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 * The contents of this file are subject to the terms of either the Universal Permissive License
 * v 1.0 as shown at http://oss.oracle.com/licenses/upl
 *
 * or the following license:
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met:
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 * 1. Redistributions of source code must retain the above copyright notice, this list of conditions
 * and the following disclaimer.
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 * conditions and the following disclaimer in the documentation and/or other materials provided with
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package org.openjdk.jmc.ui.rate;

/**
 * A refresh bufferer that limits the rate which with it forwards refresh requests. In addition,
 * refreshes will typically, subject to the {@link RateCoordinator}, be delivered in the user
 * interface thread.
 */
public abstract class RateLimitedRefresher implements Runnable {
	protected final RateCoordinator rateCoordinator;
	protected final int minPeriodMillis;
	private long lastRefreshMillis;
	private boolean needsRefresh;

	public RateLimitedRefresher(RateCoordinator rateCoordinator, int minPeriodMillis) {
		this.rateCoordinator = rateCoordinator;
		this.minPeriodMillis = minPeriodMillis;
	}

	public void setNeedsRefresh() {
		int delay = -1;
		synchronized (this) {
			if (!needsRefresh) {
				needsRefresh = true;
				delay = (int) Math.max(0, lastRefreshMillis + minPeriodMillis - System.currentTimeMillis());
			}
		}
		if (delay >= 0) {
			rateCoordinator.schedule(this, delay);
		}
	}

	@Override
	public final void run() {
		refreshIfNeeded();
	}

	/**
	 * Note: This method should only be called from the SWT display thread.
	 */
	public void refreshIfNeeded() {
		boolean refresh = false;
		synchronized (this) {
			if (needsRefresh) {
				needsRefresh = false;
				refresh = true;
				lastRefreshMillis = System.currentTimeMillis();
			}
		}
		if (refresh) {
			doRefresh();
		}
	}

	protected abstract void doRefresh();
}
