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 io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Consumer;
import io.reactivex.internal.disposables.EmptyDisposable;
import io.reactivex.plugins.RxJavaPlugins;

Calls a callback when the upstream calls onSubscribe with a disposable.
Type parameters:
<T> – the value type/**
 * Calls a callback when the upstream calls onSubscribe with a disposable.
 *
 * @param <T> the value type
 */
public final class SingleDoOnSubscribe<T> extends Single<T> {

    final SingleSource<T> source;

    final Consumer<? super Disposable> onSubscribe;

    public SingleDoOnSubscribe(SingleSource<T> source, Consumer<? super Disposable> onSubscribe) {
        this.source = source;
        this.onSubscribe = onSubscribe;
    }

    @Override
    protected void subscribeActual(final SingleObserver<? super T> observer) {
        source.subscribe(new DoOnSubscribeSingleObserver<T>(observer, onSubscribe));
    }

    static final class DoOnSubscribeSingleObserver<T> implements SingleObserver<T> {

        final SingleObserver<? super T> downstream;

        final Consumer<? super Disposable> onSubscribe;

        boolean done;

        DoOnSubscribeSingleObserver(SingleObserver<? super T> actual, Consumer<? super Disposable> onSubscribe) {
            this.downstream = actual;
            this.onSubscribe = onSubscribe;
        }

        @Override
        public void onSubscribe(Disposable d) {
            try {
                onSubscribe.accept(d);
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                done = true;
                d.dispose();
                EmptyDisposable.error(ex, downstream);
                return;
            }

            downstream.onSubscribe(d);
        }

        @Override
        public void onSuccess(T value) {
            if (done) {
                return;
            }
            downstream.onSuccess(value);
        }

        @Override
        public void onError(Throwable e) {
            if (done) {
                RxJavaPlugins.onError(e);
                return;
            }
            downstream.onError(e);
        }
    }

}