use std::sync::mpsc::{Receiver, Sender, channel};

use crate::{
    Axis, IdLike, SizeRule, SizeRules, StrongWidget, WeakWidget, Widget, WidgetData, WidgetId,
    util::{DynBorrower, HashSet, SlotVec, forget_mut, to_mut},
};

pub struct Widgets {
    pub needs_redraw: HashSet<WidgetId>,
    vec: SlotVec<WidgetData>,
    send: Sender<WidgetId>,
    recv: Receiver<WidgetId>,
    pub(crate) waiting: HashSet<WidgetId>,
}

impl Widgets {
    pub fn new() -> Self {
        let (send, recv) = channel();
        Self {
            needs_redraw: Default::default(),
            vec: Default::default(),
            waiting: Default::default(),
            send,
            recv,
        }
    }

    pub fn has_updates(&self) -> bool {
        !self.needs_redraw.is_empty()
    }

    pub fn get_dyn(&self, id: WidgetId) -> Option<&dyn Widget> {
        Some(self.vec.get(id)?.widget.as_ref())
    }

    pub fn get_dyn_mut(&mut self, id: WidgetId) -> Option<&mut dyn Widget> {
        self.needs_redraw.insert(id);
        Some(self.vec.get_mut(id)?.widget.as_mut())
    }

    /// get_dyn but dynamic borrow checking of widgets
    /// lets you do recursive (tree) operations, like the painter does
    pub(crate) fn get_dyn_dynamic<'a>(&self, id: WidgetId) -> WidgetWrapper<'a> {
        // SAFETY: must guarantee no other mutable references to this widget exist
        // done through the borrow variable
        let data = unsafe { forget_mut(to_mut(self.vec.get(id).unwrap())) };
        if data.borrowed {
            panic!("tried to mutably borrow the same widget twice");
        }
        WidgetWrapper::new(data.widget.as_mut(), &mut data.borrowed)
    }

    pub fn get<I: IdLike>(&self, id: &I) -> Option<&I::Widget>
    where
        I::Widget: Sized + Widget,
    {
        self.get_dyn(id.id())?.as_any().downcast_ref()
    }

    pub fn get_mut<I: IdLike>(&mut self, id: &I) -> Option<&mut I::Widget>
    where
        I::Widget: Sized + Widget,
    {
        self.get_dyn_mut(id.id())?.as_any_mut().downcast_mut()
    }

    pub fn add_strong<W: Widget>(&mut self, widget: W) -> StrongWidget<W> {
        let id = self.vec.add(WidgetData::new(widget));
        StrongWidget::new(id, self.send.clone())
    }

    pub fn add_weak<W: Widget>(&mut self, widget: W) -> WeakWidget<W> {
        let id = self.vec.add(WidgetData::new(widget));
        self.waiting.insert(id);
        WeakWidget::new(id)
    }

    #[track_caller]
    pub fn upgrade<W: ?Sized>(&mut self, rf: WeakWidget<W>) -> StrongWidget<W> {
        if !self.waiting.remove(&rf.id()) {
            let label = self.label(rf);
            let id = rf.id();
            panic!(
                "widget '{label}' ({id:?}) was already added\ncannot add a widget twice; consider creating two"
            )
        }
        StrongWidget::new(rf.id(), self.send.clone())
    }

    pub fn data(&self, id: impl IdLike) -> Option<&WidgetData> {
        self.vec.get(id.id())
    }

    pub fn label(&self, id: impl IdLike) -> &String {
        &self.data(id.id()).unwrap().label
    }

    /// useful for debugging
    pub fn set_label(&mut self, id: impl IdLike, label: String) {
        self.data_mut(id.id()).unwrap().label = label;
    }

    /// Whether this widget owns a movable retained region.
    pub fn is_region_node(&self, id: impl IdLike) -> bool {
        self.data(id).unwrap().region_node
    }

    /// Chooses whether this widget's retained drawing has one movable region
    /// of its own. Changing the boundary redraws the subtree once so every
    /// primitive names the right coordinate space.
    pub fn set_region_node(&mut self, id: impl IdLike, region_node: bool) {
        let id = id.id();
        let data = self.data_mut(id).unwrap();
        if data.region_node == region_node {
            return;
        }
        data.region_node = region_node;
        self.needs_redraw.insert(id);
    }

    /// The length rules whoever draws this widget applies to its box.
    pub fn size_rules(&self, id: impl IdLike) -> SizeRules {
        self.data(id).unwrap().size
    }

    /// Sets one axis's rule. The widget is marked rather than its parent
    /// because the parent is not known here; `redraw` escalates a changed
    /// declared length to whoever resolves it.
    pub fn set_size_rule(&mut self, id: impl IdLike, axis: Axis, rule: SizeRule) {
        let id = id.id();
        let data = self.data_mut(id).unwrap();
        if *data.size.axis_mut(axis) == rule {
            return;
        }
        *data.size.axis_mut(axis) = rule;
        self.needs_redraw.insert(id);
    }

    /// Both axes at once, for a caller holding a pair.
    pub fn set_size_rules(
        &mut self,
        id: impl IdLike,
        x: impl Into<SizeRule>,
        y: impl Into<SizeRule>,
    ) {
        let id = id.id();
        self.set_size_rule(id, Axis::X, x.into());
        self.set_size_rule(id, Axis::Y, y.into());
    }

    pub fn data_mut(&mut self, id: impl IdLike) -> Option<&mut WidgetData> {
        self.vec.get_mut(id.id())
    }

    pub fn free_next(&mut self) -> Option<WidgetId> {
        let next = self.recv.try_recv().ok()?;
        self.vec.free(next);
        Some(next)
    }

    #[allow(clippy::len_without_is_empty)]
    pub fn len(&self) -> usize {
        self.vec.len()
    }
}

impl Default for Widgets {
    fn default() -> Self {
        Self::new()
    }
}

pub type WidgetWrapper<'a> = DynBorrower<'a, dyn Widget>;

impl<I: IdLike> std::ops::Index<I> for Widgets
where
    I::Widget: Sized + Widget,
{
    type Output = I::Widget;

    fn index(&self, id: I) -> &Self::Output {
        self.get(&id).unwrap()
    }
}

impl<I: IdLike> std::ops::IndexMut<I> for Widgets
where
    I::Widget: Sized + Widget,
{
    fn index_mut(&mut self, id: I) -> &mut Self::Output {
        self.get_mut(&id).unwrap()
    }
}