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.flowable;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.annotations.Nullable;
import io.reactivex.internal.fuseable.QueueSubscription;
import io.reactivex.internal.subscriptions.SubscriptionHelper;

public final class FlowableIgnoreElements<T> extends AbstractFlowableWithUpstream<T, T> {

    public FlowableIgnoreElements(Flowable<T> source) {
        super(source);
    }

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

    static final class IgnoreElementsSubscriber<T> implements FlowableSubscriber<T>, QueueSubscription<T> {
        final Subscriber<? super T> downstream;

        Subscription upstream;

        IgnoreElementsSubscriber(Subscriber<? super T> downstream) {
            this.downstream = downstream;
        }

        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validate(this.upstream, s)) {
                this.upstream = s;
                downstream.onSubscribe(this);
                s.request(Long.MAX_VALUE);
            }
        }

        @Override
        public void onNext(T t) {
            // deliberately ignored
        }

        @Override
        public void onError(Throwable t) {
            downstream.onError(t);
        }

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

        @Override
        public boolean offer(T e) {
            throw new UnsupportedOperationException("Should not be called!");
        }

        @Override
        public boolean offer(T v1, T v2) {
            throw new UnsupportedOperationException("Should not be called!");
        }

        @Nullable
        @Override
        public T poll() {
            return null; // empty, always
        }

        @Override
        public boolean isEmpty() {
            return true;
        }

        @Override
        public void clear() {
            // always empty
        }

        @Override
        public void request(long n) {
            // never emits a value
        }

        @Override
        public void cancel() {
            upstream.cancel();
        }

        @Override
        public int requestFusion(int mode) {
            return mode & ASYNC;
        }
    }
}