/*
 * Copyright (C) 2015-2018 Lightbend Inc. <https://www.lightbend.com>
 */

package akka.stream.javadsl

import akka.NotUsed
import akka.japi.function.Creator

import scala.concurrent.duration.FiniteDuration

/**
 * A RestartSink wraps a [[Sink]] that gets restarted when it completes or fails.
 *
 * They are useful for graphs that need to run for longer than the [[Sink]] can necessarily guarantee it will, for
 * example, for [[Sink]] streams that depend on a remote server that may crash or become partitioned. The
 * RestartSink ensures that the graph can continue running while the [[Sink]] restarts.
 */
object RestartSink {

  /**
   * Wrap the given [[Sink]] with a [[Sink]] that will restart it when it fails or complete using an exponential
   * backoff.
   *
   * This [[Sink]] will never cancel, since cancellation by the wrapped [[Sink]] is always handled by restarting it.
   * The wrapped [[Sink]] can however be completed by feeding a completion or error into this [[Sink]]. When that
   * happens, the [[Sink]], if currently running, will terminate and will not be restarted. This can be triggered
   * simply by the upstream completing, or externally by introducing a [[KillSwitch]] right before this [[Sink]] in the
   * graph.
   *
   * The restart process is inherently lossy, since there is no coordination between cancelling and the sending of
   * messages. When the wrapped [[Sink]] does cancel, this [[Sink]] will backpressure, however any elements already
   * sent may have been lost.
   *
   * This uses the same exponential backoff algorithm as [[akka.pattern.Backoff]].
   *
   * @param minBackoff minimum (initial) duration until the child actor will
   *   started again, if it is terminated
   * @param maxBackoff the exponential back-off is capped to this duration
   * @param randomFactor after calculation of the exponential back-off an additional
   *   random delay based on this factor is added, e.g. `0.2` adds up to `20%` delay.
   *   In order to skip this additional delay pass in `0`.
   * @param sinkFactory A factory for producing the [[Sink]] to wrap.
   */
  @Deprecated
  @deprecated("Use the overloaded one which accepts java.time.Duration instead.", since = "2.5.12")
  def withBackoff[T](minBackoff: FiniteDuration, maxBackoff: FiniteDuration, randomFactor: Double,
                     sinkFactory: Creator[Sink[T, _]]): Sink[T, NotUsed] = {
    akka.stream.scaladsl.RestartSink.withBackoff(minBackoff, maxBackoff, randomFactor) { () ⇒
      sinkFactory.create().asScala
    }.asJava
  }

  /**
   * Wrap the given [[Sink]] with a [[Sink]] that will restart it when it fails or complete using an exponential
   * backoff.
   *
   * This [[Sink]] will never cancel, since cancellation by the wrapped [[Sink]] is always handled by restarting it.
   * The wrapped [[Sink]] can however be completed by feeding a completion or error into this [[Sink]]. When that
   * happens, the [[Sink]], if currently running, will terminate and will not be restarted. This can be triggered
   * simply by the upstream completing, or externally by introducing a [[KillSwitch]] right before this [[Sink]] in the
   * graph.
   *
   * The restart process is inherently lossy, since there is no coordination between cancelling and the sending of
   * messages. When the wrapped [[Sink]] does cancel, this [[Sink]] will backpressure, however any elements already
   * sent may have been lost.
   *
   * This uses the same exponential backoff algorithm as [[akka.pattern.Backoff]].
   *
   * @param minBackoff minimum (initial) duration until the child actor will
   *   started again, if it is terminated
   * @param maxBackoff the exponential back-off is capped to this duration
   * @param randomFactor after calculation of the exponential back-off an additional
   *   random delay based on this factor is added, e.g. `0.2` adds up to `20%` delay.
   *   In order to skip this additional delay pass in `0`.
   * @param sinkFactory A factory for producing the [[Sink]] to wrap.
   */
  def withBackoff[T](minBackoff: java.time.Duration, maxBackoff: java.time.Duration, randomFactor: Double,
                     sinkFactory: Creator[Sink[T, _]]): Sink[T, NotUsed] = {
    import akka.util.JavaDurationConverters._
    withBackoff(minBackoff.asScala, maxBackoff.asScala, randomFactor, sinkFactory)
  }

  /**
   * Wrap the given [[Sink]] with a [[Sink]] that will restart it when it fails or complete using an exponential
   * backoff.
   *
   * This [[Sink]] will not cancel as long as maxRestarts is not reached, since cancellation by the wrapped [[Sink]]
   * is handled by restarting it. The wrapped [[Sink]] can however be completed by feeding a completion or error into
   * this [[Sink]]. When that happens, the [[Sink]], if currently running, will terminate and will not be restarted.
   * This can be triggered simply by the upstream completing, or externally by introducing a [[KillSwitch]] right
   * before this [[Sink]] in the graph.
   *
   * The restart process is inherently lossy, since there is no coordination between cancelling and the sending of
   * messages. When the wrapped [[Sink]] does cancel, this [[Sink]] will backpressure, however any elements already
   * sent may have been lost.
   *
   * This uses the same exponential backoff algorithm as [[akka.pattern.Backoff]].
   *
   * @param minBackoff minimum (initial) duration until the child actor will
   *   started again, if it is terminated
   * @param maxBackoff the exponential back-off is capped to this duration
   * @param randomFactor after calculation of the exponential back-off an additional
   *   random delay based on this factor is added, e.g. `0.2` adds up to `20%` delay.
   *   In order to skip this additional delay pass in `0`.
   * @param maxRestarts the amount of restarts is capped to this amount within a time frame of minBackoff.
   *   Passing `0` will cause no restarts and a negative number will not cap the amount of restarts.
   * @param sinkFactory A factory for producing the [[Sink]] to wrap.
   */
  @Deprecated
  @deprecated("Use the overloaded one which accepts java.time.Duration instead.", since = "2.5.12")
  def withBackoff[T](minBackoff: FiniteDuration, maxBackoff: FiniteDuration, randomFactor: Double,
                     maxRestarts: Int, sinkFactory: Creator[Sink[T, _]]): Sink[T, NotUsed] = {
    akka.stream.scaladsl.RestartSink.withBackoff(minBackoff, maxBackoff, randomFactor, maxRestarts) { () ⇒
      sinkFactory.create().asScala
    }.asJava
  }

  /**
   * Wrap the given [[Sink]] with a [[Sink]] that will restart it when it fails or complete using an exponential
   * backoff.
   *
   * This [[Sink]] will not cancel as long as maxRestarts is not reached, since cancellation by the wrapped [[Sink]]
   * is handled by restarting it. The wrapped [[Sink]] can however be completed by feeding a completion or error into
   * this [[Sink]]. When that happens, the [[Sink]], if currently running, will terminate and will not be restarted.
   * This can be triggered simply by the upstream completing, or externally by introducing a [[KillSwitch]] right
   * before this [[Sink]] in the graph.
   *
   * The restart process is inherently lossy, since there is no coordination between cancelling and the sending of
   * messages. When the wrapped [[Sink]] does cancel, this [[Sink]] will backpressure, however any elements already
   * sent may have been lost.
   *
   * This uses the same exponential backoff algorithm as [[akka.pattern.Backoff]].
   *
   * @param minBackoff minimum (initial) duration until the child actor will
   *   started again, if it is terminated
   * @param maxBackoff the exponential back-off is capped to this duration
   * @param randomFactor after calculation of the exponential back-off an additional
   *   random delay based on this factor is added, e.g. `0.2` adds up to `20%` delay.
   *   In order to skip this additional delay pass in `0`.
   * @param maxRestarts the amount of restarts is capped to this amount within a time frame of minBackoff.
   *   Passing `0` will cause no restarts and a negative number will not cap the amount of restarts.
   * @param sinkFactory A factory for producing the [[Sink]] to wrap.
   */
  def withBackoff[T](minBackoff: java.time.Duration, maxBackoff: java.time.Duration, randomFactor: Double,
                     maxRestarts: Int, sinkFactory: Creator[Sink[T, _]]): Sink[T, NotUsed] = {
    import akka.util.JavaDurationConverters._
    withBackoff(minBackoff.asScala, maxBackoff.asScala, randomFactor, maxRestarts, sinkFactory)
  }
}
