commonMain.effekt.handler.kt Maven / Gradle / Ivy

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Provides fully-fledged multishot delimitied continuations in Kotlin with Coroutines
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package effekt

import Prompt
import Reader
import abortS0
import abortWith0
import abortWithFast
import ask
import pushReader
import reset
import takeSubCont
import takeSubContOnce
import takeSubContWithFinal
import kotlin.jvm.JvmInline

public interface Handler {
  public fun prompt(): HandlerPrompt
}

public interface StatefulHandler : Handler {
  public val reader: Reader
}

public suspend fun  StatefulHandler.get(): S = reader.ask()

public suspend inline fun  Handler.use(crossinline body: suspend (Cont) -> E): A =
  prompt().prompt.takeSubCont { sk ->
    body(Cont(sk))
  }

public suspend inline fun  Handler.useOnce(crossinline body: suspend (Cont) -> E): A =
  prompt().prompt.takeSubContOnce { sk ->
    body(Cont(sk))
  }

public suspend inline fun  Handler.useWithFinal(crossinline body: suspend (Pair, Cont>) -> E): A =
  prompt().prompt.takeSubContWithFinal { sk ->
    body(Cont(sk.first) to Cont(sk.second))
  }

public fun  Handler.discard(body: suspend () -> E): Nothing = prompt().prompt.abortS0(body)

public fun  Handler.discardWith(value: Result): Nothing = prompt().prompt.abortWith0(value)

public suspend fun  Handler.discardWithFast(value: Result): Nothing = prompt().prompt.abortWithFast(deleteDelimiter = true, value)

public suspend fun  handle(
  handler: ((() -> HandlerPrompt) -> H), body: suspend H.() -> E
): E = handle { handler { this }.body() }

public suspend fun  handle(body: suspend HandlerPrompt.() -> E): E = with(HandlerPrompt()) {
  handle { body() }
}

public suspend fun  Handler.handle(body: suspend () -> E): E = prompt().prompt.reset(body)

public suspend fun , S> handleStateful(
  handler: ((() -> StatefulPrompt) -> H), value: S, fork: S.() -> S,
  body: suspend H.() -> E
): E {
  val p = StatefulPrompt()
  val h = handler { p }
  return h.handleStateful(value, fork) { h.body() }
}

public suspend fun  handleStateful(
  value: S, fork: S.() -> S, body: suspend StatefulPrompt.() -> E
): E = with(StatefulPrompt()) {
  handleStateful(value, fork) { body() }
}

public suspend fun  StatefulHandler.handleStateful(
  value: S, fork: S.() -> S,
  body: suspend () -> E
): E = reader.pushReader(value, fork) {
  prompt().prompt.reset(body)
}

@JvmInline
public value class HandlerPrompt private constructor(@PublishedApi internal val prompt: Prompt) : Handler {
  public constructor() : this(Prompt())

  override fun prompt(): HandlerPrompt = this
}

public class StatefulPrompt(
  private val prompt: HandlerPrompt = HandlerPrompt(), override val reader: Reader = Reader()
) : StatefulHandler, Handler by prompt

@JvmInline
public value class Cont @PublishedApi internal constructor(internal val subCont: SubCont) {
  public suspend fun resumeWith(value: Result, shouldClear: Boolean = false): R =
    subCont.pushSubContWith(value, isDelimiting = true, shouldClear)

  public suspend operator fun invoke(value: T, shouldClear: Boolean = false): R =
    resumeWith(Result.success(value), shouldClear)

  public suspend fun resumeWithException(exception: Throwable, shouldClear: Boolean = false): R =
    resumeWith(Result.failure(exception), shouldClear)

  public fun copy(): Cont = Cont(subCont.copy())
  public fun clear() { subCont.clear() }
}