package org.practice;

import java.nio.FloatBuffer;
import java.nio.IntBuffer;

import javax.media.opengl.*;

import org.eclipse.swt.widgets.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.*;

import com.jogamp.newt.opengl.GLWindow;
import com.jogamp.newt.swt.NewtCanvasSWT;

public class Trangles
{
	private int programID;
	private int vertexArrayObject;
	private int vertexBufferObject;
	private final FloatBuffer data = FloatBuffer.wrap(new float[]
	{
		0.0f, 1.0f, 0.0f, -1.0f, -1.0f, 0.0f, 1.0f, -1.0f, 0.0f	
	});
	
	private final String vertexShaderSource = 
			"in vec4 vPosition;" + "\n"	+ 
			"void main()" + "\n" + 
			"{" + "\n" + 
			"    gl_Position = vPosition;" + "\n" + 
			"}";
	
	private final String fragmentShaderSource =
			"void main()" + "\n" +
			"{" + "\n" +
			"    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);" + "\n" +
			"}";

	public Trangles(GLCapabilities capabilities)
	{
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setLayout(new FillLayout());
		Composite composite = new Composite(shell, SWT.BORDER);
		GLWindow window = GLWindow.create(capabilities);
		NewtCanvasSWT canvas = new NewtCanvasSWT(composite, SWT.NO_BACKGROUND,
				window);
		window.addGLEventListener(new Event());

		shell.setSize(300, 200);
		shell.open();
		canvas.setVisible(true);
		//window.setVisible(true);

		while (!display.isDisposed())
		{
			if (!display.readAndDispatch())
				display.sleep();
		}
		display.dispose();
	}

	class Event implements GLEventListener
	{

		@Override
		public void init(GLAutoDrawable drawable)
		{
			//Set the debug code.
			GL3 gl = drawable.getGL().getGL3();
			drawable.setGL(new DebugGL3(gl));
			
			gl.glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
			initShaders(gl);
			gl.glViewport(0, 0, drawable.getWidth(), drawable.getHeight());
			initVBO(gl);
		}

		@Override
		public void display(GLAutoDrawable drawable)
		{
			GL3 gl = drawable.getGL().getGL3();
			gl.glClear(GL3.GL_COLOR_BUFFER_BIT);
			gl.glUseProgram(programID);
			
			//Render the vertex buffer object.
			gl.glBindBuffer(GL3.GL_ARRAY_BUFFER, vertexBufferObject);
			gl.glDrawArrays(GL3.GL_TRIANGLES, 0, 3);
			//gl.glFlush();
			gl.glDisableVertexAttribArray(0);
		}

		@Override
		public void reshape(GLAutoDrawable drawable, int x, int y, int width,
				int height)
		{
			GL3 gl = drawable.getGL().getGL3();
			gl.glViewport(0, 0, width, height);
		}

		@Override
		public void dispose(GLAutoDrawable drawable)
		{
			// TODO Auto-generated method stub

		}

		private void initShaders(GL3 gl)
		{
			//Create a vertex shader.
			int vertexShaderID = gl.glCreateShader(GL3.GL_VERTEX_SHADER);
			gl.glShaderSource(vertexShaderID, 1, new String[]{vertexShaderSource}, null);
			gl.glCompileShader(vertexShaderID);
			
			//Create a fragment shader.
			int fragmentShaderID = gl.glCreateShader(GL3.GL_FRAGMENT_SHADER);
			gl.glShaderSource(fragmentShaderID, 1, new String[]{fragmentShaderSource}, null);
			gl.glCompileShader(fragmentShaderID);
			
			//Create a program.
			programID = gl.glCreateProgram();
			gl.glAttachShader(programID, vertexShaderID);
			gl.glAttachShader(programID, fragmentShaderID);
			gl.glLinkProgram(programID);
			
		}
		
		private void initVBO(GL3 gl)
		{
			//Check.
			if(vertexArrayObject != 0)
			{
				gl.glDeleteVertexArrays(1, new int[]{vertexArrayObject}, 0);
				vertexArrayObject = 0;
			}
			if(vertexBufferObject != 0)
			{
				gl.glDeleteBuffers(1, new int[]{vertexBufferObject}, 0);
				vertexBufferObject = 0;
			}
			
			int[] tempArray = new int[1];
			
			//Create the vertex array object.
			gl.glGenVertexArrays(1, IntBuffer.wrap(tempArray));
			vertexArrayObject = tempArray[0];
			gl.glBindVertexArray(vertexArrayObject);
			
			//Create the vertex buffer object.
			gl.glGenBuffers(1, IntBuffer.wrap(tempArray));
			vertexBufferObject = tempArray[0];
			
			//Initialize the vertex buffer object.
			gl.glBindBuffer(GL3.GL_ARRAY_BUFFER, vertexBufferObject);
			gl.glBufferData(GL3.GL_ARRAY_BUFFER, data.capacity() * 4, data, GL3.GL_STATIC_DRAW);
			
			//Initialize the attribute location of the input shader program.
			int location = gl.glGetAttribLocation(programID, "vPosition");
			gl.glVertexAttribPointer(location, 3, GL3.GL_FLOAT, false, 0, 0);
			gl.glEnableVertexAttribArray(location);
		}
		
	}

	public static void main(String[] args)
	{
		GLCapabilities capabilities = new GLCapabilities(
				GLProfile.get(GLProfile.GL3));
		new Trangles(capabilities);
	}
}