using System;

using OpenTK.Graphics.OpenGL;
using OpenTK.Graphics;
using OpenTK;

using org.budnhead.tools;

namespace org.budnhead.graphics
{
	public class GLObject
	{
		ShaderProgram shaderProgram;

		protected float[] vertices,
			colors,
			normals;

		protected int[] elements;

		int vao,    // Vertex Array Object
			ebo,    // Element Buffer
			vbo,    // Vertex Buffer
			cbo,    // Color Buffer
			nbo;    // Normals Buffer

		Vector3 position;
		
		Matrix4 matrix;

		protected bool colorEnabled,
			normalsEnabled,
			uvEnabled;

		public GLObject(int vertexes)
		{
			shaderProgram = ResourceLibrary.getResource<ShaderProgram>("default");
			init(vertexes);
			prepareGL();
		}
		
		public GLObject(){
			shaderProgram = ResourceLibrary.getResource<ShaderProgram>("default");
			init(0);
			prepareGL();
		}
		
		private void init(int vertexes){
			this.vertices = new float[3 * vertexes];
			this.colors = new float[4 * vertexes];
			this.normals = new float[3 * vertexes];
			this.elements = null;   // Element Arrays können im Moment nicht verwendet werden

			colorEnabled = true;
			normalsEnabled = false;
			uvEnabled = false;

			this.position = new Vector3();
			this.matrix = Matrix4.Identity;
		
		}

		protected void prepareGL()
		{
			vao = GL.GenVertexArray();
			ebo = GL.GenBuffer();
			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 updateGL()
		{
			GL.BindVertexArray(vao);

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

			GL.EnableVertexAttribArray(0);

			if (colorEnabled)
			{
				GL.BindBuffer(BufferTarget.ArrayBuffer, cbo);
				GL.BufferData(BufferTarget.ArrayBuffer, 4 * this.colors.Length, this.colors, BufferUsageHint.StaticDraw);

				GL.EnableVertexAttribArray(1);
			}
			else
			{
				GL.DisableVertexAttribArray(1);
			}

			if (normalsEnabled)
			{
				GL.BindBuffer(BufferTarget.ArrayBuffer, nbo);
				GL.BufferData(BufferTarget.ArrayBuffer, 3 * this.normals.Length, this.normals, BufferUsageHint.StaticDraw);

				GL.EnableVertexAttribArray(2);
			}
			else
			{
				GL.DisableVertexAttribArray(2);
			}

			if (uvEnabled)
			{
				GL.EnableVertexAttribArray(3);
			}
			else
			{
				GL.DisableVertexAttribArray(3);
			}

			GL.BindVertexArray(0);
		}

		protected void setVertex(int n, Vector3 p)
		{
			vertices[(3 * n)] = p.X;
			vertices[(3 * n) + 1] = p.Y;
			vertices[(3 * n) + 2] = p.Z;
		}

		protected void setNormal(int n, Vector3 norm){
			normals[(3 * n)] = norm.X;
			normals[(3 * n)+1] = norm.Y;
			normals[(3 * n)+2] = norm.Z;
		}

		protected void setColor(int n, Vector4 p)
		{
			colors[(4 * n)] = p.X;
			colors[(4 * n) + 1] = p.Y;
			colors[(4 * n) + 2] = p.Z;
			colors[(4 * n) + 3] = p.W;
		}

		protected void setTriangle(int n, Vector3 a, Vector3 b, Vector3 c)
		{
			setVertex((3 * n), a);
			setVertex((3 * n) + 1, b);
			setVertex((3 * n) + 2, c);

			Vector3 normal = Vector3.Cross((b - a),(c - a));
			normal.Normalize();

            setNormal((3 * n),     normal);
            setNormal((3 * n) + 1, normal);
            setNormal((3 * n) + 2, normal);
		}

		protected void setColor(Vector4 c)
		{
			for (int n = 0; n < colors.Length / 4; n++)
			{
				setColor(n, c);
			}
		}

		protected Vector4 getColor(int n){
			return new Vector4(
						colors[(4 * n)],
						colors[(4 * n) + 1],
						colors[(4 * n) + 2],
						colors[(4 * n) + 3]);
		}

		public void paint()
		{
			paint(new GLCamera());
		}

		public void paint(GLSceneOrientation scene)
		{
			GL.BindVertexArray(this.vao);

			GL.DrawArrays(PrimitiveType.Triangles, 0, vertices.Length);

			GL.BindVertexArray(0);
		}
		
		protected void buildMatrix(){
			this.matrix = Matrix4.CreateTranslation( this.position );
		}


		public ShaderProgram ShaderProgram
		{
			get { return this.shaderProgram; }
			set { this.shaderProgram = value; }
		}

		public Vector3 Position{
			get { return this.position; }
			set { this.position = value; buildMatrix(); }
		}
		
		public Matrix4 Matrix {
			get { return this.matrix; }
			set { this.matrix = value; }
		}
	}
}