package net.minecraft.client;

import java.util.concurrent.locks.LockSupport;

public class FramerateLimiter {
	private static final double OVERSHOOT_SMOOTHING = 0.1;
	private static final long MAX_CURRENT_OVERSHOOT_NS = 25000000L;
	private static final long MAX_AVERAGE_OVERSHOOT_NS = 2000000L;
	private static final long ONE_SECOND_IN_NANOSECONDS = 1000000000L;
	private static final long SPIN_SAFETY_BUFFER_NS = 500000L;
	private static long lastFrameTime = System.nanoTime();
	private static long averageOvershootNs = 0L;
	private static int lastFramerateLimit;

	public static void limitDisplayFPS(final int framerateLimit) {
		long targetTimePerFrame = 1000000000L / framerateLimit;
		long targetTimeNs = lastFrameTime + targetTimePerFrame;
		if (framerateLimit != lastFramerateLimit) {
			averageOvershootNs = 0L;
			lastFramerateLimit = framerateLimit;
		}

		long remainingTimeNs;
		while ((remainingTimeNs = targetTimeNs - System.nanoTime()) > 0L) {
			if (remainingTimeNs > averageOvershootNs + 500000L) {
				long sleepStartTimeNs = System.nanoTime();
				long expectedSleepTimeNs = remainingTimeNs - averageOvershootNs - 500000L;
				if (!Thread.interrupted()) {
					LockSupport.parkNanos(expectedSleepTimeNs);
					long sleepDurationNs = System.nanoTime() - sleepStartTimeNs;
					long currentOvershootNs = sleepDurationNs - expectedSleepTimeNs;
					if (currentOvershootNs > 0L && currentOvershootNs < 25000000L) {
						averageOvershootNs = (long)(0.1 * currentOvershootNs + 0.9 * averageOvershootNs);
						averageOvershootNs = Math.min(averageOvershootNs, 2000000L);
					}
				}
			} else {
				Thread.onSpinWait();
			}
		}

		lastFrameTime = System.nanoTime();
	}
}