use std::collections::HashMap;

use crate::{Id, PaintCmd};

// TODO: support multiple windows
#[derive(Clone, Copy, Eq, PartialEq, Hash)]
pub enum Layer {
    Background,
    Window(Id),
    /// Tooltips etc
    Popup,
}

type PaintList = Vec<PaintCmd>;

/// TODO: improve this
#[derive(Clone, Default)]
pub struct GraphicLayers {
    bg: PaintList,
    windows: HashMap<Id, PaintList>,
    popup: PaintList,
}

impl GraphicLayers {
    pub fn layer(&mut self, layer: Layer) -> &mut PaintList {
        match layer {
            Layer::Background => &mut self.bg,
            Layer::Window(id) => self.windows.entry(id).or_default(),
            Layer::Popup => &mut self.popup,
        }
    }

    pub fn drain(&mut self, window_oreder: &[Id]) -> impl ExactSizeIterator<Item = PaintCmd> {
        let mut all_commands: Vec<_> = self.bg.drain(..).collect();

        for id in window_oreder {
            if let Some(window) = self.windows.get_mut(id) {
                all_commands.extend(window.drain(..));
            }
        }

        all_commands.extend(self.popup.drain(..));
        all_commands.into_iter()
    }
}