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.observable;

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

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 ObservableUsing<T, D> extends Observable<T> {
    final Callable<? extends D> resourceSupplier;
    final Function<? super D, ? extends ObservableSource<? extends T>> sourceSupplier;
    final Consumer<? super D> disposer;
    final boolean eager;

    public ObservableUsing(Callable<? extends D> resourceSupplier,
            Function<? super D, ? extends ObservableSource<? extends T>> sourceSupplier,
            Consumer<? super D> disposer,
            boolean eager) {
        this.resourceSupplier = resourceSupplier;
        this.sourceSupplier = sourceSupplier;
        this.disposer = disposer;
        this.eager = eager;
    }

    @Override
    public void subscribeActual(Observer<? super T> observer) {
        D resource;

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

        ObservableSource<? extends T> source;
        try {
            source = ObjectHelper.requireNonNull(sourceSupplier.apply(resource), "The sourceSupplier returned a null ObservableSource");
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            try {
                disposer.accept(resource);
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                EmptyDisposable.error(new CompositeException(e, ex), observer);
                return;
            }
            EmptyDisposable.error(e, observer);
            return;
        }

        UsingObserver<T, D> us = new UsingObserver<T, D>(observer, resource, disposer, eager);

        source.subscribe(us);
    }

    static final class UsingObserver<T, D> extends AtomicBoolean implements Observer<T>, Disposable {

        private static final long serialVersionUID = 5904473792286235046L;

        final Observer<? super T> downstream;
        final D resource;
        final Consumer<? super D> disposer;
        final boolean eager;

        Disposable upstream;

        UsingObserver(Observer<? super T> actual, D resource, Consumer<? super D> disposer, boolean eager) {
            this.downstream = actual;
            this.resource = resource;
            this.disposer = disposer;
            this.eager = eager;
        }

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

        @Override
        public void onNext(T t) {
            downstream.onNext(t);
        }

        @Override
        public void onError(Throwable t) {
            if (eager) {
                if (compareAndSet(false, true)) {
                    try {
                        disposer.accept(resource);
                    } catch (Throwable e) {
                        Exceptions.throwIfFatal(e);
                        t = new CompositeException(t, e);
                    }
                }

                upstream.dispose();
                downstream.onError(t);
            } else {
                downstream.onError(t);
                upstream.dispose();
                disposeAfter();
            }
        }

        @Override
        public void onComplete() {
            if (eager) {
                if (compareAndSet(false, true)) {
                    try {
                        disposer.accept(resource);
                    } catch (Throwable e) {
                        Exceptions.throwIfFatal(e);
                        downstream.onError(e);
                        return;
                    }
                }

                upstream.dispose();
                downstream.onComplete();
            } else {
                downstream.onComplete();
                upstream.dispose();
                disposeAfter();
            }
        }

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

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

        void disposeAfter() {
            if (compareAndSet(false, true)) {
                try {
                    disposer.accept(resource);
                } catch (Throwable e) {
                    Exceptions.throwIfFatal(e);
                    // can't call actual.onError unless it is serialized, which is expensive
                    RxJavaPlugins.onError(e);
                }
            }
        }
    }
}