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.Iterator;

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

Maps a sequence into an Iterable and emits its values.
Type parameters:
<T> – the input value type to map to Iterable
<R> – the element type of the Iterable and the output/**
 * Maps a sequence into an Iterable and emits its values.
 *
 * @param <T> the input value type to map to Iterable
 * @param <R> the element type of the Iterable and the output
 */
public final class ObservableFlattenIterable<T, R> extends AbstractObservableWithUpstream<T, R> {

    final Function<? super T, ? extends Iterable<? extends R>> mapper;

    public ObservableFlattenIterable(ObservableSource<T> source,
            Function<? super T, ? extends Iterable<? extends R>> mapper) {
        super(source);
        this.mapper = mapper;
    }

    @Override
    protected void subscribeActual(Observer<? super R> observer) {
        source.subscribe(new FlattenIterableObserver<T, R>(observer, mapper));
    }

    static final class FlattenIterableObserver<T, R> implements Observer<T>, Disposable {
        final Observer<? super R> downstream;

        final Function<? super T, ? extends Iterable<? extends R>> mapper;

        Disposable upstream;

        FlattenIterableObserver(Observer<? super R> actual, Function<? super T, ? extends Iterable<? extends R>> mapper) {
            this.downstream = actual;
            this.mapper = mapper;
        }

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

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onNext(T value) {
            if (upstream == DisposableHelper.DISPOSED) {
                return;
            }

            Iterator<? extends R> it;

            try {
                it = mapper.apply(value).iterator();
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                upstream.dispose();
                onError(ex);
                return;
            }

            Observer<? super R> a = downstream;

            for (;;) {
                boolean b;

                try {
                    b = it.hasNext();
                } catch (Throwable ex) {
                    Exceptions.throwIfFatal(ex);
                    upstream.dispose();
                    onError(ex);
                    return;
                }

                if (b) {
                    R v;

                    try {
                        v = ObjectHelper.requireNonNull(it.next(), "The iterator returned a null value");
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        upstream.dispose();
                        onError(ex);
                        return;
                    }

                    a.onNext(v);
                } else {
                    break;
                }
            }
        }

        @Override
        public void onError(Throwable e) {
            if (upstream == DisposableHelper.DISPOSED) {
                RxJavaPlugins.onError(e);
                return;
            }
            upstream = DisposableHelper.DISPOSED;
            downstream.onError(e);
        }

        @Override
        public void onComplete() {
            if (upstream == DisposableHelper.DISPOSED) {
                return;
            }
            upstream = DisposableHelper.DISPOSED;
            downstream.onComplete();
        }

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

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