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.atomic.AtomicReference;

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

Provides an API over MaybeObserver that serializes calls to onXXX and manages cancellation
in a safe manner.
Type parameters:
<T> – the value type emitted/**
 * Provides an API over MaybeObserver that serializes calls to onXXX and manages cancellation
 * in a safe manner.
 *
 * @param <T> the value type emitted
 */
public final class MaybeCreate<T> extends Maybe<T> {

    final MaybeOnSubscribe<T> source;

    public MaybeCreate(MaybeOnSubscribe<T> source) {
        this.source = source;
    }

    @Override
    protected void subscribeActual(MaybeObserver<? super T> observer) {
        Emitter<T> parent = new Emitter<T>(observer);
        observer.onSubscribe(parent);

        try {
            source.subscribe(parent);
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);
            parent.onError(ex);
        }
    }

    static final class Emitter<T>
    extends AtomicReference<Disposable>
    implements MaybeEmitter<T>, Disposable {

        final MaybeObserver<? super T> downstream;

        Emitter(MaybeObserver<? super T> downstream) {
            this.downstream = downstream;
        }

        private static final long serialVersionUID = -2467358622224974244L;

        @Override
        public void onSuccess(T value) {
            if (get() != DisposableHelper.DISPOSED) {
                Disposable d = getAndSet(DisposableHelper.DISPOSED);
                if (d != DisposableHelper.DISPOSED) {
                    try {
                        if (value == null) {
                            downstream.onError(new NullPointerException("onSuccess called with null. Null values are generally not allowed in 2.x operators and sources."));
                        } else {
                            downstream.onSuccess(value);
                        }
                    } finally {
                        if (d != null) {
                            d.dispose();
                        }
                    }
                }
            }
        }

        @Override
        public void onError(Throwable t) {
            if (!tryOnError(t)) {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public boolean tryOnError(Throwable t) {
            if (t == null) {
                t = new NullPointerException("onError called with null. Null values are generally not allowed in 2.x operators and sources.");
            }
            if (get() != DisposableHelper.DISPOSED) {
                Disposable d = getAndSet(DisposableHelper.DISPOSED);
                if (d != DisposableHelper.DISPOSED) {
                    try {
                        downstream.onError(t);
                    } finally {
                        if (d != null) {
                            d.dispose();
                        }
                    }
                    return true;
                }
            }
            return false;
        }

        @Override
        public void onComplete() {
            if (get() != DisposableHelper.DISPOSED) {
                Disposable d = getAndSet(DisposableHelper.DISPOSED);
                if (d != DisposableHelper.DISPOSED) {
                    try {
                        downstream.onComplete();
                    } finally {
                        if (d != null) {
                            d.dispose();
                        }
                    }
                }
            }
        }

        @Override
        public void setDisposable(Disposable d) {
            DisposableHelper.set(this, d);
        }

        @Override
        public void setCancellable(Cancellable c) {
            setDisposable(new CancellableDisposable(c));
        }

        @Override
        public void dispose() {
            DisposableHelper.dispose(this);
        }

        @Override
        public boolean isDisposed() {
            return DisposableHelper.isDisposed(get());
        }

        @Override
        public String toString() {
            return String.format("%s{%s}", getClass().getSimpleName(), super.toString());
        }
    }
}