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 io.reactivex.internal.functions.ObjectHelper;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.*;

import io.reactivex.ObservableSource;
import io.reactivex.Observer;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.*;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.observables.GroupedObservable;

public final class ObservableGroupBy<T, K, V> extends AbstractObservableWithUpstream<T, GroupedObservable<K, V>> {
    final Function<? super T, ? extends K> keySelector;
    final Function<? super T, ? extends V> valueSelector;
    final int bufferSize;
    final boolean delayError;

    public ObservableGroupBy(ObservableSource<T> source,
            Function<? super T, ? extends K> keySelector, Function<? super T, ? extends V> valueSelector,
            int bufferSize, boolean delayError) {
        super(source);
        this.keySelector = keySelector;
        this.valueSelector = valueSelector;
        this.bufferSize = bufferSize;
        this.delayError = delayError;
    }

    @Override
    public void subscribeActual(Observer<? super GroupedObservable<K, V>> t) {
        source.subscribe(new GroupByObserver<T, K, V>(t, keySelector, valueSelector, bufferSize, delayError));
    }

    public static final class GroupByObserver<T, K, V> extends AtomicInteger implements Observer<T>, Disposable {

        private static final long serialVersionUID = -3688291656102519502L;

        final Observer<? super GroupedObservable<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;

        static final Object NULL_KEY = new Object();

        Disposable upstream;

        final AtomicBoolean cancelled = new AtomicBoolean();

        public GroupByObserver(Observer<? super GroupedObservable<K, V>> actual, Function<? super T, ? extends K> keySelector, Function<? super T, ? extends V> valueSelector, int bufferSize, boolean delayError) {
            this.downstream = actual;
            this.keySelector = keySelector;
            this.valueSelector = valueSelector;
            this.bufferSize = bufferSize;
            this.delayError = delayError;
            this.groups = new ConcurrentHashMap<Object, GroupedUnicast<K, V>>();
            this.lazySet(1);
        }

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

        @Override
        public void onNext(T t) {
            K key;
            try {
                key = keySelector.apply(t);
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                upstream.dispose();
                onError(e);
                return;
            }

            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);

                getAndIncrement();

                downstream.onNext(group);
            }

            V v;
            try {
                v = ObjectHelper.requireNonNull(valueSelector.apply(t), "The value supplied is null");
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                upstream.dispose();
                onError(e);
                return;
            }

            group.onNext(v);
        }

        @Override
        public void onError(Throwable t) {
            List<GroupedUnicast<K, V>> list = new ArrayList<GroupedUnicast<K, V>>(groups.values());
            groups.clear();

            for (GroupedUnicast<K, V> e : list) {
                e.onError(t);
            }

            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            List<GroupedUnicast<K, V>> list = new ArrayList<GroupedUnicast<K, V>>(groups.values());
            groups.clear();

            for (GroupedUnicast<K, V> e : list) {
                e.onComplete();
            }

            downstream.onComplete();
        }

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

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

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

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

        final State<T, K> state;

        public static <T, K> GroupedUnicast<K, T> createWith(K key, int bufferSize, GroupByObserver<?, 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(Observer<? super T> observer) {
            state.subscribe(observer);
        }

        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 AtomicInteger implements Disposable, ObservableSource<T> {

        private static final long serialVersionUID = -3852313036005250360L;

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

        volatile boolean done;
        Throwable error;

        final AtomicBoolean cancelled = new AtomicBoolean();

        final AtomicBoolean once = new AtomicBoolean();

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

        State(int bufferSize, GroupByObserver<?, 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 dispose() {
            if (cancelled.compareAndSet(false, true)) {
                if (getAndIncrement() == 0) {
                    actual.lazySet(null);
                    parent.cancel(key);
                }
            }
        }

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

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

        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;
            }
            int missed = 1;

            final SpscLinkedArrayQueue<T> q = queue;
            final boolean delayError = this.delayError;
            Observer<? super T> a = actual.get();
            for (;;) {
                if (a != null) {
                    for (;;) {
                        boolean d = done;
                        T v = q.poll();
                        boolean empty = v == null;

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

                        if (empty) {
                            break;
                        }

                        a.onNext(v);
                    }
                }

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

        boolean checkTerminated(boolean d, boolean empty, Observer<? super T> a, boolean delayError) {
            if (cancelled.get()) {
                queue.clear();
                parent.cancel(key);
                actual.lazySet(null);
                return true;
            }

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

            return false;
        }
    }
}