// Copyright 2012 David J Smith, Nanch LLC
// This code is available to the general public for use in personal or commercial products free of charge with no implied or explicit liability

// This code was used in [ EZ Drop ], a fast and easy way to get files to your droid
// https://market.android.com/details?id=co.dropper.ez.android.free

package co.dropper.ez.android.free;

import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

public class LowPassBitrateEstimator {

	Queue<BitrateRecord> arrivals = new ConcurrentLinkedQueue<BitrateRecord>();
	
	long baseTime = System.currentTimeMillis();
	long millisecondInterval = 250;
	private double multiplier =  1000 / millisecondInterval;
	private double alpha = .96;
	long lastEstimatedTime = System.currentTimeMillis() - baseTime;
	double currentAverage = 0;
	
	public LowPassBitrateEstimator() {
	}

	public double estimate() {
		long now = System.currentTimeMillis() - baseTime;

		if (now - lastEstimatedTime < millisecondInterval) {
			return currentAverage * multiplier;
		}
		
		if (arrivals.size() == 0) {
			if (now > millisecondInterval) {
				for (int i = 0; i < (now - lastEstimatedTime)
						/ millisecondInterval; i++) {
					currentAverage = alpha * currentAverage + (1 - alpha) * 0;
					lastEstimatedTime += millisecondInterval;
				}
			}
		} else {
			
			
			long totalBytesReceived = 0;
			BitrateRecord br = new BitrateRecord();
			br = arrivals.peek();

			while (br.t < now - millisecondInterval) {
				while (br.t < lastEstimatedTime + millisecondInterval) {
					totalBytesReceived += br.v;
					arrivals.remove();
					if (arrivals.size() == 0) {
						break;
					}
					br = arrivals.peek();
				}

				currentAverage = alpha * currentAverage + (1 - alpha)
						* totalBytesReceived;
				lastEstimatedTime += millisecondInterval;
				totalBytesReceived = 0;

				if (arrivals.size() == 0) {
					break;
				}
			}
		}
		return currentAverage * multiplier;
	}
	
	public void push(int val){
		
		BitrateRecord br = new BitrateRecord();
		br.t = System.currentTimeMillis() - baseTime;
		br.v = val;
		arrivals.add(br);
	}
}



----------------------------- BEGIN BitrateRecord.java -----------------------------

package co.dropper.ez.android.free;
public class BitrateRecord {
	public long t;
	public long v;
}