use std::marker::PhantomData;

use crate::prelude::*;

pub struct Stack {
    pub children: Vec<StrongWidget>,
    pub size: StackSize,
}

impl Widget for Stack {
    fn draw(&mut self, painter: &mut Painter) -> Size {
        let sizing = match self.size {
            StackSize::Default => None,
            StackSize::Child(i) => Some(i),
        };
        let mut size = Size::default();
        for (i, child) in self.children.iter().enumerate() {
            match i {
                0 => painter.child_layer(),
                _ => painter.next_layer(),
            }
            let drawn = painter.widget(child);
            // Only the child that sizes the stack is read, so the others
            // changing size does not redraw it.
            if sizing == Some(i) {
                size = drawn.size();
            }
        }
        size
    }
}

#[derive(Default, Debug)]
pub enum StackSize {
    #[default]
    Default,
    Child(usize),
}

pub struct StackBuilder<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag> {
    pub children: Wa,
    pub size: StackSize,
    _pd: PhantomData<(State, Tag)>,
}

impl<Rsc, const LEN: usize, Wa: WidgetArrLike<Rsc, LEN, Tag>, Tag> WidgetFnTrait<Rsc>
    for StackBuilder<Rsc, LEN, Wa, Tag>
{
    type Widget = Stack;

    #[track_caller]
    fn run(self, rsc: &mut Rsc) -> Self::Widget {
        Stack {
            children: self.children.add(rsc).arr.into_iter().collect(),
            size: self.size,
        }
    }
}

impl<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag>
    StackBuilder<State, LEN, Wa, Tag>
{
    pub fn new(children: Wa) -> Self {
        Self {
            children,
            size: StackSize::default(),
            _pd: PhantomData,
        }
    }

    pub fn size(mut self, size: StackSize) -> Self {
        self.size = size;
        self
    }
}