/*
 * 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 org.apache.gearpump.akkastream.task

import java.time.Instant

import org.apache.gearpump.Message
import org.apache.gearpump.cluster.UserConfig
import org.apache.gearpump.streaming.task.TaskContext

class FoldTask[In, Out](context: TaskContext, userConf : UserConfig)
  extends GraphTask(context, userConf) {

  val zero = userConf.getValue[Out](FoldTask.ZERO)
  val aggregator = userConf.getValue[(Out, In) => Out](FoldTask.AGGREGATOR)
  var aggregated: Out = _
  implicit val ec = context.system.dispatcher

  override def onStart(instant: Instant): Unit = {
    zero.foreach(value => {
      aggregated = value
    })
  }

  override def onNext(msg : Message) : Unit = {
    val data = msg.msg.asInstanceOf[In]
    val time = msg.timestamp
    aggregator.foreach(func => {
      aggregated = func(aggregated, data)
      LOG.info(s"aggregated = $aggregated")
      val msg = new Message(aggregated, time)
      context.output(msg)
    })
  }
}

object FoldTask {
  val ZERO = "ZERO"
  val AGGREGATOR = "AGGREGATOR"
}