AbstractSingleSubscriberBridge.java

/*
 * Copyright (c) 2015 AsyncHttpClient Project. All rights reserved.
 *
 * This program is licensed to you under the Apache License Version 2.0,
 * and you may not use this file except in compliance with the Apache License Version 2.0.
 * You may obtain a copy of the Apache License Version 2.0 at http://www.apache.org/licenses/LICENSE-2.0.
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the Apache License Version 2.0 is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
 */
package org.asynchttpclient.extras.rxjava.single;

import static java.util.Objects.requireNonNull;
import io.netty.handler.codec.http.HttpHeaders;

import java.util.Arrays;
import java.util.concurrent.atomic.AtomicBoolean;

import org.asynchttpclient.AsyncHandler;
import org.asynchttpclient.HttpResponseBodyPart;
import org.asynchttpclient.HttpResponseStatus;
import org.asynchttpclient.extras.rxjava.UnsubscribedException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import rx.SingleSubscriber;
import rx.exceptions.CompositeException;
import rx.exceptions.Exceptions;

abstract class AbstractSingleSubscriberBridge<T> implements AsyncHandler<Void> {

    private static final Logger LOGGER = LoggerFactory.getLogger(AbstractSingleSubscriberBridge.class);

    protected final SingleSubscriber<T> subscriber;

    private final AtomicBoolean delegateTerminated = new AtomicBoolean();

    protected AbstractSingleSubscriberBridge(SingleSubscriber<T> subscriber) {
        this.subscriber = requireNonNull(subscriber);
    }

    @Override
    public State onBodyPartReceived(HttpResponseBodyPart content) throws Exception {
        return subscriber.isUnsubscribed() ? abort() : delegate().onBodyPartReceived(content);
    }

    @Override
    public State onStatusReceived(HttpResponseStatus status) throws Exception {
        return subscriber.isUnsubscribed() ? abort() : delegate().onStatusReceived(status);
    }

    @Override
    public State onHeadersReceived(HttpHeaders headers) throws Exception {
        return subscriber.isUnsubscribed() ? abort() : delegate().onHeadersReceived(headers);
    }

    @Override
    public State onTrailingHeadersReceived(HttpHeaders headers) throws Exception {
        return subscriber.isUnsubscribed() ? abort() : delegate().onTrailingHeadersReceived(headers);
    }

    @Override
    public Void onCompleted() {
        if (delegateTerminated.getAndSet(true)) {
            return null;
        }

        final T result;
        try {
            result = delegate().onCompleted();
        } catch (final Throwable t) {
            emitOnError(t);
            return null;
        }

        if (!subscriber.isUnsubscribed()) {
            subscriber.onSuccess(result);
        }

        return null;
    }

    @Override
    public void onThrowable(Throwable t) {
        if (delegateTerminated.getAndSet(true)) {
            return;
        }

        Throwable error = t;
        try {
            delegate().onThrowable(t);
        } catch (final Throwable x) {
            error = new CompositeException(Arrays.asList(t, x));
        }

        emitOnError(error);
    }

    protected AsyncHandler.State abort() {
        if (!delegateTerminated.getAndSet(true)) {
            // send a terminal event to the delegate
            // e.g. to trigger cleanup logic
            delegate().onThrowable(new UnsubscribedException());
        }

        return State.ABORT;
    }

    protected abstract AsyncHandler<? extends T> delegate();

    private void emitOnError(Throwable error) {
        Exceptions.throwIfFatal(error);
        if (!subscriber.isUnsubscribed()) {
            subscriber.onError(error);
        } else {
            LOGGER.debug("Not propagating onError after unsubscription: {}", error.getMessage(), error);
        }
    }
}