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RxJava2 utilities for use with Mobius
There is a newer version: 2.0.3
/*
 * -\-\-
 * Mobius
 * --
 * Copyright (c) 2017-2018 Spotify AB
 * --
 * 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 com.spotify.mobius.rx2;

import com.spotify.mobius.MobiusLoop;
import io.reactivex.Observable;
import io.reactivex.ObservableEmitter;
import io.reactivex.ObservableOnSubscribe;
import io.reactivex.ObservableSource;
import io.reactivex.ObservableTransformer;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Cancellable;
import io.reactivex.functions.Consumer;

/**
 * Wraps a MobiusLoop into an observable transformer.
 *
 * Compose it on top of an event of streams to convert it into a stream of models.
 */
class RxMobiusLoop implements ObservableTransformer {

  private final MobiusLoop.Factory loopFactory;
  private final M startModel;

  RxMobiusLoop(MobiusLoop.Factory loopFactory, M startModel) {
    this.loopFactory = loopFactory;
    this.startModel = startModel;
  }

  @Override
  public ObservableSource apply(final Observable events) {
    return Observable.create(
        new ObservableOnSubscribe() {
          @Override
          public void subscribe(final ObservableEmitter emitter) throws Exception {
            final MobiusLoop loop = loopFactory.startFrom(startModel);

            loop.observe(
                new com.spotify.mobius.functions.Consumer() {
                  @Override
                  public void accept(M newModel) {
                    emitter.onNext(newModel);
                  }
                });

            final Disposable eventsDisposable =
                events.subscribe(
                    new Consumer() {
                      @Override
                      public void accept(E event) throws Exception {
                        loop.dispatchEvent(event);
                      }
                    },
                    new Consumer() {
                      @Override
                      public void accept(Throwable throwable) throws Exception {
                        emitter.onError(new UnrecoverableIncomingException(throwable));
                      }
                    });

            emitter.setCancellable(
                new Cancellable() {
                  @Override
                  public void cancel() throws Exception {
                    loop.dispose();
                    eventsDisposable.dispose();
                  }
                });
          }
        });
  }
}