import lombok.SneakyThrows;

import javax.annotation.concurrent.NotThreadSafe;
import java.util.Iterator;
import java.util.concurrent.BlockingQueue;

@NotThreadSafe
public class BlockingQueueIterator<T> implements Iterator<T> {

	private final BlockingQueue<QueueEntry<T>> queue;

	private QueueEntry<T> queueEntry;

	public BlockingQueueIterator(BlockingQueue<QueueEntry<T>> queue) {
		this.queue = queue;
	}

	@SneakyThrows
	@Override
	public boolean hasNext() {
		this.queueEntry = queue.take();

		if (queueEntry.data != null) {
			return true;
		} else if (queueEntry.e != null) {
			throw queueEntry.e;
		} else {
			return false;
		}
	}

	@Override
	public T next() {
		return queueEntry.data;
	}

}