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.AtomicInteger;

import org.reactivestreams.Publisher;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.BiPredicate;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.operators.flowable.FlowableSequenceEqual.*;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.plugins.RxJavaPlugins;

public final class FlowableSequenceEqualSingle<T> extends Single<Boolean> implements FuseToFlowable<Boolean> {
    final Publisher<? extends T> first;
    final Publisher<? extends T> second;
    final BiPredicate<? super T, ? super T> comparer;
    final int prefetch;

    public FlowableSequenceEqualSingle(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(SingleObserver<? super Boolean> observer) {
        EqualCoordinator<T> parent = new EqualCoordinator<T>(observer, prefetch, comparer);
        observer.onSubscribe(parent);
        parent.subscribe(first, second);
    }

    @Override
    public Flowable<Boolean> fuseToFlowable() {
        return RxJavaPlugins.onAssembly(new FlowableSequenceEqual<T>(first, second, comparer, prefetch));
    }

    static final class EqualCoordinator<T>
    extends AtomicInteger
    implements Disposable, EqualCoordinatorHelper {

        private static final long serialVersionUID = -6178010334400373240L;

        final SingleObserver<? super Boolean> downstream;

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

        final EqualSubscriber<T> first;

        final EqualSubscriber<T> second;

        final AtomicThrowable error;

        T v1;

        T v2;

        EqualCoordinator(SingleObserver<? super Boolean> actual, int prefetch, BiPredicate<? super T, ? super T> comparer) {
            this.downstream = actual;
            this.comparer = comparer;
            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 dispose() {
            first.cancel();
            second.cancel();
            if (getAndIncrement() == 0) {
                first.clear();
                second.clear();
            }
        }

        @Override
        public boolean isDisposed() {
            return first.get() == SubscriptionHelper.CANCELLED;
        }

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

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

            int missed = 1;

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

                if (q1 != null && q2 != null) {
                    for (;;) {
                        if (isDisposed()) {
                            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) {
                            downstream.onSuccess(true);
                            return;
                        }
                        if ((d1 && d2) && (e1 != e2)) {
                            cancelAndClear();
                            downstream.onSuccess(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();
                            downstream.onSuccess(false);
                            return;
                        }

                        v1 = null;
                        v2 = null;

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

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

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

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

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

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