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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.Observable;
import rx.Observable.OnSubscribe;
import rx.Subscriber;
import rx.functions.Func0;
import rx.functions.Func1;
import rx.internal.operators.OnSubscribeDelay.Emitter;
import rx.observers.SerializedSubscriber;
import rx.subscriptions.CompositeSubscription;

/**
 * Delay the subscription and emission of the source items by a per-item observable that fires its first element.
 * @param  the item type
 * @param  the value type of the subscription-delaying observable
 * @param  the value type of the item-delaying observable
 */
public final class OnSubscribeDelayWithSelector implements OnSubscribe {
    final Observable source;
    final Func0> subscriptionDelay;
    final Func1> itemDelay;

    public OnSubscribeDelayWithSelector(Observable source, Func1> itemDelay) {
        this.source = source;
        this.subscriptionDelay = new Func0>() {
            @Override
            public Observable call() {
                return Observable.just(null);
            }
        };
        this.itemDelay = itemDelay;
    }

    public OnSubscribeDelayWithSelector(Observable source, Func0> subscriptionDelay, Func1> itemDelay) {
        this.source = source;
        this.subscriptionDelay = subscriptionDelay;
        this.itemDelay = itemDelay;
    }

    @Override
    public void call(Subscriber child) {
        final SerializedSubscriber s = new SerializedSubscriber(child);
        final CompositeSubscription csub = new CompositeSubscription();
        child.add(csub);
        
        Observable osub;
        try {
            osub = subscriptionDelay.call();
        } catch (Throwable e) {
            s.onError(e);
            return;
        }
        
        Observable> seqs = source.map(new Func1>() {
            @Override
            public Observable call(final T x) {
                final Emitter e = new Emitter(x);
                Observable itemObs = itemDelay.call(x);

                Subscriber itemSub = new Subscriber() {
                    boolean once = true;
                    @Override
                    public void onNext(V t) {
                        emit();
                    }

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

                    @Override
                    public void onCompleted() {
                        emit();
                    }
                    void emit() {
                        if (once) {
                            once = false;
                            e.call();
                            csub.remove(this);
                        }
                    }
                };
                csub.add(itemSub);
                itemObs.unsafeSubscribe(itemSub);
                
                return Observable.create(e);
            }
        });
        final Observable delayed = Observable.merge(seqs);
        
        Subscriber osubSub = new Subscriber(child) {
            boolean subscribed;
            @Override
            public void onNext(U ignored) {
                onCompleted();
            }

            @Override
            public void onError(Throwable e) {
                if (!subscribed) {
                    s.onError(e);
                    unsubscribe();
                }
            }

            @Override
            public void onCompleted() {
                if (!subscribed) {
                    subscribed = true;
                    delayed.unsafeSubscribe(s);
                }
            }
        };
        
        osub.unsafeSubscribe(osubSub);
    }
}