/*
 * Copyright (c) 2009-2021 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.aionemu.gameserver.geoEngine.utils;

import java.util.ArrayList;

import com.aionemu.gameserver.geoEngine.collision.bih.BIHNode.BIHStackData;
import com.aionemu.gameserver.geoEngine.math.Matrix3f;
import com.aionemu.gameserver.geoEngine.math.Vector3f;

/**
 * Temporary variables assigned to each thread. Engine classes may access
 * these temp variables with TempVars.get(), all retrieved TempVars
 * instances must be returned via TempVars.release().
 * This returns an available instance of the TempVar class ensuring this 
 * particular instance is never used elsewhere in the meantime.
 */
public class TempVars {

	/**
	 * Allow X instances of TempVars in a single thread.
	 */
	private static final int STACK_SIZE = 5;

	/**
	 * <code>TempVarsStack</code> contains a stack of TempVars.
	 * Every time TempVars.get() is called, a new entry is added to the stack,
	 * and the index incremented.
	 * When TempVars.release() is called, the entry is checked against
	 * the current instance and  then the index is decremented.
	 */
	private static class TempVarsStack {

		private int index = 0;
		private TempVars[] tempVars = new TempVars[STACK_SIZE];
	}
	/**
	 * ThreadLocal to store a TempVarsStack for each thread.
	 * This ensures each thread has a single TempVarsStack that is
	 * used only in method calls in that thread.
	 */
	private static final ThreadLocal<TempVarsStack> varsLocal = ThreadLocal.withInitial(TempVarsStack::new);
	/**
	 * This instance of TempVars has been retrieved but not released yet.
	 */
	private boolean isUsed = false;

	private TempVars() {
	}

	/**
	 * Acquire an instance of the TempVar class.
	 * You have to release the instance after use by calling the 
	 * release() method. 
	 * If more than STACK_SIZE (currently 5) instances are requested 
	 * in a single thread then an ArrayIndexOutOfBoundsException will be thrown.
	 *
	 * @return A TempVar instance
	 */
	public static TempVars get() {
		TempVarsStack stack = varsLocal.get();

		TempVars instance = stack.tempVars[stack.index];

		if (instance == null) {
			// Create new
			instance = new TempVars();

			// Put it in there
			stack.tempVars[stack.index] = instance;
		}

		stack.index++;

		instance.isUsed = true;

		return instance;
	}

	/**
	 * Releases this instance of TempVars.
	 * Once released, the contents of the TempVars are undefined.
	 * The TempVars must be released in the opposite order that they are retrieved,
	 * e.g. Acquiring vars1, then acquiring vars2, vars2 MUST be released 
	 * first otherwise an exception will be thrown.
	 */
	public void release() {
		if (!isUsed) {
			throw new IllegalStateException("This instance of TempVars was already released!");
		}

		isUsed = false;

		TempVarsStack stack = varsLocal.get();

		// Return it to the stack
		stack.index--;

		// Check if it is actually there
		if (stack.tempVars[stack.index] != this) {
			throw new IllegalStateException("An instance of TempVars has not been released in a called method!");
		}
	}

	/**
	 * General vectors.
	 */
	public final Vector3f vect1 = new Vector3f();
	public final Vector3f vect2 = new Vector3f();
	public final Vector3f vect3 = new Vector3f();
	public final Vector3f vect4 = new Vector3f();
	public final Vector3f vect5 = new Vector3f();
	public final Vector3f vect6 = new Vector3f();
	public final Matrix3f tempMat3 = new Matrix3f();
	/**
	 * BoundingBox ray collision
	 */
	public final float[] fWdU = new float[3];
	public final float[] fAWdU = new float[3];
	public final float[] fDdU = new float[3];
	public final float[] fADdU = new float[3];
	public final float[] fAWxDdU = new float[3];
	/**
	 * BIHTree
	 */
	public final float[] bihSwapTmp = new float[9];
	public final ArrayList<BIHStackData> bihStack = new ArrayList<>();
}