Concurrency and Fibers

/**
 * Start IO as a fiber running concurrently
 * @returns IO[Fiber[IO, Throwable, A]] - Handle to the running fiber
 */
def start: IO[Fiber[IO, Throwable, A]]

/**
 * Start IO in background with automatic cleanup
 * @returns Resource[IO, IO[Outcome[IO, Throwable, A]]] - Resource managing fiber lifecycle
 */
def background: Resource[IO, IO[Outcome[IO, Throwable, A]]]

/**
 * Cancel the fiber
 * @returns IO[Unit] that completes when cancellation is processed
 */
def cancel: IO[Unit] // On Fiber

/**
 * Wait for fiber completion
 * @returns IO[Outcome[IO, Throwable, A]] with fiber result
 */
def join: IO[Outcome[IO, Throwable, A]] // On Fiber

/**
 * Join fiber, treating cancellation as never completing
 * @returns IO[A] that waits for successful completion
 */
def joinWithNever: IO[A] // On Fiber

/**
 * Join fiber with custom cancellation handling
 * @param onCancel - IO to run if fiber was canceled
 * @returns IO[A] with custom cancellation behavior
 */
def joinWith[AA >: A](onCancel: IO[AA]): IO[AA] // On Fiber

/**
 * Race two IOs, returning the winner
 * @param other - IO to race against
 * @returns IO[Either[A, B]] with winner indicated by Left/Right
 */
def race[B](other: IO[B]): IO[Either[A, B]]

/**
 * Race two IOs, getting full outcome information
 * @param other - IO to race against  
 * @returns IO with winner outcome and loser fiber
 */
def racePair[B](other: IO[B]): IO[Either[
  (Outcome[IO, Throwable, A], Fiber[IO, Throwable, B]),
  (Fiber[IO, Throwable, A], Outcome[IO, Throwable, B])
]]

/**
 * Run two IOs in parallel, collecting both results
 * @param other - IO to run in parallel
 * @returns IO[(A, B)] with both results
 */
def both[B](other: IO[B]): IO[(A, B)]

/**
 * Run IOs in parallel using Parallel instance
 * @param ios - IOs to run in parallel
 * @returns IO with sequence of results
 */
def IO.parSequenceN[A](n: Int)(ios: List[IO[A]]): IO[List[A]]

/**
 * Traverse in parallel with limited concurrency
 * @param n - Maximum concurrent operations
 * @param f - Function to apply to each element
 * @returns IO with sequence of results
 */
def IO.parTraverseN[A, B](n: Int)(as: List[A])(f: A => IO[B]): IO[List[B]]

/**
 * Replicate IO in parallel with limited concurrency
 * @param n - Maximum concurrent operations
 * @param replicas - Number of replicas to create
 * @param ioa - IO to replicate
 * @returns IO with sequence of replica results
 */
def IO.parReplicateAN[A](n: Int)(replicas: Int, ioa: IO[A]): IO[List[A]]

/**
 * Create a concurrent mutable reference
 * @param initial - Initial value
 * @returns IO[Ref[IO, A]] containing the reference
 */
def Ref.of[A](initial: A): IO[Ref[IO, A]]

/**
 * Read current value atomically
 * @returns IO[A] with current value
 */
def get: IO[A] // On Ref

/**
 * Update value atomically
 * @param a - New value
 * @returns IO[Unit] completing when update is done
 */
def set(a: A): IO[Unit] // On Ref

/**
 * Atomic compare-and-set operation
 * @param expected - Expected current value
 * @param updated - New value to set
 * @returns IO[Boolean] indicating if update succeeded
 */
def compareAndSet(expected: A, updated: A): IO[Boolean] // On Ref

/**
 * Atomic modify with return value
 * @param f - Function to compute new value and result
 * @returns IO[B] with the computed result
 */
def modify[B](f: A => (A, B)): IO[B] // On Ref

/**
 * Atomic update
 * @param f - Update function
 * @returns IO[Unit] completing when update is done
 */
def update(f: A => A): IO[Unit] // On Ref

/**
 * Non-blocking update attempt
 * @param f - Update function
 * @returns IO[Boolean] indicating if update succeeded
 */
def tryUpdate(f: A => A): IO[Boolean] // On Ref

/**
 * Atomic access with separate getter/setter
 * @returns IO[(A, A => IO[Boolean])] with value and setter
 */
def access: IO[(A, A => IO[Boolean])] // On Ref

/**
 * Create an empty Deferred
 * @returns IO[Deferred[IO, A]] - Empty deferred value
 */
def Deferred[A]: IO[Deferred[IO, A]]

/**
 * Wait for completion (blocks until value available)
 * @returns IO[A] with the completed value
 */
def get: IO[A] // On Deferred

/**
 * Check for completion without blocking
 * @returns IO[Option[A]] - Some(value) if complete, None if still waiting
 */
def tryGet: IO[Option[A]] // On Deferred

/**
 * Complete the deferred with a value
 * @param a - Value to complete with
 * @returns IO[Unit] completing when value is set
 */
def complete(a: A): IO[Unit] // On Deferred

/**
 * Try to complete the deferred (non-blocking)
 * @param a - Value to complete with
 * @returns IO[Boolean] indicating if completion succeeded
 */
def tryComplete(a: A): IO[Boolean] // On Deferred

/**
 * Memoize an IO computation
 * @returns IO[IO[A]] - Memoized version that caches result
 */
def memoize: IO[IO[A]]

/**
 * Run IO on specific execution context
 * @param ec - ExecutionContext to use
 * @returns IO that runs on the specified context
 */
def evalOn(ec: ExecutionContext): IO[A]

/**
 * Get current execution context
 * @returns IO[ExecutionContext] with current context
 */
def IO.executionContext: IO[ExecutionContext]

/**
 * Interruptible blocking operation
 * @param thunk - Blocking computation
 * @returns IO that can be interrupted
 */
def IO.interruptible[A](thunk: => A): IO[A]

/**
 * Interruptible with many interruption points
 * @param thunk - Blocking computation with interruption checks
 * @returns IO that checks for interruption frequently
 */
def IO.interruptibleMany[A](thunk: => A): IO[A]

import cats.effect._
import cats.syntax.parallel._
import scala.concurrent.duration._

// Basic fiber usage
val fiberProgram = for {
  fiber <- IO.delay {
    Thread.sleep(1000)
    "Fiber result"
  }.start
  
  // Do other work while fiber runs
  _ <- IO.println("Doing other work...")
  
  // Wait for fiber completion
  result <- fiber.joinWithNever
  _ <- IO.println(s"Fiber completed with: $result")
} yield result

// Racing operations
val raceProgram = {
  val fast = IO.sleep(100.millis).as("Fast")
  val slow = IO.sleep(1.second).as("Slow")
  
  fast.race(slow).map {
    case Left(result) => s"Fast won: $result"
    case Right(result) => s"Slow won: $result"
  }
}

// Concurrent coordination with Ref
val coordinated = for {
  counter <- Ref.of[IO, Int](0)
  
  // Start multiple fibers updating counter
  fibers <- List.fill(10)(
    counter.update(_ + 1)
  ).parSequence
  
  finalCount <- counter.get
  _ <- IO.println(s"Final count: $finalCount")
} yield finalCount

// Producer-consumer with Deferred
val producerConsumer = for {
  deferred <- Deferred[IO, String]
  
  // Producer fiber
  producer <- (IO.sleep(1.second) >> 
               deferred.complete("Produced value")).start
  
  // Consumer fiber  
  consumer <- deferred.get.map(value => 
                s"Consumed: $value").start
                
  result <- consumer.joinWithNever
  _ <- producer.join
} yield result