using System;
using System.IO;

using OpenTK.Graphics.OpenGL4;
using OpenTK;

namespace nhengine
{
	public class SquaredMap
	{
		private int width,
					height;

		private double[]	heightMap;
		private int[] 		tileTypes;

		/* GL shared resources */
		private int vao, cao, nao, ebo;

		private int bufVertices;
		private float[]
					vertices;
		private float[]
					colors,
					normals;

		private int[] elements;

		private ShaderProgram
					shaderProgram;

		public SquaredMap(int width,int height)
		{
			this.width = width;
			this.height = height;

			this.heightMap = new double[getVertexIndex(width,height) + 1];
			this.tileTypes = new int[getTileIndex(width,height) + 1];

			shaderProgram = new ShaderProgram(
				new FileStream("shader/simple_vertex.shader",FileMode.Open),
				new FileStream("shader/simple_fragment.shader",FileMode.Open)
			);

			prepareGL();
			computeGL();

			dumpGL();
		}

		private void prepareGL(){
			vao = GL.GenVertexArray();
			cao = GL.GenBuffer();
			nao = GL.GenBuffer();
			ebo = GL.GenBuffer();
			bufVertices = GL.GenBuffer();
		}

		public void computeGL(){
			int b;

			if (vertices == null){
				vertices = new float[heightMap.Length * 3];
			}

			if (elements == null){
				elements = new int[width * height * 6];
			}

			if (colors == null){
				colors = new float[heightMap.Length * 3];
				normals = new float[colors.Length];
			}

			Random rand = new Random();

			for (int x = 0; x <= width;x++)
			{
				for (int y = 0; y <= height;y++){
					b = 3 * getVertexIndex(x, y);

					vertices[b + 0] = 128 * x;
					vertices[b + 1] = 128 * y;

					float h = (float)rand.NextDouble();
					vertices[b + 2] = (float)(256 * (h * h));

					colors[b + 0] = 0.3f + 0.7f * (float)vertices[b + 2] / 256.0f;
					colors[b + 1] = 0.2f + 0.8f * (float)vertices[b + 2] / 256.0f;
					colors[b + 2] = 0.4f + 0.6f * (float)vertices[b + 2] / 256.0f;
				}
			}

			for (int x = 0; x < width;x++)
			{
				for (int y = 0; y < height;y++){
					b = 6 * getTileIndex(x, y);

					elements[b + 0] = x + (y * (width + 1));
					elements[b + 1] = x + (y * (width + 1)) + 1;
					elements[b + 2] = x + ((y + 1) * (width + 1));

					elements[b + 3] = x + ((y + 1) * (width + 1));
					elements[b + 4] = x + (y * (width + 1)) + 1;
					elements[b + 5] = x + ((y + 1) * (width + 1)) + 1;
				}
			}

			GL.BindVertexArray(vao);

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

			GL.VertexAttribPointer(0,
			                       3,
								   VertexAttribPointerType.Float,
								   false,
								   0,
								   0);

			GL.BindBuffer(BufferTarget.ArrayBuffer, cao);
			GL.BufferData(BufferTarget.ArrayBuffer, 4 * colors.Length, colors, BufferUsageHint.StaticDraw);

			GL.VertexAttribPointer(1,
								  3,
								  VertexAttribPointerType.Float,
								  false,
								  0,
								  0);

			GL.EnableVertexAttribArray(0);
			GL.EnableVertexAttribArray(1);


			GL.BindBuffer(BufferTarget.ElementArrayBuffer,ebo);
			GL.BufferData(BufferTarget.ElementArrayBuffer, 4 * elements.Length, elements, BufferUsageHint.StaticDraw);

			GL.BindVertexArray(0);
		}

		void dumpGL(){
			Console.WriteLine("Vertices:");
			for (int x = 0; x < 8;x++){
				Console.WriteLine("{0}", vertices[x]);
			}
		}

		private int getTileIndex(int x, int y)
		{
			return x + (y * this.width);
		}
		private int getVertexIndex(int x,int y){
			return x + (y * (this.width + 1));
		}

		private int getTileType(int x, int y)
		{
			int ind = getTileIndex(x, y);
			if ((ind < 0) || (ind > tileTypes.Length))
			{
				return 0;
			}

			return this.tileTypes[ind];
		}

		private int getTileType(int ind)
		{
			if ((ind < 0) || (ind > tileTypes.Length))
			{
				return 0;
			}
			return this.tileTypes[ind];
		}

		private double getHeight(int ind)
		{
			if ((ind < 0) || (ind > heightMap.Length))
			{
				return 0;
			}

			return this.heightMap[ind];
		}

		public void paint(GLCamera camera){
			

			Matrix4 pmat = camera.Matrix;

			GL.UseProgram(shaderProgram.ID);

			int pm = GL.GetUniformLocation(shaderProgram.ID, "proj_matrix");
			GL.UniformMatrix4(pm, false, ref pmat);

			GL.BindVertexArray(vao);

			GL.DrawElements(BeginMode.Triangles, elements.Length, DrawElementsType.UnsignedInt, 0);

			GL.BindVertexArray(0);

		}

	}
}