/*
 * Copyright (c) 2009-2012 jMonkeyEngine
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
 *   may be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.jme3.system;

/**
 * <code>NanoTimer</code> is a System.nanoTime implementation of
 * <code>Timer</code>. This is primarily useful for headless applications
 * running on a server.
 * 
 * @author Matthew D. Hicks
 */
public class NanoTimer extends Timer {

	private static final long TIMER_RESOLUTION = 1000000000L;
	private static final float INVERSE_TIMER_RESOLUTION = 1f / TIMER_RESOLUTION;

	private long startTime;
	private long previousTime;
	private float tpf;
	private float fps;
	private long currentTime;

	public NanoTimer() {
		startTime = System.nanoTime();
	}

	/**
	 * Returns the time in seconds. The timer starts at 0.0 seconds.
	 *
	 * @return the current time in seconds
	 */

	protected long getTimeInternal() {
		return System.nanoTime() - startTime;
	}

	@Override
	public float getTimeInSeconds() {
		return getTime() * INVERSE_TIMER_RESOLUTION;
	}

	@Override
	public long getTime() {
		return currentTime;
	}

	@Override
	public long getResolution() {
		return TIMER_RESOLUTION;
	}

	@Override
	public float getFrameRate() {
		return fps;
	}

	@Override
	public float getTimePerFrame() {
		return tpf;
	}

	@Override
	public void update() {
		currentTime = getTimeInternal();
		tpf = (currentTime - previousTime) * (1.0f / TIMER_RESOLUTION);
		fps = 1.0f / tpf;
		previousTime = getTime();
	}

	@Override
	public void reset() {
		startTime = System.nanoTime();
		currentTime = getTimeInternal();
		previousTime = getTime();
	}
}
