/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.internal.operators.observable;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicInteger;
import io.reactivex.*;
import io.reactivex.annotations.Nullable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.EmptyDisposable;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.QueueDisposable;
import io.reactivex.plugins.RxJavaPlugins;
/**
* Utility classes to work with scalar-sourced XMap operators (where X == { flat, concat, switch }).
*/
public final class ObservableScalarXMap {
/** Utility class. */
private ObservableScalarXMap() {
throw new IllegalStateException("No instances!");
}
/**
* Tries to subscribe to a possibly Callable source's mapped ObservableSource.
* @param <T> the input value type
* @param <R> the output value type
* @param source the source ObservableSource
* @param observer the subscriber
* @param mapper the function mapping a scalar value into an ObservableSource
* @return true if successful, false if the caller should continue with the regular path.
*/
@SuppressWarnings("unchecked")
public static <T, R> boolean tryScalarXMapSubscribe(ObservableSource<T> source,
Observer<? super R> observer,
Function<? super T, ? extends ObservableSource<? extends R>> mapper) {
if (source instanceof Callable) {
T t;
try {
t = ((Callable<T>)source).call();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
EmptyDisposable.error(ex, observer);
return true;
}
if (t == null) {
EmptyDisposable.complete(observer);
return true;
}
ObservableSource<? extends R> r;
try {
r = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper returned a null ObservableSource");
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
EmptyDisposable.error(ex, observer);
return true;
}
if (r instanceof Callable) {
R u;
try {
u = ((Callable<R>)r).call();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
EmptyDisposable.error(ex, observer);
return true;
}
if (u == null) {
EmptyDisposable.complete(observer);
return true;
}
ScalarDisposable<R> sd = new ScalarDisposable<R>(observer, u);
observer.onSubscribe(sd);
sd.run();
} else {
r.subscribe(observer);
}
return true;
}
return false;
}
/**
* Maps a scalar value into an Observable and emits its values.
*
* @param <T> the scalar value type
* @param <U> the output value type
* @param value the scalar value to map
* @param mapper the function that gets the scalar value and should return
* an ObservableSource that gets streamed
* @return the new Observable instance
*/
public static <T, U> Observable<U> scalarXMap(T value,
Function<? super T, ? extends ObservableSource<? extends U>> mapper) {
return RxJavaPlugins.onAssembly(new ScalarXMapObservable<T, U>(value, mapper));
}
/**
* Maps a scalar value to an ObservableSource and subscribes to it.
*
* @param <T> the scalar value type
* @param <R> the mapped ObservableSource's element type.
*/
static final class ScalarXMapObservable<T, R> extends Observable<R> {
final T value;
final Function<? super T, ? extends ObservableSource<? extends R>> mapper;
ScalarXMapObservable(T value,
Function<? super T, ? extends ObservableSource<? extends R>> mapper) {
this.value = value;
this.mapper = mapper;
}
@SuppressWarnings("unchecked")
@Override
public void subscribeActual(Observer<? super R> s) {
ObservableSource<? extends R> other;
try {
other = ObjectHelper.requireNonNull(mapper.apply(value), "The mapper returned a null ObservableSource");
} catch (Throwable e) {
EmptyDisposable.error(e, s);
return;
}
if (other instanceof Callable) {
R u;
try {
u = ((Callable<R>)other).call();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
EmptyDisposable.error(ex, s);
return;
}
if (u == null) {
EmptyDisposable.complete(s);
return;
}
ScalarDisposable<R> sd = new ScalarDisposable<R>(s, u);
s.onSubscribe(sd);
sd.run();
} else {
other.subscribe(s);
}
}
}
/**
* Represents a Disposable that signals one onNext followed by an onComplete.
*
* @param <T> the value type
*/
public static final class ScalarDisposable<T>
extends AtomicInteger
implements QueueDisposable<T>, Runnable {
private static final long serialVersionUID = 3880992722410194083L;
final Observer<? super T> observer;
final T value;
static final int START = 0;
static final int FUSED = 1;
static final int ON_NEXT = 2;
static final int ON_COMPLETE = 3;
public ScalarDisposable(Observer<? super T> observer, T value) {
this.observer = observer;
this.value = value;
}
@Override
public boolean offer(T value) {
throw new UnsupportedOperationException("Should not be called!");
}
@Override
public boolean offer(T v1, T v2) {
throw new UnsupportedOperationException("Should not be called!");
}
@Nullable
@Override
public T poll() throws Exception {
if (get() == FUSED) {
lazySet(ON_COMPLETE);
return value;
}
return null;
}
@Override
public boolean isEmpty() {
return get() != FUSED;
}
@Override
public void clear() {
lazySet(ON_COMPLETE);
}
@Override
public void dispose() {
set(ON_COMPLETE);
}
@Override
public boolean isDisposed() {
return get() == ON_COMPLETE;
}
@Override
public int requestFusion(int mode) {
if ((mode & SYNC) != 0) {
lazySet(FUSED);
return SYNC;
}
return NONE;
}
@Override
public void run() {
if (get() == START && compareAndSet(START, ON_NEXT)) {
observer.onNext(value);
if (get() == ON_NEXT) {
lazySet(ON_COMPLETE);
observer.onComplete();
}
}
}
}
}