfirmed)
    }

    def toExit[E](cause: zio.Cause[E])(outerInterruptionConfirmed: Boolean): Exit.Failure[E] = {
      // ZIO 2, unlike ZIO 1, _does not_ guarantee that the presence of a typed failure
      // means we're NOT interrupting, so we have to check for interruption to matter what
      if ((cause.isInterrupted || {
          // deem empty cause to be interruption as well, due to occasional invalid ZIO states
          // in `ZIO.fail().uninterruptible` caused by this line https://github.com/zio/zio/blob/22921ee5ac0d2e03531f8b37dfc0d5793a467af8/core/shared/src/main/scala/zio/internal/FiberContext.scala#L415=
          // NOTE: this line is for ZIO 1, it may not apply for ZIO 2, someone needs to debunk
          // whether this is required
          cause.isEmpty
        }) && outerInterruptionConfirmed) {
        val causeNoTypedErrors = cause.stripFailures // lose typed failures if there were some. Oh well
        val trace = Trace.ZIOTrace(causeNoTypedErrors)
        Interruption(cause.defects, trace)
      } else {
        toExitUninterrupted(cause)
      }
    }

    def toExitUninterrupted[E](cause: zio.Cause[E]): Exit.FailureUninterrupted[E] = {
      cause.failureOrCause match {
        case Left(error) =>
          Error(error, Trace.ZIOTrace(cause))
        case Right(cause) =>
          val exceptions = cause.defects
          val compound = exceptions match {
            case e :: Nil => e
            case _ => zio.FiberFailure(cause)
          }
          Termination(compound, exceptions, Trace.ZIOTrace(cause))
      }
    }

    def fromExit[E, A](exit: Exit[E, A]): zio.Exit[E, A] = exit match {
      case Success(value) =>
        zio.Exit.Success(value)
      case failure: Failure[E] =>
        zio.Exit.Failure(causeFromExit(failure))
    }

    def causeFromExit[E](failure: Failure[E]): zio.Cause[E] = {
      failure.trace match {
        case Trace.ZIOTrace(cause) =>
          cause
        case _ =>
          failure match {
            case Error(error, _) =>
              zio.Cause.fail(error)

            case Termination(_, headException :: tailExceptions, _) =>
              tailExceptions.foldLeft(zio.Cause.die(headException))(_ ++ zio.Cause.die(_))
            case Termination(compoundException, _, _) =>
              zio.Cause.die(compoundException)

            case Interruption(_, headException :: tailExceptions, _) =>
              zio.Cause.interrupt(zio.FiberId.None) ++ tailExceptions.foldLeft(zio.Cause.die(headException))(_ ++ zio.Cause.die(_))
            case Interruption(_, _, _) =>
              zio.Cause.interrupt(zio.FiberId.None)
          }
      }
    }

    def ZIOSignalOnNoExternalInterruptFailure[R, E, A](f: ZIO[R, E, A])(signalOnNonInterrupt: => ZIO[R, Nothing, Any])(implicit trace: zio.Trace): ZIO[R, E, A] = {
      f.onExit {
        case zio.Exit.Success(_) =>
          ZIO.unit
        case zio.Exit.Failure(_) =>
          // we don't check if cause is interrupted
          // because we can get an invalid state Cause.empty
          // due to this line https://github.com/zio/zio/blob/22921ee5ac0d2e03531f8b37dfc0d5793a467af8/core/shared/src/main/scala/zio/internal/FiberContext.scala#L415=
          // if the last error was an uninterruptible typed error
          withIsInterruptedF(confirmedInterrupt => if (confirmedInterrupt) ZIO.unit else signalOnNonInterrupt)
      }
    }

    def withIsInterrupted[R, E, A](f: Boolean => A)(implicit trace: zio.Trace): ZIO[R, E, A] = {
      withIsInterruptedF[R, E, A](b => ZIO.succeed(f(b)))
    }

    def withIsInterruptedF[R, E, A](f: Boolean => ZIO[R, E, A])(implicit trace: zio.Trace): ZIO[R, E, A] = {
      ZIO.descriptorWith(desc => f(desc.interrupters.nonEmpty))
    }

  }

//  object MonixExit {
//    def toExit[E, A](exit: Either[Option[bio.Cause[E]], A]): Exit[E, A] = {
//      exit match {
//        case Left(None) => Interruption(new InterruptedException("The task was cancelled."), Trace.forUnknownError)
//        case Left(Some(error)) => toExit(error)
//        case Right(value) => Success(value)
//      }
//    }
//
//    def toExit[E, A](exit: Either[bio.Cause[E], A])(implicit d: DummyImplicit): Exit[E, A] = {
//      exit match {
//        case Left(error) => toExit(error)
//        case Right(value) => Success(value)
//      }
//    }
//
//    def toExit[E](cause: bio.Cause[E]): Exit.Failure[E] = {
//      cause match {
//        case bio.Cause.Error(value) => Exit.Error(value, Trace.forUnknownError)
//        case bio.Cause.Termination(value) => Exit.Termination(value, Trace.forUnknownError)
//      }
//    }
//  }

  object CatsExit {
    def exitToOutcomeThrowable[F[+_, +_], A](exit: Exit[Throwable, A])(implicit F: Applicative2[F]): Outcome[F[Throwable, +_], Throwable, A] = {
      toOutcomeThrowable(F.pure, exit)
    }
    def toOutcomeThrowable[F[_], A](pure: A => F[A], exit: Exit[Throwable, A]): Outcome[F, Throwable, A] = exit match {
      case Exit.Success(b) => Outcome.succeeded(pure(b))
      case Exit.Interruption(_, _, _) => Outcome.canceled
      case error @ Error(_, _) => Outcome.errored(error.toThrowable)
      case termination @ Termination(_, _, _) => Outcome.errored(termination.toThrowable)
    }
  }

  implicit lazy val ExitInstances: Monad2[Exit] & Bifunctor2[Exit] = new Monad2[Exit] with Bifunctor2[Exit] {
    override final val InnerF: Functor2[Exit] = this
    override final def pure[A](a: A): Exit[Nothing, A] = Exit.Success(a)
    override final def map[E, A, B](r: Exit[E, A])(f: A => B): Exit[E, B] = r.map(f)
    override final def bimap[E, A, E2, A2](r: Exit[E, A])(f: E => E2, g: A => A2): Exit[E2, A2] = r.leftMap(f).map(g)
    override final def leftMap[E, A, E2](r: Exit[E, A])(f: E => E2): Exit[E2, A] = r.leftMap(f)
    override final def flatMap[E, A, B](r: Exit[E, A])(f: A => Exit[E, B]): Exit[E, B] = r.flatMap(f)
  }

  disableAutoTrace.discard()
}




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