pub struct DrawService {
	display: Rc<Display>,
	frame: Frame,
	program: Program,
	perspective: PerspectiveMatrix3<f32>,
}

impl DrawService {
	fn build_perspective(frame: &Frame) -> PerspectiveMatrix3<f32> {
		let (width, height) = frame.get_dimensions();

		let fov: f32 = ::std::f32::consts::PI / 3.0;
		let zfar = 1024.0;
		let znear = 0.001;

		PerspectiveMatrix3::new(width as f32 / height as f32, fov, znear, zfar)
	}

	pub fn new(display: Rc<Display>, program: Program) -> DrawService {
		let mut frame = display.draw();
		frame.clear_color_and_depth((0.0, 0.0, 0.0, 1.0), 1.0);
		let perspective = DrawService::build_perspective(&frame);
		DrawService {
			display: display,
			program: program,
			frame: frame,
			perspective: perspective,
		}
	}

	// TODO: Switch to trait object when glium updates.
	pub fn facade(&self) -> &Display {
		&self.display
	}

	pub fn update_perspective(&mut self) {
		self.perspective = DrawService::build_perspective(&self.frame);
	}

	pub fn flush(&mut self) {
		// TODO: Update framerate
		self.frame.set_finish();

		self.frame = self.display.draw();
		self.frame.clear_color_and_depth((0.0, 0.0, 0.0, 1.0), 1.0);
	}

	pub fn draw_buffer<'a, 'b, I, V>(&mut self, model_view: &Matrix4<f32>, vertices: V, indices: I)
	where I: Into<IndicesSource<'a>>, V: MultiVerticesSource<'b> {
		let uniforms = uniform! {
			model_view: model_view.as_ref().clone(),
			perspective: self.perspective.as_matrix().as_ref().clone(),
		};

		use glium::{DrawParameters, Depth};
		use glium::draw_parameters::{DepthTest, BackfaceCullingMode};
		let params = DrawParameters {
			depth: Depth {
				test: DepthTest::IfLess,
				write: true,
				.. Default::default()
			},
			backface_culling: BackfaceCullingMode::CullClockwise,
			.. Default::default()
		};

		self.frame.draw(vertices, indices, &self.program, &uniforms, &params).unwrap();
	}
}