/*

 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.incubator.http;

import java.util.Optional;

import java.util.concurrent.Flow;

import java.util.function.Consumer;

/**

 * A single threaded Publisher which runs in same thread as subscriber.

 */

class PushPublisher<T> extends AbstractPushPublisher<T> {

    Subscription subscription;

    Flow.Subscriber<? super T> subscriber;

    SubscriptionState state;

    long demand;

    /**

     * Pushes/consumes the incoming objects.

     * The consumer blocks until subscriber ready to receive.

     */

    @Override

    public void acceptData(Optional<T> item) {

        SubscriptionState s = this.state;

        if (s == SubscriptionState.CANCELLED) return;

        if (s == SubscriptionState.DONE) {

            throw new IllegalStateException("subscription complete");

        }

        if (!item.isPresent()) {

            subscriber.onComplete();

            this.state = SubscriptionState.DONE;

            return;

        }

        if (demand == 0) {

            throw new IllegalStateException("demand == 0");

        }

        demand--;

        subscriber.onNext(item.get());

    }

    @Override

    public Consumer<Optional<T>> asDataConsumer() {

        return this::acceptData;

    }

    @Override

    public void subscribe(Flow.Subscriber<? super T> subscriber) {

        subscription = new Subscription(subscriber);

        subscriber.onSubscribe(subscription);

    }

    private class Subscription implements Flow.Subscription {

        Subscription(Flow.Subscriber<? super T> subscriber) {

            PushPublisher.this.subscriber = subscriber;

        }

        @Override

        public void request(long n) {

            demand += n;

        }

        @Override

        public void cancel() {

            state = SubscriptionState.CANCELLED;

        }

    }

    @Override

    public void acceptError(Throwable t) {

        if (this.state == SubscriptionState.DONE) {

            throw new IllegalStateException("subscription complete");

        }

        this.state = SubscriptionState.CANCELLED;

        subscriber.onError(t);

    }

}