/**
* Copyright 2014 Netflix, Inc.
*
* 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 rx.internal.operators;
import java.util.ArrayList;
import java.util.List;
import rx.Observable;
import rx.Observable.Operator;
import rx.Subscriber;
import rx.observers.SerializedSubscriber;
import rx.subscriptions.SerialSubscription;
/**
* Transforms an Observable that emits Observables into a single Observable that
* emits the items emitted by the most recently published of those Observables.
* <p>
* <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/switchDo.png" alt="">
*
* @param <T> the value type
*/
public final class OperatorSwitch<T> implements Operator<T, Observable<? extends T>> {
@Override
public Subscriber<? super Observable<? extends T>> call(final Subscriber<? super T> child) {
final SerializedSubscriber<T> s = new SerializedSubscriber<T>(child);
final SerialSubscription ssub = new SerialSubscription();
child.add(ssub);
return new Subscriber<Observable<? extends T>>(child) {
final Object guard = new Object();
final NotificationLite<?> nl = NotificationLite.instance();
/** Guarded by guard. */
int index;
/** Guarded by guard. */
boolean active;
/** Guarded by guard. */
boolean mainDone;
/** Guarded by guard. */
List<Object> queue;
/** Guarded by guard. */
boolean emitting;
@Override
public void onNext(Observable<? extends T> t) {
final int id;
synchronized (guard) {
id = ++index;
active = true;
}
Subscriber<T> sub = new Subscriber<T>() {
@Override
public void onNext(T t) {
emit(t, id);
}
@Override
public void onError(Throwable e) {
error(e, id);
}
@Override
public void onCompleted() {
complete(id);
}
};
ssub.set(sub);
t.unsafeSubscribe(sub);
}
@Override
public void onError(Throwable e) {
s.onError(e);
unsubscribe();
}
@Override
public void onCompleted() {
List<Object> localQueue;
synchronized (guard) {
mainDone = true;
if (active) {
return;
}
if (emitting) {
if (queue == null) {
queue = new ArrayList<Object>();
}
queue.add(nl.completed());
return;
}
localQueue = queue;
queue = null;
emitting = true;
}
drain(localQueue);
s.onCompleted();
unsubscribe();
}
void emit(T value, int id) {
List<Object> localQueue;
synchronized (guard) {
if (id != index) {
return;
}
if (emitting) {
if (queue == null) {
queue = new ArrayList<Object>();
}
queue.add(value);
return;
}
localQueue = queue;
queue = null;
emitting = true;
}
boolean once = true;
boolean skipFinal = false;
try {
do {
drain(localQueue);
if (once) {
once = false;
s.onNext(value);
}
synchronized (guard) {
localQueue = queue;
queue = null;
if (localQueue == null) {
emitting = false;
skipFinal = true;
break;
}
}
} while (!s.isUnsubscribed());
} finally {
if (!skipFinal) {
synchronized (guard) {
emitting = false;
}
}
}
}
void drain(List<Object> localQueue) {
if (localQueue == null) {
return;
}
for (Object o : localQueue) {
if (nl.isCompleted(o)) {
s.onCompleted();
break;
} else
if (nl.isError(o)) {
s.onError(nl.getError(o));
break;
} else {
@SuppressWarnings("unchecked")
T t = (T)o;
s.onNext(t);
}
}
}
void error(Throwable e, int id) {
List<Object> localQueue;
synchronized (guard) {
if (id != index) {
return;
}
if (emitting) {
if (queue == null) {
queue = new ArrayList<Object>();
}
queue.add(nl.error(e));
return;
}
localQueue = queue;
queue = null;
emitting = true;
}
drain(localQueue);
s.onError(e);
unsubscribe();
}
void complete(int id) {
List<Object> localQueue;
synchronized (guard) {
if (id != index) {
return;
}
active = false;
if (!mainDone) {
return;
}
if (emitting) {
if (queue == null) {
queue = new ArrayList<Object>();
}
queue.add(nl.completed());
return;
}
localQueue = queue;
queue = null;
emitting = true;
}
drain(localQueue);
s.onCompleted();
unsubscribe();
}
};
}
}