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.single;

import java.util.concurrent.atomic.AtomicInteger;

import io.reactivex.*;
import io.reactivex.disposables.*;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.plugins.RxJavaPlugins;

public final class SingleEquals<T> extends Single<Boolean> {

    final SingleSource<? extends T> first;
    final SingleSource<? extends T> second;

    public SingleEquals(SingleSource<? extends T> first, SingleSource<? extends T> second) {
        this.first = first;
        this.second = second;
    }

    @Override
    protected void subscribeActual(final SingleObserver<? super Boolean> observer) {

        final AtomicInteger count = new AtomicInteger();
        final Object[] values = { null, null };

        final CompositeDisposable set = new CompositeDisposable();
        observer.onSubscribe(set);

        first.subscribe(new InnerObserver<T>(0, set, values, observer, count));
        second.subscribe(new InnerObserver<T>(1, set, values, observer, count));
    }

    static class InnerObserver<T> implements SingleObserver<T> {
        final int index;
        final CompositeDisposable set;
        final Object[] values;
        final SingleObserver<? super Boolean> downstream;
        final AtomicInteger count;

        InnerObserver(int index, CompositeDisposable set, Object[] values, SingleObserver<? super Boolean> observer, AtomicInteger count) {
            this.index = index;
            this.set = set;
            this.values = values;
            this.downstream = observer;
            this.count = count;
        }

        @Override
        public void onSubscribe(Disposable d) {
            set.add(d);
        }

        @Override
        public void onSuccess(T value) {
            values[index] = value;

            if (count.incrementAndGet() == 2) {
                downstream.onSuccess(ObjectHelper.equals(values[0], values[1]));
            }
        }

        @Override
        public void onError(Throwable e) {
            for (;;) {
                int state = count.get();
                if (state >= 2) {
                    RxJavaPlugins.onError(e);
                    return;
                }
                if (count.compareAndSet(state, 2)) {
                    set.dispose();
                    downstream.onError(e);
                    return;
                }
            }
        }

    }

}