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.Callable;
import java.util.concurrent.atomic.AtomicReference;

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

public final class SingleUsing<T, U> extends Single<T> {

    final Callable<U> resourceSupplier;
    final Function<? super U, ? extends SingleSource<? extends T>> singleFunction;
    final Consumer<? super U> disposer;
    final boolean eager;

    public SingleUsing(Callable<U> resourceSupplier,
                       Function<? super U, ? extends SingleSource<? extends T>> singleFunction,
                       Consumer<? super U> disposer,
                       boolean eager) {
        this.resourceSupplier = resourceSupplier;
        this.singleFunction = singleFunction;
        this.disposer = disposer;
        this.eager = eager;
    }

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

        final U resource; // NOPMD

        try {
            resource = resourceSupplier.call();
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);
            EmptyDisposable.error(ex, observer);
            return;
        }

        SingleSource<? extends T> source;

        try {
            source = ObjectHelper.requireNonNull(singleFunction.apply(resource), "The singleFunction returned a null SingleSource");
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);

            if (eager) {
                try {
                    disposer.accept(resource);
                } catch (Throwable exc) {
                    Exceptions.throwIfFatal(exc);
                    ex = new CompositeException(ex, exc);
                }
            }
            EmptyDisposable.error(ex, observer);
            if (!eager) {
                try {
                    disposer.accept(resource);
                } catch (Throwable exc) {
                    Exceptions.throwIfFatal(exc);
                    RxJavaPlugins.onError(exc);
                }
            }
            return;
        }

        source.subscribe(new UsingSingleObserver<T, U>(observer, resource, eager, disposer));
    }

    static final class UsingSingleObserver<T, U> extends
    AtomicReference<Object> implements SingleObserver<T>, Disposable {

        private static final long serialVersionUID = -5331524057054083935L;

        final SingleObserver<? super T> downstream;

        final Consumer<? super U> disposer;

        final boolean eager;

        Disposable upstream;

        UsingSingleObserver(SingleObserver<? super T> actual, U resource, boolean eager,
                Consumer<? super U> disposer) {
            super(resource);
            this.downstream = actual;
            this.eager = eager;
            this.disposer = disposer;
        }

        @Override
        public void dispose() {
            upstream.dispose();
            upstream = DisposableHelper.DISPOSED;
            disposeAfter();
        }

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

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;

                downstream.onSubscribe(this);
            }
        }

        @SuppressWarnings("unchecked")
        @Override
        public void onSuccess(T value) {
            upstream = DisposableHelper.DISPOSED;

            if (eager) {
                Object u = getAndSet(this);
                if (u != this) {
                    try {
                        disposer.accept((U)u);
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        downstream.onError(ex);
                        return;
                    }
                } else {
                    return;
                }
            }

            downstream.onSuccess(value);

            if (!eager) {
                disposeAfter();
            }
        }

        @SuppressWarnings("unchecked")
        @Override
        public void onError(Throwable e) {
            upstream = DisposableHelper.DISPOSED;

            if (eager) {
                Object u = getAndSet(this);
                if (u != this) {
                    try {
                        disposer.accept((U)u);
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        e = new CompositeException(e, ex);
                    }
                } else {
                    return;
                }
            }

            downstream.onError(e);

            if (!eager) {
                disposeAfter();
            }
        }

        @SuppressWarnings("unchecked")
        void disposeAfter() {
            Object u = getAndSet(this);
            if (u != this) {
                try {
                    disposer.accept((U)u);
                } catch (Throwable ex) {
                    Exceptions.throwIfFatal(ex);
                    RxJavaPlugins.onError(ex);
                }
            }
        }
    }
}