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 java.util.concurrent.atomic.AtomicReference;

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.*;
import io.reactivex.plugins.RxJavaPlugins;

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

    public ObservableBufferBoundarySupplier(ObservableSource<T> source, Callable<? extends ObservableSource<B>> boundarySupplier, Callable<U> bufferSupplier) {
        super(source);
        this.boundarySupplier = boundarySupplier;
        this.bufferSupplier = bufferSupplier;
    }

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

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

        final Callable<U> bufferSupplier;
        final Callable<? extends ObservableSource<B>> boundarySupplier;

        Disposable upstream;

        final AtomicReference<Disposable> other = new AtomicReference<Disposable>();

        U buffer;

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

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

                Observer<? super U> actual = this.downstream;

                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, actual);
                    return;
                }

                buffer = b;

                ObservableSource<B> boundary;

                try {
                    boundary = ObjectHelper.requireNonNull(boundarySupplier.call(), "The boundary ObservableSource supplied is null");
                } catch (Throwable ex) {
                    Exceptions.throwIfFatal(ex);
                    cancelled = true;
                    d.dispose();
                    EmptyDisposable.error(ex, actual);
                    return;
                }

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

                actual.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;
                upstream.dispose();
                disposeOther();

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

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

        void disposeOther() {
            DisposableHelper.dispose(other);
        }

        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;
            }

            ObservableSource<B> boundary;

            try {
                boundary = ObjectHelper.requireNonNull(boundarySupplier.call(), "The boundary ObservableSource supplied is null");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                cancelled = true;
                upstream.dispose();
                downstream.onError(ex);
                return;
            }

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

            if (DisposableHelper.replace(other, bs)) {
                U b;
                synchronized (this) {
                    b = buffer;
                    if (b == null) {
                        return;
                    }
                    buffer = next;
                }

                boundary.subscribe(bs);

                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 BufferBoundarySupplierObserver<T, U, B> parent;

        boolean once;

        BufferBoundaryObserver(BufferBoundarySupplierObserver<T, U, B> parent) {
            this.parent = parent;
        }

        @Override
        public void onNext(B t) {
            if (once) {
                return;
            }
            once = true;
            dispose();
            parent.next();
        }

        @Override
        public void onError(Throwable t) {
            if (once) {
                RxJavaPlugins.onError(t);
                return;
            }
            once = true;
            parent.onError(t);
        }

        @Override
        public void onComplete() {
            if (once) {
                return;
            }
            once = true;
            parent.next();
        }
    }
}