use crate::{
    Mask, MoveOffset, Paints, TextData, Textures, WeakWidget, WidgetId, Widgets, util::TrackedArena,
};
use std::{
    cell::{Ref, RefCell, RefMut},
    ops::{Deref, DerefMut},
    rc::Rc,
};

mod access;
mod active;
mod painter;
mod render_state;

pub use access::*;
pub use active::*;
pub use painter::{DrawResult, Painter};
pub use render_state::*;

#[derive(Default)]
pub struct UiData {
    pub widgets: Widgets,
    pub paints: Paints,
    pub textures: Textures,
    pub text: TextData,
    pub masks: TrackedArena<Mask, u32>,
    pub move_offsets: TrackedArena<MoveOffset, u32>,
    animating: Vec<WidgetId>,
}

#[derive(Clone)]
pub struct RenderHandle {
    pub(crate) render_state: Rc<RefCell<UiRenderState>>,
}

impl RenderHandle {
    /// The retained result of the last completed frame. The framework holds
    /// the corresponding mutable borrow for the whole of a render update, so
    /// a read attempted while that state is incomplete fails at the boundary
    /// instead of observing half a frame.
    pub fn get(&self) -> Ref<'_, UiRenderState> {
        self.render_state
            .try_borrow()
            .expect("render state cannot be read while a frame is being rendered")
    }

    pub(crate) fn get_mut(&self) -> RefMut<'_, UiRenderState> {
        self.render_state
            .try_borrow_mut()
            .expect("render state cannot be mutated while it is being read")
    }
}

impl Default for RenderHandle {
    fn default() -> Self {
        Self {
            render_state: Rc::new(RefCell::new(UiRenderState::new())),
        }
    }
}

#[derive(Default)]
pub struct Ui {
    data: UiData,
    pub(crate) render_state: RenderHandle,
}

impl Ui {
    /// A read-only handle to the retained result of the last completed frame.
    /// The handle is owned so a caller may keep its read guard while mutating
    /// unrelated resources on the `Rsc` that owns this `Ui`.
    pub fn render_state(&self) -> RenderHandle {
        self.render_state.clone()
    }

    pub fn resize(&self, size: impl Into<crate::util::Vec2>) {
        self.render_state.get_mut().resize(size);
    }

    pub fn set_density(&mut self, density: f32) {
        self.data.text.density = density;
        self.render_state.get_mut().set_density(density);
    }
}

impl Deref for Ui {
    type Target = UiData;

    fn deref(&self) -> &Self::Target {
        &self.data
    }
}

impl DerefMut for Ui {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.data
    }
}

impl UiData {
    /// Ask for `id`'s [`crate::Widget::tick`] to run every frame until it
    /// says it is done. Idempotent -- registering an already-animating
    /// widget is the ordinary case (a second fling before the first
    /// settled) and must not tick it twice per frame.
    pub fn animate(&mut self, id: WidgetId) {
        if !self.animating.contains(&id) {
            self.animating.push(id);
        }
    }

    pub fn tick_animations(&mut self, now: std::time::Instant) -> bool {
        let mut registered = std::mem::take(&mut self.animating);
        registered.retain(|&id| match self.widgets.get_dyn_mut(id) {
            Some(widget) => widget.tick(now),
            None => false,
        });
        for id in registered {
            self.animate(id);
        }
        !self.animating.is_empty()
    }
}

pub trait UiRsc {
    fn ui(&self) -> &Ui;
    fn ui_mut(&mut self) -> &mut Ui;

    fn draw<'a>(&mut self, root: impl Into<Option<&'a crate::StrongWidget>>)
    where
        Self: Sized,
    {
        let render_state = self.ui().render_state.clone();
        render_state.get_mut().update(root, self);
    }

    #[allow(unused_variables)]
    fn on_add(&mut self, id: WeakWidget) {}
    #[allow(unused_variables)]
    fn on_remove(&mut self, id: WidgetId) {}
    #[allow(unused_variables)]
    fn on_draw(&mut self, active: &ActiveData) {}
    #[allow(unused_variables)]
    fn on_undraw(&mut self, active: &ActiveData) {}

    fn widgets(&self) -> &Widgets {
        &self.ui().widgets
    }
    fn widgets_mut(&mut self) -> &mut Widgets {
        &mut self.ui_mut().widgets
    }
    fn free(&mut self) {
        while let Some(id) = self.widgets_mut().free_next() {
            self.on_remove(id);
        }
        self.ui_mut().textures.free();
        self.ui_mut().paints.free_released();
    }
}