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.Collection;
import java.util.concurrent.Callable;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.queue.MpscLinkedQueue;
import io.reactivex.internal.subscribers.QueueDrainSubscriber;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.internal.util.QueueDrainHelper;
import io.reactivex.subscribers.*;

public final class FlowableBufferExactBoundary<T, U extends Collection<? super T>, B>
extends AbstractFlowableWithUpstream<T, U> {
    final Publisher<B> boundary;
    final Callable<U> bufferSupplier;

    public FlowableBufferExactBoundary(Flowable<T> source, Publisher<B> boundary, Callable<U> bufferSupplier) {
        super(source);
        this.boundary = boundary;
        this.bufferSupplier = bufferSupplier;
    }

    @Override
    protected void subscribeActual(Subscriber<? super U> s) {
        source.subscribe(new BufferExactBoundarySubscriber<T, U, B>(new SerializedSubscriber<U>(s), bufferSupplier, boundary));
    }

    static final class BufferExactBoundarySubscriber<T, U extends Collection<? super T>, B>
    extends QueueDrainSubscriber<T, U, U> implements FlowableSubscriber<T>, Subscription, Disposable {

        final Callable<U> bufferSupplier;
        final Publisher<B> boundary;

        Subscription upstream;

        Disposable other;

        U buffer;

        BufferExactBoundarySubscriber(Subscriber<? super U> actual, Callable<U> bufferSupplier,
                                             Publisher<B> boundary) {
            super(actual, new MpscLinkedQueue<U>());
            this.bufferSupplier = bufferSupplier;
            this.boundary = boundary;
        }

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

            U b;

            try {
                b = ObjectHelper.requireNonNull(bufferSupplier.call(), "The buffer supplied is null");
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                cancelled = true;
                s.cancel();
                EmptySubscription.error(e, downstream);
                return;
            }

            buffer = b;

            BufferBoundarySubscriber<T, U, B> bs = new BufferBoundarySubscriber<T, U, B>(this);
            other = bs;

            downstream.onSubscribe(this);

            if (!cancelled) {
                s.request(Long.MAX_VALUE);

                boundary.subscribe(bs);
            }
        }

        @Override
        public void onNext(T t) {
            synchronized (this) {
                U b = buffer;
                if (b == null) {
                    return;
                }
                b.add(t);
            }
        }

        @Override
        public void onError(Throwable t) {
            cancel();
            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            U b;
            synchronized (this) {
                b = buffer;
                if (b == null) {
                    return;
                }
                buffer = null;
            }
            queue.offer(b);
            done = true;
            if (enter()) {
                QueueDrainHelper.drainMaxLoop(queue, downstream, false, this, this);
            }
        }

        @Override
        public void request(long n) {
            requested(n);
        }

        @Override
        public void cancel() {
            if (!cancelled) {
                cancelled = true;
                other.dispose();
                upstream.cancel();

                if (enter()) {
                    queue.clear();
                }
            }
        }

        void next() {

            U next;

            try {
                next = ObjectHelper.requireNonNull(bufferSupplier.call(), "The buffer supplied is null");
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                cancel();
                downstream.onError(e);
                return;
            }

            U b;
            synchronized (this) {
                b = buffer;
                if (b == null) {
                    return;
                }
                buffer = next;
            }

            fastPathEmitMax(b, false, this);
        }

        @Override
        public void dispose() {
            cancel();
        }

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

        @Override
        public boolean accept(Subscriber<? super U> a, U v) {
            downstream.onNext(v);
            return true;
        }

    }

    static final class BufferBoundarySubscriber<T, U extends Collection<? super T>, B> extends DisposableSubscriber<B> {
        final BufferExactBoundarySubscriber<T, U, B> parent;

        BufferBoundarySubscriber(BufferExactBoundarySubscriber<T, U, B> parent) {
            this.parent = parent;
        }

        @Override
        public void onNext(B t) {
            parent.next();
        }

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

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