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/**
 * Copyright 2014 Netflix, Inc.
 *
 * 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 rx.internal.operators;

import rx.*;
import rx.Observable.Operator;
import rx.functions.Action1;

/**
 * This operator modifies an {@link rx.Observable} so a given action is invoked when the 
 * {@link rx.Producer} receives a request.
 * 
 * @param 
 *            The type of the elements in the {@link rx.Observable} that this operator modifies
 */
public class OperatorDoOnRequest implements Operator {

    final Action1 request;

    public OperatorDoOnRequest(Action1 request) {
        this.request = request;
    }

    @Override
    public Subscriber call(final Subscriber child) {

        final ParentSubscriber parent = new ParentSubscriber(child);

        child.setProducer(new Producer() {

            @Override
            public void request(long n) {
                request.call(n);
                parent.requestMore(n);
            }

        });
        child.add(parent);
        return parent;
    }

    static final class ParentSubscriber extends Subscriber {
        private final Subscriber child;

        ParentSubscriber(Subscriber child) {
            this.child = child;
            this.request(0);
        }

        private void requestMore(long n) {
            request(n);
        }

        @Override
        public void onCompleted() {
            child.onCompleted();
        }

        @Override
        public void onError(Throwable e) {
            child.onError(e);
        }

        @Override
        public void onNext(T t) {
            child.onNext(t);
        }
    }
}