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.maybe;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.fuseable.HasUpstreamSingleSource;

Wrap a Single into a Maybe.
Type parameters:
<T> – the value type/**
 * Wrap a Single into a Maybe.
 *
 * @param <T> the value type
 */
public final class MaybeFromSingle<T> extends Maybe<T> implements HasUpstreamSingleSource<T> {

    final SingleSource<T> source;

    public MaybeFromSingle(SingleSource<T> source) {
        this.source = source;
    }

    @Override
    public SingleSource<T> source() {
        return source;
    }

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

    static final class FromSingleObserver<T> implements SingleObserver<T>, Disposable {
        final MaybeObserver<? super T> downstream;

        Disposable upstream;

        FromSingleObserver(MaybeObserver<? super T> downstream) {
            this.downstream = downstream;
        }

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

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

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

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T value) {
            upstream = DisposableHelper.DISPOSED;
            downstream.onSuccess(value);
        }

        @Override
        public void onError(Throwable e) {
            upstream = DisposableHelper.DISPOSED;
            downstream.onError(e);
        }
    }
}