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/**
 * 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.mixed;

import java.util.concurrent.atomic.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.plugins.RxJavaPlugins;

/**
 * Maps the upstream items into {@link SingleSource}s and switches (subscribes) to the newer ones
 * while disposing the older ones and emits the latest success value if available, optionally delaying
 * errors from the main source or the inner sources.
 * 

History: 2.1.11 - experimental * @param the upstream value type * @param the downstream value type * @since 2.2 */ public final class ObservableSwitchMapSingle extends Observable { final Observable source; final Function> mapper; final boolean delayErrors; public ObservableSwitchMapSingle(Observable source, Function> mapper, boolean delayErrors) { this.source = source; this.mapper = mapper; this.delayErrors = delayErrors; } @Override protected void subscribeActual(Observer observer) { if (!ScalarXMapZHelper.tryAsSingle(source, mapper, observer)) { source.subscribe(new SwitchMapSingleMainObserver(observer, mapper, delayErrors)); } } static final class SwitchMapSingleMainObserver extends AtomicInteger implements Observer, Disposable { private static final long serialVersionUID = -5402190102429853762L; final Observer downstream; final Function> mapper; final boolean delayErrors; final AtomicThrowable errors; final AtomicReference> inner; static final SwitchMapSingleObserver INNER_DISPOSED = new SwitchMapSingleObserver(null); Disposable upstream; volatile boolean done; volatile boolean cancelled; SwitchMapSingleMainObserver(Observer downstream, Function> mapper, boolean delayErrors) { this.downstream = downstream; this.mapper = mapper; this.delayErrors = delayErrors; this.errors = new AtomicThrowable(); this.inner = new AtomicReference>(); } @Override public void onSubscribe(Disposable d) { if (DisposableHelper.validate(upstream, d)) { upstream = d; downstream.onSubscribe(this); } } @Override @SuppressWarnings({ "unchecked", "rawtypes" }) public void onNext(T t) { SwitchMapSingleObserver current = inner.get(); if (current != null) { current.dispose(); } SingleSource ss; try { ss = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper returned a null SingleSource"); } catch (Throwable ex) { Exceptions.throwIfFatal(ex); upstream.dispose(); inner.getAndSet((SwitchMapSingleObserver)INNER_DISPOSED); onError(ex); return; } SwitchMapSingleObserver observer = new SwitchMapSingleObserver(this); for (;;) { current = inner.get(); if (current == INNER_DISPOSED) { break; } if (inner.compareAndSet(current, observer)) { ss.subscribe(observer); break; } } } @Override public void onError(Throwable t) { if (errors.addThrowable(t)) { if (!delayErrors) { disposeInner(); } done = true; drain(); } else { RxJavaPlugins.onError(t); } } @Override public void onComplete() { done = true; drain(); } @SuppressWarnings({ "unchecked", "rawtypes" }) void disposeInner() { SwitchMapSingleObserver current = inner.getAndSet((SwitchMapSingleObserver)INNER_DISPOSED); if (current != null && current != INNER_DISPOSED) { current.dispose(); } } @Override public void dispose() { cancelled = true; upstream.dispose(); disposeInner(); } @Override public boolean isDisposed() { return cancelled; } void innerError(SwitchMapSingleObserver sender, Throwable ex) { if (inner.compareAndSet(sender, null)) { if (errors.addThrowable(ex)) { if (!delayErrors) { upstream.dispose(); disposeInner(); } drain(); return; } } RxJavaPlugins.onError(ex); } void drain() { if (getAndIncrement() != 0) { return; } int missed = 1; Observer downstream = this.downstream; AtomicThrowable errors = this.errors; AtomicReference> inner = this.inner; for (;;) { for (;;) { if (cancelled) { return; } if (errors.get() != null) { if (!delayErrors) { Throwable ex = errors.terminate(); downstream.onError(ex); return; } } boolean d = done; SwitchMapSingleObserver current = inner.get(); boolean empty = current == null; if (d && empty) { Throwable ex = errors.terminate(); if (ex != null) { downstream.onError(ex); } else { downstream.onComplete(); } return; } if (empty || current.item == null) { break; } inner.compareAndSet(current, null); downstream.onNext(current.item); } missed = addAndGet(-missed); if (missed == 0) { break; } } } static final class SwitchMapSingleObserver extends AtomicReference implements SingleObserver { private static final long serialVersionUID = 8042919737683345351L; final SwitchMapSingleMainObserver parent; volatile R item; SwitchMapSingleObserver(SwitchMapSingleMainObserver parent) { this.parent = parent; } @Override public void onSubscribe(Disposable d) { DisposableHelper.setOnce(this, d); } @Override public void onSuccess(R t) { item = t; parent.drain(); } @Override public void onError(Throwable e) { parent.innerError(this, e); } void dispose() { DisposableHelper.dispose(this); } } } }