/*
 * Copyright (C) 2009-2018 Lightbend Inc. <https://www.lightbend.com>
 */

package akka.actor

import java.util.concurrent.atomic.AtomicReference

import akka.routing._
import akka.util.WildcardIndex
import com.typesafe.config._

import scala.annotation.tailrec

object Deploy {
  final val NoDispatcherGiven = ""
  final val NoMailboxGiven = ""
  val local = Deploy(scope = LocalScope)
}

/**
 * This class represents deployment configuration for a given actor path. It is
 * marked final in order to guarantee stable merge semantics (i.e. what
 * overrides what in case multiple configuration sources are available) and is
 * fully extensible via its Scope argument, and by the fact that an arbitrary
 * Config section can be passed along with it (which will be merged when merging
 * two Deploys).
 *
 * The path field is used only when inserting the Deploy into a deployer and
 * not needed when just doing deploy-as-you-go:
 *
 * {{{
 * val remoteProps = someProps.withDeploy(Deploy(scope = RemoteScope("someOtherNodeName")))
 * }}}
 */
@SerialVersionUID(2L)
final case class Deploy(
  path:         String       = "",
  config:       Config       = ConfigFactory.empty,
  routerConfig: RouterConfig = NoRouter,
  scope:        Scope        = NoScopeGiven,
  dispatcher:   String       = Deploy.NoDispatcherGiven,
  mailbox:      String       = Deploy.NoMailboxGiven) {

  /**
   * Java API to create a Deploy with the given RouterConfig
   */
  def this(routing: RouterConfig) = this("", ConfigFactory.empty, routing)

  /**
   * Java API to create a Deploy with the given RouterConfig with Scope
   */
  def this(routing: RouterConfig, scope: Scope) = this("", ConfigFactory.empty, routing, scope)

  /**
   * Java API to create a Deploy with the given Scope
   */
  def this(scope: Scope) = this("", ConfigFactory.empty, NoRouter, scope)

  /**
   * Do a merge between this and the other Deploy, where values from “this” take
   * precedence. The “path” of the other Deploy is not taken into account. All
   * other members are merged using `X.withFallback(other.X)`.
   */
  def withFallback(other: Deploy): Deploy = {
    Deploy(
      path,
      config.withFallback(other.config),
      routerConfig.withFallback(other.routerConfig),
      scope.withFallback(other.scope),
      if (dispatcher == Deploy.NoDispatcherGiven) other.dispatcher else dispatcher,
      if (mailbox == Deploy.NoMailboxGiven) other.mailbox else mailbox)
  }
}

/**
 * The scope of a [[akka.actor.Deploy]] serves two purposes: as a marker for
 * pattern matching the “scope” (i.e. local/remote/cluster) as well as for
 * extending the information carried by the final Deploy class. Scopes can be
 * used in conjunction with a custom [[akka.actor.ActorRefProvider]], making
 * Akka actors fully extensible.
 */
trait Scope {
  /**
   * When merging [[akka.actor.Deploy]] instances using ``withFallback()`` on
   * the left one, this is propagated to “merging” scopes in the same way.
   * The setup is biased towards preferring the callee over the argument, i.e.
   * ``a.withFallback(b)`` is called expecting that ``a`` should in general take
   * precedence.
   */
  def withFallback(other: Scope): Scope
}

@SerialVersionUID(1L)
abstract class LocalScope extends Scope

/**
 * The Local Scope is the default one, which is assumed on all deployments
 * which do not set a different scope. It is also the only scope handled by
 * the LocalActorRefProvider.
 */
@SerialVersionUID(1L)
case object LocalScope extends LocalScope {
  /**
   * Java API: get the singleton instance
   */
  def getInstance = this

  def withFallback(other: Scope): Scope = this
}

/**
 * This is the default value and as such allows overrides.
 */
@SerialVersionUID(1L)
abstract class NoScopeGiven extends Scope
@SerialVersionUID(1L)
case object NoScopeGiven extends NoScopeGiven {
  def withFallback(other: Scope): Scope = other

  /**
   * Java API: get the singleton instance
   */
  def getInstance = this
}

/**
 * Deployer maps actor paths to actor deployments.
 */
private[akka] class Deployer(val settings: ActorSystem.Settings, val dynamicAccess: DynamicAccess) {

  import scala.collection.JavaConverters._

  private val resizerEnabled: Config = ConfigFactory.parseString("resizer.enabled=on")
  private val deployments = new AtomicReference(WildcardIndex[Deploy]())
  private val config = settings.config.getConfig("akka.actor.deployment")
  protected val default = config.getConfig("default")
  val routerTypeMapping: Map[String, String] =
    settings.config.getConfig("akka.actor.router.type-mapping").root.unwrapped.asScala.collect {
      case (key, value: String) ⇒ (key → value)
    }.toMap

  config.root.asScala flatMap {
    case ("default", _)             ⇒ None
    case (key, value: ConfigObject) ⇒ parseConfig(key, value.toConfig)
    case _                          ⇒ None
  } foreach deploy

  def lookup(path: ActorPath): Option[Deploy] = lookup(path.elements.drop(1))

  def lookup(path: Iterable[String]): Option[Deploy] = deployments.get().find(path)

  def deploy(d: Deploy): Unit = {
    @tailrec def add(path: Array[String], d: Deploy, w: WildcardIndex[Deploy] = deployments.get): Unit = {
      for (i ← path.indices) path(i) match {
        case "" ⇒ throw InvalidActorNameException(s"Actor name in deployment [${d.path}] must not be empty")
        case el ⇒ ActorPath.validatePathElement(el, fullPath = d.path)
      }

      if (!deployments.compareAndSet(w, w.insert(path, d))) add(path, d)
    }

    add(d.path.split("/").drop(1), d)
  }

  def parseConfig(key: String, config: Config): Option[Deploy] = {
    val deployment = config.withFallback(default)
    val router = createRouterConfig(deployment.getString("router"), key, config, deployment)
    val dispatcher = deployment.getString("dispatcher")
    val mailbox = deployment.getString("mailbox")
    Some(Deploy(key, deployment, router, NoScopeGiven, dispatcher, mailbox))
  }

  /**
   * Factory method for creating `RouterConfig`
   * @param routerType the configured name of the router, or FQCN
   * @param key the full configuration key of the deployment section
   * @param config the user defined config of the deployment, without defaults
   * @param deployment the deployment config, with defaults
   */
  protected def createRouterConfig(routerType: String, key: String, config: Config, deployment: Config): RouterConfig =
    if (routerType == "from-code") NoRouter
    else {
      // need this for backwards compatibility, resizer enabled when including (parts of) resizer section in the deployment
      val deployment2 =
        if (config.hasPath("resizer") && !deployment.getBoolean("resizer.enabled"))
          resizerEnabled.withFallback(deployment)
        else deployment

      val fqn = routerTypeMapping.getOrElse(routerType, routerType)

      def throwCannotInstantiateRouter(args: Seq[(Class[_], AnyRef)], cause: Throwable) =
        throw new IllegalArgumentException(
          s"Cannot instantiate router [$fqn], defined in [$key], " +
            s"make sure it extends [${classOf[RouterConfig]}] and has constructor with " +
            s"[${args(0)._1.getName}] and optional [${args(1)._1.getName}] parameter", cause)

      // first try with Config param, and then with Config and DynamicAccess parameters
      val args1 = List(classOf[Config] → deployment2)
      val args2 = List(classOf[Config] → deployment2, classOf[DynamicAccess] → dynamicAccess)
      dynamicAccess.createInstanceFor[RouterConfig](fqn, args1).recover({
        case e @ (_: IllegalArgumentException | _: ConfigException) ⇒ throw e
        case e: NoSuchMethodException ⇒
          dynamicAccess.createInstanceFor[RouterConfig](fqn, args2).recover({
            case e @ (_: IllegalArgumentException | _: ConfigException) ⇒ throw e
            case e2 ⇒ throwCannotInstantiateRouter(args2, e)
          }).get
        case e ⇒ throwCannotInstantiateRouter(args2, e)
      }).get
    }

}
