using System;

using OpenTK.Graphics.OpenGL;
using OpenTK;

namespace org.niclasundharald.engine.graphics {
	
	public class Model3D {

		protected int	vao,
			vbo,    // Vertex Buffer
			cbo,    // Color Buffer
			nbo;    // Normals Buffer

		protected int nTriangles;

		protected Model3D(){
			vao = GL.GenVertexArray();
			nTriangles = 0;

			prepare();
		}

		protected void prepare(){
			vbo = GL.GenBuffer();
			cbo = GL.GenBuffer();
			nbo = GL.GenBuffer();

			GL.BindVertexArray(vao);

			GL.BindBuffer(BufferTarget.ArrayBuffer, vbo);
			GL.VertexAttribPointer(0,
			                       3,
			                       VertexAttribPointerType.Float,
			                       false,
			                       0,
			                       0);

			GL.BindBuffer(BufferTarget.ArrayBuffer, cbo);
			GL.VertexAttribPointer(1,
			                       4,
			                       VertexAttribPointerType.Float,
			                       false,
			                       0,
			                       0);

			GL.BindBuffer(BufferTarget.ArrayBuffer, nbo);
			GL.VertexAttribPointer(2,
			                       3,
			                       VertexAttribPointerType.Float,
			                       false,
			                       0,
			                       0);

			GL.BindVertexArray(0);
		}

		protected void bind(Vector3[] vertexes){
			bind( vertexes, null, null, null );
		}

		protected void bind(Vector3[] vertexes,Vector4[] colors){
			bind( vertexes, colors, null, null );
		}

		protected void bind(Vector3[] vertexes,Vector4[] colors,Vector3[] normals){
			bind( vertexes, colors, normals, null );
		}

		protected void bind(Vector3[] vertexes,Vector4[] colors,Vector3[] normals,Vector2[] uvs){
			float[] fv = new float[vertexes.Length * 3];

			for (int n=0;n<vertexes.Length;n++){
				fv[(n * 3)    ] = vertexes[n].X;
				fv[(n * 3) + 1] = vertexes[n].Y;
				fv[(n * 3) + 2] = vertexes[n].Z;
			}

			GL.BindVertexArray(vao);

			GL.BindBuffer(BufferTarget.ArrayBuffer, vbo);
			GL.BufferData(BufferTarget.ArrayBuffer, 4 * fv.Length, fv, BufferUsageHint.StaticDraw);

			GL.EnableVertexAttribArray(0);

			nTriangles = vertexes.Length / 3;

			if (colors != null){
				float[] fc = new float[ colors.Length * 4 ];

				for (int n=0;n < colors.Length; n++){
					fc[ (4*n)     ] = colors[n].X;
					fc[ (4*n) + 1 ] = colors[n].Y;
					fc[ (4*n) + 2 ] = colors[n].Z;
					fc[ (4*n) + 3 ] = colors[n].W;
				}

				GL.BindBuffer(BufferTarget.ArrayBuffer, cbo);
				GL.BufferData(BufferTarget.ArrayBuffer, 4 * fc.Length, fc, BufferUsageHint.StaticDraw);

				GL.EnableVertexAttribArray(1);
			} else {
				float[] fc = new float[ vertexes.Length * 4 ];

				for (int n=0;n<fc.Length;n++){
					fc[n] = n % 4 == 3 ? 1.0f : 0.5f;
				}

				GL.BindBuffer(BufferTarget.ArrayBuffer, cbo);
				GL.BufferData(BufferTarget.ArrayBuffer, 4 * fc.Length, fc, BufferUsageHint.StaticDraw);

				GL.EnableVertexAttribArray(1);
			}

			if (normals != null){
				float[] fn = new float[ normals.Length * 3];

				for (int n=0;n<normals.Length;n++){
					fn[(n * 3)    ] = normals[n].X;
					fn[(n * 3) + 1] = normals[n].Y;
					fn[(n * 3) + 2] = normals[n].Z;
				}

				GL.BindBuffer(BufferTarget.ArrayBuffer, nbo);
				GL.BufferData(BufferTarget.ArrayBuffer, 3 * fn.Length, fn, BufferUsageHint.StaticDraw);

				GL.EnableVertexAttribArray(2);
			} else {
				float[] fn = new float[fv.Length];

				for (int n=0;n<vertexes.Length;n+=3){
					Vector3 normal = Vector3.Cross( vertexes[n+1] - vertexes[n], vertexes[n+2] - vertexes[n] );
					normal.Normalize();
					fn[(n * 3)    ] = normal.X;
					fn[(n * 3) + 1] = normal.Y;
					fn[(n * 3) + 2] = normal.Z;
					fn[(n * 3) + 3] = normal.X;
					fn[(n * 3) + 4] = normal.Y;
					fn[(n * 3) + 5] = normal.Z;
					fn[(n * 3) + 6] = normal.X;
					fn[(n * 3) + 7] = normal.Y;
					fn[(n * 3) + 8] = normal.Z;
				}

				GL.BindBuffer(BufferTarget.ArrayBuffer, nbo);
				GL.BufferData(BufferTarget.ArrayBuffer, 3 * fn.Length, fn, BufferUsageHint.StaticDraw);

				GL.EnableVertexAttribArray(2);
			}



		}

		public virtual void draw(){
			GL.BindVertexArray(this.vao);
			GL.DrawArrays(PrimitiveType.Triangles, 0, nTriangles * 3);
			GL.BindVertexArray(0);
		}


		public static void setTriangle(Vector3[] vertexes,int n, Vector3 a, Vector3 b, Vector3 c)
		{
			vertexes[(3 * n)] = a;
			vertexes[(3 * n)+1] = b;
			vertexes[(3 * n)+2] = c;
		}


	}
}