OperatorSwitchIfMatch.java

import rx.*;
import rx.functions.Func1;
import rx.internal.producers.ProducerArbiter;
import rx.subscriptions.SerialSubscription;


public final class OperatorSwitchIfMatch<T> implements Observable.Operator<T, T> {
    private final Observable<? extends T> alternate;
    private final Func1<T, Boolean> selector ;
    public OperatorSwitchIfMatch(Observable<? extends T> alternate, Func1<T, Boolean> selector) {
        this.alternate = alternate;
        this.selector  = selector;
    }

    @Override
    public Subscriber<? super T> call(Subscriber<? super T> child) {
        final SerialSubscription ssub = new SerialSubscription();
        ProducerArbiter arbiter = new ProducerArbiter();
        final ParentSubscriber<T> parent = new ParentSubscriber<T>(child, ssub, arbiter, alternate,selector);
        ssub.set(parent);
        child.add(ssub);
        child.setProducer(arbiter);
        return parent;
    }

    private static final class ParentSubscriber<T> extends Subscriber<T> {

        private boolean matched = true;
        private final Subscriber<? super T> child;
        private final SerialSubscription ssub;
        private final ProducerArbiter arbiter;
        private final Observable<? extends T> alternate;
        private final Func1<T, Boolean> selector ;

        ParentSubscriber(Subscriber<? super T> child, final SerialSubscription ssub, ProducerArbiter arbiter, Observable<? extends T> alternate, Func1<T, Boolean> selector) {
            this.child = child;
            this.ssub = ssub;
            this.arbiter = arbiter;
            this.alternate = alternate;
            this.selector = selector;
        }

        @Override
        public void setProducer(final Producer producer) {
            arbiter.setProducer(producer);
        }

        @Override
        public void onCompleted() {            
                child.onCompleted();
        }

        private void subscribeToAlternate() {
            AlternateSubscriber<T> as = new AlternateSubscriber<T>(child, arbiter);
            ssub.set(as);
            alternate.unsafeSubscribe(as);
        }

        @Override
        public void onError(Throwable e) {
            child.onError(e);
        }

        @Override
        public void onNext(T t) {
            if (selector.call(t)) {
                if (!child.isUnsubscribed()) {
                    subscribeToAlternate();
                }
            } else {
                child.onNext(t);
            }
            arbiter.produced(1);
        }
    }

    private static final class AlternateSubscriber<T> extends Subscriber<T> {

        private final ProducerArbiter arbiter;
        private final Subscriber<? super T> child;

        AlternateSubscriber(Subscriber<? super T> child, ProducerArbiter arbiter) {
            this.child = child;
            this.arbiter = arbiter;
        }

        @Override
        public void setProducer(final Producer producer) {
            arbiter.setProducer(producer);
        }

        @Override
        public void onCompleted() {
            child.onCompleted();
        }

        @Override
        public void onError(Throwable e) {
            child.onError(e);
        }

        @Override
        public void onNext(T t) {
            child.onNext(t);
            arbiter.produced(1);
        }        
    }
}