using Silk.NET.OpenGL;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Nebulix.Rendering
{
	public sealed class Mesh
	{
		public float[] Vertices { get => vertices; set { vertices = value; regenerate = true; } }
		public float[] Indices { get => indices; set { indices = value; regenerate = true; } }
		public float[] Normals { get => normals; }
		
		private uint vao = 0, vbo = 0, ebo = 0;
		private bool regenerate = true;

		private float[] vertices = [];
		private float[] indices = [];
		private float[] normals = [];


		// getting called by "Engine" which currently is in other assembly, meaning I probably need to make this public
		internal void Use(GL gl) 
		{
			if (regenerate) Generate(gl);

			gl.BindVertexArray(vao);

		}

		private unsafe void Generate(GL gl)
		{
			if(vao == 0)
				vao = gl.CreateVertexArray();
			if(vbo == 0)
				vbo = gl.GenBuffer();
			if(ebo == 0) 
				ebo = gl.GenBuffer();

			gl.BindVertexArray(vao);

			// TODO: verticesData needs to also contain "normals" not just vertices (and uv coords if I decide to add some)
			ReadOnlySpan<float> verticesData = new(vertices);
			gl.BindBuffer(BufferTargetARB.ArrayBuffer, vbo);
			gl.BufferData(BufferTargetARB.ArrayBuffer, (nuint)(verticesData.Length * sizeof(float)), verticesData, BufferUsageARB.StaticDraw);

			ReadOnlySpan<float> indicesData = new(indices);
			gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, ebo);
			gl.BufferData(BufferTargetARB.ElementArrayBuffer, (nuint)(indicesData.Length * sizeof(uint)), indicesData, BufferUsageARB.StaticDraw);

			// vertices
			gl.EnableVertexAttribArray(0);
			gl.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 6 * sizeof(float), (void*)0);
			gl.EnableVertexAttribArray(1);
			gl.VertexAttribPointer(1, 3, VertexAttribPointerType.Float, false, 6 * sizeof(float), (void*)(3 * sizeof(float)));
		}
	}
}