monix.reactive.internal.consumers.FirstNotificationConsumer.scala Maven / Gradle / Ivy

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Sub-module of Monix, exposing the Observable pattern for modeling of reactive streams. See: https://monix.io

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/*
 * Copyright (c) 2014-2021 by The Monix Project Developers.
 * See the project homepage at: https://monix.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package monix.reactive.internal.consumers

import monix.execution.Callback
import monix.execution.Ack.Stop
import monix.execution.cancelables.AssignableCancelable
import monix.execution.{Ack, Scheduler}
import monix.reactive.observers.Subscriber
import monix.reactive.{Consumer, Notification}

/** Implementation for [[monix.reactive.Consumer.firstNotification]]. */
private[reactive] final class FirstNotificationConsumer[A] extends Consumer.Sync[A, Notification[A]] {
  override def createSubscriber(
    cb: Callback[Throwable, Notification[A]],
    s: Scheduler): (Subscriber.Sync[A], AssignableCancelable) = {
    val out = new Subscriber.Sync[A] {
      implicit val scheduler = s
      private[this] var isDone = false

      def onNext(elem: A): Ack = {
        isDone = true
        cb.onSuccess(Notification.OnNext(elem))
        Stop
      }

      def onComplete(): Unit =
        if (!isDone) {
          isDone = true
          cb.onSuccess(Notification.OnComplete)
        }

      def onError(ex: Throwable): Unit =
        if (!isDone) {
          isDone = true
          cb.onSuccess(Notification.OnError(ex))
        }
    }

    (out, AssignableCancelable.dummy)
  }
}