Actor System Management

/**
 * Abstract base class for actor systems providing core functionality
 */
abstract class ActorSystem extends ActorRefFactory with ClassicActorSystemProvider {
  /** The name of this actor system */
  def name: String
  
  /** The configuration settings for this system */
  def settings: Settings
  
  /** The event stream for system-wide event publishing */
  def eventStream: EventStream
  
  /** The scheduler for delayed and periodic tasks */
  def scheduler: Scheduler
  
  /** The dispatcher registry for message processing */
  def dispatchers: Dispatchers
  
  /** The log instance for this system */
  def log: LoggingAdapter
  
  /** The uptime of this system in milliseconds */
  def uptime: Long
  
  /** The start time of this system */
  def startTime: Long
  
  /** Terminates this actor system gracefully */
  def terminate(): Future[Terminated]
  
  /** Future that completes when the system has terminated */
  def whenTerminated: Future[Terminated]
}

object ActorSystem {
  /** Create an ActorSystem with default name and configuration */
  def create(): ActorSystem
  
  /** Create an ActorSystem with specified name */
  def create(name: String): ActorSystem
  
  /** Create an ActorSystem with specified name and configuration */
  def create(name: String, config: Config): ActorSystem
  
  /** Create an ActorSystem with name, config, and classloader */
  def create(name: String, config: Config, classLoader: ClassLoader): ActorSystem
  
  /** Create an ActorSystem with name, config, classloader, and executor */
  def create(name: String, config: Config, classLoader: ClassLoader, defaultExecutionContext: Option[ExecutionContext]): ActorSystem
  
  // Scala API methods
  def apply(): ActorSystem
  def apply(name: String): ActorSystem  
  def apply(name: String, config: Config): ActorSystem
  def apply(name: String, config: Config, classLoader: ClassLoader): ActorSystem
  def apply(name: String, config: Config, classLoader: ClassLoader, defaultExecutionContext: Option[ExecutionContext]): ActorSystem
}

import akka.actor.ActorSystem
import com.typesafe.config.ConfigFactory

// Create with default settings
val system = ActorSystem("MySystem")

// Create with custom configuration
val config = ConfigFactory.parseString("""
  akka {
    actor {
      provider = "local"
      default-dispatcher {
        throughput = 1
      }
    }
  }
""")
val configuredSystem = ActorSystem("ConfiguredSystem", config)

// Shutdown system
system.terminate()

/**
 * System configuration settings
 */
class Settings(cfg: Config, name: String, classLoader: ClassLoader) {
  /** The configuration object backing this settings */
  val config: Config = cfg
  
  /** The name of the actor system */
  val name: String
  
  /** The class loader used by this system */
  val classLoader: ClassLoader
  
  /** Configuration root path */
  val ConfigPath: String = "akka"
  
  /** The log level for this system */
  val LogLevel: String
  
  /** Whether to log configuration on start */
  val LogConfigOnStart: Boolean
  
  /** Home directory for the actor system */
  val Home: Option[String]
  
  /** The provider class for actor references */
  val ProviderClass: String
  
  /** Supervisor strategy for guardian actors */
  val SupervisorStrategyClass: String
  
  /** Creation timeout for actors */
  val CreationTimeout: Timeout
  
  /** Ask timeout for actor asks */
  val AskTimeout: Timeout
}

/**
 * Extended actor system providing additional internal functionality
 */
abstract class ExtendedActorSystem extends ActorSystem {
  /** The provider for actor references in this system */
  def provider: ActorRefProvider
  
  /** The guardian actor responsible for user actors */
  def guardian: InternalActorRef
  
  /** The system guardian actor */
  def systemGuardian: InternalActorRef
  
  /** The dead letters actor */
  def deadLetters: ActorRef
  
  /** Dynamic access for reflective operations */
  def dynamicAccess: DynamicAccess
  
  /** Thread factory for creating threads */
  def threadFactory: ThreadFactory
  
  /** Create a UID for actors */
  def uid: Int
  
  /** Looks up an extension by its ID */
  def extension[T <: Extension](ext: ExtensionId[T]): T
  
  /** Checks if an extension is registered */
  def hasExtension(ext: ExtensionId[_ <: Extension]): Boolean
}

/**
 * Bootstrap setup for actor system creation
 */
final class BootstrapSetup private (
  val config: Option[Config],
  val classLoader: Option[ClassLoader],
  val defaultExecutionContext: Option[ExecutionContext]
) extends Setup

object BootstrapSetup {
  /** Create bootstrap setup with default values */
  def apply(): BootstrapSetup
  
  /** Create bootstrap setup with specified config */
  def apply(config: Config): BootstrapSetup
  
  /** Create bootstrap setup with config and classloader */
  def apply(config: Config, classLoader: ClassLoader): BootstrapSetup
  
  /** Create bootstrap setup with all options */
  def apply(
    config: Config,
    classLoader: ClassLoader, 
    defaultExecutionContext: ExecutionContext
  ): BootstrapSetup
}

/**
 * Actor system setup combining multiple setup instances
 */
final class ActorSystemSetup private (private val setups: immutable.Seq[Setup]) {
  /** Get setup of specific type */
  def get[T <: Setup: ClassTag]: Option[T]
  
  /** Add or replace setup */
  def withSetup[T <: Setup](setup: T): ActorSystemSetup
}

object ActorSystemSetup {
  /** Create empty actor system setup */  
  def apply(): ActorSystemSetup
  
  /** Create setup with initial setup instances */
  def apply(setups: Setup*): ActorSystemSetup
}

/**
 * Actor reference provider selection
 */
abstract class ProviderSelection extends Setup

object ProviderSelection {
  /** Local provider for single-JVM deployments */
  case object Local extends ProviderSelection
  
  /** Remote provider for distributed deployments */  
  case object Remote extends ProviderSelection
  
  /** Cluster provider for clustered deployments */
  case object Cluster extends ProviderSelection
  
  /** Custom provider with specified class name */
  final case class Custom(fqcn: String) extends ProviderSelection
}

/**
 * Represents a terminated actor system
 */
final case class Terminated(ref: ActorRef) extends AutoReceivedMessage

/**
 * Coordinated shutdown management for graceful system termination
 */
class CoordinatedShutdown(system: ExtendedActorSystem) extends Extension {
  /** Run shutdown process */
  def run(reason: CoordinatedShutdown.Reason): Future[Done]
  
  /** Add task to shutdown phase */
  def addTask(phase: String, taskName: String)(task: () => Future[Done]): Unit
  
  /** Get shutdown reason if shutdown is in progress */
  def shutdownReason(): Option[CoordinatedShutdown.Reason]
}

object CoordinatedShutdown extends ExtensionId[CoordinatedShutdown] {
  /** Shutdown reasons */
  abstract class Reason(val name: String)
  
  case object ActorSystemTerminateReason extends Reason("actor-system-terminate")
  case object JvmExitReason extends Reason("jvm-exit")
  case object CLusterLeavingReason extends Reason("cluster-leaving")
  case object CLusterDowningReason extends Reason("cluster-downing")
  
  /** Shutdown phases */
  val PhaseBeforeServiceUnbind = "before-service-unbind"
  val PhaseServiceUnbind = "service-unbind"
  val PhaseServiceRequestsDone = "service-requests-done"
  val PhaseServiceStop = "service-stop"
  val PhaseBeforeClusterShutdown = "before-cluster-shutdown"
  val PhaseClusterShutdown = "cluster-shutdown"
  val PhaseBeforeActorSystemTerminate = "before-actor-system-terminate"
  val PhaseActorSystemTerminate = "actor-system-terminate"
}

import akka.actor.{ActorSystem, CoordinatedShutdown}
import scala.concurrent.duration._

val system = ActorSystem("MySystem")
val coordShutdown = CoordinatedShutdown(system)

// Add custom shutdown task
coordShutdown.addTask(CoordinatedShutdown.PhaseServiceStop, "cleanup-resources") { () =>
  // Cleanup logic here
  Future.successful(Done)
}

// Shutdown the system
coordShutdown.run(CoordinatedShutdown.ActorSystemTerminateReason)