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ixjava developed by David Karnok
There is a newer version: 1.0.0
/*
 * Copyright 2011-2016 David Karnok
 *
 * 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 ix.internal.util;

import rx.Observer;
import ix.CloseableIterator;

import java.util.NoSuchElementException;

import rx.Subscription;

/**
 * Base class to help transition from reactive to interactive
 * world.
 * @param  the observed type
 * @param  the returned value type
 */
public abstract class ObserverToIteratorSink implements Observer,
        CloseableIterator {
    /** Indicate that the stream has finished. */
    protected boolean done;
    /** The original handle to the observer registration. */
    protected final Subscription handle;
    /** The current value. */
    protected final SingleOption current = new SingleOption();
    /**
     * Constructor, saves the handle.
     * @param handle the handle to close when the stream finishes.
     */
    public ObserverToIteratorSink(Subscription handle) {
        this.handle = handle;
    }
    @Override
    public boolean hasNext() {
        if (!done) {
            if (current.isEmpty()) {
                if (!tryNext(current)) {
                    done = true;
                    unsubscribe();
                    return false;
                }
            }
            return true;
        }
        return false;
    }
    
    @Override
    public U next() {
        if (hasNext()) {
            if (current.hasError()) {
                done = true;
                unsubscribe();
            }
            return current.take();
        }
        throw new NoSuchElementException();
    }
    
    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }
    @Override
    public void unsubscribe() {
        handle.unsubscribe();
    }
    @Override
    public boolean isUnsubscribed() {
    	return handle.isUnsubscribed();
    }
    /** Closes this iterator and suppresses exceptions. */
    protected void done() {
        unsubscribe();
    }
    /**
     * Try to get the next value.
     * @param out the output where to put the value
     * @return true if value was available
     */
    public abstract boolean tryNext(SingleOption out);
}