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

import org.reactivestreams.Subscription;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.MissingBackpressureException;
import io.reactivex.internal.queue.SpscArrayQueue;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.*;

public final class BlockingFlowableIterable<T> implements Iterable<T> {
    final Flowable<T> source;

    final int bufferSize;

    public BlockingFlowableIterable(Flowable<T> source, int bufferSize) {
        this.source = source;
        this.bufferSize = bufferSize;
    }

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

    static final class BlockingFlowableIterator<T>
    extends AtomicReference<Subscription>
    implements FlowableSubscriber<T>, Iterator<T>, Runnable, Disposable {

        private static final long serialVersionUID = 6695226475494099826L;

        final SpscArrayQueue<T> queue;

        final long batchSize;

        final long limit;

        final Lock lock;

        final Condition condition;

        long produced;

        volatile boolean done;
        Throwable error;

        BlockingFlowableIterator(int batchSize) {
            this.queue = new SpscArrayQueue<T>(batchSize);
            this.batchSize = batchSize;
            this.limit = batchSize - (batchSize >> 2);
            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) {
                    BlockingHelper.verifyNonBlocking();
                    lock.lock();
                    try {
                        while (!done && queue.isEmpty()) {
                            condition.await();
                        }
                    } catch (InterruptedException ex) {
                        run();
                        throw ExceptionHelper.wrapOrThrow(ex);
                    } finally {
                        lock.unlock();
                    }
                } else {
                    return true;
                }
            }
        }

        @Override
        public T next() {
            if (hasNext()) {
                T v = queue.poll();

                long p = produced + 1;
                if (p == limit) {
                    produced = 0;
                    get().request(p);
                } else {
                    produced = p;
                }

                return v;
            }
            throw new NoSuchElementException();
        }

        @Override
        public void onSubscribe(Subscription s) {
            SubscriptionHelper.setOnce(this, s, batchSize);
        }

        @Override
        public void onNext(T t) {
            if (!queue.offer(t)) {
                SubscriptionHelper.cancel(this);

                onError(new MissingBackpressureException("Queue full?!"));
            } else {
                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
        public void run() {
            SubscriptionHelper.cancel(this);
            signalConsumer();
        }

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

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

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