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

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.subjects.UnicastSubject;

public final class ObservableWindow<T> extends AbstractObservableWithUpstream<T, Observable<T>> {
    final long count;
    final long skip;
    final int capacityHint;

    public ObservableWindow(ObservableSource<T> source, long count, long skip, int capacityHint) {
        super(source);
        this.count = count;
        this.skip = skip;
        this.capacityHint = capacityHint;
    }

    @Override
    public void subscribeActual(Observer<? super Observable<T>> t) {
        if (count == skip) {
            source.subscribe(new WindowExactObserver<T>(t, count, capacityHint));
        } else {
            source.subscribe(new WindowSkipObserver<T>(t, count, skip, capacityHint));
        }
    }

    static final class WindowExactObserver<T>
    extends AtomicInteger
    implements Observer<T>, Disposable, Runnable {

        private static final long serialVersionUID = -7481782523886138128L;
        final Observer<? super Observable<T>> downstream;
        final long count;
        final int capacityHint;

        long size;

        Disposable upstream;

        UnicastSubject<T> window;

        volatile boolean cancelled;

        WindowExactObserver(Observer<? super Observable<T>> actual, long count, int capacityHint) {
            this.downstream = actual;
            this.count = count;
            this.capacityHint = capacityHint;
        }

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

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onNext(T t) {
            UnicastSubject<T> w = window;
            if (w == null && !cancelled) {
                w = UnicastSubject.create(capacityHint, this);
                window = w;
                downstream.onNext(w);
            }

            if (w != null) {
                w.onNext(t);
                if (++size >= count) {
                    size = 0;
                    window = null;
                    w.onComplete();
                    if (cancelled) {
                        upstream.dispose();
                    }
                }
            }
        }

        @Override
        public void onError(Throwable t) {
            UnicastSubject<T> w = window;
            if (w != null) {
                window = null;
                w.onError(t);
            }
            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            UnicastSubject<T> w = window;
            if (w != null) {
                window = null;
                w.onComplete();
            }
            downstream.onComplete();
        }

        @Override
        public void dispose() {
            cancelled = true;
        }

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

        @Override
        public void run() {
            if (cancelled) {
                upstream.dispose();
            }
        }
    }

    static final class WindowSkipObserver<T> extends AtomicBoolean
    implements Observer<T>, Disposable, Runnable {

        private static final long serialVersionUID = 3366976432059579510L;
        final Observer<? super Observable<T>> downstream;
        final long count;
        final long skip;
        final int capacityHint;
        final ArrayDeque<UnicastSubject<T>> windows;

        long index;

        volatile boolean cancelled;

        
Counts how many elements were emitted to the very first window in windows. /** Counts how many elements were emitted to the very first window in windows. */
        long firstEmission;

        Disposable upstream;

        final AtomicInteger wip = new AtomicInteger();

        WindowSkipObserver(Observer<? super Observable<T>> actual, long count, long skip, int capacityHint) {
            this.downstream = actual;
            this.count = count;
            this.skip = skip;
            this.capacityHint = capacityHint;
            this.windows = new ArrayDeque<UnicastSubject<T>>();
        }

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

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onNext(T t) {
            final ArrayDeque<UnicastSubject<T>> ws = windows;

            long i = index;

            long s = skip;

            if (i % s == 0 && !cancelled) {
                wip.getAndIncrement();
                UnicastSubject<T> w = UnicastSubject.create(capacityHint, this);
                ws.offer(w);
                downstream.onNext(w);
            }

            long c = firstEmission + 1;

            for (UnicastSubject<T> w : ws) {
                w.onNext(t);
            }

            if (c >= count) {
                ws.poll().onComplete();
                if (ws.isEmpty() && cancelled) {
                    this.upstream.dispose();
                    return;
                }
                firstEmission = c - s;
            } else {
                firstEmission = c;
            }

            index = i + 1;
        }

        @Override
        public void onError(Throwable t) {
            final ArrayDeque<UnicastSubject<T>> ws = windows;
            while (!ws.isEmpty()) {
                ws.poll().onError(t);
            }
            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            final ArrayDeque<UnicastSubject<T>> ws = windows;
            while (!ws.isEmpty()) {
                ws.poll().onComplete();
            }
            downstream.onComplete();
        }

        @Override
        public void dispose() {
            cancelled = true;
        }

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

        @Override
        public void run() {
            if (wip.decrementAndGet() == 0) {
                if (cancelled) {
                    upstream.dispose();
                }
            }
        }
    }
}