// SPDX-License-Identifier: GPL-3.0-only

use crate::state::Common;
#[cfg(feature = "debug")]
use crate::{
    debug::{debug_ui, fps_ui, log_ui, EguiFrame},
    state::Fps,
};

use slog::Logger;
use smithay::{
    backend::renderer::{
        gles2::{Gles2Renderbuffer, Gles2Renderer, Gles2Texture},
        multigpu::{egl::EglGlesBackend, Error as MultiError, MultiFrame, MultiRenderer},
        ImportAll, Renderer,
    },
    desktop::space::{RenderElement, RenderError, SpaceOutputTuple, SurfaceTree},
    utils::{Logical, Point, Rectangle},
    wayland::output::Output,
};

mod cursor;
use self::cursor::PointerElement;

pub type GlMultiRenderer<'a> =
    MultiRenderer<'a, 'a, EglGlesBackend, EglGlesBackend, Gles2Renderbuffer>;
pub type GlMultiFrame = MultiFrame<EglGlesBackend, EglGlesBackend>;

smithay::custom_elements! {
    pub CustomElem<=Gles2Renderer>;
    SurfaceTree=SurfaceTree,
    PointerElement=PointerElement::<Gles2Texture>,
    #[cfg(feature = "debug")]
    EguiFrame=EguiFrame,
}

// TODO: due to the lifetime, we cannot be generic over CustomElem's renderer
// util after GATs land. So we generate with the macro for Gles2 and then
// do a manual impl for MultiRenderer.
impl RenderElement<GlMultiRenderer<'_>> for CustomElem {
    fn id(&self) -> usize {
        RenderElement::<Gles2Renderer>::id(self)
    }

    fn geometry(&self) -> Rectangle<i32, Logical> {
        RenderElement::<Gles2Renderer>::geometry(self)
    }

    fn accumulated_damage(
        &self,
        for_values: Option<SpaceOutputTuple<'_, '_>>,
    ) -> Vec<Rectangle<i32, Logical>> {
        RenderElement::<Gles2Renderer>::accumulated_damage(self, for_values)
    }

    fn draw(
        &self,
        renderer: &mut GlMultiRenderer<'_>,
        frame: &mut GlMultiFrame,
        scale: f64,
        location: Point<i32, Logical>,
        damage: &[Rectangle<i32, Logical>],
        log: &Logger,
    ) -> Result<(), MultiError<EglGlesBackend, EglGlesBackend>> {
        RenderElement::<Gles2Renderer>::draw(
            self,
            renderer.as_mut(),
            frame.as_mut(),
            scale,
            location,
            damage,
            log,
        )
        .map_err(MultiError::Render)
    }

    fn z_index(&self) -> u8 {
        RenderElement::<Gles2Renderer>::z_index(self)
    }
}

pub trait AsGles2Renderer {
    fn as_gles2(&mut self) -> &mut Gles2Renderer;
}
impl AsGles2Renderer for Gles2Renderer {
    fn as_gles2(&mut self) -> &mut Gles2Renderer {
        self
    }
}
impl AsGles2Renderer for GlMultiRenderer<'_> {
    fn as_gles2(&mut self) -> &mut Gles2Renderer {
        self.as_mut()
    }
}

pub fn render_output<R>(
    renderer: &mut R,
    age: u8,
    state: &mut Common,
    output: &Output,
    hardware_cursor: bool,
    #[cfg(feature = "debug")] fps: &mut Fps,
) -> Result<Option<Vec<Rectangle<i32, Logical>>>, RenderError<R>>
where
    R: Renderer + ImportAll + AsGles2Renderer,
    <R as Renderer>::TextureId: Clone + 'static,
    CustomElem: RenderElement<R>,
{
    #[cfg(feature = "debug")]
    {
        fps.start();
    }

    #[allow(unused_mut)]
    let mut custom_elements = Vec::<CustomElem>::new();

    #[cfg(feature = "debug")]
    {
        let space = state.spaces.active_space(output);
        let output_geo = space
            .output_geometry(output)
            .unwrap_or(Rectangle::from_loc_and_size((0, 0), (0, 0)));
        let scale = space.output_scale(output).unwrap();

        let fps_overlay = fps_ui(state, fps, output_geo, scale);
        custom_elements.push(fps_overlay.into());

        let mut area = state.spaces.global_space();
        area.loc = state.spaces.space_relative_output_geometry((0, 0), output);
        if let Some(log_ui) = log_ui(state, area, scale, output_geo.size.w as f32 * 0.6) {
            custom_elements.push(log_ui.into());
        }
        if let Some(debug_overlay) = debug_ui(state, area, scale) {
            custom_elements.push(debug_overlay.into());
        }
    }

    for seat in &state.seats {
        let pointer = match seat.get_pointer() {
            Some(ptr) => ptr,
            None => continue,
        };
        let location = state
            .spaces
            .space_relative_output_geometry(pointer.current_location().to_i32_round(), output);

        if let Some(cursor) = cursor::draw_cursor(
            renderer.as_gles2(),
            seat,
            location,
            &state.start_time,
            !hardware_cursor,
        ) {
            custom_elements.push(cursor)
        }
    }

    let res = state.spaces.active_space_mut(output).render_output(
        renderer,
        &output,
        age as usize,
        [0.153, 0.161, 0.165, 1.0],
        &*custom_elements,
    );

    #[cfg(feature = "debug")]
    {
        fps.end();
    }

    res
}