use crate::prelude::*;
use std::marker::Unsize;

/// One widget in a box of its own, doing as little as possible on the way:
/// it draws its child in the whole of its box and reports back what the child
/// said. It exists because a length and an alignment are properties of one
/// widget, so a widget cannot both be 100 wide and take two shares of a row
/// -- the two lengths need two widgets, and this is the smaller one.
///
/// Its child is optional so it can also be the swappable slot a tab bar
/// needs, which is what it was written for.
pub struct Wrapper {
    pub inner: Option<StrongWidget>,
}

impl Widget for Wrapper {
    fn draw(&mut self, painter: &mut Painter) -> Size {
        match &self.inner {
            Some(id) => painter.widget(id).size(),
            None => Size::default(),
        }
    }
}

impl Wrapper {
    pub fn new() -> Self {
        Self::default()
    }
    pub fn empty() -> Self {
        Self {
            inner: Default::default(),
        }
    }
    pub fn set<W: ?Sized + Unsize<dyn Widget>>(&mut self, to: StrongWidget<W>) {
        self.inner = Some(to)
    }

    pub fn replace<W: ?Sized + Unsize<dyn Widget>>(
        &mut self,
        to: StrongWidget<W>,
    ) -> Option<StrongWidget> {
        self.inner.replace(to)
    }
}

impl Default for Wrapper {
    fn default() -> Self {
        Self::empty()
    }
}