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.maybe;

import java.util.concurrent.Callable;

import io.reactivex.*;
import io.reactivex.disposables.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.plugins.RxJavaPlugins;

Executes a callable and signals its value as success or signals an exception.
Type parameters:
<T> – the value type/**
 * Executes a callable and signals its value as success or signals an exception.
 *
 * @param <T> the value type
 */
public final class MaybeFromCallable<T> extends Maybe<T> implements Callable<T> {

    final Callable<? extends T> callable;

    public MaybeFromCallable(Callable<? extends T> callable) {
        this.callable = callable;
    }

    @Override
    protected void subscribeActual(MaybeObserver<? super T> observer) {
        Disposable d = Disposables.empty();
        observer.onSubscribe(d);

        if (!d.isDisposed()) {

            T v;

            try {
                v = callable.call();
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                if (!d.isDisposed()) {
                    observer.onError(ex);
                } else {
                    RxJavaPlugins.onError(ex);
                }
                return;
            }

            if (!d.isDisposed()) {
                if (v == null) {
                    observer.onComplete();
                } else {
                    observer.onSuccess(v);
                }
            }
        }
    }

    @Override
    public T call() throws Exception {
        return callable.call();
    }
}