/*
 * Copyright (c) 2011-2018 Pivotal Software Inc, All Rights Reserved.
 *
 * 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 reactor.core.publisher;

import java.util.Objects;
import java.util.concurrent.CompletionStage;

import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.core.Scannable;
import reactor.util.Logger;
import reactor.util.Loggers;

Emits the value or error produced by the wrapped CompletionStage.

Note that if Subscribers cancel their subscriptions, the CompletionStage
is not cancelled.
Type parameters:
<T> – the value type/**
 * Emits the value or error produced by the wrapped CompletionStage.
 * <p>
 * Note that if Subscribers cancel their subscriptions, the CompletionStage
 * is not cancelled.
 *
 * @param <T> the value type
 */
final class MonoCompletionStage<T> extends Mono<T>
        implements Fuseable, Scannable {

    static final Logger LOGGER = Loggers.getLogger(MonoCompletionStage.class);

    final CompletionStage<? extends T> future;

    MonoCompletionStage(CompletionStage<? extends T> future) {
        this.future = Objects.requireNonNull(future, "future");
    }

    @Override
    public void subscribe(CoreSubscriber<? super T> actual) {
        Operators.MonoSubscriber<T, T>
                sds = new Operators.MonoSubscriber<>(actual);

        actual.onSubscribe(sds);

        if (sds.isCancelled()) {
            return;
        }

        future.whenComplete((v, e) -> {
            try {
                if (e != null) {
                    actual.onError(e);
                }
                else if (v != null) {
                    sds.complete(v);
                }
                else {
                    actual.onComplete();
                }
            }
            catch (Throwable e1) {
                Operators.onErrorDropped(e1, actual.currentContext());
                throw Exceptions.bubble(e1);
            }
        });
    }

    @Override
    public Object scanUnsafe(Attr key) {
        return null; //no particular key to be represented, still useful in hooks
    }
}