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.completable;

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;

public final class CompletableAmb extends Completable {
    private final CompletableSource[] sources;
    private final Iterable<? extends CompletableSource> sourcesIterable;

    public CompletableAmb(CompletableSource[] sources, Iterable<? extends CompletableSource> sourcesIterable) {
        this.sources = sources;
        this.sourcesIterable = sourcesIterable;
    }

    @Override
    public void subscribeActual(final CompletableObserver observer) {
        CompletableSource[] sources = this.sources;
        int count = 0;
        if (sources == null) {
            sources = new CompletableSource[8];
            try {
                for (CompletableSource element : sourcesIterable) {
                    if (element == null) {
                        EmptyDisposable.error(new NullPointerException("One of the sources is null"), observer);
                        return;
                    }
                    if (count == sources.length) {
                        CompletableSource[] b = new CompletableSource[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;
        }

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

        final AtomicBoolean once = new AtomicBoolean();

        for (int i = 0; i < count; i++) {
            CompletableSource c = sources[i];
            if (set.isDisposed()) {
                return;
            }
            if (c == null) {
                NullPointerException npe = new NullPointerException("One of the sources is null");
                if (once.compareAndSet(false, true)) {
                    set.dispose();
                    observer.onError(npe);
                } else {
                    RxJavaPlugins.onError(npe);
                }
                return;
            }

            // no need to have separate subscribers because inner is stateless
            c.subscribe(new Amb(once, set, observer));
        }

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

    static final class Amb implements CompletableObserver {

        final AtomicBoolean once;

        final CompositeDisposable set;

        final CompletableObserver downstream;

        Disposable upstream;

        Amb(AtomicBoolean once, CompositeDisposable set, CompletableObserver observer) {
            this.once = once;
            this.set = set;
            this.downstream = observer;
        }

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

        @Override
        public void onError(Throwable e) {
            if (once.compareAndSet(false, true)) {
                set.delete(upstream);
                set.dispose();
                downstream.onError(e);
            } else {
                RxJavaPlugins.onError(e);
            }
        }

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