com.outbrain.ob1k.concurrent.stream.FutureProviderToStreamHandler Maven / Gradle / Ivy

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package com.outbrain.ob1k.concurrent.stream;

import com.outbrain.ob1k.concurrent.ComposableFuture;
import com.outbrain.ob1k.concurrent.Consumer;
import com.outbrain.ob1k.concurrent.Try;
import com.outbrain.ob1k.concurrent.handlers.FutureProvider;
import rx.Observable;
import rx.Subscriber;

/**
 * Created by aronen on 11/9/14.
 * 
 * creates a stream from a future provider.
 * each time a future provides the value, the next future is generated.
 */
public class FutureProviderToStreamHandler implements Observable.OnSubscribe {
  private final FutureProvider provider;
  volatile Subscriber subscriber;

  public FutureProviderToStreamHandler(final FutureProvider provider) {
    this.provider = provider;
  }

  @Override
  public void call(final Subscriber subscriber) {
    this.subscriber = subscriber;
    final boolean next = provider.moveNext();
    if (next) {
      final ComposableFuture nextFuture = provider.current();
      handleNextFuture(nextFuture);
    } else {
      subscriber.onCompleted();
    }
  }

  private void handleNextFuture(final ComposableFuture nextFuture) {
    nextFuture.consume(new Consumer() {
      @Override
      public void consume(final Try result) {
        if (result.isSuccess()) {
          subscriber.onNext(result.getValue());
          final boolean next = provider.moveNext();
          if (next) {
            handleNextFuture(provider.current());
          } else {
            subscriber.onCompleted();
          }
        } else {
          subscriber.onError(result.getError());
        }
      }
    });
 }

}