using System.Runtime.InteropServices;
using Engine.Renderer.Buffer.Vertex;
using OpenTK.Graphics.OpenGL;
using Serilog;

namespace Engine.Renderer.Buffer;

public class VertexBuffer<T> : OpenGlObject
    where T : struct, IVertex
{
    internal int Count { get; }

    private readonly int _stride = Marshal.SizeOf<T>();

    public VertexBuffer(int count, BufferStorageFlags flags)
    {
        if (!IVertex.IsValid(typeof(T)))
            throw new ArgumentException($"Type {typeof(T).Name} is not a valid vertex type");

        if (count <= 0)
            throw new ArgumentException("Count must be greater than 0");

        Count = count;

        GL.CreateBuffers(1, out int handle);
        Handle = handle;

        GL.NamedBufferStorage(Handle, Count * _stride, IntPtr.Zero, flags);
        
        Log.Debug("Vertex buffer {Handle} created with {Count} elements of type {Type}", Handle, Count, typeof(T).Name);
    }

    public void UploadData(T[] data)
    {
        UploadData(0, data);
    }

    public void UploadData(int offset, T[] data)
    {
        if (offset < 0)
            throw new ArgumentException("Offset must be greater than 0");

        if (data.Length + offset > Count)
            throw new ArgumentException("Data array is too large");

        GL.NamedBufferSubData(Handle, offset * _stride, data.Length * _stride, data);
    }

    internal override void Bind()
    {
        GL.BindBuffer(BufferTarget.ArrayBuffer, Handle);
    }

    internal override void Unbind()
    {
        GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
    }

    protected override void Destroy()
    {
        GL.DeleteBuffer(Handle);
    }
}