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

import io.reactivex.ObservableSource;
import io.reactivex.Observer;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.disposables.*;

public final class ObservableBuffer<T, U extends Collection<? super T>> extends AbstractObservableWithUpstream<T, U> {
    final int count;
    final int skip;
    final Callable<U> bufferSupplier;

    public ObservableBuffer(ObservableSource<T> source, int count, int skip, Callable<U> bufferSupplier) {
        super(source);
        this.count = count;
        this.skip = skip;
        this.bufferSupplier = bufferSupplier;
    }

    @Override
    protected void subscribeActual(Observer<? super U> t) {
        if (skip == count) {
            BufferExactObserver<T, U> bes = new BufferExactObserver<T, U>(t, count, bufferSupplier);
            if (bes.createBuffer()) {
                source.subscribe(bes);
            }
        } else {
            source.subscribe(new BufferSkipObserver<T, U>(t, count, skip, bufferSupplier));
        }
    }

    static final class BufferExactObserver<T, U extends Collection<? super T>> implements Observer<T>, Disposable {
        final Observer<? super U> downstream;
        final int count;
        final Callable<U> bufferSupplier;
        U buffer;

        int size;

        Disposable upstream;

        BufferExactObserver(Observer<? super U> actual, int count, Callable<U> bufferSupplier) {
            this.downstream = actual;
            this.count = count;
            this.bufferSupplier = bufferSupplier;
        }

        boolean createBuffer() {
            U b;
            try {
                b = ObjectHelper.requireNonNull(bufferSupplier.call(), "Empty buffer supplied");
            } catch (Throwable t) {
                Exceptions.throwIfFatal(t);
                buffer = null;
                if (upstream == null) {
                    EmptyDisposable.error(t, downstream);
                } else {
                    upstream.dispose();
                    downstream.onError(t);
                }
                return false;
            }

            buffer = b;

            return true;
        }

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

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

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

        @Override
        public void onNext(T t) {
            U b = buffer;
            if (b != null) {
                b.add(t);

                if (++size >= count) {
                    downstream.onNext(b);

                    size = 0;
                    createBuffer();
                }
            }
        }

        @Override
        public void onError(Throwable t) {
            buffer = null;
            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            U b = buffer;
            if (b != null) {
                buffer = null;
                if (!b.isEmpty()) {
                    downstream.onNext(b);
                }
                downstream.onComplete();
            }
        }
    }

    static final class BufferSkipObserver<T, U extends Collection<? super T>>
    extends AtomicBoolean implements Observer<T>, Disposable {

        private static final long serialVersionUID = -8223395059921494546L;
        final Observer<? super U> downstream;
        final int count;
        final int skip;
        final Callable<U> bufferSupplier;

        Disposable upstream;

        final ArrayDeque<U> buffers;

        long index;

        BufferSkipObserver(Observer<? super U> actual, int count, int skip, Callable<U> bufferSupplier) {
            this.downstream = actual;
            this.count = count;
            this.skip = skip;
            this.bufferSupplier = bufferSupplier;
            this.buffers = new ArrayDeque<U>();
        }

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

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

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

        @Override
        public void onNext(T t) {
            if (index++ % skip == 0) {
                U b;

                try {
                    b = ObjectHelper.requireNonNull(bufferSupplier.call(), "The bufferSupplier returned a null collection. Null values are generally not allowed in 2.x operators and sources.");
                } catch (Throwable e) {
                    buffers.clear();
                    upstream.dispose();
                    downstream.onError(e);
                    return;
                }

                buffers.offer(b);
            }

            Iterator<U> it = buffers.iterator();
            while (it.hasNext()) {
                U b = it.next();
                b.add(t);
                if (count <= b.size()) {
                    it.remove();

                    downstream.onNext(b);
                }
            }
        }

        @Override
        public void onError(Throwable t) {
            buffers.clear();
            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            while (!buffers.isEmpty()) {
                downstream.onNext(buffers.poll());
            }
            downstream.onComplete();
        }
    }
}