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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.rxjava3.internal.operators.mixed;

import java.util.Objects;
import java.util.concurrent.atomic.*;

import org.reactivestreams.*;

import io.reactivex.rxjava3.core.*;
import io.reactivex.rxjava3.disposables.Disposable;
import io.reactivex.rxjava3.exceptions.Exceptions;
import io.reactivex.rxjava3.functions.Function;
import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
import io.reactivex.rxjava3.internal.util.*;
import io.reactivex.rxjava3.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, 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 FlowableSwitchMapSingle extends Flowable { final Flowable source; final Function> mapper; final boolean delayErrors; public FlowableSwitchMapSingle(Flowable source, Function> mapper, boolean delayErrors) { this.source = source; this.mapper = mapper; this.delayErrors = delayErrors; } @Override protected void subscribeActual(Subscriber s) { source.subscribe(new SwitchMapSingleSubscriber<>(s, mapper, delayErrors)); } static final class SwitchMapSingleSubscriber extends AtomicInteger implements FlowableSubscriber, Subscription { private static final long serialVersionUID = -5402190102429853762L; final Subscriber downstream; final Function> mapper; final boolean delayErrors; final AtomicThrowable errors; final AtomicLong requested; final AtomicReference> inner; static final SwitchMapSingleObserver INNER_DISPOSED = new SwitchMapSingleObserver<>(null); Subscription upstream; volatile boolean done; volatile boolean cancelled; long emitted; SwitchMapSingleSubscriber(Subscriber downstream, Function> mapper, boolean delayErrors) { this.downstream = downstream; this.mapper = mapper; this.delayErrors = delayErrors; this.errors = new AtomicThrowable(); this.requested = new AtomicLong(); this.inner = new AtomicReference<>(); } @Override public void onSubscribe(Subscription s) { if (SubscriptionHelper.validate(upstream, s)) { upstream = s; downstream.onSubscribe(this); s.request(Long.MAX_VALUE); } } @Override @SuppressWarnings({ "unchecked", "rawtypes" }) public void onNext(T t) { SwitchMapSingleObserver current = inner.get(); if (current != null) { current.dispose(); } SingleSource ss; try { ss = Objects.requireNonNull(mapper.apply(t), "The mapper returned a null SingleSource"); } catch (Throwable ex) { Exceptions.throwIfFatal(ex); upstream.cancel(); 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.tryAddThrowableOrReport(t)) { if (!delayErrors) { disposeInner(); } done = true; drain(); } } @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 request(long n) { BackpressureHelper.add(requested, n); drain(); } @Override public void cancel() { cancelled = true; upstream.cancel(); disposeInner(); errors.tryTerminateAndReport(); } void innerError(SwitchMapSingleObserver sender, Throwable ex) { if (inner.compareAndSet(sender, null)) { if (errors.tryAddThrowableOrReport(ex)) { if (!delayErrors) { upstream.cancel(); disposeInner(); } drain(); } } else { RxJavaPlugins.onError(ex); } } void drain() { if (getAndIncrement() != 0) { return; } int missed = 1; Subscriber downstream = this.downstream; AtomicThrowable errors = this.errors; AtomicReference> inner = this.inner; AtomicLong requested = this.requested; long emitted = this.emitted; for (;;) { for (;;) { if (cancelled) { return; } if (errors.get() != null) { if (!delayErrors) { errors.tryTerminateConsumer(downstream); return; } } boolean d = done; SwitchMapSingleObserver current = inner.get(); boolean empty = current == null; if (d && empty) { errors.tryTerminateConsumer(downstream); return; } if (empty || current.item == null || emitted == requested.get()) { break; } inner.compareAndSet(current, null); downstream.onNext(current.item); emitted++; } this.emitted = emitted; missed = addAndGet(-missed); if (missed == 0) { break; } } } static final class SwitchMapSingleObserver extends AtomicReference implements SingleObserver { private static final long serialVersionUID = 8042919737683345351L; final SwitchMapSingleSubscriber parent; volatile R item; SwitchMapSingleObserver(SwitchMapSingleSubscriber 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); } } } }