namespace TheLabs;
using LearnOpenTK.Common;
using OpenTK.Graphics.OpenGL4;
using OpenTK.Mathematics;
using System;

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

    public enum VertexLayout { PosColor, PosTex, PosTexNormal, PosTexNormalTangent }

    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);

        SetupAttributes(layout); // Refactored into a helper method to avoid duplication

        GL.BindVertexArray(0);
    }
    
    public Mesh(float[] vertices, VertexLayout layout)
    {
        // Calculate vertex count based on the layout size
        int strideCount = 0;
        if (layout == VertexLayout.PosColor) strideCount = 7;
        else if (layout == VertexLayout.PosTex) strideCount = 5;
        else if (layout == VertexLayout.PosTexNormal) strideCount = 8;

        _vertexCount = vertices.Length / strideCount;
        _useIndices = false;
        _ebo = 0;

        _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);

        SetupAttributes(layout);

        GL.BindVertexArray(0);
    }

    // Helper method to set up pointers (shared by both constructors)
    private void SetupAttributes(VertexLayout layout)
    {
        if (layout == VertexLayout.PosColor)
        {
            // Stride = 7 floats (3 Pos + 4 Color)
            var stride = 14 * sizeof(float); 
            
            // Location 0: Position
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
            GL.EnableVertexAttribArray(0);
            
            // Location 1: Color
            GL.VertexAttribPointer(1, 4, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(1);
            
            GL.VertexAttribPointer(2, 2, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(2);
            
            GL.VertexAttribPointer(3, 3, VertexAttribPointerType.Float, false, stride, 8 * sizeof(float));
            GL.EnableVertexAttribArray(3);
            
            // Loc 4: Bitangent (Offset 11) <-- NEW
            GL.VertexAttribPointer(4, 3, VertexAttribPointerType.Float, false, stride, 11 * sizeof(float));
            GL.EnableVertexAttribArray(4);
        }
        else if (layout == VertexLayout.PosTex)
        {
            // Stride = 5 floats (3 Pos + 2 Tex)
            var stride = 5 * sizeof(float);
            
            // Location 0: Position
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
            GL.EnableVertexAttribArray(0);

            // Location 2: TexCoord (I used 2 to match the Normal layout below, but 1 works too if you change shader)
            // Let's keep it at 1 for now to break less code, but for lighting we usually move Tex to 2.
            // For now, let's assume your shader uses Location 2 for Texture if using Normals.
            GL.VertexAttribPointer(2, 2, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(2);
        }
        else if (layout == VertexLayout.PosTexNormal)
        {
            // Stride = 8 floats (3 Pos + 3 Normal + 2 Tex)
            var stride = 14 * sizeof(float);

            // Location 0: Position
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
            GL.EnableVertexAttribArray(0);

            // Location 1: Normal (Offset 3 floats)
            GL.VertexAttribPointer(1, 3, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(1);

            // Location 2: TexCoord (Offset 6 floats: 3 pos + 3 normal)
            GL.VertexAttribPointer(2, 2, VertexAttribPointerType.Float, false, stride, 6 * sizeof(float));
            GL.EnableVertexAttribArray(2);
            
        }
        else if (layout == VertexLayout.PosTexNormalTangent)
        {
            // --- NEW LOGIC FOR CUBES (Stride 14) ---
            var stride = 14 * sizeof(float);

            // Loc 0: Position
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
            GL.EnableVertexAttribArray(0);

            // Loc 1: Normal
            GL.VertexAttribPointer(1, 3, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
            GL.EnableVertexAttribArray(1);

            // Loc 2: TexCoord
            GL.VertexAttribPointer(2, 2, VertexAttribPointerType.Float, false, stride, 6 * sizeof(float));
            GL.EnableVertexAttribArray(2);
            
            // Loc 3: Tangent
            GL.VertexAttribPointer(3, 3, VertexAttribPointerType.Float, false, stride, 8 * sizeof(float));
            GL.EnableVertexAttribArray(3);

            // Loc 4: Bitangent
            GL.VertexAttribPointer(4, 3, VertexAttribPointerType.Float, false, stride, 11 * sizeof(float));
            GL.EnableVertexAttribArray(4);
        }
    }

    public void Draw()
    {
        GL.BindVertexArray(_vao);
        if (_useIndices)
        {
            GL.DrawElements(PrimitiveType.Triangles, _vertexCount, DrawElementsType.UnsignedInt, 0);
        }
        else
        {
            GL.DrawArrays(PrimitiveType.TriangleFan, 0, _vertexCount);
        }
    }

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