/**
 * 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.interop.internal.operators;

import org.reactivestreams.Subscriber;

import io.reactivex.common.Disposable;
import io.reactivex.common.internal.disposables.DisposableHelper;
import io.reactivex.flowable.Flowable;
import io.reactivex.flowable.internal.subscriptions.DeferredScalarSubscription;
import io.reactivex.observable.*;
import io.reactivex.observable.extensions.HasUpstreamMaybeSource;

/**
 * Wraps a MaybeSource and exposes it as a Flowable, relaying signals in a backpressure-aware manner
 * and composes cancellation through.
 *
 * @param <T> the value type
 */
public final class MaybeToFlowable<T> extends Flowable<T> implements HasUpstreamMaybeSource<T> {

    final MaybeSource<T> source;

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

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

    @Override
    protected void subscribeActual(Subscriber<? super T> s) {
        source.subscribe(new MaybeToRelaxedSubscriber<T>(s));
    }

    static final class MaybeToRelaxedSubscriber<T> extends DeferredScalarSubscription<T>
    implements MaybeObserver<T> {

        private static final long serialVersionUID = 7603343402964826922L;

        Disposable d;

        MaybeToRelaxedSubscriber(Subscriber<? super T> actual) {
            super(actual);
        }

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

                actual.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T value) {
            complete(value);
        }

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

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

        @Override
        public void cancel() {
            super.cancel();
            d.dispose();
        }
    }
}
