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.Map;
import java.util.Queue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.*;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.annotations.Nullable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.flowables.GroupedFlowable;
import io.reactivex.functions.Consumer;
import io.reactivex.functions.Function;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.internal.util.BackpressureHelper;
import io.reactivex.internal.util.EmptyComponent;
import io.reactivex.plugins.RxJavaPlugins;

public final class FlowableGroupBy<T, K, V> extends AbstractFlowableWithUpstream<T, GroupedFlowable<K, V>> {
    final Function<? super T, ? extends K> keySelector;
    final Function<? super T, ? extends V> valueSelector;
    final int bufferSize;
    final boolean delayError;
    final Function<? super Consumer<Object>, ? extends Map<K, Object>> mapFactory;

    public FlowableGroupBy(Flowable<T> source, Function<? super T, ? extends K> keySelector, Function<? super T, ? extends V> valueSelector,
            int bufferSize, boolean delayError, Function<? super Consumer<Object>, ? extends Map<K, Object>> mapFactory) {
        super(source);
        this.keySelector = keySelector;
        this.valueSelector = valueSelector;
        this.bufferSize = bufferSize;
        this.delayError = delayError;
        this.mapFactory = mapFactory;
    }

    @Override
    @SuppressWarnings({ "unchecked", "rawtypes" })
    protected void subscribeActual(Subscriber<? super GroupedFlowable<K, V>> s) {

        final Map<Object, GroupedUnicast<K, V>> groups;
        final Queue<GroupedUnicast<K, V>> evictedGroups;

        try {
            if (mapFactory == null) {
                evictedGroups = null;
                groups = new ConcurrentHashMap<Object, GroupedUnicast<K, V>>();
            } else {
                evictedGroups = new ConcurrentLinkedQueue<GroupedUnicast<K, V>>();
                Consumer<Object> evictionAction = (Consumer) new EvictionAction<K, V>(evictedGroups);
                groups = (Map) mapFactory.apply(evictionAction);
            }
        } catch (Exception e) {
            Exceptions.throwIfFatal(e);
            s.onSubscribe(EmptyComponent.INSTANCE);
            s.onError(e);
            return;
        }
        GroupBySubscriber<T, K, V> subscriber =
                new GroupBySubscriber<T, K, V>(s, keySelector, valueSelector, bufferSize, delayError, groups, evictedGroups);
        source.subscribe(subscriber);
    }

    public static final class GroupBySubscriber<T, K, V>
    extends BasicIntQueueSubscription<GroupedFlowable<K, V>>
    implements FlowableSubscriber<T> {

        private static final long serialVersionUID = -3688291656102519502L;

        final Subscriber<? super GroupedFlowable<K, V>> downstream;
        final Function<? super T, ? extends K> keySelector;
        final Function<? super T, ? extends V> valueSelector;
        final int bufferSize;
        final boolean delayError;
        final Map<Object, GroupedUnicast<K, V>> groups;
        final SpscLinkedArrayQueue<GroupedFlowable<K, V>> queue;
        final Queue<GroupedUnicast<K, V>> evictedGroups;

        static final Object NULL_KEY = new Object();

        Subscription upstream;

        final AtomicBoolean cancelled = new AtomicBoolean();

        final AtomicLong requested = new AtomicLong();

        final AtomicInteger groupCount = new AtomicInteger(1);

        Throwable error;
        volatile boolean finished;
        boolean done;

        boolean outputFused;

        public GroupBySubscriber(Subscriber<? super GroupedFlowable<K, V>> actual, Function<? super T, ? extends K> keySelector,
                Function<? super T, ? extends V> valueSelector, int bufferSize, boolean delayError,
                Map<Object, GroupedUnicast<K, V>> groups, Queue<GroupedUnicast<K, V>> evictedGroups) {
            this.downstream = actual;
            this.keySelector = keySelector;
            this.valueSelector = valueSelector;
            this.bufferSize = bufferSize;
            this.delayError = delayError;
            this.groups = groups;
            this.evictedGroups = evictedGroups;
            this.queue = new SpscLinkedArrayQueue<GroupedFlowable<K, V>>(bufferSize);
        }

        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validate(this.upstream, s)) {
                this.upstream = s;
                downstream.onSubscribe(this);
                s.request(bufferSize);
            }
        }

        @Override
        public void onNext(T t) {
            if (done) {
                return;
            }

            final SpscLinkedArrayQueue<GroupedFlowable<K, V>> q = this.queue;

            K key;
            try {
                key = keySelector.apply(t);
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                upstream.cancel();
                onError(ex);
                return;
            }

            boolean newGroup = false;
            Object mapKey = key != null ? key : NULL_KEY;
            GroupedUnicast<K, V> group = groups.get(mapKey);
            if (group == null) {
                // if the main has been cancelled, stop creating groups
                // and skip this value
                if (cancelled.get()) {
                    return;
                }

                group = GroupedUnicast.createWith(key, bufferSize, this, delayError);
                groups.put(mapKey, group);

                groupCount.getAndIncrement();

                newGroup = true;
            }

            V v;
            try {
                v = ObjectHelper.requireNonNull(valueSelector.apply(t), "The valueSelector returned null");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                upstream.cancel();
                onError(ex);
                return;
            }

            group.onNext(v);

            completeEvictions();

            if (newGroup) {
                q.offer(group);
                drain();
            }
        }

        @Override
        public void onError(Throwable t) {
            if (done) {
                RxJavaPlugins.onError(t);
                return;
            }
            done = true;
            for (GroupedUnicast<K, V> g : groups.values()) {
                g.onError(t);
            }
            groups.clear();
            if (evictedGroups != null) {
                evictedGroups.clear();
            }
            error = t;
            finished = true;
            drain();
        }

        @Override
        public void onComplete() {
            if (!done) {
                for (GroupedUnicast<K, V> g : groups.values()) {
                    g.onComplete();
                }
                groups.clear();
                if (evictedGroups != null) {
                    evictedGroups.clear();
                }
                done = true;
                finished = true;
                drain();
            }
        }

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

        @Override
        public void cancel() {
            // cancelling the main source means we don't want any more groups
            // but running groups still require new values
            if (cancelled.compareAndSet(false, true)) {
                completeEvictions();
                if (groupCount.decrementAndGet() == 0) {
                    upstream.cancel();
                }
            }
        }

        private void completeEvictions() {
            if (evictedGroups != null) {
                int count = 0;
                GroupedUnicast<K, V> evictedGroup;
                while ((evictedGroup = evictedGroups.poll()) != null) {
                    evictedGroup.onComplete();
                    count++;
                }
                if (count != 0) {
                    groupCount.addAndGet(-count);
                }
            }
        }

        public void cancel(K key) {
            Object mapKey = key != null ? key : NULL_KEY;
            groups.remove(mapKey);
            if (groupCount.decrementAndGet() == 0) {
                upstream.cancel();

                if (getAndIncrement() == 0) {
                    queue.clear();
                }
            }
        }

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

            if (outputFused) {
                drainFused();
            } else {
                drainNormal();
            }
        }

        void drainFused() {
            int missed = 1;

            final SpscLinkedArrayQueue<GroupedFlowable<K, V>> q = this.queue;
            final Subscriber<? super GroupedFlowable<K, V>> a = this.downstream;

            for (;;) {
                if (cancelled.get()) {
                    q.clear();
                    return;
                }

                boolean d = finished;

                if (d && !delayError) {
                    Throwable ex = error;
                    if (ex != null) {
                        q.clear();
                        a.onError(ex);
                        return;
                    }
                }

                a.onNext(null);

                if (d) {
                    Throwable ex = error;
                    if (ex != null) {
                        a.onError(ex);
                    } else {
                        a.onComplete();
                    }
                    return;
                }

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

        void drainNormal() {
            int missed = 1;

            final SpscLinkedArrayQueue<GroupedFlowable<K, V>> q = this.queue;
            final Subscriber<? super GroupedFlowable<K, V>> a = this.downstream;

            for (;;) {

                long r = requested.get();
                long e = 0L;

                while (e != r) {
                    boolean d = finished;

                    GroupedFlowable<K, V> t = q.poll();

                    boolean empty = t == null;

                    if (checkTerminated(d, empty, a, q)) {
                        return;
                    }

                    if (empty) {
                        break;
                    }

                    a.onNext(t);

                    e++;
                }

                if (e == r && checkTerminated(finished, q.isEmpty(), a, q)) {
                    return;
                }

                if (e != 0L) {
                    if (r != Long.MAX_VALUE) {
                        requested.addAndGet(-e);
                    }
                    upstream.request(e);
                }

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

        boolean checkTerminated(boolean d, boolean empty, Subscriber<?> a, SpscLinkedArrayQueue<?> q) {
            if (cancelled.get()) {
                q.clear();
                return true;
            }

            if (delayError) {
                if (d && empty) {
                    Throwable ex = error;
                    if (ex != null) {
                        a.onError(ex);
                    } else {
                        a.onComplete();
                    }
                    return true;
                }
            } else {
                if (d) {
                    Throwable ex = error;
                    if (ex != null) {
                        q.clear();
                        a.onError(ex);
                        return true;
                    } else if (empty) {
                        a.onComplete();
                        return true;
                    }
                }
            }

            return false;
        }

        @Override
        public int requestFusion(int mode) {
            if ((mode & ASYNC) != 0) {
                outputFused = true;
                return ASYNC;
            }
            return NONE;
        }

        @Nullable
        @Override
        public GroupedFlowable<K, V> poll() {
            return queue.poll();
        }

        @Override
        public void clear() {
            queue.clear();
        }

        @Override
        public boolean isEmpty() {
            return queue.isEmpty();
        }
    }

    static final class EvictionAction<K, V> implements Consumer<GroupedUnicast<K, V>> {

        final Queue<GroupedUnicast<K, V>> evictedGroups;

        EvictionAction(Queue<GroupedUnicast<K, V>> evictedGroups) {
            this.evictedGroups = evictedGroups;
        }

        @Override
        public void accept(GroupedUnicast<K, V> value) {
            evictedGroups.offer(value);
        }
    }

    static final class GroupedUnicast<K, T> extends GroupedFlowable<K, T> {

        final State<T, K> state;

        public static <T, K> GroupedUnicast<K, T> createWith(K key, int bufferSize, GroupBySubscriber<?, K, T> parent, boolean delayError) {
            State<T, K> state = new State<T, K>(bufferSize, parent, key, delayError);
            return new GroupedUnicast<K, T>(key, state);
        }

        protected GroupedUnicast(K key, State<T, K> state) {
            super(key);
            this.state = state;
        }

        @Override
        protected void subscribeActual(Subscriber<? super T> s) {
            state.subscribe(s);
        }

        public void onNext(T t) {
            state.onNext(t);
        }

        public void onError(Throwable e) {
            state.onError(e);
        }

        public void onComplete() {
            state.onComplete();
        }
    }

    static final class State<T, K> extends BasicIntQueueSubscription<T> implements Publisher<T> {

        private static final long serialVersionUID = -3852313036005250360L;

        final K key;
        final SpscLinkedArrayQueue<T> queue;
        final GroupBySubscriber<?, K, T> parent;
        final boolean delayError;

        final AtomicLong requested = new AtomicLong();

        volatile boolean done;
        Throwable error;

        final AtomicBoolean cancelled = new AtomicBoolean();

        final AtomicReference<Subscriber<? super T>> actual = new AtomicReference<Subscriber<? super T>>();

        final AtomicBoolean once = new AtomicBoolean();

        boolean outputFused;

        int produced;

        State(int bufferSize, GroupBySubscriber<?, K, T> parent, K key, boolean delayError) {
            this.queue = new SpscLinkedArrayQueue<T>(bufferSize);
            this.parent = parent;
            this.key = key;
            this.delayError = delayError;
        }

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

        @Override
        public void cancel() {
            if (cancelled.compareAndSet(false, true)) {
                parent.cancel(key);
            }
        }

        @Override
        public void subscribe(Subscriber<? super T> s) {
            if (once.compareAndSet(false, true)) {
                s.onSubscribe(this);
                actual.lazySet(s);
                drain();
            } else {
                EmptySubscription.error(new IllegalStateException("Only one Subscriber allowed!"), s);
            }
        }

        public void onNext(T t) {
            queue.offer(t);
            drain();
        }

        public void onError(Throwable e) {
            error = e;
            done = true;
            drain();
        }

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

        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }
            if (outputFused) {
                drainFused();
            } else {
                drainNormal();
            }
        }

        void drainFused() {
            int missed = 1;

            final SpscLinkedArrayQueue<T> q = this.queue;
            Subscriber<? super T> a = this.actual.get();

            for (;;) {
                if (a != null) {
                    if (cancelled.get()) {
                        q.clear();
                        return;
                    }

                    boolean d = done;

                    if (d && !delayError) {
                        Throwable ex = error;
                        if (ex != null) {
                            q.clear();
                            a.onError(ex);
                            return;
                        }
                    }

                    a.onNext(null);

                    if (d) {
                        Throwable ex = error;
                        if (ex != null) {
                            a.onError(ex);
                        } else {
                            a.onComplete();
                        }
                        return;
                    }
                }

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

                if (a == null) {
                    a = this.actual.get();
                }
            }
        }

        void drainNormal() {
            int missed = 1;

            final SpscLinkedArrayQueue<T> q = queue;
            final boolean delayError = this.delayError;
            Subscriber<? super T> a = actual.get();
            for (;;) {
                if (a != null) {
                    long r = requested.get();
                    long e = 0;

                    while (e != r) {
                        boolean d = done;
                        T v = q.poll();
                        boolean empty = v == null;

                        if (checkTerminated(d, empty, a, delayError)) {
                            return;
                        }

                        if (empty) {
                            break;
                        }

                        a.onNext(v);

                        e++;
                    }

                    if (e == r && checkTerminated(done, q.isEmpty(), a, delayError)) {
                        return;
                    }

                    if (e != 0L) {
                        if (r != Long.MAX_VALUE) {
                            requested.addAndGet(-e);
                        }
                        parent.upstream.request(e);
                    }
                }

                missed = addAndGet(-missed);
                if (missed == 0) {
                    break;
                }
                if (a == null) {
                    a = actual.get();
                }
            }
        }

        boolean checkTerminated(boolean d, boolean empty, Subscriber<? super T> a, boolean delayError) {
            if (cancelled.get()) {
                queue.clear();
                return true;
            }

            if (d) {
                if (delayError) {
                    if (empty) {
                        Throwable e = error;
                        if (e != null) {
                            a.onError(e);
                        } else {
                            a.onComplete();
                        }
                        return true;
                    }
                } else {
                    Throwable e = error;
                    if (e != null) {
                        queue.clear();
                        a.onError(e);
                        return true;
                    } else
                    if (empty) {
                        a.onComplete();
                        return true;
                    }
                }
            }

            return false;
        }

        @Override
        public int requestFusion(int mode) {
            if ((mode & ASYNC) != 0) {
                outputFused = true;
                return ASYNC;
            }
            return NONE;
        }

        @Nullable
        @Override
        public T poll() {
            T v = queue.poll();
            if (v != null) {
                produced++;
                return v;
            }
            int p = produced;
            if (p != 0) {
                produced = 0;
                parent.upstream.request(p);
            }
            return null;
        }

        @Override
        public boolean isEmpty() {
            return queue.isEmpty();
        }

        @Override
        public void clear() {
            queue.clear();
        }
    }
}