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
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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 org.reactivestreams.Subscription;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.*;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.SimplePlainQueue;
import io.reactivex.internal.queue.SpscArrayQueue;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;

Maps the upstream items into CompletableSources and subscribes to them one after the other completes or terminates (in error-delaying mode). 
History: 2.1.11 - experimental
Type parameters:
<T> – the upstream value type
Since:
2.2/**
 * Maps the upstream items into {@link CompletableSource}s and subscribes to them one after the
 * other completes or terminates (in error-delaying mode).
 * <p>History: 2.1.11 - experimental
 * @param <T> the upstream value type
 * @since 2.2
 */
public final class FlowableConcatMapCompletable<T> extends Completable {

    final Flowable<T> source;

    final Function<? super T, ? extends CompletableSource> mapper;

    final ErrorMode errorMode;

    final int prefetch;

    public FlowableConcatMapCompletable(Flowable<T> source,
            Function<? super T, ? extends CompletableSource> mapper,
            ErrorMode errorMode,
            int prefetch) {
        this.source = source;
        this.mapper = mapper;
        this.errorMode = errorMode;
        this.prefetch = prefetch;
    }

    @Override
    protected void subscribeActual(CompletableObserver observer) {
        source.subscribe(new ConcatMapCompletableObserver<T>(observer, mapper, errorMode, prefetch));
    }

    static final class ConcatMapCompletableObserver<T>
    extends AtomicInteger
    implements FlowableSubscriber<T>, Disposable {

        private static final long serialVersionUID = 3610901111000061034L;

        final CompletableObserver downstream;

        final Function<? super T, ? extends CompletableSource> mapper;

        final ErrorMode errorMode;

        final AtomicThrowable errors;

        final ConcatMapInnerObserver inner;

        final int prefetch;

        final SimplePlainQueue<T> queue;

        Subscription upstream;

        volatile boolean active;

        volatile boolean done;

        volatile boolean disposed;

        int consumed;

        ConcatMapCompletableObserver(CompletableObserver downstream,
                Function<? super T, ? extends CompletableSource> mapper,
                ErrorMode errorMode, int prefetch) {
            this.downstream = downstream;
            this.mapper = mapper;
            this.errorMode = errorMode;
            this.prefetch = prefetch;
            this.errors = new AtomicThrowable();
            this.inner = new ConcatMapInnerObserver(this);
            this.queue = new SpscArrayQueue<T>(prefetch);
        }

        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validate(upstream, s)) {
                this.upstream = s;
                downstream.onSubscribe(this);
                s.request(prefetch);
            }
        }

        @Override
        public void onNext(T t) {
            if (queue.offer(t)) {
                drain();
            } else {
                upstream.cancel();
                onError(new MissingBackpressureException("Queue full?!"));
            }
        }

        @Override
        public void onError(Throwable t) {
            if (errors.addThrowable(t)) {
                if (errorMode == ErrorMode.IMMEDIATE) {
                    inner.dispose();
                    t = errors.terminate();
                    if (t != ExceptionHelper.TERMINATED) {
                        downstream.onError(t);
                    }
                    if (getAndIncrement() == 0) {
                        queue.clear();
                    }
                } else {
                    done = true;
                    drain();
                }
            } else {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public void onComplete() {
            done = true;
            drain();
        }

        @Override
        public void dispose() {
            disposed = true;
            upstream.cancel();
            inner.dispose();
            if (getAndIncrement() == 0) {
                queue.clear();
            }
        }

        @Override
        public boolean isDisposed() {
            return disposed;
        }

        void innerError(Throwable ex) {
            if (errors.addThrowable(ex)) {
                if (errorMode == ErrorMode.IMMEDIATE) {
                    upstream.cancel();
                    ex = errors.terminate();
                    if (ex != ExceptionHelper.TERMINATED) {
                        downstream.onError(ex);
                    }
                    if (getAndIncrement() == 0) {
                        queue.clear();
                    }
                } else {
                    active = false;
                    drain();
                }
            } else {
                RxJavaPlugins.onError(ex);
            }
        }

        void innerComplete() {
            active = false;
            drain();
        }

        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }

            do {
                if (disposed) {
                    queue.clear();
                    return;
                }

                if (!active) {

                    if (errorMode == ErrorMode.BOUNDARY) {
                        if (errors.get() != null) {
                            queue.clear();
                            Throwable ex = errors.terminate();
                            downstream.onError(ex);
                            return;
                        }
                    }

                    boolean d = done;
                    T v = queue.poll();
                    boolean empty = v == null;

                    if (d && empty) {
                        Throwable ex = errors.terminate();
                        if (ex != null) {
                            downstream.onError(ex);
                        } else {
                            downstream.onComplete();
                        }
                        return;
                    }

                    if (!empty) {

                        int limit = prefetch - (prefetch >> 1);
                        int c = consumed + 1;
                        if (c == limit) {
                            consumed = 0;
                            upstream.request(limit);
                        } else {
                            consumed = c;
                        }

                        CompletableSource cs;

                        try {
                            cs = ObjectHelper.requireNonNull(mapper.apply(v), "The mapper returned a null CompletableSource");
                        } catch (Throwable ex) {
                            Exceptions.throwIfFatal(ex);
                            queue.clear();
                            upstream.cancel();
                            errors.addThrowable(ex);
                            ex = errors.terminate();
                            downstream.onError(ex);
                            return;
                        }
                        active = true;
                        cs.subscribe(inner);
                    }
                }
            } while (decrementAndGet() != 0);
        }

        static final class ConcatMapInnerObserver extends AtomicReference<Disposable>
        implements CompletableObserver {

            private static final long serialVersionUID = 5638352172918776687L;

            final ConcatMapCompletableObserver<?> parent;

            ConcatMapInnerObserver(ConcatMapCompletableObserver<?> parent) {
                this.parent = parent;
            }

            @Override
            public void onSubscribe(Disposable d) {
                DisposableHelper.replace(this, d);
            }

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

            @Override
            public void onComplete() {
                parent.innerComplete();
            }

            void dispose() {
                DisposableHelper.dispose(this);
            }
        }
    }
}