jnidzwetzki/bitfinex-v2-wss-api-java

/*******************************************************************************
 *
 *    Copyright (C) 2015-2018 Jan Kristof Nidzwetzki
 *  
 *    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 com.github.jnidzwetzki.bitfinex.v2.util;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;

/**
 * This class limits the amount of events to t_events in a 
 * definable time period. recordNewEvent() records a new 
 * event, waitForNewTimeslot() blocks until less then
 * t_events occurred in the period of time.
 *
 */
public class EventsInTimeslotManager {
    
    /**
     * The number of events in the timeslot
     */
    private final int numberOfEvents;
    
    /**
     * The size of the timeslot
     */
    private final long timeslotInMilliseconds;

    /**
     * The event list
     */
    private final List<Long> events;

    public EventsInTimeslotManager(final int numberOfEvents, final int timeslot, final TimeUnit timeUnit) {
        
        if(numberOfEvents <= 0) {
            throw new IllegalArgumentException("Number of events must be >= 1");
        }
        
        if(timeslot <= 0) {
            throw new IllegalArgumentException("Timeslot must be >= 1");
        }
        
        this.numberOfEvents = numberOfEvents;
        this.timeslotInMilliseconds = timeUnit.toMillis(timeslot);
        this.events = new ArrayList<>();
    }
    
    /**
     * Record a new event
     */
    public void recordNewEvent() {
        
        // Remove old events from record
        final double thresholdTime = System.currentTimeMillis() - (timeslotInMilliseconds * 2.0);
        events.removeIf(e -> e < thresholdTime);
        
        // Record new event
        events.add(System.currentTimeMillis());
    }
    
    /**
     * Wait for a new timeslot
     * @return 
     * @throws InterruptedException 
     */
    public boolean waitForNewTimeslot() throws InterruptedException {
        
        boolean hasWaited = false;
        
        while(true) {
            final long numberOfEventsInTimeSlot = getNumberOfEventsInTimeslot();
            
            if(numberOfEventsInTimeSlot > numberOfEvents) {
                hasWaited = true;
                Thread.sleep(timeslotInMilliseconds / 10);
            } else {
                return hasWaited;
            }
        }
    }

    /**
     * Get the number of events in the timeslot
     * @param thresholdTime
     * @return
     */
    public long getNumberOfEventsInTimeslot() {

        final double thresholdTime = System.currentTimeMillis() - (timeslotInMilliseconds);
        
        return events.stream()
                .filter(e -> e >= thresholdTime)
                .count();
    }
}