/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * license agreements; and to You under the Apache License, version 2.0:
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * This file is part of the Apache Pekko project, which was derived from Akka.
 */

/*
 * Copyright (C) 2009-2022 Lightbend Inc. <https://www.lightbend.com>
 */

package org.apache.pekko.stream

import scala.annotation.nowarn
import scala.concurrent.Await
import scala.concurrent.Promise
import scala.jdk.DurationConverters._

import org.apache.pekko
import pekko.actor.ActorSystem
import pekko.actor.ClassicActorSystemProvider
import pekko.actor.Deploy
import pekko.actor.ExtendedActorSystem
import pekko.actor.Extension
import pekko.actor.ExtensionId
import pekko.actor.ExtensionIdProvider
import pekko.annotation.InternalApi
import pekko.dispatch.Dispatchers
import pekko.pattern.ask
import pekko.stream.impl.MaterializerGuardian
import pekko.util.Timeout

/**
 * The system materializer is a default materializer to use for most cases running streams, it is a single instance
 * per actor system that is tied to the lifecycle of that system.
 *
 * Not intended to be manually used in user code.
 */
object SystemMaterializer extends ExtensionId[SystemMaterializer] with ExtensionIdProvider {
  override def get(system: ActorSystem): SystemMaterializer = super.get(system)
  override def get(system: ClassicActorSystemProvider): SystemMaterializer = super.get(system)

  override def lookup = SystemMaterializer

  override def createExtension(system: ExtendedActorSystem): SystemMaterializer =
    new SystemMaterializer(system)
}

final class SystemMaterializer(system: ExtendedActorSystem) extends Extension {
  private val systemMaterializerPromise = Promise[Materializer]()

  // load these here so we can share the same instance across materializer guardian and other uses
  /**
   * INTERNAL API
   */
  @InternalApi @nowarn("msg=deprecated")
  private[pekko] val materializerSettings = ActorMaterializerSettings(system)

  private implicit val materializerTimeout: Timeout =
    system.settings.config.getDuration("pekko.stream.materializer.creation-timeout").toScala

  @InternalApi @nowarn("msg=deprecated")
  private val materializerGuardian = system.systemActorOf(
    MaterializerGuardian
      .props(systemMaterializerPromise, materializerSettings)
      // #28037 run on internal dispatcher to make sure default dispatcher starvation doesn't stop materializer creation
      .withDispatcher(Dispatchers.InternalDispatcherId)
      .withDeploy(Deploy.local),
    "Materializers")

  /**
   * INTERNAL API
   */
  @InternalApi
  private[pekko] def createAdditionalSystemMaterializer(): Materializer = {
    val started = (materializerGuardian ? MaterializerGuardian.StartMaterializer).mapTo[
      MaterializerGuardian.MaterializerStarted]
    Await.result(started, materializerTimeout.duration).materializer
  }

  /**
   * INTERNAL API
   */
  @InternalApi
  @nowarn("msg=deprecated")
  private[pekko] def createAdditionalLegacySystemMaterializer(
      namePrefix: String,
      settings: ActorMaterializerSettings): Materializer = {
    val started = (materializerGuardian ? MaterializerGuardian.LegacyStartMaterializer(namePrefix, settings))
      .mapTo[MaterializerGuardian.MaterializerStarted]
    Await.result(started, materializerTimeout.duration).materializer
  }

  val materializer: Materializer = {
    // block on async creation to make it effectively final
    val future = systemMaterializerPromise.future
    future.value match {
      case Some(value) => value.get
      case _           => Await.result(future, materializerTimeout.duration)
    }
  }

}
