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.atomic.AtomicLong;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.annotations.Nullable;
import io.reactivex.exceptions.*;
import io.reactivex.functions.Action;
import io.reactivex.internal.fuseable.SimplePlainQueue;
import io.reactivex.internal.queue.*;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.internal.util.BackpressureHelper;

public final class FlowableOnBackpressureBuffer<T> extends AbstractFlowableWithUpstream<T, T> {
    final int bufferSize;
    final boolean unbounded;
    final boolean delayError;
    final Action onOverflow;

    public FlowableOnBackpressureBuffer(Flowable<T> source, int bufferSize, boolean unbounded,
            boolean delayError, Action onOverflow) {
        super(source);
        this.bufferSize = bufferSize;
        this.unbounded = unbounded;
        this.delayError = delayError;
        this.onOverflow = onOverflow;
    }

    @Override
    protected void subscribeActual(Subscriber<? super T> s) {
        source.subscribe(new BackpressureBufferSubscriber<T>(s, bufferSize, unbounded, delayError, onOverflow));
    }

    static final class BackpressureBufferSubscriber<T> extends BasicIntQueueSubscription<T> implements FlowableSubscriber<T> {

        private static final long serialVersionUID = -2514538129242366402L;

        final Subscriber<? super T> downstream;
        final SimplePlainQueue<T> queue;
        final boolean delayError;
        final Action onOverflow;

        Subscription upstream;

        volatile boolean cancelled;

        volatile boolean done;
        Throwable error;

        final AtomicLong requested = new AtomicLong();

        boolean outputFused;

        BackpressureBufferSubscriber(Subscriber<? super T> actual, int bufferSize,
                boolean unbounded, boolean delayError, Action onOverflow) {
            this.downstream = actual;
            this.onOverflow = onOverflow;
            this.delayError = delayError;

            SimplePlainQueue<T> q;

            if (unbounded) {
                q = new SpscLinkedArrayQueue<T>(bufferSize);
            } else {
                q = new SpscArrayQueue<T>(bufferSize);
            }

            this.queue = q;
        }

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

        @Override
        public void onNext(T t) {
            if (!queue.offer(t)) {
                upstream.cancel();
                MissingBackpressureException ex = new MissingBackpressureException("Buffer is full");
                try {
                    onOverflow.run();
                } catch (Throwable e) {
                    Exceptions.throwIfFatal(e);
                    ex.initCause(e);
                }
                onError(ex);
                return;
            }
            if (outputFused) {
                downstream.onNext(null);
            } else {
                drain();
            }
        }

        @Override
        public void onError(Throwable t) {
            error = t;
            done = true;
            if (outputFused) {
                downstream.onError(t);
            } else {
                drain();
            }
        }

        @Override
        public void onComplete() {
            done = true;
            if (outputFused) {
                downstream.onComplete();
            } else {
                drain();
            }
        }

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

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

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

        void drain() {
            if (getAndIncrement() == 0) {
                int missed = 1;
                final SimplePlainQueue<T> q = queue;
                final Subscriber<? super T> a = downstream;
                for (;;) {

                    if (checkTerminated(done, q.isEmpty(), a)) {
                        return;
                    }

                    long r = requested.get();

                    long e = 0L;

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

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

                        if (empty) {
                            break;
                        }

                        a.onNext(v);

                        e++;
                    }

                    if (e == r) {
                        boolean d = done;
                        boolean empty = q.isEmpty();

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

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

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

        boolean checkTerminated(boolean d, boolean empty, Subscriber<? super T> a) {
            if (cancelled) {
                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() throws Exception {
            return queue.poll();
        }

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

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