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.observable;

import java.util.concurrent.atomic.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.observers.SerializedObserver;

public final class ObservableSampleWithObservable<T> extends AbstractObservableWithUpstream<T, T> {

    final ObservableSource<?> other;

    final boolean emitLast;

    public ObservableSampleWithObservable(ObservableSource<T> source, ObservableSource<?> other, boolean emitLast) {
        super(source);
        this.other = other;
        this.emitLast = emitLast;
    }

    @Override
    public void subscribeActual(Observer<? super T> t) {
        SerializedObserver<T> serial = new SerializedObserver<T>(t);
        if (emitLast) {
            source.subscribe(new SampleMainEmitLast<T>(serial, other));
        } else {
            source.subscribe(new SampleMainNoLast<T>(serial, other));
        }
    }

    abstract static class SampleMainObserver<T> extends AtomicReference<T>
    implements Observer<T>, Disposable {

        private static final long serialVersionUID = -3517602651313910099L;

        final Observer<? super T> downstream;
        final ObservableSource<?> sampler;

        final AtomicReference<Disposable> other = new AtomicReference<Disposable>();

        Disposable upstream;

        SampleMainObserver(Observer<? super T> actual, ObservableSource<?> other) {
            this.downstream = actual;
            this.sampler = other;
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;
                downstream.onSubscribe(this);
                if (other.get() == null) {
                    sampler.subscribe(new SamplerObserver<T>(this));
                }
            }
        }

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

        @Override
        public void onError(Throwable t) {
            DisposableHelper.dispose(other);
            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            DisposableHelper.dispose(other);
            completion();
        }

        boolean setOther(Disposable o) {
            return DisposableHelper.setOnce(other, o);
        }

        @Override
        public void dispose() {
            DisposableHelper.dispose(other);
            upstream.dispose();
        }

        @Override
        public boolean isDisposed() {
            return other.get() == DisposableHelper.DISPOSED;
        }

        public void error(Throwable e) {
            upstream.dispose();
            downstream.onError(e);
        }

        public void complete() {
            upstream.dispose();
            completion();
        }

        void emit() {
            T value = getAndSet(null);
            if (value != null) {
                downstream.onNext(value);
            }
        }

        abstract void completion();

        abstract void run();
    }

    static final class SamplerObserver<T> implements Observer<Object> {
        final SampleMainObserver<T> parent;
        SamplerObserver(SampleMainObserver<T> parent) {
            this.parent = parent;

        }

        @Override
        public void onSubscribe(Disposable d) {
            parent.setOther(d);
        }

        @Override
        public void onNext(Object t) {
            parent.run();
        }

        @Override
        public void onError(Throwable t) {
            parent.error(t);
        }

        @Override
        public void onComplete() {
            parent.complete();
        }
    }

    static final class SampleMainNoLast<T> extends SampleMainObserver<T> {

        private static final long serialVersionUID = -3029755663834015785L;

        SampleMainNoLast(Observer<? super T> actual, ObservableSource<?> other) {
            super(actual, other);
        }

        @Override
        void completion() {
            downstream.onComplete();
        }

        @Override
        void run() {
            emit();
        }
    }

    static final class SampleMainEmitLast<T> extends SampleMainObserver<T> {

        private static final long serialVersionUID = -3029755663834015785L;

        final AtomicInteger wip;

        volatile boolean done;

        SampleMainEmitLast(Observer<? super T> actual, ObservableSource<?> other) {
            super(actual, other);
            this.wip = new AtomicInteger();
        }

        @Override
        void completion() {
            done = true;
            if (wip.getAndIncrement() == 0) {
                emit();
                downstream.onComplete();
            }
        }

        @Override
        void run() {
            if (wip.getAndIncrement() == 0) {
                do {
                    boolean d = done;
                    emit();
                    if (d) {
                        downstream.onComplete();
                        return;
                    }
                } while (wip.decrementAndGet() != 0);
            }
        }
    }
}