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.Iterator;
import java.util.concurrent.atomic.*;

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

public final class CompletableMergeIterable extends Completable {
    final Iterable<? extends CompletableSource> sources;

    public CompletableMergeIterable(Iterable<? extends CompletableSource> sources) {
        this.sources = sources;
    }

    @Override
    public void subscribeActual(final CompletableObserver observer) {
        final CompositeDisposable set = new CompositeDisposable();

        observer.onSubscribe(set);

        Iterator<? extends CompletableSource> iterator;

        try {
            iterator = ObjectHelper.requireNonNull(sources.iterator(), "The source iterator returned is null");
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            observer.onError(e);
            return;
        }

        final AtomicInteger wip = new AtomicInteger(1);

        MergeCompletableObserver shared = new MergeCompletableObserver(observer, set, wip);
        for (;;) {
            if (set.isDisposed()) {
                return;
            }

            boolean b;
            try {
                b = iterator.hasNext();
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                set.dispose();
                shared.onError(e);
                return;
            }

            if (!b) {
                break;
            }

            if (set.isDisposed()) {
                return;
            }

            CompletableSource c;

            try {
                c = ObjectHelper.requireNonNull(iterator.next(), "The iterator returned a null CompletableSource");
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                set.dispose();
                shared.onError(e);
                return;
            }

            if (set.isDisposed()) {
                return;
            }

            wip.getAndIncrement();

            c.subscribe(shared);
        }

        shared.onComplete();
    }

    static final class MergeCompletableObserver extends AtomicBoolean implements CompletableObserver {

        private static final long serialVersionUID = -7730517613164279224L;

        final CompositeDisposable set;

        final CompletableObserver downstream;

        final AtomicInteger wip;

        MergeCompletableObserver(CompletableObserver actual, CompositeDisposable set, AtomicInteger wip) {
            this.downstream = actual;
            this.set = set;
            this.wip = wip;
        }

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

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

        @Override
        public void onComplete() {
            if (wip.decrementAndGet() == 0) {
                if (compareAndSet(false, true)) {
                    downstream.onComplete();
                }
            }
        }
    }
}