/**
 * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
 */

package akka.remote

import akka.actor._
import akka.dispatch.sysmsg._
import akka.event.{ Logging, LoggingAdapter, EventStream }
import akka.event.Logging.Error
import akka.serialization.{ JavaSerializer, Serialization, SerializationExtension }
import akka.pattern.pipe
import scala.util.control.NonFatal
import akka.actor.SystemGuardian.{ TerminationHookDone, TerminationHook, RegisterTerminationHook }
import scala.util.control.Exception.Catcher
import scala.concurrent.{ ExecutionContext, Future }
import scala.concurrent.forkjoin.ThreadLocalRandom
import com.typesafe.config.Config
import akka.ConfigurationException

/**
 * INTERNAL API
 */
private[akka] object RemoteActorRefProvider {
  private case class Internals(transport: RemoteTransport, serialization: Serialization, remoteDaemon: InternalActorRef)

  sealed trait TerminatorState
  case object Uninitialized extends TerminatorState
  case object Idle extends TerminatorState
  case object WaitDaemonShutdown extends TerminatorState
  case object WaitTransportShutdown extends TerminatorState
  case object Finished extends TerminatorState

  private class RemotingTerminator(systemGuardian: ActorRef) extends Actor with FSM[TerminatorState, Option[Internals]] {
    import context.dispatcher

    startWith(Uninitialized, None)

    when(Uninitialized) {
      case Event(i: Internals, _) ⇒
        systemGuardian ! RegisterTerminationHook
        goto(Idle) using Some(i)
    }

    when(Idle) {
      case Event(TerminationHook, Some(internals)) ⇒
        log.info("Shutting down remote daemon.")
        internals.remoteDaemon ! TerminationHook
        goto(WaitDaemonShutdown)
    }

    // TODO: state timeout
    when(WaitDaemonShutdown) {
      case Event(TerminationHookDone, Some(internals)) ⇒
        log.info("Remote daemon shut down; proceeding with flushing remote transports.")
        internals.transport.shutdown() pipeTo self
        goto(WaitTransportShutdown)
    }

    when(WaitTransportShutdown) {
      case Event((), _) ⇒
        log.info("Remoting shut down.")
        systemGuardian ! TerminationHookDone
        stop()
    }

  }

  /*
   * Remoting wraps messages destined to a remote host in a remoting specific envelope: EndpointManager.Send
   * As these wrapped messages might arrive to the dead letters of an EndpointWriter, they need to be unwrapped
   * and handled as dead letters to the original (remote) destination. Without this special case, DeathWatch related
   * functionality breaks, like the special handling of Watch messages arriving to dead letters.
   */
  private class RemoteDeadLetterActorRef(_provider: ActorRefProvider,
                                         _path: ActorPath,
                                         _eventStream: EventStream) extends DeadLetterActorRef(_provider, _path, _eventStream) {
    import EndpointManager.Send

    override def !(message: Any)(implicit sender: ActorRef): Unit = message match {
      case Send(m, senderOption, _, seqOpt) ⇒
        // else ignore: it is a reliably delivered message that might be retried later, and it has not yet deserved
        // the dead letter status
        if (seqOpt.isEmpty) super.!(m)(senderOption.orNull)
      case DeadLetter(Send(m, senderOption, recipient, seqOpt), _, _) ⇒
        // else ignore: it is a reliably delivered message that might be retried later, and it has not yet deserved
        // the dead letter status
        if (seqOpt.isEmpty) super.!(m)(senderOption.orNull)
      case _ ⇒ super.!(message)(sender)
    }

    @throws(classOf[java.io.ObjectStreamException])
    override protected def writeReplace(): AnyRef = DeadLetterActorRef.serialized
  }
}

/**
 * INTERNAL API
 * Depending on this class is not supported, only the [[akka.actor.ActorRefProvider]] interface is supported.
 *
 * Remote ActorRefProvider. Starts up actor on remote node and creates a RemoteActorRef representing it.
 *
 */
private[akka] class RemoteActorRefProvider(
  val systemName: String,
  val settings: ActorSystem.Settings,
  val eventStream: EventStream,
  val dynamicAccess: DynamicAccess) extends ActorRefProvider {
  import RemoteActorRefProvider._

  val remoteSettings: RemoteSettings = new RemoteSettings(settings.config)

  override val deployer: Deployer = createDeployer

  /**
   * Factory method to make it possible to override deployer in subclass
   * Creates a new instance every time
   */
  protected def createDeployer: RemoteDeployer = new RemoteDeployer(settings, dynamicAccess)

  private val local = new LocalActorRefProvider(systemName, settings, eventStream, dynamicAccess, deployer,
    Some(deadLettersPath ⇒ new RemoteDeadLetterActorRef(this, deadLettersPath, eventStream)))

  @volatile
  private var _log = local.log
  def log: LoggingAdapter = _log

  override def rootPath: ActorPath = local.rootPath
  override def deadLetters: InternalActorRef = local.deadLetters

  // these are only available after init()
  override def rootGuardian: InternalActorRef = local.rootGuardian
  override def guardian: LocalActorRef = local.guardian
  override def systemGuardian: LocalActorRef = local.systemGuardian
  override def terminationFuture: Future[Unit] = local.terminationFuture
  override def registerTempActor(actorRef: InternalActorRef, path: ActorPath): Unit = local.registerTempActor(actorRef, path)
  override def unregisterTempActor(path: ActorPath): Unit = local.unregisterTempActor(path)
  override def tempPath(): ActorPath = local.tempPath()
  override def tempContainer: VirtualPathContainer = local.tempContainer

  @volatile private var _internals: Internals = _

  def transport: RemoteTransport = _internals.transport
  def serialization: Serialization = _internals.serialization
  def remoteDaemon: InternalActorRef = _internals.remoteDaemon

  // This actor ensures the ordering of shutdown between remoteDaemon and the transport
  @volatile private var remotingTerminator: ActorRef = _

  @volatile private var remoteWatcher: ActorRef = _
  @volatile private var remoteDeploymentWatcher: ActorRef = _

  def init(system: ActorSystemImpl): Unit = {
    local.init(system)

    remotingTerminator = system.systemActorOf(Props(classOf[RemotingTerminator], local.systemGuardian), "remoting-terminator")

    val internals = Internals(
      remoteDaemon = {
        val d = new RemoteSystemDaemon(
          system,
          local.rootPath / "remote",
          rootGuardian,
          remotingTerminator,
          log,
          untrustedMode = remoteSettings.UntrustedMode)
        local.registerExtraNames(Map(("remote", d)))
        d
      },
      serialization = SerializationExtension(system),
      transport = new Remoting(system, this))

    _internals = internals
    remotingTerminator ! internals

    _log = Logging(eventStream, "RemoteActorRefProvider")

    // this enables reception of remote requests
    transport.start()

    remoteWatcher = createRemoteWatcher(system)
    remoteDeploymentWatcher = createRemoteDeploymentWatcher(system)
  }

  protected def createRemoteWatcher(system: ActorSystemImpl): ActorRef = {
    import remoteSettings._
    val failureDetector = createRemoteWatcherFailureDetector(system)
    system.systemActorOf(RemoteWatcher.props(
      failureDetector,
      heartbeatInterval = WatchHeartBeatInterval,
      unreachableReaperInterval = WatchUnreachableReaperInterval,
      heartbeatExpectedResponseAfter = WatchHeartbeatExpectedResponseAfter,
      numberOfEndHeartbeatRequests = WatchNumberOfEndHeartbeatRequests), "remote-watcher")
  }

  protected def createRemoteWatcherFailureDetector(system: ExtendedActorSystem): FailureDetectorRegistry[Address] = {
    def createFailureDetector(): FailureDetector = {
      import remoteSettings.{ WatchFailureDetectorImplementationClass ⇒ fqcn }
      system.dynamicAccess.createInstanceFor[FailureDetector](
        fqcn, List(classOf[Config] -> remoteSettings.WatchFailureDetectorConfig)).recover({
          case e ⇒ throw new ConfigurationException(
            s"Could not create custom remote watcher failure detector [$fqcn] due to: ${e.toString}", e)
        }).get
    }

    new DefaultFailureDetectorRegistry(() ⇒ createFailureDetector())
  }

  protected def createRemoteDeploymentWatcher(system: ActorSystemImpl): ActorRef =
    system.systemActorOf(Props[RemoteDeploymentWatcher], "remote-deployment-watcher")

  def actorOf(system: ActorSystemImpl, props: Props, supervisor: InternalActorRef, path: ActorPath,
              systemService: Boolean, deploy: Option[Deploy], lookupDeploy: Boolean, async: Boolean): InternalActorRef = {
    if (systemService) local.actorOf(system, props, supervisor, path, systemService, deploy, lookupDeploy, async)
    else {

      /*
       * This needs to deal with “mangled” paths, which are created by remote
       * deployment, also in this method. The scheme is the following:
       *
       * Whenever a remote deployment is found, create a path on that remote
       * address below “remote”, including the current system’s identification
       * as “sys@host:port” (typically; it will use whatever the remote
       * transport uses). This means that on a path up an actor tree each node
       * change introduces one layer or “remote/scheme/sys@host:port/” within the URI.
       *
       * Example:
       *
       * akka://sys@home:1234/remote/akka/sys@remote:6667/remote/akka/sys@other:3333/user/a/b/c
       *
       * means that the logical parent originates from “akka://sys@other:3333” with
       * one child (may be “a” or “b”) being deployed on “akka://sys@remote:6667” and
       * finally either “b” or “c” being created on “akka://sys@home:1234”, where
       * this whole thing actually resides. Thus, the logical path is
       * “/user/a/b/c” and the physical path contains all remote placement
       * information.
       *
       * Deployments are always looked up using the logical path, which is the
       * purpose of the lookupRemotes internal method.
       */

      @scala.annotation.tailrec
      def lookupRemotes(p: Iterable[String]): Option[Deploy] = {
        p.headOption match {
          case None           ⇒ None
          case Some("remote") ⇒ lookupRemotes(p.drop(3))
          case Some("user")   ⇒ deployer.lookup(p.drop(1))
          case Some(_)        ⇒ None
        }
      }

      val elems = path.elements
      val lookup =
        if (lookupDeploy)
          elems.head match {
            case "user"   ⇒ deployer.lookup(elems.drop(1))
            case "remote" ⇒ lookupRemotes(elems)
            case _        ⇒ None
          }
        else None

      val deployment = {
        deploy.toList ::: lookup.toList match {
          case Nil ⇒ Nil
          case l   ⇒ List(l reduce ((a, b) ⇒ b withFallback a))
        }
      }

      Iterator(props.deploy) ++ deployment.iterator reduce ((a, b) ⇒ b withFallback a) match {
        case d @ Deploy(_, _, _, RemoteScope(addr), _) ⇒
          if (hasAddress(addr)) {
            local.actorOf(system, props, supervisor, path, false, deployment.headOption, false, async)
          } else {
            try {
              val localAddress = transport.localAddressForRemote(addr)
              val rpath = (RootActorPath(addr) / "remote" / localAddress.protocol / localAddress.hostPort / path.elements).
                withUid(path.uid)
              new RemoteActorRef(transport, localAddress, rpath, supervisor, Some(props), Some(d))
            } catch {
              case NonFatal(e) ⇒
                log.error(e, "Error while looking up address [{}]", addr)
                new EmptyLocalActorRef(this, path, eventStream)
            }
          }

        case _ ⇒ local.actorOf(system, props, supervisor, path, systemService, deployment.headOption, false, async)
      }
    }
  }

  @deprecated("use actorSelection instead of actorFor", "2.2")
  def actorFor(path: ActorPath): InternalActorRef = {
    if (hasAddress(path.address)) actorFor(rootGuardian, path.elements)
    else try {
      new RemoteActorRef(transport, transport.localAddressForRemote(path.address),
        path, Nobody, props = None, deploy = None)
    } catch {
      case NonFatal(e) ⇒
        log.error(e, "Error while looking up address [{}]", path.address)
        new EmptyLocalActorRef(this, path, eventStream)
    }
  }

  @deprecated("use actorSelection instead of actorFor", "2.2")
  def actorFor(ref: InternalActorRef, path: String): InternalActorRef = path match {
    case ActorPathExtractor(address, elems) ⇒
      if (hasAddress(address)) actorFor(rootGuardian, elems)
      else {
        val rootPath = RootActorPath(address) / elems
        try {
          new RemoteActorRef(transport, transport.localAddressForRemote(address),
            rootPath, Nobody, props = None, deploy = None)
        } catch {
          case NonFatal(e) ⇒
            log.error(e, "Error while looking up address [{}]", rootPath.address)
            new EmptyLocalActorRef(this, rootPath, eventStream)
        }
      }
    case _ ⇒ local.actorFor(ref, path)
  }

  @deprecated("use actorSelection instead of actorFor", "2.2")
  def actorFor(ref: InternalActorRef, path: Iterable[String]): InternalActorRef =
    local.actorFor(ref, path)

  def rootGuardianAt(address: Address): ActorRef =
    if (hasAddress(address)) rootGuardian
    else new RemoteActorRef(transport, transport.localAddressForRemote(address),
      RootActorPath(address), Nobody, props = None, deploy = None)

  /**
   * INTERNAL API
   * Called in deserialization of incoming remote messages where the correct local address is known.
   */
  private[akka] def resolveActorRefWithLocalAddress(path: String, localAddress: Address): InternalActorRef = {
    path match {
      case ActorPathExtractor(address, elems) ⇒
        if (hasAddress(address)) local.resolveActorRef(rootGuardian, elems)
        else
          new RemoteActorRef(transport, localAddress, RootActorPath(address) / elems,
            Nobody, props = None, deploy = None)
      case _ ⇒
        log.debug("resolve of unknown path [{}] failed", path)
        deadLetters
    }
  }

  def resolveActorRef(path: String): ActorRef = path match {
    case ActorPathExtractor(address, elems) ⇒
      if (hasAddress(address)) local.resolveActorRef(rootGuardian, elems)
      else {
        val rootPath = RootActorPath(address) / elems
        try {
          new RemoteActorRef(transport, transport.localAddressForRemote(address),
            rootPath, Nobody, props = None, deploy = None)
        } catch {
          case NonFatal(e) ⇒
            log.error(e, "Error while resolving address [{}]", rootPath.address)
            new EmptyLocalActorRef(this, rootPath, eventStream)
        }
      }
    case _ ⇒
      log.debug("resolve of unknown path [{}] failed", path)
      deadLetters
  }

  def resolveActorRef(path: ActorPath): ActorRef = {
    if (hasAddress(path.address)) local.resolveActorRef(rootGuardian, path.elements)
    else try {
      new RemoteActorRef(transport, transport.localAddressForRemote(path.address),
        path, Nobody, props = None, deploy = None)
    } catch {
      case NonFatal(e) ⇒
        log.error(e, "Error while resolving address [{}]", path.address)
        new EmptyLocalActorRef(this, path, eventStream)
    }
  }

  /**
   * Using (checking out) actor on a specific node.
   */
  def useActorOnNode(ref: ActorRef, props: Props, deploy: Deploy, supervisor: ActorRef): Unit = {
    log.debug("[{}] Instantiating Remote Actor [{}]", rootPath, ref.path)

    // we don’t wait for the ACK, because the remote end will process this command before any other message to the new actor
    // actorSelection can't be used here because then it is not guaranteed that the actor is created
    // before someone can send messages to it
    resolveActorRef(RootActorPath(ref.path.address) / "remote") !
      DaemonMsgCreate(props, deploy, ref.path.toSerializationFormat, supervisor)

    remoteDeploymentWatcher ! RemoteDeploymentWatcher.WatchRemote(ref, supervisor)
  }

  def getExternalAddressFor(addr: Address): Option[Address] = {
    addr match {
      case _ if hasAddress(addr)           ⇒ Some(local.rootPath.address)
      case Address(_, _, Some(_), Some(_)) ⇒ try Some(transport.localAddressForRemote(addr)) catch { case NonFatal(_) ⇒ None }
      case _                               ⇒ None
    }
  }

  def getDefaultAddress: Address = transport.defaultAddress

  private def hasAddress(address: Address): Boolean =
    address == local.rootPath.address || address == rootPath.address || transport.addresses(address)

  def quarantine(address: Address, uid: Int): Unit = {
    // FIXME send to EndpointManager
  }

  /**
   * INTERNAL API
   */
  private[akka] def afterSendSystemMessage(message: SystemMessage): Unit =
    message match {
      // Sending to local remoteWatcher relies strong delivery guarantees of local send, i.e.
      // default dispatcher must not be changed to an implementation that defeats that
      case Watch(watchee, watcher)   ⇒ remoteWatcher ! RemoteWatcher.WatchRemote(watchee, watcher)
      case Unwatch(watchee, watcher) ⇒ remoteWatcher ! RemoteWatcher.UnwatchRemote(watchee, watcher)
      case _                         ⇒
    }

}

private[akka] trait RemoteRef extends ActorRefScope {
  final def isLocal = false
}

/**
 * INTERNAL API
 * Remote ActorRef that is used when referencing the Actor on a different node than its "home" node.
 * This reference is network-aware (remembers its origin) and immutable.
 */
private[akka] class RemoteActorRef private[akka] (
  remote: RemoteTransport,
  val localAddressToUse: Address,
  val path: ActorPath,
  val getParent: InternalActorRef,
  props: Option[Props],
  deploy: Option[Deploy])
  extends InternalActorRef with RemoteRef {

  def getChild(name: Iterator[String]): InternalActorRef = {
    val s = name.toStream
    s.headOption match {
      case None       ⇒ this
      case Some("..") ⇒ getParent getChild name
      case _          ⇒ new RemoteActorRef(remote, localAddressToUse, path / s, Nobody, props = None, deploy = None)
    }
  }

  @deprecated("Use context.watch(actor) and receive Terminated(actor)", "2.2") override def isTerminated: Boolean = false

  private def handleException: Catcher[Unit] = {
    case e: InterruptedException ⇒
      remote.system.eventStream.publish(Error(e, path.toString, getClass, "interrupted during message send"))
      Thread.currentThread.interrupt()
    case NonFatal(e) ⇒
      remote.system.eventStream.publish(Error(e, path.toString, getClass, "swallowing exception during message send"))
  }

  def sendSystemMessage(message: SystemMessage): Unit =
    try {
      remote.send(message, None, this)
      provider.afterSendSystemMessage(message)
    } catch handleException

  override def !(message: Any)(implicit sender: ActorRef = Actor.noSender): Unit = {
    if (message == null) throw new InvalidMessageException("Message is null")
    try remote.send(message, Option(sender), this) catch handleException
  }

  override def provider: RemoteActorRefProvider = remote.provider

  def start(): Unit =
    if (props.isDefined && deploy.isDefined) remote.provider.useActorOnNode(this, props.get, deploy.get, getParent)

  def suspend(): Unit = sendSystemMessage(Suspend())

  def resume(causedByFailure: Throwable): Unit = sendSystemMessage(Resume(causedByFailure))

  def stop(): Unit = sendSystemMessage(Terminate())

  def restart(cause: Throwable): Unit = sendSystemMessage(Recreate(cause))

  @throws(classOf[java.io.ObjectStreamException])
  private def writeReplace(): AnyRef = SerializedActorRef(this)
}