kernel/src/test/scala/test/utils/StackActor.scala

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 test.utils

import org.apache.pekko.actor.Actor

/**
 * A stack which will block when popping items.
 */
class BlockingStack {
  private var items = List[Any]()

  /**
   * Puts an item onto the stack
   * @param item The item to put on the stack
   */
  def put(item : Any) {
    items.synchronized {
      items = item +: items
    }
  }

  /**
   * Tries to pop an item off the stack, will sleep if nothing is there.
   * Will block for 1 second and return an Option.empty if
   * nothing makes it onto the stack.
   * @return The item on the top of the stack or Option.empty
   */
  def pop() : Any = {
    popN(10)
  }

  private def popN(count: Int) : Any = {
    if(count == 0)
      Option.empty
    else if( items.synchronized{ items.isEmpty }) {
      Thread.sleep(100)
      popN(count - 1)
    } else
      items.synchronized {
        val value = items.head
        items = items.tail
        value
      }
    }
}

/**
 * An actor that will push anything it receives onto a BlockingStack
 * @param stack The stack to push items onto
 */
class StackActor(stack : BlockingStack) extends Actor {
  override def receive = {
    case m =>
      stack.put(m)
  }
}