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.flowable;

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

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.queue.SpscArrayQueue;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;

public final class FlowableConcatMap<T, R> extends AbstractFlowableWithUpstream<T, R> {

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

    final int prefetch;

    final ErrorMode errorMode;

    public FlowableConcatMap(Flowable<T> source,
            Function<? super T, ? extends Publisher<? extends R>> mapper,
            int prefetch, ErrorMode errorMode) {
        super(source);
        this.mapper = mapper;
        this.prefetch = prefetch;
        this.errorMode = errorMode;
    }

    public static <T, R> Subscriber<T> subscribe(Subscriber<? super R> s, Function<? super T, ? extends Publisher<? extends R>> mapper,
            int prefetch, ErrorMode errorMode) {
        switch (errorMode) {
        case BOUNDARY:
            return new ConcatMapDelayed<T, R>(s, mapper, prefetch, false);
        case END:
            return new ConcatMapDelayed<T, R>(s, mapper, prefetch, true);
        default:
            return new ConcatMapImmediate<T, R>(s, mapper, prefetch);
        }
    }

    @Override
    protected void subscribeActual(Subscriber<? super R> s) {

        if (FlowableScalarXMap.tryScalarXMapSubscribe(source, s, mapper)) {
            return;
        }

        source.subscribe(subscribe(s, mapper, prefetch, errorMode));
    }

    abstract static class BaseConcatMapSubscriber<T, R>
    extends AtomicInteger
    implements FlowableSubscriber<T>, ConcatMapSupport<R>, Subscription {

        private static final long serialVersionUID = -3511336836796789179L;

        final ConcatMapInner<R> inner;

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

        final int prefetch;

        final int limit;

        Subscription upstream;

        int consumed;

        SimpleQueue<T> queue;

        volatile boolean done;

        volatile boolean cancelled;

        final AtomicThrowable errors;

        volatile boolean active;

        int sourceMode;

        BaseConcatMapSubscriber(
                Function<? super T, ? extends Publisher<? extends R>> mapper,
                int prefetch) {
            this.mapper = mapper;
            this.prefetch = prefetch;
            this.limit = prefetch - (prefetch >> 2);
            this.inner = new ConcatMapInner<R>(this);
            this.errors = new AtomicThrowable();
        }

        @Override
        public final void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validate(this.upstream, s))  {
                this.upstream = s;

                if (s instanceof QueueSubscription) {
                    @SuppressWarnings("unchecked") QueueSubscription<T> f = (QueueSubscription<T>)s;
                    int m = f.requestFusion(QueueSubscription.ANY | QueueSubscription.BOUNDARY);
                    if (m == QueueSubscription.SYNC) {
                        sourceMode = m;
                        queue = f;
                        done = true;

                        subscribeActual();

                        drain();
                        return;
                    }
                    if (m == QueueSubscription.ASYNC) {
                        sourceMode = m;
                        queue = f;

                        subscribeActual();

                        s.request(prefetch);
                        return;
                    }
                }

                queue = new SpscArrayQueue<T>(prefetch);

                subscribeActual();

                s.request(prefetch);
            }
        }

        abstract void drain();

        abstract void subscribeActual();

        @Override
        public final void onNext(T t) {
            if (sourceMode != QueueSubscription.ASYNC) {
                if (!queue.offer(t)) {
                    upstream.cancel();
                    onError(new IllegalStateException("Queue full?!"));
                    return;
                }
            }
            drain();
        }

        @Override
        public final void onComplete() {
            done = true;
            drain();
        }

        @Override
        public final void innerComplete() {
            active = false;
            drain();
        }

    }

    static final class ConcatMapImmediate<T, R>
    extends BaseConcatMapSubscriber<T, R> {

        private static final long serialVersionUID = 7898995095634264146L;

        final Subscriber<? super R> downstream;

        final AtomicInteger wip;

        ConcatMapImmediate(Subscriber<? super R> actual,
                Function<? super T, ? extends Publisher<? extends R>> mapper,
                int prefetch) {
            super(mapper, prefetch);
            this.downstream = actual;
            this.wip = new AtomicInteger();
        }

        @Override
        void subscribeActual() {
            downstream.onSubscribe(this);
        }

        @Override
        public void onError(Throwable t) {
            if (errors.addThrowable(t)) {
                inner.cancel();

                if (getAndIncrement() == 0) {
                    downstream.onError(errors.terminate());
                }
            } else {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public void innerNext(R value) {
            if (get() == 0 && compareAndSet(0, 1)) {
                downstream.onNext(value);
                if (compareAndSet(1, 0)) {
                    return;
                }
                downstream.onError(errors.terminate());
            }
        }

        @Override
        public void innerError(Throwable e) {
            if (errors.addThrowable(e)) {
                upstream.cancel();

                if (getAndIncrement() == 0) {
                    downstream.onError(errors.terminate());
                }
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        @Override
        public void request(long n) {
            inner.request(n);
        }

        @Override
        public void cancel() {
            if (!cancelled) {
                cancelled = true;

                inner.cancel();
                upstream.cancel();
            }
        }

        @Override
        void drain() {
            if (wip.getAndIncrement() == 0) {
                for (;;) {
                    if (cancelled) {
                        return;
                    }

                    if (!active) {
                        boolean d = done;

                        T v;

                        try {
                            v = queue.poll();
                        } catch (Throwable e) {
                            Exceptions.throwIfFatal(e);
                            upstream.cancel();
                            errors.addThrowable(e);
                            downstream.onError(errors.terminate());
                            return;
                        }

                        boolean empty = v == null;

                        if (d && empty) {
                            downstream.onComplete();
                            return;
                        }

                        if (!empty) {
                            Publisher<? extends R> p;

                            try {
                                p = ObjectHelper.requireNonNull(mapper.apply(v), "The mapper returned a null Publisher");
                            } catch (Throwable e) {
                                Exceptions.throwIfFatal(e);

                                upstream.cancel();
                                errors.addThrowable(e);
                                downstream.onError(errors.terminate());
                                return;
                            }

                            if (sourceMode != QueueSubscription.SYNC) {
                                int c = consumed + 1;
                                if (c == limit) {
                                    consumed = 0;
                                    upstream.request(c);
                                } else {
                                    consumed = c;
                                }
                            }

                            if (p instanceof Callable) {
                                @SuppressWarnings("unchecked")
                                Callable<R> callable = (Callable<R>) p;

                                R vr;

                                try {
                                    vr = callable.call();
                                } catch (Throwable e) {
                                    Exceptions.throwIfFatal(e);
                                    upstream.cancel();
                                    errors.addThrowable(e);
                                    downstream.onError(errors.terminate());
                                    return;
                                }

                                if (vr == null) {
                                    continue;
                                }

                                if (inner.isUnbounded()) {
                                    if (get() == 0 && compareAndSet(0, 1)) {
                                        downstream.onNext(vr);
                                        if (!compareAndSet(1, 0)) {
                                            downstream.onError(errors.terminate());
                                            return;
                                        }
                                    }
                                    continue;
                                } else {
                                    active = true;
                                    inner.setSubscription(new WeakScalarSubscription<R>(vr, inner));
                                }

                            } else {
                                active = true;
                                p.subscribe(inner);
                            }
                        }
                    }
                    if (wip.decrementAndGet() == 0) {
                        break;
                    }
                }
            }
        }
    }

    static final class WeakScalarSubscription<T> implements Subscription {
        final Subscriber<? super T> downstream;
        final T value;
        boolean once;

        WeakScalarSubscription(T value, Subscriber<? super T> downstream) {
            this.value = value;
            this.downstream = downstream;
        }

        @Override
        public void request(long n) {
            if (n > 0 && !once) {
                once = true;
                Subscriber<? super T> a = downstream;
                a.onNext(value);
                a.onComplete();
            }
        }

        @Override
        public void cancel() {

        }
    }

    static final class ConcatMapDelayed<T, R>
    extends BaseConcatMapSubscriber<T, R> {

        private static final long serialVersionUID = -2945777694260521066L;

        final Subscriber<? super R> downstream;

        final boolean veryEnd;

        ConcatMapDelayed(Subscriber<? super R> actual,
                Function<? super T, ? extends Publisher<? extends R>> mapper,
                int prefetch, boolean veryEnd) {
            super(mapper, prefetch);
            this.downstream = actual;
            this.veryEnd = veryEnd;
        }

        @Override
        void subscribeActual() {
            downstream.onSubscribe(this);
        }

        @Override
        public void onError(Throwable t) {
            if (errors.addThrowable(t)) {
                done = true;
                drain();
            } else {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public void innerNext(R value) {
            downstream.onNext(value);
        }

        @Override
        public void innerError(Throwable e) {
            if (errors.addThrowable(e)) {
                if (!veryEnd) {
                    upstream.cancel();
                    done = true;
                }
                active = false;
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        @Override
        public void request(long n) {
            inner.request(n);
        }

        @Override
        public void cancel() {
            if (!cancelled) {
                cancelled = true;

                inner.cancel();
                upstream.cancel();
            }
        }

        @Override
        void drain() {
            if (getAndIncrement() == 0) {

                for (;;) {
                    if (cancelled) {
                        return;
                    }

                    if (!active) {

                        boolean d = done;

                        if (d && !veryEnd) {
                            Throwable ex = errors.get();
                            if (ex != null) {
                                downstream.onError(errors.terminate());
                                return;
                            }
                        }

                        T v;

                        try {
                            v = queue.poll();
                        } catch (Throwable e) {
                            Exceptions.throwIfFatal(e);
                            upstream.cancel();
                            errors.addThrowable(e);
                            downstream.onError(errors.terminate());
                            return;
                        }

                        boolean empty = v == null;

                        if (d && empty) {
                            Throwable ex = errors.terminate();
                            if (ex != null) {
                                downstream.onError(ex);
                            } else {
                                downstream.onComplete();
                            }
                            return;
                        }

                        if (!empty) {
                            Publisher<? extends R> p;

                            try {
                                p = ObjectHelper.requireNonNull(mapper.apply(v), "The mapper returned a null Publisher");
                            } catch (Throwable e) {
                                Exceptions.throwIfFatal(e);

                                upstream.cancel();
                                errors.addThrowable(e);
                                downstream.onError(errors.terminate());
                                return;
                            }

                            if (sourceMode != QueueSubscription.SYNC) {
                                int c = consumed + 1;
                                if (c == limit) {
                                    consumed = 0;
                                    upstream.request(c);
                                } else {
                                    consumed = c;
                                }
                            }

                            if (p instanceof Callable) {
                                @SuppressWarnings("unchecked")
                                Callable<R> supplier = (Callable<R>) p;

                                R vr;

                                try {
                                    vr = supplier.call();
                                } catch (Throwable e) {
                                    Exceptions.throwIfFatal(e);
                                    errors.addThrowable(e);
                                    if (!veryEnd) {
                                        upstream.cancel();
                                        downstream.onError(errors.terminate());
                                        return;
                                    }
                                    vr = null;
                                }

                                if (vr == null) {
                                    continue;
                                }

                                if (inner.isUnbounded()) {
                                    downstream.onNext(vr);
                                    continue;
                                } else {
                                    active = true;
                                    inner.setSubscription(new WeakScalarSubscription<R>(vr, inner));
                                }
                            } else {
                                active = true;
                                p.subscribe(inner);
                            }
                        }
                    }
                    if (decrementAndGet() == 0) {
                        break;
                    }
                }
            }
        }
    }

    interface ConcatMapSupport<T> {

        void innerNext(T value);

        void innerComplete();

        void innerError(Throwable e);
    }

    static final class ConcatMapInner<R>
    extends SubscriptionArbiter
    implements FlowableSubscriber<R> {

        private static final long serialVersionUID = 897683679971470653L;

        final ConcatMapSupport<R> parent;

        long produced;

        ConcatMapInner(ConcatMapSupport<R> parent) {
            super(false);
            this.parent = parent;
        }

        @Override
        public void onSubscribe(Subscription s) {
            setSubscription(s);
        }

        @Override
        public void onNext(R t) {
            produced++;

            parent.innerNext(t);
        }

        @Override
        public void onError(Throwable t) {
            long p = produced;

            if (p != 0L) {
                produced = 0L;
                produced(p);
            }

            parent.innerError(t);
        }

        @Override
        public void onComplete() {
            long p = produced;

            if (p != 0L) {
                produced = 0L;
                produced(p);
            }

            parent.innerComplete();
        }
    }
}