commonMain.reset.kt Maven / Gradle / Ivy

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Provides fully-fledged multishot delimitied continuations in Kotlin with Coroutines
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import arrow.core.identity
import kotlinx.coroutines.CancellationException
import kotlin.coroutines.*
import kotlin.coroutines.intrinsics.*

@Target(AnnotationTarget.CLASS, AnnotationTarget.TYPE, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY)
@DslMarker
public annotation class ResetDsl

public class SubCont internal constructor(
  private var init: Segment?,
  private val prompt: Prompt
) {
  public fun clear() {
    init = null
  }

  private fun composedWith(
    k: Continuation, isDelimiting: Boolean, shouldClear: Boolean
  ) = (init!! prependTo collectStack(k).let { if (isDelimiting) it.pushPrompt(prompt) else it }).also {
    if (shouldClear) clear()
  }

  @ResetDsl
  public suspend fun pushSubContWith(
    value: Result,
    isDelimiting: Boolean = false,
    shouldClear: Boolean = false,
  ): R = suspendCoroutineUnintercepted { k ->
    composedWith(k, isDelimiting, shouldClear).resumeWith(value, isIntercepted = true)
  }

  @ResetDsl
  public suspend fun pushSubCont(
    isDelimiting: Boolean = false,
    shouldClear: Boolean = false,
    value: suspend () -> T
  ): R = suspendCoroutineUnintercepted { k ->
    value.startCoroutine(WrapperCont(composedWith(k, isDelimiting, shouldClear)))
  }

  public fun copy(): SubCont = SubCont(init, prompt)
}

@ResetDsl
public suspend fun  Prompt.pushPrompt(
  body: suspend () -> R
): R = suspendCoroutineUnintercepted { k ->
  val stack = collectStack(k)
  body.startCoroutine(WrapperCont(stack.pushPrompt(this)))
}

/*
suspendCoroutineUnintercepted { k ->
  val stack = collectStack(k).pushPrompt(this)
  stack.resumeWith(runCatching {
    body.startCoroutineUninterceptedOrReturn(WrapperCont(stack)).also {
      if (it == COROUTINE_SUSPENDED) return@suspendCoroutineUnintercepted
    } as R
  }, isIntercepted = true)
}
 */

public suspend fun  Reader.pushReader(value: T, fork: T.() -> T = ::identity, body: suspend () -> R): R =
  suspendCoroutineUnintercepted { k ->
    val stack = collectStack(k)
    body.startCoroutine(WrapperCont(stack.pushReader(this, value, fork)))
  }


@ResetDsl
public suspend fun  nonReentrant(
  body: suspend () -> R
): R = runCC(body)

public suspend fun  Reader.deleteBinding(): Unit = suspendCoroutineUnintercepted { k ->
  val stack = collectStack(k)
  val toResume: SplitSeq = when (stack) {
    is EmptyCont -> error("Reader not found $this")
    is FramesCont<*, *, *, *> -> {
      stack.rest!!.deleteReader(this, stack)
      stack
    }

    is PromptCont -> {
      stack.rest!!.deleteReader(this, stack)
      stack
    }

    is ReaderCont<*, Unit, *, *> -> {
      if (this === stack.p) {
        stack.rest!!
      } else {
        stack.rest!!.deleteReader(this, stack)
        stack
      }
    }
  }
  toResume.resumeWith(Result.success(Unit), isIntercepted = true)
}

private fun  SplitSeq<*, *, *>.holeFor(prompt: Prompt, deleteDelimiter: Boolean): SplitSeq {
  val splitSeq = find(prompt)
  return if (deleteDelimiter) splitSeq else splitSeq.pushPrompt(prompt)
}

@ResetDsl
public suspend fun  Prompt.takeSubCont(
  deleteDelimiter: Boolean = true, body: suspend (SubCont) -> R
): T = suspendCoroutineUnintercepted { k ->
  val stack = collectStack(k)
  val (init, rest) = stack.splitAt(this)
  body.startCoroutine(SubCont(init, this), WrapperCont(if (deleteDelimiter) rest else rest.pushPrompt(this)))
}

@ResetDsl
public suspend fun  Prompt.takeSubContOnce(
  deleteDelimiter: Boolean = true, body: suspend (SubCont) -> R
): T = suspendCoroutineUnintercepted { k ->
  val stack = collectStack(k)
  val (init, rest) = stack.splitAtOnce(this)
  body.startCoroutine(SubCont(init, this), WrapperCont(if (deleteDelimiter) rest else rest.pushPrompt(this)))
}

@ResetDsl
public suspend fun  Prompt.takeSubContWithFinal(
  deleteDelimiter: Boolean = true, body: suspend (Pair, SubCont>) -> R
): T = suspendCoroutineUnintercepted { k ->
  val stack = collectStack(k)
  val (reusableInit, _) = stack.splitAt(this)
  val (init, rest) = stack.splitAtOnce(this)
  body.startCoroutine(
    SubCont(reusableInit, this) to SubCont(init, this),
    WrapperCont(if (deleteDelimiter) rest else rest.pushPrompt(this))
  )
}

// Acts like shift0/control { it(body()) }
// TODO make it faster
@ResetDsl
public suspend fun  Prompt.inHandlingContext(
  includeBodyContext: Boolean = false, body: suspend () -> T
): T = takeSubCont(!includeBodyContext) { k ->
  k.pushSubContWith(runCatching { body() }, isDelimiting = !includeBodyContext)
}

@Suppress("UNCHECKED_CAST")
internal fun  Prompt.abortWith(deleteDelimiter: Boolean, value: Result): Nothing =
  throw AbortWithValueException(this as Prompt, value, deleteDelimiter)

@Suppress("UNCHECKED_CAST")
internal suspend fun  Prompt.abortWithFast(deleteDelimiter: Boolean, value: Result): Nothing =
  suspendCoroutineUnintercepted { k ->
    collectStack(k).holeFor(this, deleteDelimiter).resumeWith(value, isIntercepted = true)
  }

private class AbortWithValueException(
  private val prompt: Prompt, private val value: Result, private val deleteDelimiter: Boolean
) : SeekingStackException() {
  override fun use(stack: SplitSeq<*, *, *>) =
    stack.holeFor(prompt, deleteDelimiter).resumeWith(value, isIntercepted = true)
}

@Suppress("UNCHECKED_CAST")
internal fun  Prompt.abortS(deleteDelimiter: Boolean = false, value: suspend () -> R): Nothing =
  throw AbortWithProducerException(this as Prompt, value, deleteDelimiter)

private class AbortWithProducerException(
  private val prompt: Prompt, private val value: suspend () -> Any?, private val deleteDelimiter: Boolean
) : SeekingStackException() {
  override fun use(stack: SplitSeq<*, *, *>) = value.startCoroutine(WrapperCont(stack.holeFor(prompt, deleteDelimiter)))
}

public class Prompt
public class Reader

@Suppress("EXPECT_ACTUAL_CLASSIFIERS_ARE_IN_BETA_WARNING")
internal expect abstract class SeekingStackException() : CancellationException {
  abstract fun use(stack: SplitSeq<*, *, *>)
}

public suspend fun  runCC(body: suspend () -> R): R = suspendCoroutine {
  body.startCoroutine(WrapperCont(EmptyCont(it)))
}

private suspend inline fun  suspendCoroutineUnintercepted(
  crossinline block: (Continuation) -> Unit
): T = suspendCoroutineUninterceptedOrReturn {
  block(it)
  COROUTINE_SUSPENDED
}