using System;
using System.IO;
            
using OpenTK.Graphics.OpenGL;
using OpenTK;

using org.budnhead.tools;

/**
 * ShaderProgram Class
 * 
 * Defines a shading program to use for drawing operations
 * 
 * The coordinate space used to describe the world is called "WorldSpace"
 * 
 * Each object to be drawn/used in the "World" is based on its individual coordinate space "ObjectSpace"
 * Each object provides a Transformation Matrix "mObject" which translates ObjectSpace to WorldSpace.
 * 
 * WorldSpace = mObject * ObjectSpace
 * 
 * To render the scene another coordinate space is used, which is called "CameraSpace"
 * The transformation matrix used to translate from WorldSpace to CameraSpace is called "mCamera"
 * 
 * CameraSpace = (mObject * mCamera) * ObjectSpace
 * 
 * As convention the following data will be given to shaders:
 * 
 * Uniform:
 * 
 * mObject			Transformation Matrix ObjectSpace -> WorldSpace
 * mCamera			Transformation Matrix WorldSpace -> CameraSpace
 * mProjection		Projection Matrix for 2D Rendering
 * 
 * mObjectCamera	mObject * mCamera
 * 
 * mObjectCameraIT	(mObjectCamera^-1)^T
 * 
 * 
 * Stream Data:
 * 
 * iv_position		Vertex coordinate
 * iv_color			Vertex Color
 * iv_normal		Vertex normal
 * iv_uv			Vertex texture coordinate
 * 
 * 
 **/


namespace org.budnhead.graphics
{
	public class ShaderProgram
	{

		Shader vertexShader;
		Shader fragmentShader;

		int id;

		int nm_Object,
			nm_Camera,
			nm_Projection,
			nm_ObjectCamera,
			nm_ObjectCameraIT,
			nm_Scene;

		public ShaderProgram(Shader vertexShader, Shader fragmentShader)
		{
			init(vertexShader, fragmentShader);
		}

		public ShaderProgram(String vertexShader, String fragmentShader)
		{
			init(
				ResourceLibrary.getResource<Shader>(vertexShader),
				ResourceLibrary.getResource<Shader>(fragmentShader)
				);
		}

		public ShaderProgram(Stream vertexShader, Stream fragmentShader)
		{
			init(
				new Shader(ShaderType.VertexShader, 	new StreamReader(vertexShader).ReadToEnd()),
				new Shader(ShaderType.FragmentShader,	new StreamReader(fragmentShader).ReadToEnd())
				);
		}


		private void init(Shader vertexShader, Shader fragmentShader){
            this.vertexShader = vertexShader;
			this.fragmentShader = fragmentShader;

			this.id = GL.CreateProgram();

			GL.AttachShader(this.id, this.vertexShader.ID);
			GL.AttachShader(this.id, this.fragmentShader.ID);

			GL.BindAttribLocation(this.id, 0, "iv_position");
			GL.BindAttribLocation(this.id, 1, "iv_color");
			GL.BindAttribLocation(this.id, 2, "iv_normal");
			GL.BindAttribLocation(this.id, 3, "iv_uv");

			GL.LinkProgram(this.id);
			Console.WriteLine("Shader Program Result: {0}", GL.GetProgramInfoLog(this.id));

			nm_Object		= GL.GetUniformLocation(this.ID, "mObject");
			nm_Camera		= GL.GetUniformLocation(this.ID, "mCamera");
			nm_ObjectCamera	= GL.GetUniformLocation(this.ID, "mObjectCamera");
			nm_ObjectCameraIT
							= GL.GetUniformLocation(this.ID, "mObjectCameraIT");

			nm_Projection	= GL.GetUniformLocation(this.ID, "mProjection");
			nm_Scene		= GL.GetUniformLocation(this.ID, "mScene");
		}

		public int ID
		{
			get { return this.id; }
		}

		public int nmObject
		{
			get
			{
				return nm_Object;
			}
		}
		public int nmCamera
		{
			get
			{
				return nm_Camera;
			}
		}

		public int nmObjectCamera
		{
			get
			{
				return nm_ObjectCamera;
			}
		}

		public int nmObjectCameraIT
		{
			get
			{
				return nm_ObjectCameraIT;	}
		}

		public int nmProjection
		{
			get
			{
				return nm_Projection;
			}
		}

		public int nmScene
		{
			get
			{
				return nm_Scene;
			}
		}

		public void use(){
			GL.UseProgram(this.id);
		}

		public void setup(Matrix4 _mObject,GLSceneOrientation scene){
			Matrix4 mObject,
				mCamera,
				mObjectCamera,
				mObjectCameraIT,
				mProjection,
				mScene;

			mObject = _mObject;
			mCamera = scene.mCamera();
			mObjectCamera = mObject * mCamera;
			
			mObjectCameraIT = mObjectCamera.Inverted();
			mObjectCameraIT.Transpose();
			
			mProjection = scene.mProjection();
			mScene = mObjectCamera * mProjection;

			GL.UniformMatrix4(nm_Object,		false, ref mObject);
			GL.UniformMatrix4(nm_Camera, 		false, ref mCamera);
			GL.UniformMatrix4(nm_ObjectCamera,	false, ref mObjectCamera);
			GL.UniformMatrix4(nm_Projection,	false, ref mProjection);
			GL.UniformMatrix4(nm_ObjectCameraIT,false, ref mObjectCameraIT);
			GL.UniformMatrix4(nm_Scene,			false, ref mScene);
		}
	}
}