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.single;

import java.util.concurrent.atomic.AtomicReference;

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

Maps the success value of the source SingleSource into a Completable.
Type parameters:
<T> – the value type of the source SingleSource/**
 * Maps the success value of the source SingleSource into a Completable.
 * @param <T> the value type of the source SingleSource
 */
public final class SingleFlatMapCompletable<T> extends Completable {

    final SingleSource<T> source;

    final Function<? super T, ? extends CompletableSource> mapper;

    public SingleFlatMapCompletable(SingleSource<T> source, Function<? super T, ? extends CompletableSource> mapper) {
        this.source = source;
        this.mapper = mapper;
    }

    @Override
    protected void subscribeActual(CompletableObserver observer) {
        FlatMapCompletableObserver<T> parent = new FlatMapCompletableObserver<T>(observer, mapper);
        observer.onSubscribe(parent);
        source.subscribe(parent);
    }

    static final class FlatMapCompletableObserver<T>
    extends AtomicReference<Disposable>
    implements SingleObserver<T>, CompletableObserver, Disposable {

        private static final long serialVersionUID = -2177128922851101253L;

        final CompletableObserver downstream;

        final Function<? super T, ? extends CompletableSource> mapper;

        FlatMapCompletableObserver(CompletableObserver actual,
                Function<? super T, ? extends CompletableSource> mapper) {
            this.downstream = actual;
            this.mapper = mapper;
        }

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

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

        @Override
        public void onSubscribe(Disposable d) {
            DisposableHelper.replace(this, d);
        }

        @Override
        public void onSuccess(T value) {
            CompletableSource cs;

            try {
                cs = ObjectHelper.requireNonNull(mapper.apply(value), "The mapper returned a null CompletableSource");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                onError(ex);
                return;
            }

            if (!isDisposed()) {
                cs.subscribe(this);
            }
        }

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

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