1pub use derive_refineable::Refineable;
 2
 3pub trait Refineable: Clone {
 4    type Refinement: Refineable<Refinement = Self::Refinement> + Default;
 5
 6    fn refine(&mut self, refinement: &Self::Refinement);
 7    fn refined(self, refinement: Self::Refinement) -> Self;
 8    fn from_cascade(cascade: &Cascade<Self>) -> Self
 9    where
10        Self: Default + Sized,
11    {
12        Self::default().refined(cascade.merged())
13    }
14}
15
16pub struct Cascade<S: Refineable>(Vec<Option<S::Refinement>>);
17
18impl<S: Refineable + Default> Default for Cascade<S> {
19    fn default() -> Self {
20        Self(vec![Some(Default::default())])
21    }
22}
23
24#[derive(Copy, Clone)]
25pub struct CascadeSlot(usize);
26
27impl<S: Refineable + Default> Cascade<S> {
28    pub fn reserve(&mut self) -> CascadeSlot {
29        self.0.push(None);
30        CascadeSlot(self.0.len() - 1)
31    }
32
33    pub fn base(&mut self) -> &mut S::Refinement {
34        self.0[0].as_mut().unwrap()
35    }
36
37    pub fn set(&mut self, slot: CascadeSlot, refinement: Option<S::Refinement>) {
38        self.0[slot.0] = refinement
39    }
40
41    pub fn merged(&self) -> S::Refinement {
42        let mut merged = self.0[0].clone().unwrap();
43        for refinement in self.0.iter().skip(1).flatten() {
44            merged.refine(refinement);
45        }
46        merged
47    }
48}