quicksilver 0.3.5

use crate::{
    Result,
    geom::{Rectangle, Vector},
    graphics::{Background::Col, BlendMode, Color, GpuTriangle, Image, ImageScaleStrategy, PixelFormat, Surface, Vertex},
    input::MouseCursor,
};

pub(crate) trait Backend {
    type Platform;

    unsafe fn new(platform: Self::Platform, texture_mode: ImageScaleStrategy, multisample: bool) -> Result<Self> where Self: Sized;

    unsafe fn set_blend_mode(&mut self, blend: BlendMode);
    unsafe fn reset_blend_mode(&mut self);

    unsafe fn clear(&mut self, color: Color);
    unsafe fn draw(&mut self, vertices: &[Vertex], triangles: &[GpuTriangle]) -> Result<()>;
    unsafe fn flush(&mut self);
    fn present(&self) -> Result<()>;

    unsafe fn create_texture(&mut self, data: &[u8], width: u32, height: u32, format: PixelFormat) -> Result<ImageData>;
    unsafe fn destroy_texture(&mut self, data: &mut ImageData);

    unsafe fn create_surface(&mut self, image: &Image) -> Result<SurfaceData>;
    unsafe fn bind_surface(&mut self, surface: &Surface);
    unsafe fn unbind_surface(&mut self, surface: &Surface, viewport: &[i32]);
    unsafe fn destroy_surface(&mut self, surface: &SurfaceData);

    unsafe fn viewport(&self) -> [i32; 4];
    unsafe fn set_viewport(&mut self, area: Rectangle) where Self: Sized;

    unsafe fn screenshot(&self, format: PixelFormat) -> (Vector, Vec<u8>);

    fn set_cursor(&mut self, cursor: MouseCursor);
    fn set_title(&mut self, title: &str);

    fn set_fullscreen(&mut self, fullscreen: bool) -> Option<Vector>;
    fn resize(&mut self, size: Vector);

    unsafe fn clear_color(&mut self, color: Color, letterbox: Color) -> Result<()> {
        self.clear(letterbox);
        self.draw(&[
            Vertex::new((-1, -1), None, Col(color)),
            Vertex::new((1, -1), None, Col(color)),
            Vertex::new((1, 1), None, Col(color)),
            Vertex::new((-1, 1), None, Col(color)),
        ], &[
            GpuTriangle::new(0, [0, 1, 2], 0.0, Col(color)),
            GpuTriangle::new(0, [2, 3, 0], 0.0, Col(color))
        ])?;
        self.flush();
        Ok(())
    }
}

const VERTEX_SIZE: usize = 9; // the number of floats in a vertex

mod image_data;
mod surface_data;

pub use self::image_data::ImageData;
pub use self::surface_data::SurfaceData;

// Backends
#[cfg(not(target_arch="wasm32"))]
mod gl3;
#[cfg(target_arch="wasm32")]
mod webgl;

#[cfg(not(target_arch="wasm32"))]
pub use self::gl3::GL3Backend;
#[cfg(target_arch="wasm32")]
pub use self::webgl::WebGLBackend;

#[cfg(not(target_arch="wasm32"))]
pub type BackendImpl = GL3Backend;
#[cfg(target_arch="wasm32")]
pub type BackendImpl = WebGLBackend;

static mut BACKEND_INSTANCE: Option<BackendImpl> = None;

pub unsafe fn instance() -> &'static mut BackendImpl {
    BACKEND_INSTANCE.as_mut().unwrap()
}

pub unsafe fn set_instance(instance: BackendImpl) {
    BACKEND_INSTANCE = Some(instance);
}