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 io.reactivex.*;
import io.reactivex.annotations.Experimental;
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 to a Notification, then
maps it back to the corresponding signal type.
Type parameters:
<T> – the element type of the source
<R> – the element type of the Notification and result
Since:
2.2.4 - experimental/**
 * Maps the success value of the source to a Notification, then
 * maps it back to the corresponding signal type.
 * @param <T> the element type of the source
 * @param <R> the element type of the Notification and result
 * @since 2.2.4 - experimental
 */
@Experimental
public final class SingleDematerialize<T, R> extends Maybe<R> {

    final Single<T> source;

    final Function<? super T, Notification<R>> selector;

    public SingleDematerialize(Single<T> source, Function<? super T, Notification<R>> selector) {
        this.source = source;
        this.selector = selector;
    }

    @Override
    protected void subscribeActual(MaybeObserver<? super R> observer) {
        source.subscribe(new DematerializeObserver<T, R>(observer, selector));
    }

    static final class DematerializeObserver<T, R> implements SingleObserver<T>, Disposable {

        final MaybeObserver<? super R> downstream;

        final Function<? super T, Notification<R>> selector;

        Disposable upstream;

        DematerializeObserver(MaybeObserver<? super R> downstream,
                Function<? super T, Notification<R>> selector) {
            this.downstream = downstream;
            this.selector = selector;
        }

        @Override
        public void dispose() {
            upstream.dispose();
        }

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

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(upstream, d)) {
                upstream = d;
                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T t) {
            Notification<R> notification;

            try {
                notification = ObjectHelper.requireNonNull(selector.apply(t), "The selector returned a null Notification");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                downstream.onError(ex);
                return;
            }
            if (notification.isOnNext()) {
                downstream.onSuccess(notification.getValue());
            } else if (notification.isOnComplete()) {
                downstream.onComplete();
            } else {
                downstream.onError(notification.getError());
            }
        }

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