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.AtomicInteger;

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

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

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

    @Override
    public void subscribeActual(CompletableObserver observer) {

        Iterator<? extends CompletableSource> it;

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

        ConcatInnerObserver inner = new ConcatInnerObserver(observer, it);
        observer.onSubscribe(inner.sd);
        inner.next();
    }

    static final class ConcatInnerObserver extends AtomicInteger implements CompletableObserver {

        private static final long serialVersionUID = -7965400327305809232L;

        final CompletableObserver downstream;
        final Iterator<? extends CompletableSource> sources;

        final SequentialDisposable sd;

        ConcatInnerObserver(CompletableObserver actual, Iterator<? extends CompletableSource> sources) {
            this.downstream = actual;
            this.sources = sources;
            this.sd = new SequentialDisposable();
        }

        @Override
        public void onSubscribe(Disposable d) {
            sd.replace(d);
        }

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

        @Override
        public void onComplete() {
            next();
        }

        void next() {
            if (sd.isDisposed()) {
                return;
            }

            if (getAndIncrement() != 0) {
                return;
            }

            Iterator<? extends CompletableSource> a = sources;
            do {
                if (sd.isDisposed()) {
                    return;
                }

                boolean b;
                try {
                    b = a.hasNext();
                } catch (Throwable ex) {
                    Exceptions.throwIfFatal(ex);
                    downstream.onError(ex);
                    return;
                }

                if (!b) {
                    downstream.onComplete();
                    return;
                }

                CompletableSource c;

                try {
                    c = ObjectHelper.requireNonNull(a.next(), "The CompletableSource returned is null");
                } catch (Throwable ex) {
                    Exceptions.throwIfFatal(ex);
                    downstream.onError(ex);
                    return;
                }

                c.subscribe(this);
            } while (decrementAndGet() != 0);
        }
    }
}