using OpenTK.Graphics.OpenGL4;

namespace VoxelEngine.Rendering;

public sealed class LoadingScreen : IDisposable
{
    private readonly int _vao;
    private readonly int _vbo;
    private readonly Shader _shader;

    public LoadingScreen()
    {
        this._shader = new Shader("Assets/shaders/loading.vert", "Assets/shaders/loading.frag");

        // Single triangle covering the entire NDC quad.
        float[] vertices =
        {
            -1f, -1f,
             3f, -1f,
            -1f,  3f,
        };

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

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

        GL.VertexAttribPointer(0, 2, VertexAttribPointerType.Float, false, 2 * sizeof(float), 0);
        GL.EnableVertexAttribArray(0);

        GL.BindVertexArray(0);
    }

    public void Draw()
    {
        GL.Disable(EnableCap.DepthTest);
        this._shader.Use();
        GL.BindVertexArray(this._vao);
        GL.DrawArrays(PrimitiveType.Triangles, 0, 3);
        GL.BindVertexArray(0);
        GL.Enable(EnableCap.DepthTest);
    }

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