use crate::*;

pub enum Collected<'a, E: Engine> {
    Box(Box<dyn Render<E> + 'a>),
    Ref(&'a (dyn Render<E> + 'a)),
}

impl<'a, E: Engine> Render<E> for Collected<'a, E> {
    fn render (&self, to: &mut E) -> Perhaps<E::Rendered> {
        match self {
            Self::Box(item) => (*item).render(to),
            Self::Ref(item) => (*item).render(to),
        }
    }
}

pub struct Collection<'a, E: Engine>(
    pub Vec<Collected<'a, E>>
);

impl<'a, E: Engine> Collection<'a, E> {
    pub fn new () -> Self {
        Self(vec![])
    }
}

pub trait Collect<'a, E: Engine> {
    fn add_box (self, item: Box<dyn Render<E> + 'a>) -> Self;
    fn add_ref (self, item: &'a dyn Render<E>) -> Self;
    fn add <R: Render<E> + Sized + 'a> (self, item: R) -> Self
        where Self: Sized
    {
        self.add_box(Box::new(item))
    }
}

impl<'a, E: Engine> Collect<'a, E> for Collection<'a, E> {
    fn add_box (mut self, item: Box<dyn Render<E> + 'a>) -> Self {
        self.0.push(Collected::Box(item));
        self
    }
    fn add_ref (mut self, item: &'a dyn Render<E>) -> Self {
        self.0.push(Collected::Ref(item));
        self
    }
}