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package io.ray.streaming.operator.impl;

import io.ray.streaming.api.collector.Collector;
import io.ray.streaming.api.context.RuntimeContext;
import io.ray.streaming.api.function.impl.ReduceFunction;
import io.ray.streaming.message.KeyRecord;
import io.ray.streaming.message.Record;
import io.ray.streaming.operator.ChainStrategy;
import io.ray.streaming.operator.OneInputOperator;
import io.ray.streaming.operator.StreamOperator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ReduceOperator extends StreamOperator>
    implements OneInputOperator {

  private Map reduceState;

  public ReduceOperator(ReduceFunction reduceFunction) {
    super(reduceFunction);
    setChainStrategy(ChainStrategy.HEAD);
  }

  @Override
  public void open(List collectorList, RuntimeContext runtimeContext) {
    super.open(collectorList, runtimeContext);
    this.reduceState = new HashMap<>();
  }

  @Override
  public void processElement(Record record) throws Exception {
    KeyRecord keyRecord = (KeyRecord) record;
    K key = keyRecord.getKey();
    T value = keyRecord.getValue();
    if (reduceState.containsKey(key)) {
      T oldValue = reduceState.get(key);
      T newValue = this.function.reduce(oldValue, value);
      reduceState.put(key, newValue);
      collect(new Record(newValue));
    } else {
      reduceState.put(key, value);
      collect(record);
    }
  }
}