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 java.util.*;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.*;

import io.reactivex.ObservableSource;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.util.*;

public final class BlockingObservableIterable<T> implements Iterable<T> {
    final ObservableSource<? extends T> source;

    final int bufferSize;

    public BlockingObservableIterable(ObservableSource<? extends T> source, int bufferSize) {
        this.source = source;
        this.bufferSize = bufferSize;
    }

    @Override
    public Iterator<T> iterator() {
        BlockingObservableIterator<T> it = new BlockingObservableIterator<T>(bufferSize);
        source.subscribe(it);
        return it;
    }

    static final class BlockingObservableIterator<T>
    extends AtomicReference<Disposable>
    implements io.reactivex.Observer<T>, Iterator<T>, Disposable {

        private static final long serialVersionUID = 6695226475494099826L;

        final SpscLinkedArrayQueue<T> queue;

        final Lock lock;

        final Condition condition;

        volatile boolean done;
        Throwable error;

        BlockingObservableIterator(int batchSize) {
            this.queue = new SpscLinkedArrayQueue<T>(batchSize);
            this.lock = new ReentrantLock();
            this.condition = lock.newCondition();
        }

        @Override
        public boolean hasNext() {
            for (;;) {
                boolean d = done;
                boolean empty = queue.isEmpty();
                if (d) {
                    Throwable e = error;
                    if (e != null) {
                        throw ExceptionHelper.wrapOrThrow(e);
                    } else
                    if (empty) {
                        return false;
                    }
                }
                if (empty) {
                    try {
                        BlockingHelper.verifyNonBlocking();
                        lock.lock();
                        try {
                            while (!done && queue.isEmpty()) {
                                condition.await();
                            }
                        } finally {
                            lock.unlock();
                        }
                    } catch (InterruptedException ex) {
                        DisposableHelper.dispose(this);
                        signalConsumer();
                        throw ExceptionHelper.wrapOrThrow(ex);
                    }
                } else {
                    return true;
                }
            }
        }

        @Override
        public T next() {
            if (hasNext()) {
                return queue.poll();
            }
            throw new NoSuchElementException();
        }

        @Override
        public void onSubscribe(Disposable d) {
            DisposableHelper.setOnce(this, d);
        }

        @Override
        public void onNext(T t) {
            queue.offer(t);
            signalConsumer();
        }

        @Override
        public void onError(Throwable t) {
            error = t;
            done = true;
            signalConsumer();
        }

        @Override
        public void onComplete() {
            done = true;
            signalConsumer();
        }

        void signalConsumer() {
            lock.lock();
            try {
                condition.signalAll();
            } finally {
                lock.unlock();
            }
        }

        @Override // otherwise default method which isn't available in Java 7
        public void remove() {
            throw new UnsupportedOperationException("remove");
        }

        @Override
        public void dispose() {
            DisposableHelper.dispose(this);
        }

        @Override
        public boolean isDisposed() {
            return DisposableHelper.isDisposed(get());
        }
    }
}