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.flowable;

import java.util.concurrent.atomic.*;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.exceptions.*;
import io.reactivex.functions.BiPredicate;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.queue.SpscArrayQueue;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.plugins.RxJavaPlugins;

public final class FlowableSequenceEqual<T> extends Flowable<Boolean> {
    final Publisher<? extends T> first;
    final Publisher<? extends T> second;
    final BiPredicate<? super T, ? super T> comparer;
    final int prefetch;

    public FlowableSequenceEqual(Publisher<? extends T> first, Publisher<? extends T> second,
            BiPredicate<? super T, ? super T> comparer, int prefetch) {
        this.first = first;
        this.second = second;
        this.comparer = comparer;
        this.prefetch = prefetch;
    }

    @Override
    public void subscribeActual(Subscriber<? super Boolean> s) {
        EqualCoordinator<T> parent = new EqualCoordinator<T>(s, prefetch, comparer);
        s.onSubscribe(parent);
        parent.subscribe(first, second);
    }

    
Provides callbacks for the EqualSubscribers.
/**
     * Provides callbacks for the EqualSubscribers.
     */
    interface EqualCoordinatorHelper {

        void drain();

        void innerError(Throwable ex);
    }

    static final class EqualCoordinator<T> extends DeferredScalarSubscription<Boolean>
    implements EqualCoordinatorHelper {

        private static final long serialVersionUID = -6178010334400373240L;

        final BiPredicate<? super T, ? super T> comparer;

        final EqualSubscriber<T> first;

        final EqualSubscriber<T> second;

        final AtomicThrowable error;

        final AtomicInteger wip;

        T v1;

        T v2;

        EqualCoordinator(Subscriber<? super Boolean> actual, int prefetch, BiPredicate<? super T, ? super T> comparer) {
            super(actual);
            this.comparer = comparer;
            this.wip = new AtomicInteger();
            this.first = new EqualSubscriber<T>(this, prefetch);
            this.second = new EqualSubscriber<T>(this, prefetch);
            this.error = new AtomicThrowable();
        }

        void subscribe(Publisher<? extends T> source1, Publisher<? extends T> source2) {
            source1.subscribe(first);
            source2.subscribe(second);
        }

        @Override
        public void cancel() {
            super.cancel();
            first.cancel();
            second.cancel();
            if (wip.getAndIncrement() == 0) {
                first.clear();
                second.clear();
            }
        }

        void cancelAndClear() {
            first.cancel();
            first.clear();
            second.cancel();
            second.clear();
        }

        @Override
        public void drain() {
            if (wip.getAndIncrement() != 0) {
                return;
            }

            int missed = 1;

            for (;;) {
                SimpleQueue<T> q1 = first.queue;
                SimpleQueue<T> q2 = second.queue;

                if (q1 != null && q2 != null) {
                    for (;;) {
                        if (isCancelled()) {
                            first.clear();
                            second.clear();
                            return;
                        }

                        Throwable ex = error.get();
                        if (ex != null) {
                            cancelAndClear();

                            downstream.onError(error.terminate());
                            return;
                        }

                        boolean d1 = first.done;

                        T a = v1;
                        if (a == null) {
                            try {
                                a = q1.poll();
                            } catch (Throwable exc) {
                                Exceptions.throwIfFatal(exc);
                                cancelAndClear();
                                error.addThrowable(exc);
                                downstream.onError(error.terminate());
                                return;
                            }
                            v1 = a;
                        }
                        boolean e1 = a == null;

                        boolean d2 = second.done;
                        T b = v2;
                        if (b == null) {
                            try {
                                b = q2.poll();
                            } catch (Throwable exc) {
                                Exceptions.throwIfFatal(exc);
                                cancelAndClear();
                                error.addThrowable(exc);
                                downstream.onError(error.terminate());
                                return;
                            }
                            v2 = b;
                        }

                        boolean e2 = b == null;

                        if (d1 && d2 && e1 && e2) {
                            complete(true);
                            return;
                        }
                        if ((d1 && d2) && (e1 != e2)) {
                            cancelAndClear();
                            complete(false);
                            return;
                        }

                        if (e1 || e2) {
                            break;
                        }

                        boolean c;

                        try {
                            c = comparer.test(a, b);
                        } catch (Throwable exc) {
                            Exceptions.throwIfFatal(exc);
                            cancelAndClear();
                            error.addThrowable(exc);
                            downstream.onError(error.terminate());
                            return;
                        }

                        if (!c) {
                            cancelAndClear();
                            complete(false);
                            return;
                        }

                        v1 = null;
                        v2 = null;

                        first.request();
                        second.request();
                    }

                } else {
                    if (isCancelled()) {
                        first.clear();
                        second.clear();
                        return;
                    }

                    Throwable ex = error.get();
                    if (ex != null) {
                        cancelAndClear();

                        downstream.onError(error.terminate());
                        return;
                    }
                }

                missed = wip.addAndGet(-missed);
                if (missed == 0) {
                    break;
                }
            }
        }

        @Override
        public void innerError(Throwable t) {
            if (error.addThrowable(t)) {
                drain();
            } else {
                RxJavaPlugins.onError(t);
            }
        }
    }

    static final class EqualSubscriber<T>
    extends AtomicReference<Subscription>
    implements FlowableSubscriber<T> {

        private static final long serialVersionUID = 4804128302091633067L;

        final EqualCoordinatorHelper parent;

        final int prefetch;

        final int limit;

        long produced;

        volatile SimpleQueue<T> queue;

        volatile boolean done;

        int sourceMode;

        EqualSubscriber(EqualCoordinatorHelper parent, int prefetch) {
            this.parent = parent;
            this.limit = prefetch - (prefetch >> 2);
            this.prefetch = prefetch;
        }

        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.setOnce(this, s)) {
                if (s instanceof QueueSubscription) {
                    @SuppressWarnings("unchecked")
                    QueueSubscription<T> qs = (QueueSubscription<T>) s;

                    int m = qs.requestFusion(QueueSubscription.ANY);
                    if (m == QueueSubscription.SYNC) {
                        sourceMode = m;
                        queue = qs;
                        done = true;
                        parent.drain();
                        return;
                    }
                    if (m == QueueSubscription.ASYNC) {
                        sourceMode = m;
                        queue = qs;
                        s.request(prefetch);
                        return;
                    }
                }

                queue = new SpscArrayQueue<T>(prefetch);

                s.request(prefetch);
            }
        }

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

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

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

        public void request() {
            if (sourceMode != QueueSubscription.SYNC) {
                long p = produced + 1;
                if (p >= limit) {
                    produced = 0;
                    get().request(p);
                } else {
                    produced = p;
                }
            }
        }

        public void cancel() {
            SubscriptionHelper.cancel(this);
        }

        void clear() {
            SimpleQueue<T> sq = queue;
            if (sq != null) {
                sq.clear();
            }
        }
    }
}