use crate::{geometry, handles::{self, MeshHandle}, math};
use std::ffi::CString;


pub struct DrawCommand<'a> {
  pub mesh: handles::MeshHandle,
  pub shader: handles::ShaderHandle,
  pub uniforms: &'a [Uniform],
  pub textures: &'a [(u32, u32)],
}

#[derive(Clone, Debug)]
pub enum Uniform {
  Float(CString, f32),
  Vec2(CString, math::Vec2),
  Vec3(CString, math::Vec3),
  Vec4(CString, math::Vec4),
  Mat4(CString, math::Mat4),
  Int(CString, i32)
}

pub trait RenderBackend {
  type ShaderSource: Default;
  fn new() -> Self;

  fn resume(&mut self, event_loop: &winit::event_loop::ActiveEventLoop);
  fn resize(&mut self, width: u32, height: u32);
  fn suspend(&mut self);

  fn begin_frame(&mut self);
  fn draw(&self, cmd: &DrawCommand);
  fn end_frame(&self);

  fn create_shader(&mut self, desc: &Self::ShaderSource) -> Result<handles::ShaderHandle, String>;
  fn create_mesh(&mut self, mesh: &geometry::Mesh) -> Result<MeshHandle, String>;
  // fn create_buffer(&mut self, data: &[u8], usage: BufferUsage) -> BufferHandle;
  // fn create_texture(&mut self, desc: TextureDescriptor) -> TextureHandle;

  fn set_target_fps(&mut self, fps: u32);

}

// pub struct FrameContext<'a> {
//     backend: &'a mut dyn RenderBackend,
// }
//
// impl FrameContext<'_> {
//     pub fn draw(&mut self, mesh: &Mesh, material: MaterialHandle, transform: Mat4);
// }