using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using OpenTK;
using OpenTK.Graphics.OpenGL;
using MathNet.Numerics.LinearAlgebra.Single;


namespace bbiwarg.Graphics
{
    class VertexBufferObject : GameWindow
    {
        int VBOid = new int();
        int IBOid = new int();
        float[] vertices;
        uint[] triangles;

        static void Main(string[] args)
        {
            VertexBufferObject demo = new VertexBufferObject();
            demo.initSource();
            demo.Run(30);
        }

        public void initSource()
        {

            GL.EnableClientState(ArrayCap.VertexArray);

            vertices = new float[] {
                1.0f, 0.0f, 0.0f, 
                0.0f, 0.0f, -5.0f,
                
                0.0f, 1.0f, 0.0f,
                0.0f, 1.0f, -5.0f, 
                
                0.0f, 0.0f, 1.0f,
                1.0f, 0.0f, -5.0f};
            triangles = new uint[] { 0, 1, 2 };



            GL.GenBuffers(1, out VBOid);
            GL.GenBuffers(1, out IBOid);

            GL.BindBuffer(BufferTarget.ArrayBuffer, VBOid);
            GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(vertices.Length * sizeof(float)), vertices, BufferUsageHint.StreamDraw);
            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);


            GL.BindBuffer(BufferTarget.ElementArrayBuffer, IBOid);
            GL.BufferData(BufferTarget.ElementArrayBuffer, (IntPtr)(triangles.Length * sizeof(int)), triangles, BufferUsageHint.StaticDraw);
            GL.BindBuffer(BufferTarget.ElementArrayBuffer, 0);


            //GL.DeleteBuffers(1, ref VBOid); GL.DeleteBuffers(1, ref IBOid);

        }

        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            Title = "vbo test";
            GL.ClearColor(Color.Black);
        }

        protected override void OnRenderFrame(FrameEventArgs e)
        {
            base.OnRenderFrame(e);

            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
            Matrix4 modelview = Matrix4.LookAt(Vector3.Zero, -Vector3.UnitZ, Vector3.UnitY);
            GL.MatrixMode(MatrixMode.Modelview);
            GL.LoadMatrix(ref modelview);

            GL.Color3(Color.Red);

            GL.BindBuffer(BufferTarget.ArrayBuffer, VBOid);
            GL.BindBuffer(BufferTarget.ElementArrayBuffer, IBOid);

            GL.InterleavedArrays(InterleavedArrayFormat.C3fV3f, 0, IntPtr.Zero);
            GL.DrawElements(BeginMode.Triangles, triangles.Length, DrawElementsType.UnsignedInt, 0);

            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
            GL.BindBuffer(BufferTarget.ElementArrayBuffer, 0);

            SwapBuffers();
        }

        protected override void OnResize(EventArgs e)
        {
            base.OnResize(e);
            GL.Viewport(ClientRectangle.X, ClientRectangle.Y, ClientRectangle.Width, ClientRectangle.Height);
            Matrix4 projection = Matrix4.CreatePerspectiveFieldOfView((float)Math.PI / 4, Width / (float)Height, 1.0f, 3000.0f);
            GL.MatrixMode(MatrixMode.Projection);
            GL.LoadMatrix(ref projection);
        }
    }
}