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.mixed;

import java.util.concurrent.atomic.*;

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 a Single onto an ObservableSource and
relays its signals to the downstream observer.
Type parameters:
<T> – the success value type of the Single source
<R> – the result type of the ObservableSource and this operator
Since:
2.1.15/**
 * Maps the success value of a Single onto an ObservableSource and
 * relays its signals to the downstream observer.
 * 
 * @param <T> the success value type of the Single source
 * @param <R> the result type of the ObservableSource and this operator
 * @since 2.1.15
 */
public final class SingleFlatMapObservable<T, R> extends Observable<R> {

    final SingleSource<T> source;

    final Function<? super T, ? extends ObservableSource<? extends R>> mapper;

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

    @Override
    protected void subscribeActual(Observer<? super R> observer) {
        FlatMapObserver<T, R> parent = new FlatMapObserver<T, R>(observer, mapper);
        observer.onSubscribe(parent);
        source.subscribe(parent);
    }

    static final class FlatMapObserver<T, R>
    extends AtomicReference<Disposable>
    implements Observer<R>, SingleObserver<T>, Disposable {

        private static final long serialVersionUID = -8948264376121066672L;

        final Observer<? super R> downstream;

        final Function<? super T, ? extends ObservableSource<? extends R>> mapper;

        FlatMapObserver(Observer<? super R> downstream, Function<? super T, ? extends ObservableSource<? extends R>> mapper) {
            this.downstream = downstream;
            this.mapper = mapper;
        }

        @Override
        public void onNext(R t) {
            downstream.onNext(t);
        }

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

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

        @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 t) {
            ObservableSource<? extends R> o;

            try {
                o = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper returned a null Publisher");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                downstream.onError(ex);
                return;
            }

            o.subscribe(this);
        }

    }
}