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.maybe;

import java.util.concurrent.atomic.AtomicBoolean;

import io.reactivex.*;
import io.reactivex.disposables.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.disposables.EmptyDisposable;
import io.reactivex.plugins.RxJavaPlugins;

Signals the event of the first MaybeSource that signals.
Type parameters:
<T> – the value type emitted/**
 * Signals the event of the first MaybeSource that signals.
 *
 * @param <T> the value type emitted
 */
public final class MaybeAmb<T> extends Maybe<T> {
    private final MaybeSource<? extends T>[] sources;
    private final Iterable<? extends MaybeSource<? extends T>> sourcesIterable;

    public MaybeAmb(MaybeSource<? extends T>[] sources, Iterable<? extends MaybeSource<? extends T>> sourcesIterable) {
        this.sources = sources;
        this.sourcesIterable = sourcesIterable;
    }

    @Override
    @SuppressWarnings("unchecked")
    protected void subscribeActual(MaybeObserver<? super T> observer) {
        MaybeSource<? extends T>[] sources = this.sources;
        int count = 0;
        if (sources == null) {
            sources = new MaybeSource[8];
            try {
                for (MaybeSource<? extends T> element : sourcesIterable) {
                    if (element == null) {
                        EmptyDisposable.error(new NullPointerException("One of the sources is null"), observer);
                        return;
                    }
                    if (count == sources.length) {
                        MaybeSource<? extends T>[] b = new MaybeSource[count + (count >> 2)];
                        System.arraycopy(sources, 0, b, 0, count);
                        sources = b;
                    }
                    sources[count++] = element;
                }
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                EmptyDisposable.error(e, observer);
                return;
            }
        } else {
            count = sources.length;
        }

        CompositeDisposable set = new CompositeDisposable();
        observer.onSubscribe(set);

        AtomicBoolean winner = new AtomicBoolean();

        for (int i = 0; i < count; i++) {
            MaybeSource<? extends T> s = sources[i];
            if (set.isDisposed()) {
                return;
            }

            if (s == null) {
                set.dispose();
                NullPointerException ex = new NullPointerException("One of the MaybeSources is null");
                if (winner.compareAndSet(false, true)) {
                    observer.onError(ex);
                } else {
                    RxJavaPlugins.onError(ex);
                }
                return;
            }

            s.subscribe(new AmbMaybeObserver<T>(observer, set, winner));
        }

        if (count == 0) {
            observer.onComplete();
        }
    }

    static final class AmbMaybeObserver<T>
    implements MaybeObserver<T> {

        final MaybeObserver<? super T> downstream;

        final AtomicBoolean winner;

        final CompositeDisposable set;

        Disposable upstream;

        AmbMaybeObserver(MaybeObserver<? super T> downstream, CompositeDisposable set, AtomicBoolean winner) {
            this.downstream = downstream;
            this.set = set;
            this.winner = winner;
        }

        @Override
        public void onSubscribe(Disposable d) {
            upstream = d;
            set.add(d);
        }

        @Override
        public void onSuccess(T value) {
            if (winner.compareAndSet(false, true)) {
                set.delete(upstream);
                set.dispose();

                downstream.onSuccess(value);
            }
        }

        @Override
        public void onError(Throwable e) {
            if (winner.compareAndSet(false, true)) {
                set.delete(upstream);
                set.dispose();

                downstream.onError(e);
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        @Override
        public void onComplete() {
            if (winner.compareAndSet(false, true)) {
                set.delete(upstream);
                set.dispose();

                downstream.onComplete();
            }
        }
    }
}