org.mongodb.scala.internal.FoldLeftObservable.scala Maven / Gradle / Ivy

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A Scala wrapper of the MongoDB Reactive Streams Java driver

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/*
 * Copyright 2015 MongoDB, Inc.
 *
 * 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 org.mongodb.scala.internal

import org.mongodb.scala.{ Observable, Observer, Subscription }

private[scala] case class FoldLeftObservable[T, S](observable: Observable[T], initialValue: S, accumulator: (S, T) => S) extends Observable[S] {

  @volatile
  private var currentValue: S = initialValue

  override def subscribe(observer: Observer[_ >: S]): Unit = {
    observable.subscribe(
      new Observer[T] {

        override def onError(throwable: Throwable): Unit = observer.onError(throwable)

        override def onSubscribe(subscription: Subscription): Unit = observer.onSubscribe(subscription)

        override def onComplete(): Unit = {
          observer.onNext(currentValue)
          observer.onComplete()
        }

        override def onNext(tResult: T): Unit = {
          currentValue = accumulator(currentValue, tResult)
        }
      }
    )
  }
}