namespace TheLabs;
using LearnOpenTK.Common;
using OpenTK.Graphics.OpenGL4;
using OpenTK.Mathematics;
using OpenTK.Windowing.Desktop;
using StbImageSharp;

public class Mesh : IDisposable
{
    private readonly int _vao;
    private readonly int _vbo;
    private readonly int _ebo;
    private readonly int _vertexCount;
    private readonly bool _useIndices;

    // A flexible way to define vertex layout
    // (Could be an enum or a struct)
    public enum VertexLayout { PosColor, PosTex }

    public Mesh(float[] vertices, uint[] indices, VertexLayout layout)
    {
        _vertexCount = indices.Length;
        _useIndices = true;

        _vao = GL.GenVertexArray();
        GL.BindVertexArray(_vao);

        _vbo = GL.GenBuffer();
        GL.BindBuffer(BufferTarget.ArrayBuffer, _vbo);
        GL.BufferData(BufferTarget.ArrayBuffer, vertices.Length * sizeof(float), vertices, BufferUsageHint.StaticDraw);

        _ebo = GL.GenBuffer();
        GL.BindBuffer(BufferTarget.ElementArrayBuffer, _ebo);
        GL.BufferData(BufferTarget.ElementArrayBuffer, indices.Length * sizeof(uint), indices, BufferUsageHint.StaticDraw);

        // --- Set up Vertex Attributes based on layout ---
        if (layout == VertexLayout.PosColor)
        {
            // layout(location = 0) in shader: vec3 position
            var stride = 7 * sizeof(float);
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
            GL.EnableVertexAttribArray(0);
            
            // layout(location = 1) in shader: vec4 color
            GL.VertexAttribPointer(1, 4, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(1);
        }
        else if (layout == VertexLayout.PosTex)
        {
            // layout(location = 0) in shader: vec3 position
            var stride = 5 * sizeof(float);
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
            GL.EnableVertexAttribArray(0);

            // layout(location = 1) in shader: vec2 texCoord
            GL.VertexAttribPointer(1, 2, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(1);
        }
        // ... (you could add more layouts)
        
        GL.BindVertexArray(0);
    }
    
    // Constructor for non-indexed drawing (like your Circle)
    public Mesh(float[] vertices, VertexLayout layout)
    {
        // Calculate vertex count based on stride
        if (layout == VertexLayout.PosColor)
            _vertexCount = vertices.Length / 7;
        else // PosTex
            _vertexCount = vertices.Length / 5;

        _useIndices = false;
        _ebo = 0; // No EBO

        _vao = GL.GenVertexArray();
        GL.BindVertexArray(_vao);

        _vbo = GL.GenBuffer();
        GL.BindBuffer(BufferTarget.ArrayBuffer, _vbo);
        GL.BufferData(BufferTarget.ArrayBuffer, vertices.Length * sizeof(float), vertices, BufferUsageHint.StaticDraw);

        // --- Set up Vertex Attributes based on layout ---
        if (layout == VertexLayout.PosColor)
        {
            // layout(location = 0) in shader: vec3 position
            var stride = 7 * sizeof(float);
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
            GL.EnableVertexAttribArray(0);
    
            // layout(location = 1) in shader: vec4 color
            GL.VertexAttribPointer(1, 4, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(1);
        }
        else if (layout == VertexLayout.PosTex)
        {
            // layout(location = 0) in shader: vec3 position
            var stride = 5 * sizeof(float);
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
            GL.EnableVertexAttribArray(0);

            // layout(location = 1) in shader: vec2 texCoord
            GL.VertexAttribPointer(1, 2, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(1);
        }
    
        GL.BindVertexArray(0);
    }

    // Draw the mesh. Notice it doesn't know about shaders or matrices!
    public void Draw()
    {
        GL.BindVertexArray(_vao);
        
        if (_useIndices)
        {
            GL.DrawElements(PrimitiveType.Triangles, _vertexCount, DrawElementsType.UnsignedInt, 0);
        }
        else
        {
            // For your Circle (which used TriangleFan)
            GL.DrawArrays(PrimitiveType.TriangleFan, 0, _vertexCount);
        }
    }

    public void Dispose()
    {
        GL.DeleteBuffer(_vbo);
        GL.DeleteBuffer(_ebo);
        GL.DeleteVertexArray(_vao);
    }
}