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.
/**
 * 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.completable;

import java.util.concurrent.atomic.*;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.*;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.queue.*;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.plugins.RxJavaPlugins;

public final class CompletableConcat extends Completable {
    final Publisher<? extends CompletableSource> sources;
    final int prefetch;

    public CompletableConcat(Publisher<? extends CompletableSource> sources, int prefetch) {
        this.sources = sources;
        this.prefetch = prefetch;
    }

    @Override
    public void subscribeActual(CompletableObserver observer) {
        sources.subscribe(new CompletableConcatSubscriber(observer, prefetch));
    }

    static final class CompletableConcatSubscriber
    extends AtomicInteger
    implements FlowableSubscriber<CompletableSource>, Disposable {
        private static final long serialVersionUID = 9032184911934499404L;

        final CompletableObserver downstream;

        final int prefetch;

        final int limit;

        final ConcatInnerObserver inner;

        final AtomicBoolean once;

        int sourceFused;

        int consumed;

        SimpleQueue<CompletableSource> queue;

        Subscription upstream;

        volatile boolean done;

        volatile boolean active;

        CompletableConcatSubscriber(CompletableObserver actual, int prefetch) {
            this.downstream = actual;
            this.prefetch = prefetch;
            this.inner = new ConcatInnerObserver(this);
            this.once = new AtomicBoolean();
            this.limit = prefetch - (prefetch >> 2);
        }

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

                long r = prefetch == Integer.MAX_VALUE ? Long.MAX_VALUE : prefetch;

                if (s instanceof QueueSubscription) {
                    @SuppressWarnings("unchecked")
                    QueueSubscription<CompletableSource> qs = (QueueSubscription<CompletableSource>) s;

                    int m = qs.requestFusion(QueueSubscription.ANY);

                    if (m == QueueSubscription.SYNC) {
                        sourceFused = m;
                        queue = qs;
                        done = true;
                        downstream.onSubscribe(this);
                        drain();
                        return;
                    }
                    if (m == QueueSubscription.ASYNC) {
                        sourceFused = m;
                        queue = qs;
                        downstream.onSubscribe(this);
                        s.request(r);
                        return;
                    }
                }

                if (prefetch == Integer.MAX_VALUE) {
                    queue = new SpscLinkedArrayQueue<CompletableSource>(Flowable.bufferSize());
                } else {
                    queue = new SpscArrayQueue<CompletableSource>(prefetch);
                }

                downstream.onSubscribe(this);

                s.request(r);
            }
        }

        @Override
        public void onNext(CompletableSource t) {
            if (sourceFused == QueueSubscription.NONE) {
                if (!queue.offer(t)) {
                    onError(new MissingBackpressureException());
                    return;
                }
            }
            drain();
        }

        @Override
        public void onError(Throwable t) {
            if (once.compareAndSet(false, true)) {
                DisposableHelper.dispose(inner);
                downstream.onError(t);
            } else {
                RxJavaPlugins.onError(t);
            }
        }

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

        @Override
        public void dispose() {
            upstream.cancel();
            DisposableHelper.dispose(inner);
        }

        @Override
        public boolean isDisposed() {
            return DisposableHelper.isDisposed(inner.get());
        }

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

            for (;;) {
                if (isDisposed()) {
                    return;
                }

                if (!active) {

                    boolean d = done;

                    CompletableSource cs;

                    try {
                        cs = queue.poll();
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        innerError(ex);
                        return;
                    }

                    boolean empty = cs == null;

                    if (d && empty) {
                        if (once.compareAndSet(false, true)) {
                            downstream.onComplete();
                        }
                        return;
                    }

                    if (!empty) {
                        active = true;
                        cs.subscribe(inner);
                        request();
                    }
                }

                if (decrementAndGet() == 0) {
                    break;
                }
            }
        }

        void request() {
            if (sourceFused != QueueSubscription.SYNC) {
                int p = consumed + 1;
                if (p == limit) {
                    consumed = 0;
                    upstream.request(p);
                } else {
                    consumed = p;
                }
            }
        }

        void innerError(Throwable e) {
            if (once.compareAndSet(false, true)) {
                upstream.cancel();
                downstream.onError(e);
            } else {
                RxJavaPlugins.onError(e);
            }
        }

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

        static final class ConcatInnerObserver extends AtomicReference<Disposable> implements CompletableObserver {
            private static final long serialVersionUID = -5454794857847146511L;

            final CompletableConcatSubscriber parent;

            ConcatInnerObserver(CompletableConcatSubscriber 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();
            }
        }
    }
}