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.HasUpstreamMaybeSource;

Signals 1L if the source signalled an item or 0L if the source is empty.
Type parameters:
<T> – the source value type/**
 * Signals 1L if the source signalled an item or 0L if the source is empty.
 *
 * @param <T> the source value type
 */
public final class MaybeCount<T> extends Single<Long> implements HasUpstreamMaybeSource<T> {

    final MaybeSource<T> source;

    public MaybeCount(MaybeSource<T> source) {
        this.source = source;
    }

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

    @Override
    protected void subscribeActual(SingleObserver<? super Long> observer) {
        source.subscribe(new CountMaybeObserver(observer));
    }

    static final class CountMaybeObserver implements MaybeObserver<Object>, Disposable {
        final SingleObserver<? super Long> downstream;

        Disposable upstream;

        CountMaybeObserver(SingleObserver<? super Long> downstream) {
            this.downstream = downstream;
        }

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

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(Object value) {
            upstream = DisposableHelper.DISPOSED;
            downstream.onSuccess(1L);
        }

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

        @Override
        public void onComplete() {
            upstream = DisposableHelper.DISPOSED;
            downstream.onSuccess(0L);
        }

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

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