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A JVM-based REST/WS wrapper for the official Discord Bot API
There is a newer version: 3.3.0-RC1
/*
 * This file is part of Discord4J.
 *
 * Discord4J is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Discord4J is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Discord4J.  If not, see .
 */
package discord4j.common;

import reactor.core.Disposable;
import reactor.core.Disposables;
import reactor.core.publisher.Flux;
import reactor.core.publisher.SignalType;
import reactor.core.publisher.Sinks;
import reactor.core.scheduler.Scheduler;
import reactor.util.concurrent.Queues;

import java.time.Duration;
import java.util.concurrent.locks.LockSupport;

/**
 * Emit ticks at a constant rate specified at {@link #start(Duration, Duration)} and will continue until
 * {@link #stop()} is called or {@link #start(Duration, Duration)} is re-invoked, resetting the previous emitter.
 * The ticks are available from the {@link #ticks()} method.
 */
public class ResettableInterval implements Sinks.EmitFailureHandler {

    private final Scheduler scheduler;
    private final Disposable.Swap task;
    private final Sinks.Many sink = Sinks.many().multicast()
            .onBackpressureBuffer(Queues.SMALL_BUFFER_SIZE, false);

    /**
     * Create a {@link ResettableInterval} that emits ticks on the given {@link Scheduler} upon calling
     * {@link #start(Duration, Duration)}.
     *
     * @param scheduler the Reactor {@link Scheduler} to use to emit ticks
     */
    public ResettableInterval(Scheduler scheduler) {
        this.scheduler = scheduler;
        this.task = Disposables.swap();
    }

    /**
     * Begin producing ticks at the given rate.
     *
     * @param delay the {@link Duration} to wait before emitting the first tick
     * @param period the period {@link Duration} used to emit ticks.
     * @see Flux#interval(Duration, Duration, Scheduler)
     */
    public void start(Duration delay, Duration period) {
        this.task.update(Flux.interval(delay, period, scheduler)
                .subscribe(tick -> sink.emitNext(tick, this)));
    }

    /**
     * Dispose the current emitter task without completing or cancelling existing subscriptions to {@link #ticks()}.
     */
    public void stop() {
        if (task.get() != null) {
            task.get().dispose();
        }
    }

    /**
     * Return a {@link Flux} that emits ticks at the currently configured rate.
     *
     * @return a {@link Flux} of increasing values since the last {@link #start(Duration, Duration)} call
     */
    public Flux ticks() {
        return sink.asFlux();
    }

    @Override
    public boolean onEmitFailure(SignalType signalType, Sinks.EmitResult result) {
        if (task.get() == null) {
            return false;
        }

        switch (result) {
            case FAIL_NON_SERIALIZED:
                return true;
            case FAIL_OVERFLOW:
                LockSupport.parkNanos(10);
                return true;
            default:
                return false;
        }
    }
}