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.observable;

import io.reactivex.internal.functions.ObjectHelper;
import java.util.Collection;
import java.util.concurrent.Callable;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.disposables.*;
import io.reactivex.internal.observers.QueueDrainObserver;
import io.reactivex.internal.queue.MpscLinkedQueue;
import io.reactivex.internal.util.QueueDrainHelper;
import io.reactivex.observers.*;

public final class ObservableBufferExactBoundary<T, U extends Collection<? super T>, B>
extends AbstractObservableWithUpstream<T, U> {
    final ObservableSource<B> boundary;
    final Callable<U> bufferSupplier;

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

    @Override
    protected void subscribeActual(Observer<? super U> t) {
        source.subscribe(new BufferExactBoundaryObserver<T, U, B>(new SerializedObserver<U>(t), bufferSupplier, boundary));
    }

    static final class BufferExactBoundaryObserver<T, U extends Collection<? super T>, B>
    extends QueueDrainObserver<T, U, U> implements Observer<T>, Disposable {

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

        Disposable upstream;

        Disposable other;

        U buffer;

        BufferExactBoundaryObserver(Observer<? super U> actual, Callable<U> bufferSupplier,
                                             ObservableSource<B> boundary) {
            super(actual, new MpscLinkedQueue<U>());
            this.bufferSupplier = bufferSupplier;
            this.boundary = boundary;
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;

                U b;

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

                buffer = b;

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

                downstream.onSubscribe(this);

                if (!cancelled) {
                    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) {
            dispose();
            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.drainLoop(queue, downstream, false, this, this);
            }
        }

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

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

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

        void next() {

            U next;

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

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

            fastPathEmit(b, false, this);
        }

        @Override
        public void accept(Observer<? super U> a, U v) {
            downstream.onNext(v);
        }

    }

    static final class BufferBoundaryObserver<T, U extends Collection<? super T>, B>
    extends DisposableObserver<B> {
        final BufferExactBoundaryObserver<T, U, B> parent;

        BufferBoundaryObserver(BufferExactBoundaryObserver<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();
        }
    }
}