package hu.akarnokd.rxjava2;

import java.util.Iterator;
import java.util.concurrent.atomic.*;

import org.reactivestreams.*;

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.util.BackpressureHelper;
import rsc.subscriber.SubscriptionHelper;

public final class SingleFlatMapIterableFlowable<T, R> extends Flowable<R> {

    final SingleSource<T> source;

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

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

    @Override
    protected void subscribeActual(Subscriber<? super R> s) {
        source.subscribe(new FlatMapIterableObserver<T, R>(s, mapper));
    }

    static final class FlatMapIterableObserver<T, R>
    extends AtomicInteger
    implements SingleObserver<T>, Subscription {

        private static final long serialVersionUID = -8938804753851907758L;

        final Subscriber<? super R> actual;

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

        final AtomicLong requested;

        Disposable d;

        volatile Iterator<? extends R> it;

        volatile boolean cancelled;

        FlatMapIterableObserver(Subscriber<? super R> actual,
                Function<? super T, ? extends Iterable<? extends R>> mapper) {
            this.actual = actual;
            this.mapper = mapper;
            this.requested = new AtomicLong();
        }

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

                actual.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T value) {
            Iterator<? extends R> iter;
            boolean has;
            try {

                iter = mapper.apply(value).iterator();

                has = iter.hasNext();
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                actual.onError(ex);
                return;
            }

            if (!has) {
                actual.onComplete();
                return;
            }
            this.it = iter;
            drain();
        }

        @Override
        public void onError(Throwable e) {
            d = DisposableHelper.DISPOSED;
            actual.onError(e);
        }

        @Override
        public void request(long n) {
            if (SubscriptionHelper.validate(n)) {
                BackpressureHelper.add(requested, n);
                drain();
            }
        }

        @Override
        public void cancel() {
            cancelled = true;
            d.dispose();
            d = DisposableHelper.DISPOSED;
        }

        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }

            int missed = 1;

            Iterator<? extends R> iter = this.it;

            Subscriber<? super R> a = actual;

            for (;;) {

                if (iter != null) {
                    long r = requested.get();
                    long e = 0L;

                    if (r == Long.MAX_VALUE) {
                        for (;;) {
                            if (cancelled) {
                                return;
                            }

                            R v;

                            try {
                                v = iter.next();
                            } catch (Throwable ex) {
                                Exceptions.throwIfFatal(ex);
                                a.onError(ex);
                                return;
                            }

                            a.onNext(v);

                            if (cancelled) {
                                return;
                            }


                            boolean b;

                            try {
                                b = iter.hasNext();
                            } catch (Throwable ex) {
                                Exceptions.throwIfFatal(ex);
                                a.onError(ex);
                                return;
                            }

                            if (!b) {
                                a.onComplete();
                                return;
                            }
                        }
                    }

                    while (e != r) {
                        if (cancelled) {
                            return;
                        }

                        R v;

                        try {
                            v = iter.next();
                        } catch (Throwable ex) {
                            Exceptions.throwIfFatal(ex);
                            a.onError(ex);
                            return;
                        }

                        a.onNext(v);

                        if (cancelled) {
                            return;
                        }


                        e++;

                        boolean b;

                        try {
                            b = iter.hasNext();
                        } catch (Throwable ex) {
                            Exceptions.throwIfFatal(ex);
                            a.onError(ex);
                            return;
                        }

                        if (!b) {
                            a.onComplete();
                            return;
                        }
                    }

                    if (e != 0L) {
                        BackpressureHelper.produced(requested, e);
                    }
                }

                missed = addAndGet(-missed);
                if (missed == 0) {
                    break;
                }

                if (iter == null) {
                    iter = it;
                }
            }
        }
    }
}