use std::marker::PhantomData;

use crate::{Painter, Widget, WidgetFn, WidgetId, WidgetLike};

pub struct Sensor<F: SenseFn<Ctx>, Ctx> {
    inner: WidgetId,
    f: F,
    _pd: PhantomData<Ctx>,
}

impl<F: SenseFn<Ctx>, Ctx: 'static> Widget<Ctx> for Sensor<F, Ctx> {
    fn draw(&self, painter: &mut Painter<Ctx>) {
        (self.f)(painter.ctx_mut());
        painter.draw(&self.inner);
    }
}

pub trait SenseFn<Ctx> = Fn(&mut Ctx) + 'static;

pub trait Sensable<Ctx: 'static, Tag> {
    fn sense<F: SenseFn<Ctx>>(self, f: F) -> impl WidgetFn<Sensor<F, Ctx>, Ctx>;
}

impl<W: WidgetLike<Ctx, Tag>, Ctx: 'static, Tag> Sensable<Ctx, Tag> for W {
    fn sense<F: SenseFn<Ctx>>(self, f: F) -> impl WidgetFn<Sensor<F, Ctx>, Ctx> {
        |ui| {
            let inner = self.add(ui).erase_type();
            Sensor {
                inner,
                f,
                _pd: PhantomData,
            }
        }
    }
}