/***********************************************************************

 * mt4j Copyright (c) 2008 - 2010 Christopher Ruff, Fraunhofer-Gesellschaft All rights reserved.

 *  

 *   This program is free software: you can redistribute it and/or modify

 *   it under the terms of the GNU General Public License as published by

 *   the Free Software Foundation, either version 3 of the License, or

 *   (at your option) any later version.

 *

 *   This program is distributed in the hope that it will be useful,

 *   but WITHOUT ANY WARRANTY; without even the implied warranty of

 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *   GNU General Public License for more details.

 *

 *   You should have received a copy of the GNU General Public License

 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.

 *

 ***********************************************************************/

package org.mt4j.util.opengl;



import java.util.Stack;



import javax.media.opengl.GL;

import javax.media.opengl.glu.GLU;



import org.mt4j.util.logging.ILogger;

import org.mt4j.util.logging.MTLoggerFactory;



/**

 * The FBO stack manages the current opengl drawing target. It allows to switch drawing to/from different

 * frame buffer objects.

 * Usage:<br>

 * <br>GLFboStack.getInstance(gl).pushFBO(); //saves the current render target/frame buffer 

 * <br>GLFboStack.getInstance(gl).useFBO(glFBO); //changes to another frame buffer

 * <br>GLFboStack.getInstance(gl).popFBO() //switches back to the previously saved frame buffer

 * @author Christopher Ruff

 */

public class GLFboStack{

	/** The Constant logger. */

	private static final ILogger logger = MTLoggerFactory.getLogger(GLFboStack.class.getName());

	static{

		logger.setLevel(ILogger.ERROR);

	}

	

	/** The gl. */

	public GL gl;

	

	/** The current fbo. */

	protected int currentFBO;

	

	/** The fbo name stack. */

	protected Stack<Integer> fboNameStack;

	

	/** The instance. */

	private static GLFboStack instance = null;



	/**

	 * Instantiates a new gL fbo stack.

	 * @param gl the gl

	 */

	private GLFboStack(GL gl){

		this.gl = gl;

		fboNameStack = new Stack<Integer>();

		currentFBO = 0;

	}

	

	/**

	 * Gets the single instance of GLFboStack.

	 *

	 * @return single instance of GLFboStack

	 */

	public static GLFboStack getInstance(){

		if (instance == null){

			instance = new GLFboStack(GLU.getCurrentGL());

			return instance;

		}else{

			return instance;

		}

	}



	/**

	 * Pushes the currently used render target ID on the stack.

	 */

	public void pushFBO(){

		fboNameStack.push(currentFBO);

	}



	/**

	 * Binds the specified render target ID and sets it as current.

	 * 

	 * @param fbo the fbo

	 */

	public void useFBO(int fbo){

		currentFBO = fbo;

		gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, currentFBO);

	}



	/**

	 * Binds the specified frame buffer object and sets it as current.

	 * 

	 * @param fbo the fbo

	 */

	public void useFBO(GLFBO fbo){

		currentFBO = fbo.getName();

		fbo.bind();

	}

	

	/**

	 * Peek fbo.

	 *

	 * @return the int

	 */

	public int peekFBO(){

		if (fboNameStack.isEmpty()){

			return 0;

		}else{

//			return fboNameStack.peek();

			return currentFBO;

		}

	}



	//NOTE THIS UNBINDS A CURRENT FBO IF SET! -> no need for calling unbind()!

	/**

	 * Pops the fbo.

	 * This switches back (binds) to the formely pushed fbo. 

	 * <br>NOTE: THIS UNBINDS A CURRENT FBO IF SET! -> no need for calling unbind()!

	 */

	public void popFBO(){

		if (fboNameStack.isEmpty()){

			logger.error("Trying to pop() from an empty framebuffer stack!"); //TODO -> just bind 0 !?

		}else{

			currentFBO = fboNameStack.pop();

			gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, currentFBO);

		}

	}

	

}